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Degradation of carbon-supported Pt nanocatalysts in fuel cells and electrolyzers hinders widespread commercialization of these green technologies. Transition between oxidized and reduced states of Pt during fast potential spikes triggers significant Pt dissolution. Therefore, designing Pt-based catalysts able to withstand such conditions is of critical importance. We report here on a strategy to suppress Pt dissolution by using an organic matrix tris(aza)pentacene (TAP) as an alternative support material for Pt. The major benefit of TAP is its potential-dependent conductivity in aqueous media, which was directly evidenced by electrochemical impedance spectroscopy. At potentials below ∼0.45 VRHE, TAP is protonated and its conductivity is improved, which enables supported Pt to run hydrogen reactions. At potentials corresponding to Pt oxidation/reduction (>∼0.45 VRHE), TAP is deprotonated and its conductivity is restricted. Tunable conductivity of TAP enhanced the durability of the Pt/TAP with respect to Pt/C when these two materials were subjected to the same degradation protocol (0.1 M HClO4 electrolyte, 3000 voltammetric scans, 1 V/s, 0.05–1.4 VRHE). The exceptional stability of Pt/TAP composite on a nanoscale level was confirmed by identical location TEM imaging before and after the used degradation protocol. Suppression of transient Pt dissolution from Pt/TAP with respect to the Pt/C benchmark was directly measured in a setup consisting of an electrochemical flow cell connected to inductively coupled plasma-mass spectrometry., This work was supported by the Ministry of Education, Science and Sport of the Republic of Slovenia through Raziskovalci-2.1-KI-952007 and by the Slovenian Research Agency through the research programs/projects P1-0034 and P2-0393, NC-0007, NC-0016, and N2-0106, by European Research Council (ERC) Starting Grant 123STABLE (Grant agreement ID: 852208) and NATO Science for Peace and Security Program under Grant G5729.

Nasl. z nasl. zaslona. Opis vira z dne 3. 4. 2023. Bibliografija: str. 7986-7987. Abstract.

Water electrolysis powered by renewables is regarded as the feasible route for the production of hydrogen, obtained at the cathode side through electrochemical hydrogen evolution reaction (HER). Herein, we present a rational strategy to improve the overall HER catalytic performance of Pt, which is known as the best monometallic catalyst for this reaction, by supporting it on a conductive titanium oxynitride (TiON$_x$) dispersed over reduced graphene oxide nanoribbons. Characterization of the Pt/TiON$_x$ composite revealed the presence of small Pt particles with diameters between 2 and 3 nm, which are well dispersed over the TiON$_x$ support. The Pt/TiON$_x$ nanocomposite exhibited improved HER activity and stability with respect to the Pt/C benchmark in an acid electrolyte, which was ascribed to the strong metal−support interaction (SMSI) triggered between the TiON$_x$ support and grafted Pt nanoparticles. SMSI between TiON$_x$ and Pt was evidenced by X-ray photoelectron spectroscopy (XPS) through a shift of the binding energies of the characteristic Pt 4f photoelectron lines with respect to Pt/C. Density functional theory (DFT) calculations confirmed the strong interaction between Pt nanoparticles and the TiON$_x$ support. This strong interaction improves the stability of Pt nanoparticles and weakens the binding of chemisorbed H atoms thereon. Both of these effects may result in enhanced HER activity.

Nasl. z nasl. zaslona. Opis vira z dne 23. 1. 2023. Bibliografija: str. 62-63. Abstract.

In the past, platinum–copper catalysts have proven to be highly active for the oxygen reduction reaction (ORR), but transferring the high activities measured in thin-film rotating disk electrodes (TF-RDEs) to high-performing membrane electrode assemblies (MEAs) has proven difficult due to stability issues during operation. High initial performance can be achieved. However, fast performance decay on a timescale of 24 h is induced by repeated voltage load steps with H2/air supplied. This performance decay is accelerated if high relative humidity (>60% RH) is set for a prolonged time and low voltages are applied during polarization. The reasons and possible solutions for this issue have been investigated by means of electrochemical impedance spectroscopy and distribution of relaxation time analysis (EIS–DRT). The affected electrochemical sub-processes have been identified by comparing the PtCu electrocatalyst with commercial Pt/C benchmark materials in homemade catalyst-coated membranes (CCMs). The proton transport resistance (Rpt) increased by a factor of ~2 compared to the benchmark materials. These results provide important insight into the challenges encountered with the de-alloyed PtCu/KB electrocatalyst during cell break-in and operation. This provides a basis for improvements in the catalysts’ design and break-in procedures for the highly attractive PtCu/KB catalyst system.

Voltametrija je jedna od elektrokemijskih tehnika, a predstavlja skupinu elektrokemijskih metoda koje se temelje na mjerenju ovisnosti struja – potencijal koji se odvija na radnoj elektrodi u elektrokemijskoj ćeliji. Za mjerenja u voltametriji, najčešće se koristi troelektrodna elektrokemijska ćelija. Troelektrodna elektrokemijska ćelija sastoji se od tri elektrode i to radne, pomoćne i referente elektrode. Pomoćna elektroda omogućuje tijek struje – napona kroz elektrokemijsku ćeliju i najčešće je ova elektroda platinasta žica. Referenta elektroda je elektroda konstantnoga poznatog potencijala koji ne ovisi o sastavu otopine i najčešće su zasićena kalomelna elektroda i elektroda Ag/AgCl. Radna elektroda predstavlja elektrodu na čijoj se površini odvija elektrokemijska reakcija koja se proučava. Najčešće radne elektrode su elektroda od staklastog ugljika, zatim dijamantna elektroda dopirana borom, grafitna elektroda, zlatna elektroda i slično. Zadatak ovog završnog rada je opisati elektrokemijsku tehniku voltametriju, elektrokemijsku ćeliju te radne elektrode koje se primjenjuju za istraživanje elektrokemijskog redoks-procesa za analizu hrane s naglaskom na elektrodu od staklastog ugljika, dijamantnu elektrodu dopiranu borom i zlatnu elektrodu. Voltammetry is one of the electrochemical techniques, and represents a group of electrochemical methods that are based on measuring the dependence of currents and the potential that occurs on the working electrode in an electrochemical cell. For measurements in voltammetry, a three-electrode electrochemical cell is most often used. A three-electrode electrochemical cell consists of three electrodes: working, auxiliary and reference electrodes. The auxiliary electrode enables the flow of current-voltage through the electrochemical cell and most often this electrode is a platinum wire. The reference electrode is an electrode with a constant known potential that does not depend on the composition of the solution and is most often a saturated calomel electrode and an Ag/AgCl electrode. The working electrode represents the electrode on the surface on which the electrochemical reaction being studied takes place. The most common working electrodes are glassy carbon electrodes, followed by the boron-doped diamond electrode, graphite electrode, and gold electrode. The task of this final thesis is to describe the electrochemical voltammetry technique, the electrochemical cell and the working electrodes that are used for the research of the electrochemical redox process for food analysis with emphasis on the glassy carbon electrode, the boron-doped diamond electrode and the gold electrode.

Pripravljeni su koordinacijski polimeri kobaltovog(II) iona s miješanim ligandima: derivatima nikotinske kiseline (2-bromnikotinska kiselina ili 2-klornikotinska kiselina) te 1,2-bis(4-piridil)etanom ili 1,2-bis(4- piridil)etenom. Kao metalna sol korišten je kobaltov(II) nitrat heksahidrat, a kao otapala korišteni su DMF i voda. Spojevi su karakterizirani IR spektroskopijom, UV-Vis-NIR spektroskopijom termogravimetrijskom analizom (TGA), diferencijalnom skenirajućom kalorimetrijom (DSC) te cikličkom voltametrijom. Dobiveni su koordinacijski polimeri molekulskih formula: [Co(2-Cl-nic) 2 (1,2-bpeten)] n , [Co(2-Br-nic) 2 (1,2-bpeten)] n , [Co(2- Cl-nic) 2 (1,2-bpetan)] n. Kobaltov(II) ion oktaedarski je koordiniran s četiri O donirajuća liganda (karboksilatni kisici derivata nikotinske kiseline i/ili vode) i s dva piridinska dušikova atoma. Molekule 1,2-bis(4-piridil)etana i 1,2-bis(4-piridil)etena premošćuju kobaltove(II) ione dajući beskonačni jednodimenzijski polimerni lanac. Coordination polymers of cobalt(II) ion with mixed ligands: nicotinic acid derivatives (2- bromonicotinic acid or 2-chloronicotinic acid) and 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethene were prepared. Cobalt(II) nitrate hexahydrate was used as the metal salt, and DMF and water were used as the solvent. The compounds were characterized by IR spectroscopy, UV-Vis-NIR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cyclic voltammetry. Coordination polymers of molecular formulae were obtained: [Co(2-Cl-nic) 2 (1,2-bpetene)]n, [Co(2-Br-nic) 2 (1,2-bpetene)] n , [Co(2-Cl-nic) 2 (1,2- butane)] n . The cobalt(II) ion is octahedrally coordinated with four donating O ligand (carboxylate oxygens of nicotinic acid derivatives and/or water and with two pyridine nitrogen atoms. Molecules of 1,2-bis(4-pyridyl)ethane and 1,2- bis(4-pyridyl)ethene bridge cobalt(II) ions to give an infinite one-dimensional polymer chain.

The surface of bronze undergoes changes when it is exposed to a polluted atmosphere, and bronze should therefore be protected from this natural deterioration. The most common protective coating currently in use is Incralac, which includes toxic components and is reported to dissolve a few months after application. This work therefore investigates a fluoropolymer-based coating (FA-MS), and compares it to the protection offered by Incralac. Bronze samples (non-patinated, sulphide-patinated or chloride-patinated) were exposed to simulated urban rain for four months. The corrosion products formed were characterised using SEM/EDS and Raman analyses. To study the protection efficiency of the newly developed fluoropolymer coating (FA-MS) and Incralac protection, various electrochemical methods were used: measurements of open circuit potential linear polarisation and potentiodynamic measurements. Findings show that the FA-MS coating provides a protection efficiency of 71 % for chloride-patinated bronze and 99.5 % for sulphide-patinated bronze. Contact angles of the FA-MS samples were higher than those of the unprotected samples or the samples protected by Incralac, indicating better hydrophobic properties of the FA-MS coating. Povšina brona se z izpostavljenostjo onesnaženemu okolju spreminja, zato mora biti pred naravnim propadanjem zaščitena. Trenutno je najbolj pogosto uporabljen zaščitni premaz Incralac, ki vsebuje okolju škodljive snovi, hkrati pa poročajo, da po nanosu razpade že po nekaj mesecih. Na podlagi tega je bil v tej študiji raziskan zaščitni premaz na osnovi fluoropolimera (FA-MS), ter primerjava z Incralac premazom. Vzorci brona (ne-patiniran, rjavo-patiniran in kloridno-patiniran) so bili za štiri mesece izpostavljeni simulaciji deževnice v urbanem okolju. Tvorjeni korozijski produkti so bili nato označeni s pomočjo SEM/EDS in ramanske analize. Za študij učinkovitosti zaščite novo razvitega fluoropolimernega premaza (FA-MS) in Incralac zaščite smo uporabili različne elektrokemijske metode: meritve potenciala odprtega kroga, linearno polarizacijo in potenciodinamske meritve. Prav tako smo določili hidrofobnost z meritvami kontaktnih kotov in izmerili spremembe v barvi pred in po nanosu zaščite. Ugotovitve preiskav so, da FA-MS premaz nudi učinkovitost zaščite v vrednosti 71 % za kloridno patiniran bron in 99,5 % za sulfidno patiniran bron. Izmerjene vrednosti kontaktnih kotov vzorcev, zaščitenih s FA-MS prevleko, so bili višje kot pri nezaščitenih vzorcih in vzorcih, zaščitenih z Incralacom, kar kaže na izboljšane hidrofobne lastnosti FA-MS zaščite.

Multivalent batteries are often hyped as a next-generation high-energy density battery technology, but in reality, both literature reports and practical research are plagued by poor reproducibility of electrochemical results. Within the present work, we take a look at the electrochemical testing of organic cathodes that can be used with a variety of mono- and multivalent cations and propose a cyclable symmetric cell approach, already applied to the field of lithium-ion batteries. By using a model organic system based on poly(anthraquinonyl sulfide) (PAQS) active material, we demonstrate that the symmetric cell approach elegantly removes the limitations of multivalent metal anodes, and for the first time, reveals the full potential of organic cathodes in multivalent batteries. Furthermore, symmetric cells enable reliable EIS measurements on organic cathodes and open a pathway to optimize electrochemical/transport parameters through the design of next generation organic cathode materials and advanced electrode design(s). We suggest that the cyclable symmetric cell approach should be generally applicable in multivalent and all other batteries where electrochemical characterization requires the elimination of the counter electrode contribution.

Baker in bron ob izpostavljenosti atmosferskim pogojem ob prisotnosti vlage, kisika in korozivnih specij oksidirata. Oksidacija poteka stopenjsko. Najprej se tvori kuprit, Cu2O, ta pa se ob dolgotrajni izpostavljenosti atmosferskim pogojem nadalje oksidira. Pri tem se tvorijo zeleni Cu(II) produkti. Za vzdrževanje stanja in izgleda se bronaste površine, izpostavljene atmosferskim pogojem, lahko zaščiti. V magistrskem delu smo spremljali nastanek korozijskih produktov na različno patiniranih (nezaščitenih) bronih in jih primerjali s korozijskimi produkti brona. Preverili in ovrednotili smo novo razvito fluoropolimerno (FA-MS) zaščito za patinirane površine. Poleg tega smo preverjali obstojnost komercialno uporabljene zaščite v restavratorski praksi in jo primerjali z novo razvitim premazom FA-MS. Tri nezaščitene bronaste vzorce (ne-patiniran, sulfidno patiniran in kloridno patiniran) smo za 4 mesece izpostavili v simulirani ljubljanski deževnici. Nastale korozijske produkte smo opazovali in okarakterizirali s pomočjo SEM/EDS, ramanske in XRD analize. Elektrokemijsko obnašanje posameznega nezaščitenega in zaščitenega (FA-MS ali Incralac) vzorca ter njihove učinkovitosti smo določili s pomočjo elektrokemijskih meritev. Lastnosti zaščite smo dodatno ovrednotili z meritvami kontaktnega kota, z AFM analizo in meritvami spremembe barve po nanosu zaščite, mehanizem vezave pa ugotavljali s pomočjo XPS analize. Učinkovitost FA-MS zaščite je na bronu in sulfidno-patiniranem bronu primerljiva z učinkovitostjo Incralac zaščite (~ 99 %), medtem ko je pri kloridno-patiniranem bronu nižja, pri 71 %. Kljub dobri učinkovitosti smo slabo obstojnost Incralac zaščite ugotovili že po 1 mesecu izpostavitve v umetno pripravljeni ljubljanski deževnici. Hidrofobnost FA-MS zaščitenih vzorcev se poveča na račun fluoroakrilatne komponente v premazu. Z XPS analizo smo ugotovili, da se po nanosu FA komponenta orientira na površino in veže na MS preko siloksanske vezi, medtem ko je MS orientirana med FA komponento in preko silanolnih skupin na substrat. Copper and bronze oxidise when exposed to atmospheric conditions in the presence of moisture, oxygen, and corrosive species. Oxidation takes place in stages, where cuprite, Cu2O, forms first and is then further oxidised upon long-term exposure. In this process, green Cu(II) products are formed. To maintain condition and appearance, bronze surfaces exposed to atmospheric conditions can be protected. In this master's thesis, we monitored the formation of corrosion products on different (unprotected) patinated bronzes and compared them with corrosion products formed on bronze. We checked and evaluated the newly developed fluoropolymer (FA-MS) protection for patinated surfaces. In addition, we studied the durability of the commercially used protection in restorative practice and compared it with the newly developed FA-MS coating. Three unprotected bronze samples (non-patinated, sulphide-patinated and chloride-patinated) were exposed for 4 months in simulated Ljubljana rainwater. Corrosion products were observed and characterized using SEM/EDS, Raman and XRD analysis. The electrochemical behaviour of unprotected and protected (FA-MS or Incralac) samples and their efficiencies were determined by means of electrochemical measurements. The properties of the protection were additionally evaluated with contact angle measurements, AFM analysis and colour change analysis after the addition of protection, also the binding mechanism was determined with the help of XPS analysis. The efficiency of FA-MS protection on bronze and sulphide-patinated bronze is comparable to that of Incralac protection (~ 99 %), while it is lower on chloride-patinated bronze, at 71 %. Despite the good efficiency, the poor stability of Incralac protection was confirmed after only 1 month of exposure in artificially prepared Ljubljana rainwater. Hydrophobicity of FA-MS protection system is increased due to fluoroacrylate component in the coating. XPS analysis revealed that the FA component is oriented on the surface and binds to the MS via siloxane bonds, while the MS is oriented between the FA component and via the silanol groups on the substrate.

Antibiotiki se uporabljajo za zdravljenje ali preprečevanje bakterijskih okužb. Linkozamidna antibiotika, ki sta preučevana v sklopu te magistrske naloge, sta klindamicin in linkomicin. Namen magistrske naloge je preučiti možnost in vitro tvorbe metabolitov in oksidacijskih produktov klindamicina z uporabo elektrokemijske analize sklopljene z masno spektrometrijo, kar bi predstavljalo veliko cenejši način pridobivanja metabolitov, saj so standardi na trgu zelo dragi in hkrati postavilo izhodišče za nadaljnje raziskave aktivnosti in neželenih učinkov metabolitov. Klindamicin je kloriran, biološko aktivni, semisintetični derivat z višjo in vivo in in vitro aktivnostjo od linkomicina. Po absorpciji se klindamicin večinoma metabolizira do oksidiranega produkta klindamicin sulfoksida in v manjši meri do N-desmetil klindamicina. V člankih je prisotno protislovje, saj nekateri trdijo, da sta metabolita aktivna, drugi pa, da sta metabolita neaktivni spojini. Za pridobitev podatkov za izdelavo masnega spektra klindamicina smo uporabili masno spektrometrijo. Izvedli smo tudi tandemsko masno spektrometrijo z izbiro vrhov pridobljenih iz masnega spektra klindamicina, ki smo jih nadalje fragmentirali. Za proizvodnjo oksidacijskih produktov klindamicina in vitro smo uporabili elektrokemijsko nastavitev Roxy. Iz rezultatov je bilo razvidno, da je pri večjih hitrostih čas napetostnega gradienta krajši. Zamenjava elektrode iz steklastega ogljika z diamantno elektrodo dopirano z borom je pokazala, da daje v našem primeru elektroda iz steklastega ogljika boljše rezultate. V nadaljevanju je bil apliciran enosmerni tok v vrednosti 1 V. Z masno spektrometrijo smo analizirali tudi analizne standarde metabolitov klindamicina. Iz rezultatov je razvidno, da smo uspešno proizvedli N-desmetil klindamicin in v manjši meri klindamicin sulfoksid. Masno spektrometrijo sklopljeno z elektrokemijo smo aplicirali tudi na linkomicin. Dobili smo ustrezen masni spekter, ki je v primerjavi s klindamicinovim brez vrha izotopa klora ob osnovnem vrhu. Rezultatov linkomicina nismo primerjali z analiznimi standardi. Vsi pridobljeni podatki so bili obdelani s programskim jezikom R Studio. Antibiotics are used for treatment or prevention of bacterial infections. Lincosamide antibiotics analysed in the scope of this master's thesis were lincomycin and clindamycin. The aim of this master’s thesis is to examine the possibility of the in vitro production of the metabolites and oxidation products of antibiotic drug clindamycin using electrochemistry coupled to mass spectrometry which would represent much cheaper way of acquiring metabolites as analytical standard metabolites on the market are very expensive and also the basis for further research on the activity of the metabolites or their side effects. Clindamycin is a chlorinated highly biologically active semisynthetic lincosamide derivate with higher in vivo and in vitro activity than lincomycin. When absorbed, the compound is metabolized mainly to the oxidized product clindamycin sulfoxide and to a lesser extent to N-desmethyl clindamycin. There is a contradiction in the articles as some claim the metabolites are active and others that metabolites are inactive compounds. Mass spectrometry was used to obtain mass spectrum data of clindamycin. Additionally, tandem mass spectrometry was performed by selecting the peaks obtained from mass spectrum of clindamycin and fragmenting them to further extent. The Roxy electrochemical setup was used to produce clindamycin oxidation products in vitro. Results showed that at higher scan rates the time of voltage gradient was shorter. Switch of electrode from boron doped diamond electrode to glassy carbon electrode showed that glassy carbon electrode gave better results in our case. Further, direct current of 1 V was applied. Additionally, commercially available metabolites were examined by mass spectrometry coupled to electrochemistry to compare the results. The results show that we successfully produced N-desmethyl clindamycin and to a lesser extent clindamycin sulfoxide. Mass spectrometry coupled with electrochemistry technique was performed for lincomycin as well. We obtained the mass spectrum which has, comparing to clindamycin, no chlorine isotope peak around base peak. We did not compare lincomycin results with analytical standard metabolites. All data obtained were introduced in R Scripts in R Studio program.

V tem delu so predstavljene osnove voltametrije in voltametrije z izmenično napetostjo. Predstavitev je narejena kvalitativno in kvantitativno s pomočjo uporabe numeričnih izračunov. Predstavljene so osnove minimizacijskega problema iskanja optimalnih parametrov. Simulacija voltametrije in optimizacija parametrov je tudi aplicirana na preprosto elektrokemijsko reakcijo redukcije in oksidacije ferocianata. In this work we present basics of voltammetry and large-amplitude AC voltammetry. The basics are presented from both a qualitative and quantitative view, with the use of numerical simulation. Also shown is some basics of minimisation and its use in optimising simulation parametrs. We apply this theory on a simple redox reaction of ferrocyanide.

Magnezij organski akumulatorji predstavljajo napredno rešitev nove generacije akumulatorskih sistemov iz okoljsko trajnostnih materialov. Energijska gostota magnezija in organskih spojin ter razlika v njunem redoks potencialu zagotavlja atraktiven galvanski člen z zmožnostjo reverzibilnega delovanja. Težava magnezij organskih akumulatorjev je izkoriščenost kapacitete zaradi številnih kinetičnih ovir. V diplomskem delu smo sistematično preučevali vpliv katode, anode in elektrolita na kinetiko akumulatorja, s pomočjo elektrokemijskih metod. Uporabili smo pulzno metodo, kjer pri določeni stopnji praznjenja uporabimo tokovne pulze različnih velikosti in merimo spremembo napetosti v odvisnosti od časa. Magnesium organic batteries represent an advanced solution for a new generation of battery systems made from environmentally sustainable materials. The energy density of magnesium and organic compounds and the difference in their redox potential provides an attractive galvanic cell with reversible performance. The problem with magnesium-organic batteries is capacity utilisation due to several kinetic barriers. In the thesis, the influence of the cathode, anode, and electrolyte on the kinetics of the battery was systematically studied using electrochemical methods. We used the pulse method, where current pulses of different magnitudes are applied at a given discharge rate and the voltage change is measured as a function of time.

Decreasing iridium loading in the electrocatalyst presents a crucial challenge in the implementation of proton exchange membrane (PEM) electrolyzers. In this respect, fine dispersion of Ir on electrically conductive ceramic supports is a promising strategy. However, the supporting material needs to meet the demanding requirements such as structural stability and electrical conductivity under harsh oxygen evolution reaction (OER) conditions. Herein, nanotubular titanium oxynitride (TiON) is studied as a support for iridium nanoparticles. Atomically resolved structural and compositional transformations of TiON during OER were followed using a task-specific advanced characterization platform. This combined the electrochemical treatment under floating electrode configuration and identical location transmission electron microscopy (IL-TEM) analysis of an in-house-prepared Ir-TiON TEM grid. Exhaustive characterization, supported by density functional theory (DFT) calculations, demonstrates and confirms that both the Ir nanoparticles and single atoms induce a stabilizing effect on the ceramic support via marked suppression of the oxidation tendency of TiON under OER conditions.

Nasl. z nasl. zaslona. Opis vira z dne 05. 8. 2022. Abstract. Bibliografija: str. 17082-17083.

Electroporation is employed ever more frequently and broadly to deliver energy to tissues and liquid media in various applications, thus answering questions on the associated electrochemistry and electrode material alteration is becoming important. The aim of the present study is firstly to introduce and elucidate the basic relations between voltage, current, electrical impedance, and heat generation in the medium, and secondly, to characterize electrode material alteration due to pulse delivery, both by performing an in vitro and an in-silico study. Saline was used as a(n) (over)simplified model medium representing biological tissue, and exposed to high-amplitude, high-current electroporation pulses of varying duration, polarity, and pulse repetition rate. The controlled experiment was conducted by using seven different electrode metals of high purity, delivering pulses using three different protocols, and concurrently or sequentially measuring as many physical properties as available (electric current, voltage, electrode-electrolyte impedance, temperature). The intent is to present a multi-physics approach to what is occurring during procedures such as in vivo electrochemotherapy, gene delivery and in vitro gene transfection, intracardiac irreversible electroporation/pulsed-field ablation, or indeed electroporation in liquid food products such as juice. Modelling is also used to see whether it is possible to detect, via electrical measurements, any alterations in medium properties (e.g. composition) due to electrochemical effects, and if any such effects can be decoupled from the ohmic and thermal effects. Water electrolysis was observed indirectly (gas production), but not detected by electrical measurements during pulse application. Reactions at the electrodes alter the electrode electrical properties depending on the electrode material as expected, which might be important especially in applications where the same electrodes are used for delivery of electroporation pulses and also for sensing small electrical signals such as ECG for example. The demonstrated approach using saline as a model medium allows for rapid validation, and can more easily be developed further, as compared to experiments with more complex electrode materials (e.g. alloys), media (e.g. fluids, growth media, biological cell suspensions), or tissues.

Electrochemical stability of a commercial Au/C catalyst in an acidic electrolyte has been investigated by an accelerated stress test (AST), which consisted of 10,000 voltammetric scans (1 V/s) in the potential range between 0.58 and 1.41 VRHE. Loss of Au electrochemical surface area (ESA) during the AST pointed out to the degradation of Au/C. Coupling of an electrochemical flow cell with ICP-MS showed that only a minor amount of gold is dissolved despite the substantial loss of gold ESA during the AST (∼35% of initial value remains at the end of the AST). According to the electrochemical mass spectrometry experiments, carbon corrosion occurs during the AST but to a minor extent. By using identical location scanning electron microscopy and identical location transmission electron microscopy, it was possible to discern that the dissolution of small Au particles (

Commercial LiMn2O4 powder was used as the base material for probing magnesiation, cycling behavior, and structural stability/changes in (MgxLi1-x)Mn2O4 spinel cathodes in aqueous Mg(NO3)2 and non-aqueous Mg(TFSI)2/diglyme and Mg(Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolytes. Each of the samples was delithiated and, then, magnesiated electrochemically in the corresponding electrolyte. The electrochemical activity of the cathode cycled in aqueous electrolyte showed high reversibility during the oxidation process, however, large polarization and a relatively fast capacity fading were the culprits of the system. Cycling in Mg(TFSI)2/diglyme electrolyte solution resulted in much lower initial specific capacity compared to an aqueous counterpart, as well as a much faster failure. On the other hand, cycling in Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolyte solution demonstrated excellent cycling performance with very low polarization in the first cycles. The observed voltages for this system were near theoretical values for the Mg insertion. Although the electrochemical measurements suggest reversible magnesiation, detailed structural and analytical STEM investigation revealed the differences in the atomic structure and Mn valence of all three cathode samples upon cycling. The electrolytes’ influence on the structural rearrangement during Mg insertion is discussed for each of the three systems.

The detection of volatile organic compounds with electrochemical gas sensors is still very challenging regarding their sensitivity, selectivity, and operation at room temperature. There is a need for robust, sensitive, inexpensive, and yet easy-to-operate sensors for phenol and other phenolic compounds that function reliably under ambient conditions. Herein, we present a phenol gas sensor based on a combination of a semisolid, alkaline sodium polyacrylate, and commercial screen-printed electrodes. Sodium polyacrylate was employed as a multifunctional sensing material serving as a (i) gel-like electrolyte, (ii) accumulation milieu, and (iii) derivatization medium. Under ambient conditions, the sensor showed excellent sensitivity in the low ppbv (μg m–3) range, a good linear operation in the examined concentration range of 0.1–1.0 ppmv for up to 105 min accumulation, and low sensitivity toward examined interferences. The sensor also indicated a possibility to differentiate between several phenolic compounds based on their oxidation potential. Given its favorable electroanalytical performance, a strong application potential is envisioned in topical fields such as environmental monitoring, cultural heritage preservation, and occupational health and safety.

Bibliografija: str. 254-255. Abstract. European Comission, Horizon 2020, CarbON Valorisation in Energy-efficient Green fuels, CONVERGE Slovenian Research Agency, P2-0152, J2-2492, J2-1723, J7-1816

We report on a detailed structural versus electrochemical property investigation of the corncob-derived non-graphitizable carbons prepared at different carbonization temperatures using a combination of structural characterization methodology unique to this field. Non-graphitizable carbons are currently the most viable option for the negative electrode in sodium-ion batteries. However, many challenges arise from the strong dependence of the precursor’s choice and carbonization parameters on the evolution of the carbon matrix and its resulting electrochemistry. We followed structure development upon the increase in carbonization temperature with thorough structural characterization and electrochemical testing. With the increase of carbonization temperature from 900 to 1600 °C, our prepared materials exhibited a trend toward increasing structural order, an increase in the specific surface area of micropores, the development of ultramicroporosity, and an increase in conductivity. This was clearly demonstrated by a synergy of small- and wide-angle X-ray scattering, scanning transmission electron microscopy, and electron-energy loss spectroscopy techniques. Three-electrode full cell measurements confirmed incomplete desodiation of Na+ions from the non-graphitizable carbons in the first cycle due to the formation of a solid–electrolyte interface and Na trapping in the pores, followed by a stable second cycle. The study of cycling stability over 100 cycles in a half-cell configuration confirmed the observed high irreversible capacity in the first cycle, which stabilized to a slow decrease afterward, with the Coulombic efficiency reaching 99% after 30 cycles and then stabilizing between 99.3 and 99.5%. Subsequently, a strong correlation between the determined structural properties and the electrochemical behavior was established.

Jodove(I) spojine so koristni reagenti za elektrofilno jodiranje. Raziskal sem novo pot priprave diklorojodatov(I) ([ICl2]-) s pomočjo elektrokemije. Gonilna reakcija za to pretvorbo je anodna oksidacija klorida v klor. Klor nato v naslednjem koraku oksidira jod, kar vodi v nastanek [ICl2]-. V ta namen sem raziskal elektrokatalitske lastnosti iridijevih nanodelcev in iridijevega oksida. Katalizatorja sem primerjal na osnovi njunih ciklovoltamogramov v prisotnosti enega ali obeh reagentov (37% vodne raztopine HCl in I2) v MeCN. Iridijevi nanodelci so se izkazali kot boljši, saj so pri nižjih napetostih dosegli višje tokove kot IrO2. V namen določanja potencialnega okna v katerem lahko izvajamo anodno oksidacijo klorida v klor, sem posnel tudi ciklovoltamogram HICl2. Ta je pokazal nadaljnje oksidacije HICl2 pri potencialih, višjih kot 1,2 V. Generacija klora prične potekati pri 1 V. Naše potencialno okno je tako med 1 - 1,2 V. Tudi tu so se iridijevi nanodelci izkazali kot boljši, saj so omogočili večji razmik med reakcijo generacije klora in nadaljno oksidacijo produkta. Pregledal sem vpliv napetosti in hitrosti rotacije na generacijo HICl2. Napetost je imela majhen vpliv na izkoristek. Izkazalo pa se je, da ima hitrost rotacije velik vpliv na tvorbo HICl2 in pod določeno hitrostjo praktično ne poteka. Pogledal sem tudi vpliv pomožnega elektrolita na potek reakcije. Primerjal sem tetrabutilamonijev perklorat in LiClO4. Slednji se je izkazal kot slabši, saj je reakcija potekala počasneje, izkoristki pa so bili slabši. Nato sem poskusil uporabiti elektrokemijsko generirano raztopino HICl2 za jodiranje stirena. Reakcija zaradi vpliva pomožnega elektrolita ni potekla. Zato sem generacijo HICl2 izvedel še v brezvodni raztopini HCl/MeOH. Ta sistem se je izkazal kot boljši od MeCN/pomožni elektrolit in reakcija s stirenom je bila uspešna. Raziskal sem tudi, ali lahko reagent generiramo v prisotnosti organskih substratov in jih tako jodiramo. Pomeril sem ciklovoltamograme organskih spojin in izbral tiste, ki niso reagirale pod potencialnim oknom generacije klora (anisol, 1-deken in stiren). Nato sem s kronoamperometrijo izvedel elektrokemijsko sintezo HICl2 in analiziral nastale raztopine. Anisol je bil premalo aktriviran za jodiranje, na 1-decen in stiren pa je potekla elektrofilna adicija joda in klorida kot nukleofila. Iodine(I) compounds are useful reagents for electrophilic iodination. I investigated a new pathway for the preparation of dichloroiodates(I) ([ICl2]-) using electrochemistry. The driving reaction for this conversion is the anodic oxidation of chloride to chlorine. Chlorine then oxidizes iodine in the next step, leading to the formation of [ICl2]-. To this end, I investigated the electrocatalytic properties of iridium nanoparticles and IrO2. The catalysts were compared based on their cyclovoltamograms in the presence of one or both reagents (37% aqueous solution of HCl and I2) in MeCN. Iridium nanoparticles have been proven to be a better electrocatalyst than IrO2, achieving higher currents at lower voltages. In order to determine the potential window in which the anodic oxidation of chloride to chlorine can be performed, I also recorded a HICl2 cyclovoltamogram. This showed further oxidations of HICl2 at potentials higher than 1.2 V while chlorine generation begins at 1 V. Our potential window is thus between 1 - 1.2 V. Iridium nanoparticles have proven to be better, as they have allowed for a greater interval between chlorine generation reaction and further oxidation of the product. I studied the influence of voltage and rotation speed on HICl2 generation. The voltage had little effect on efficiency. However, the rate of rotation has been shown to have a large influence on the formation of HICl2 and formation practically does not occur below a certain rotation rate. I also looked at the effect of the auxiliary electrolyte on the course of the reaction. I compared tetrabutylammonium perchlorate and LiClO4. The latter proved to be worse as the reaction proceeded more slowly and the faradaic efficiencies were poorer. I then tried to use an electrochemically generated HICl2 solution to perform a iodination reaction with styrene. The reaction did not proceed due to the influence of the auxiliary electrolyte. As a solution to this problem, I performed HICl2 generation in anhydrous HCl / MeOH solution. This system proved to be better than MeCN / auxiliary electrolyte and the reaction with styrene was successful. I also investigated whether the reagent can be generated in the presence of organic substrates, which would subsequently react to form iodinated products. I compared cyclovoltamograms of organic compounds and selected those that did not react under the chlorine generation potential window (anisole, 1-decane, and styrene). I then performed electrochemical synthesis of HICl2 by use of chronoamperometry and analysed the resulting solutions. Anisole was insufficiently activated for iodination, 1-decane and styrene however were successfully iodinated.

Tehnologija gorivnih celic omogoča pridobivanje električne energije neposredno iz kemijske z visokimi izkoristki in brez sežiga. Deluje na osnovi redoks reakcij, stranska produkta procesa pa sta le voda in toplota. Diplomsko delo vsebuje pregled osnov delovanja, klasifikacijo glede na uporabljen elektrolit in karakterizacijo pomembnejših vrst, prikaz zvez Gibbsove proste energije in Nernstovega potenciala v povezavi s storilnostjo ter pregled implementacije tehnologije v prenosnih, rezervnih, transportnih in stacionarnih aplikacijah. Fuel cell technology enables the production of electricity directly from the chemical energy with high efficiencies and without combustion. It works through a redox reactions and the by-products of the process are only water and heat. The diploma thesis contains a review of the basics of operation, classification according to the electrolyte used and characterization of major cell types, presentation of Gibbs free energy and Nernst potential in relation to performance and an overview of technology implementation in portable, backup, transport and stationary applications.

Z naraščanjem svetovne populacije ljudi se povečujejo tudi potrebe po energiji. Znatno povečanje svetovne porabe energije skupaj z rastjo števila prebivalstva vodi do prekomernih emisij ogljika v ozračje in pojava podnebnih sprememb. To zahteva razvoj učinkovitih energetskih naprav, da bi zadovoljili ogromno povpraševanje po energiji in zahteve po zniževanju ogljikovih izpustov. Primarni vir energije za življenje na planetu Zemlji je sončna energija. Sončna energija se s fotosintezo vstavi v biosfero. To je fizikalno-kemijski proces, pri katerem rastline, alge in nekatere bakterije pretvarjajo sončno energijo v kemično energijo preko organskih snovi. Proizvodnjo električne energije s strani fototrofnih organizmov med osvetljevanjem imenujemo biofotovoltaika (BPV). Biofotovoltaika je tehnologija za pridobivanje energije iz kisikovih fotoavtotrofnih organizmov. Naprave BPV lahko opišemo kot biološki elektrokemični sistem ali "žive sončne celice". V sistemu BPV fotoliza vode generira elektrone, ki se nato prenesejo na anodo. Ustvari se relativno visoka potencialna reakcija na katodi in tok teče skozi zunanje vezje zaradi nastale razlike potencialov. Uporaba živega organizma kot medija za nabiranje svetlobe, ki se lahko sam sestavi in popravi lahko naredi BPV stroškovno učinkovitejšo od drugih fotovoltaičnih tehnik. Raziskave biofotovoltaike so še v začetni fazi razvoja. To je glavni razlog, da trenutno še ne moremo uspešno uporabljati biofotovoltaike kot vir energije in celostno zamenjati fosilnega goriva. Veliko do sedaj izvedenih raziskav je neprimerljivih, saj manjkajo statistični podatki. As the world's population grows, so does the need for energy. A significant increase in global energy consumption together with population growth leads to excessive carbon emissions into the atmosphere and the emergence of climate change. This requires the development of efficient energy devices to meet the huge demand for energy and the demand to reduce carbon emissions. The primary source of energy for life on the planet Earth is solar energy. Solar energy is inserted into the biosphere through photosynthesis. It is a physico-chemical process in which plants, algae and some bacteria convert solar energy into chemical energy through organic matter. The production of electricity by phototrophic organisms during illumination is called biophotovoltaics (BPV). Biophotovoltaics is a technology for obtaining energy from oxygen photoautotrophic organisms. BPV devices can be described as a biological electrochemical system or “living solar cells”. In the BPV system, the photolysis of water generates electrons, which are then transferred to the anode. A relatively high potential reaction is created at the cathode and current flows through the external circuit due to the resulting potential difference. The use of a living organism as a self-assembling and self-assembling light-collecting medium can make BPV more cost-effective than other photovoltaic techniques. Scientific research into biophotovoltaics is still in the early stages of development. This is the main reason why we cannot currently successfully use biophotovoltaics as an energy source and completely replace fossil fuels. Many of the reasearches conducted so far are incomparable, as statistical information are missing.

Laboratorij na papirju, ena od miniaturiziranih naprav v analizni kemiji, je veliko doprinesla k razvoju analiznih metod. Nekoč napravi niso namenili veliko pozornosti, a so jo pozitivne lastnosti, kot so preprostost, cenovna ugodnost, prenosljivost, prijaznost do okolja, uvrstile na sam vrh. Papir, ki je glavni element laboratorija na papirju, je tanek, lahek in prilagodljiv material, sestavljen iz celuloznih vlaken. Prenos tekočine preko papirja temelji na mikrofluidiki. Ker v papirju deluje kapilarni vlek, za premikanje tekočin ne potrebujemo dodatnega vira energije. Diplomsko delo je sestavljeno s preučevanjem člankov, ki laboratorij na papirju ne uporabijo samo kot zamenjavo tradicionalnih tehnik, pač pa tudi kot prenosno analizno napravo. Laboratorij na papirju še ni tako zanesljiv, da bi popolnoma zamenjal tehnike, ki se dandanes najbolj uporabljajo. Problem je predvsem veliko število lažno negativnih in lažno pozitivnih izidov, ki jih raziskovalci skozi obsežne raziskave poskušajo kar se najbolj da zmanjšati. Lab on paper, a miniaturized device in analytical chemistry, has contributed a lot to the development of analytical methods. In the past, this device did not receive much attention, but its positive characteristics, such as simplicity, low price, portability, and environmental friendliness, have put it at the forefront. Paper, the main element of lab on paper, is a thin, light, and adjustable material, made from cellulose fibres. The transfer of liquids through paper is based on microfluidics. Since capillary forces are characteristic of paper, no additional source of energy is required to move liquids. This paper was made by studying articles, in which lab on paper is used not only as a substitute for traditional methods, but also as a portable analytical device. However, lab on paper is not reliable enough to entirely replace most frequently used methods. The problem is associated with the high number of falsely positive and falsely negative results, which researchers try to reduce as much as possible through extensive further research.

A general transmission line model that is able to describe accurately the measured impedance spectra of uncycled and cycled lithium electrodes is introduced. The model has all the essential features that are contained in analytical solutions for determining the impedance response of porous electrodes. In addition to that, it allows easy coupling between the various phenomena met in lithium anodes in contact with a separator: transport through a solid electrolyte interphase film, transport across “live lithium dendrites”, reaction inside “live lithium dendrites”, transport across “dead dendrites”, diffusion in a porous separator, and so forth. The model is used for quantitative analysis of measured impedance spectra collected at different C-rates and after different numbers of charge–discharge cycles. Further, combining impedance spectroscopy with scanning electron microscopy, several unique correlations between the morphological development of lithium anodes and development of impedance spectra are identi...

IR spectroscopy can be a non-destructive and straightforward probing tool in the battery research. However, its application has been limited due to the difficulties related to the handling and interpretation of ex situ samples along with the lack of widely applicable in situ and operando cells. Herein, we show a simple, operando ATR-IR two electrode pouch cell with an IR-transmissive silicon window and discuss its advantages and limitations. This setup is applied to the study of the polyanthraquinone (PAQ) reaction mechanism in Li- and Mg-organic batteries. During the reduction/oxidation process of the PAQ, not only the conversion of both C O groups into C–O– species is observed, but also the formation of an intermediate semiquinone radical anion as an intermediate product. Furthermore, continuous measurement of IR spectra allows visualization of the gradual solid-electrolyte interphase (SEI) buildup on the cathode during cycling.

Understanding of less-noble-metal (M) dissolution from Pt-alloy-based oxygen reduction reaction (ORR) electrocatalysts, as well its interaction with Pt surface, is crucial for maximizing their performance. In pursuing this goal, two ORR electrocatalysts—a benchmark Pt–Co/C and an in-house designed Pt–Cu/C materials—are investigated. Both are characterized with a range of standard techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with energy dispersive spectroscopy (EDX) and thin film-rotating disc electrode (TF-RDE) measurements. A special focus is put on combining the latter with a highly sensitive electrochemical flow cell (EFC) online connected to inductively coupled plasma mass spectrometry (ICP-MS) measurements. A combination of standard and novel techniques provides unprecedented insights into the dissolution behavior and dynamics of metals, as well as their subsequent surface interactions and effects on the electrochemical performance. A special focus is d...

The impact of the solid film deposit (mainly Li2S) on the complex electrochemistry of a Li–S cell is studied in detail. Already a simple, straightforward experiment strongly indicates that this imp...

A multifunctional electrocatalytic composite was synthesized for use as a generic catalytic material in the polymer electrolyte membrane (PEM) type reactors, working in either fuel cell, direct met...

Catalytic properties of advanced functional materials are determined by their surface and near-surface atomic structure, composition, morphology, defects, compressive and tensile stresses, etc; also known as a structure–activity relationship. The catalysts structural properties are dynamically changing as they perform via complex phenomenon dependent on the reaction conditions. In turn, not just the structural features but even more importantly, catalytic characteristics of nanoparticles get altered. Definitive conclusions about these phenomena are not possible with imaging of random nanoparticles with unknown atomic structure history. Using a contemporary PtCu-alloy electrocatalyst as a model system, a unique approach allowing unprecedented insight into the morphological dynamics on the atomic-scale caused by the process of dealloying is presented. Observing the detailed structure and morphology of the same nanoparticle at different stages of electrochemical treatment reveals new insights into atomic-scale processes such as size, faceting, strain and porosity development. Furthermore, based on precise atomically resolved microscopy data, Kinetic Monte Carlo (KMC) simulations provide further feedback into the physical parameters governing electrochemically induced structural dynamics. This work introduces a unique approach toward observation and understanding of nanoparticles dynamic changes on the atomic level and paves the way for an understanding of the structure–stability relationship.

Tehnologija 3D tiskanja ali v industriji pogosteje poimenovana z izrazom aditivna proizvodnja se konstantno razvija že vse od sredine 90. let prejšnjega stoletja. Pojem aditivne proizvodnje zajema številne tehnike 3D tiskanja, kjer najpogostejšo metodo tiskanja predstavlja metoda ekstrudiranja polnila, ki je že dodobra razvita. Kljub dosegu tehnološke limite metode, se implementacija tehnologije na druga področja znanosti šele začenja. Eno aplikacijo izmed neskončne množice možnosti predstavlja združitev tehnologije tiskanja, reakcijskega inženirstva ter področja elektrokemije, kar je predstavljeno v nadaljnjem delu. Združitev teh področij je prikazana s pomočjo izdelave v celoti natisnjenega pretočnega reaktorskega sistema za izvajanje elektrokemijske pretvorbe 1,4-benzokinona v njegovo reducirano obliko, hidrokinon. Gre za reaktorski sistem narejen iz strukturnega polimera polietilen tereftalat glikola (PET-G) skupaj s prevodnim kompozitnim termoplastom polimlečne kisline in črnega ogljika (PLA-CB). Reakcijo sem testiral tako na šaržnem reaktorskem sistemu, ki potrjuje elektrokemijsko aktivnost kompozitnega materiala, kot tudi na končnem pretočnem reaktorskem sistemu, ki omogoča boljše razmerje volumna reakcijske mešanice na površino elektrode. Za namene kvalitativne potrditve sem izvedel analitične metode spektroskopije in ciklične voltametrije (CV). Prav tako sem opravil karakteristične metode analize s pomočjo vrstičnega elektronskega mikroskopa (SEM) za boljše razumevanje strukture elektrod ter prevodnosti samega kompozitnega materiala. Dodatno točko dela predstavlja simulacijska primerjava fluidne dinamike, natančneje hitrostnih profilov, med konvencionalnimi in 3D natisnjenimi reaktorskimi sistemi, kjer pri slednjih pride do pojava neravne oz. narebrene zgradbe pretočnega kanala. 3D printing technology or additive manufacturing as more commonly referred to in industry, has been constantly evolving since the mid-90s of the previous century. The term of additive manufacturing encompasses a number of 3D printing techniques, where the fused filament fabrication presents the most common and well-known printing methodology. Despite reaching the technological limit of the method, the implementation of technology in other fields of science is just beginning. One of the applications among the infinite number of possibilities is the combination of printing technology, reaction engineering and the field of electrochemistry, which is presented in the following part of the work. The combination of these fields is illustrated by the fabrication of a fully printed flow reactor system to perform the electrochemical conversion of 1,4-benzoquinone to its reduced form, hydroquinone. A reactor system made of the structural polymer polyethylene glycol terephthalate (PET-G) together with a conductive composite thermoplastic of polylactic acid and black carbon (PLA-CB) is used for the reaction. The reaction was first demonstrated on the batch reactor system, which confirmed the electrochemical activity of the composite material, and secondly on the final flow reactor system, which allows a better volume to surface ratio of the of the reaction mixture to the electrode surface. Analytical methods of spectroscopy and cyclic voltammetry were performed for the purposes of qualitative confirmation. Characteristic methods of analysis using a scanning electron microscope (SEM) were also performed for better understanding of the electrode’s structures and the conductivity of the composite material itself. An additional point of the work represents the computer aided comparison of fluid dynamics, and velocity profiles, between conventional and 3D printed reactor systems, where the latter have the uneven surface structure of the flow channel.

V delu bo predstavljen matematični opis transporta gibalne količine in snovi pri uporabi rotirajočih elektrod, bolj poznanih pod angleškim izrazom »rotating disk electrode« ali RDE. Za opis se bom poslužil matematičnih zvez iz hidrodinamike, to so Navier-Stokesove enačbe, ter zvez iz prenosa snovi, to je 1. in 2. Fickov zakon. Sistem, ki ga rešujemo, je za iskanje analitične rešitve pretežek in se zato poslužujemo numeričnih metod. Za reševanje problema hitrostnega profila ob elektrodi se poslužujemo psevdo-analitičnih metod, ki nam potem dajo enačbe za opis hitrosti v sistemu. S poznavanjem hitrostnega profila lahko potem opišemo sam prenos snovi v sistemu. Izvedel bom tudi oceno numerične napake pri uporabljenih metodah. In this work, I will present a mathematical treatment of the transport phenomena occurring at a rotating disk electrode, also known as RDE. For the treatment I will use known laws of hydrodynamics, such as Navier-Stokes equations, and laws of mass transport, namely Fick's laws. The system in question is hard to solve analytically, so we will use numerical methods to solve our problem. First we consider the velocity profile at the electrode. This is done by pseudo-analytical mathematical treatment. Then we use the explicit forward Euler method to solve the partial differential equation for mass transport. Finally, the numerical error is also considered.

V tej zaključni nalogi iščemo odvisnost polarizacijske krivulje gorivne celice s protonsko izmenjalno membrano (angl. Proton Exchange Membrane Fuel Cell – PEMFC) na spreminjajočo se temperaturo in optimalno temperaturo delovanja nizkotemperaturne PEMFC. Meritve smo v okviru diplomske naloge izvedli na Kemijskem inštitutu v Ljubljani in z njimi analizirali aktivacijo gorivne celice ter gledali odziv polarizacijskih krivulj glede na delovno temperaturo celice. Temperatura ima velik vpliv na maksimalno izhodno napetost in na kvaliteto trifaznega stika. Ugotovili smo, da tako previsoka in prenizka temperatura nista primerni za optimalno delovanje PEMFC. Padec napetosti je bil pri visokih tokovih pri 55 °C in 85 °C okoli 20 % referenčne vrednosti. In this thesis, we are looking for the temperature dependance of the polarization curve of a PEM fuel cell and the optimal temperature for the most efficient activity of a low temperature PEM fuel cell. The measurements in this thesis were conducted at the Chemistry institute in Ljubljana and have been used to analyze the activation protocol of fuel cells and to find the temperature dependance of the polarization curves. Temperature has a big impact on the highest attainable voltage of a fuel cell, as well as an impact on the quality of electrode kinetics. The results show, that nor too high or too low temperatures result in less optimal performance of PEMFC. The voltage drop in measurements at 55 °C and 85°C reached around 20 % of the reference measurement value.

Li-ionski akumulatorji, ki trenutno prevladujejo na trgu akumulatorskih sistemov, se počasi približujejo svoji teoretični kapaciteti. V zadnjem času smo zato priča intenzivnem raziskovanju novih tipov akumulatorjev. Med različnimi tipi akumulatorjev vse popularnejši postajajo organski katodni materiali, predvsem zaradi njihove vsestranskosti in dostopnosti. Zanimiva skupina elektroaktivnih organskih molekul so kinoni. V organskih topilih se kinoni ponavadi reverzibilno reducirajo v dveh eno-elektronskih korakih ali v enem dvoelektronskem koraku do dianiona. Mednje spada tudi molekula antrakinon (AQ). V magistrski nalogi sem raziskoval mehanizem redukcije antrakinona v dveh različnih sistemih, v klasični elektrokemijski celici in v akumulatorskem sistemu. Postavil ter opisal sem sistem za preučevanje elektrokemije v suhi komori. V klasični elektrokemijski celici sem izvajal eksperimente s šestimi različnimi solmi (LiTFSI, NaTFSI, KTFSI, TBATFSI, Mg(TFSI)2, Ca(TFSI)2). Ugotavljal sem vpliv kationa na mehanizem reakcije. Rezultati so pokazali, da ima kation velik vpliv na reakcijo, predvsem na stabilizacijo anionskega radikala. TBA+ kation je med enovalentnimi kationi izkazal najboljše rezultate. Pri dvovaletnih kationih je bila reakcija močno ireverzibilna. Elektrokemijo smo nato raziskovali v akumulatorskem sistemu, v 2-elektrodnem in 3-elektrodnem sistemu. Raziskovali smo vpliv Li+, Na+ in K+ kationov na elektrokemijo akumulatroskih sistemov. Iz rezultatov lahko sklepamo, da so opaženi platoji posledica katodnih reakcij. Ko primerjamo rezultate iz klasične celice in iz akumulatorskega sistema, vidimo, da kation ne vpliva na prvi vrh oziroma plato, ampak šele na naslednji vrh oziroma plato. Rezultati so pokazali, da je elektrokemija AQ zanimiva za nadaljnje študije. Li-ion batteries are slowly reaching their theoretical capacity. Researchers are therefore researching new types of batteries. For this reason research into organic cathode materials is gaining popularity in recent years because of their versatility and availability. Attractive group of organic materials are quinones. In organic solvents they are usually reduced in two one-electron steps or in one twoelectron step to dianion. Among this group is a molecule anthraquinone (AQ). In this thesis we have been researching the mechanism of reduction of anthraquinone in two different systems, in a beaker cell system and in a battery system. We have built a glovebox system for studying electrochemistry. In the beaker cell we have made several experiments with six different salts (LiTFSI, NaTFSI, KTFSI, TBATFSI, Mg(TFSI)2, Ca(TFSI)2). We have been researching the influence of a cation on the mechanism of the reaction. The results have shown that a cation has a great influence on a reaction, especially on the stabilization of anion radical. For the monovalent cations, TBA+ cation gave us best results. Reactions with divalent cations was highly irreversible. Next we studied electrochemistry in a battery system, in a 2-electrode and 3-electrode system. We researched Li+, Na+ in K+ cations. From the results of the battery system, we can conclude that cathode is the sole reason for visible plateaus. When comparing results from a battery system and a beaker cell system, we discovered that cation does not influence the first peak/plateau, but the second one. Results have shown that electrochemistry of AQ has potential for further studies.

V magistrskem delu je predstavljena delna validacija metod z modificiranimi elektrodami kombinacij Bi-Cu na steklastem ogljiku za določanje Zn(II), Cd(II) in Pb(II). Analize smo izvajali z elektrokemijsko tehniko square wave anodno striping voltametrijo (SWASV). Dvanajst različnih elektrod smo pripravili in situ pri dveh različnih skupnih masnih koncentracijah Bi(III) in Cu(II) ter njunih različnih razmerjih v raztopini. Za vsako in situ elektrodo so bila določena območja linearnega odziva za Zn(II), Cd(II) in Pb(II), ki so morala zadoščati dvema kriterijema linearnosti: koeficientu kvalitete, QC (QC ≤ 5 %), in kvadratu korelacijskega koeficienta, R2 (R2 ≥ 0,995). Mejo zaznavnosti (LOD) in mejo določljivosti (LOQ) smo določili s pomočjo razmerja signal/šum, občutljivost pa iz naklonov umeritvene premice. Iz izkoristka pri določeni koncentraciji Zn(II), Cd(II) in Pb(II) smo določili točnost, natančnost metode in sistema pa smo določili na podlagi relativnega standardnega odmika v odstotkih (RSD [%]). Izmed vseh in situ elektrod smo na koncu izbrali dve: eno z najboljšo točnostjo (izkoristkom najbližje 100,0 %) in eno z najboljšo natančnostjo (najnižjim RSD [%]). Na obeh smo preučili vpliv interferenc in izvedli test realnega vzorca. In this master's thesis, a partial method validation with modified Bi-Cu electrodes on glassy carbon was performed for the determination of Zn(II), Cd(II) and Pb(II). Analyses were performed with an electrochemical technique square-wave anodic stripping voltammetry (SWASV). Twelve electrodes were designed in situ, at two different total mass concentrations of Bi(III) and Cu(II) and their different ratios in the solution. For every in situ electrode, a linearity for Zn(II), Cd(II) and Pb(II) were determined, which had to meet the two criteria of linearity: the quality coefficient QC had to be ≤ 5,0 % and the square of the correlation coefficient R2 had to be ≥ 0,995. Limit of detection (LOD) and limit of quantification (LOQ) were determined based on the signal-to-noise ratio, while sensitivity was determined using calibration plot slopes. Recovery at a given concentration of Zn(II), Cd(II) and Pb(II) was used to determine accuracy, while precision of the method and the system was determined on the basis of percentage relative standard deviation (RSD [%]). Among the in situ electrodes tested, two were selected to test interference effect and real sample analysis: one with the highest accuracy (recovery closest to 100,0 %) and one with the highest precision (lowest RSD [%]).

Kontrola kakovosti olj in maščob se dnevno izvaja v prehrambeni kemiji in industriji. Vsebnost antioksidantov v rastlinskih oljih je zelo pomembna pri določanju stabilnosti izdelkov. Vitamin E sodi v eno največjih skupin naravnih antioksidantov, ki vključuje več tokoferolov in tokotrienolov. Za te naravne fenolne spojine je značilno, da so elektrokemijsko aktivne. V diplomski nalogi sem določal vitamin E z uporabo elektrokemijske tehnike - diferenčne pulzne voltametrije (DPV) v sončničnem, ekstra deviškem oljčnem in konopljinem olju. Metodo sem najprej optimiral z določanjem najustreznejših reakcijskih pogojev. Po določitvi optimalnih pogojev sem vitamin E iz vzorcev rastlinskih olj ekstrahiral z dvema različnima postopkoma - prvi je bil postopek direktne ekstrakcije vitamina E v absolutni etanol, drugi pa je vseboval saponifikacijo olja in nadaljnjo ekstrakcijo. Za določanje sem uporabil metodo direktne ekstrakcije, ker se je izkazala za ustreznejšo in dobro ponovljivo. Slednjega pri metodi s saponifikacijo nisem dosegel. Določanje vitamina E v rastlinskih oljih z diferenčno pulzno voltametrijo na elektrodi iz steklastega ogljika(GCE) se je izkazalo za dobro in učinkovito pri oljih z višjo koncentracijo α-tokoferola. Quality control of oils and fats is important in food chemistry and in the food industry. The content of antioxidant substances in vegetable oil products is of great importance for determining the stability of the products. Vitamin E represents one of the largest groups of natural antioxidants, including several tocopherols and tocotrienol compounds. These phenolic compounds are among the many naturally occurring substances known to be electrochemically active. In my work, I have determined vitamin E using differential pulse voltammetry (DPV). I have specified vitamin E in sunflower oil, extra virgin olive oil and hemp oil. First I optimized the method by determining optimal conditions. Then I tried to extract vitamin E from vegetable oil samples using two different techniques. The first was the method of direct extraction of vitamin E in absolute ethanol and the second involved saponification of the oil and further extraction. For the determination of vitamin E, I used the method of direct extraction because it was repeatable. I did not achieve this with the saponification method. The determination of vitamin E by differential pulse voltammetry has proven to be an effective method in oils with a higher concentration of α- tocopherol.

Uporaba pametnih telefonov sunkovito narašča, ravno tako pa narašča tudi zmogljivost pametnih telefonov. Razširjenost uporabe ter same zmogljivosti so zbudili razmišljanje o uporabi pametnih telefonov in z njimi povezanih tehnologij v namene znanstvenih raziskav. Z razvojem informacijsko komunikacijskih tehnologij ter dostopnostjo podatkov in znanja se pojavlja vse večje zanimanje za možnost sodelovanja splošne javnosti z različnimi raziskovalnimi skupinami v različnih projektih državljanske znanosti. V tem delu si pogledamo nekaj primerov objavljenih analiznih metod, v katerih se pametne telefone uporabi na različne načine ter možnost uporabe takih metod v projektih državljanske znanosti. The use of smartphones is rising sharply, and so is the performance of smartphones. The widespread use and performance itself have given rise to thought about the use of smartphones and related technologies for scientific research purposes. With the development of information and communication technologies and the accessibility of data and knowledge, there is a growing interest in the possibility for the general public to engage with different research groups in different citizen science projects. In this work we look at some examples of published analytical methods where smartphones are used in different ways and the possibility of using such methods in citizen science projects.

Priručnik čini 12 laboratorijskih vježbi koje se sastoje od teorijskog uvoda, ciljeva, popisa opreme, pribora i kemikalija potrebnih za izvođenje vježbe, postupka izvođenja te upute za prezentaciju rezultata u obliku skice, izračuna, grafičkog i tabličnog prikaza ili pisanog zaključka. Praktikum započinje pripremom otopina i metodama za razdvajanje pojedinih komponenti iz smjese: destilacijom, filtracijom, vakuum-filtracijom, ekstrakcijom, kromatografijom i kombiniranim metodama razdvajanja višekomponentne smjese, te se postupno stječu potrebne vještine za izvođenje narednih vježbi. Nakon što studenti steknu osnovna znanja i vještine za rad, u kemijskom laboratoriju izvode tematske vježbe: određuju standardni molarni volumen plinova kisika i vodika, entalpiju otapanja soli i reakcije neutralizacije, određuju provodnost elektrolita, sagledavaju kemijsku ravnotežu i Le Châtelierovo načelo kroz niz primjera kemijskih reakcija, upoznaju se sa zakonima kemijske kinetike kroz izračunavanje brzine kemijske reakcije, pripremaju acetatni i fosfatni puferski sustav i određuju kapacitet fosfatnog pufera. Praktikum završava elektrokemijskim procesima u sklopu kojih studenti sklapaju galvanske članke i mjere njihove elektrodne potencijale te provode postupak elektrolitičkog razlaganja vode.

Ferrocene-substituted nucleobases have diverse biological and electrochemical properties since they combine biogenic and redox-active parts. [1] Ferrocene undergoes a reversible one-electron oxidation producing a stable ferrocenium cation and serves as an internal standard for electrochemistry in non-aqueous solution. Ferrocenyl compounds are known to exhibit anticancer activity through a redox mechanism by generating reactive oxygen species – hydroxyl radicals (•OH) causing the DNA cleavage and oxidative stress. [2] In continuation of our work [3, 4] we synthesized a series of ferrocene- substituted purine- and pyrimidine-nucleobase derivatives and measured their redox potential by the cyclic voltammetry in dichloromethane. All measured compounds showed a reversible oneelectron oxidation in the range of 300-450 mV. Interestingly, we can easily distinguish the two ferrocenoyl-purine regioisomers, N7 and N9, simply by the redox potential value. In the case of bis- ferrocene substituted compounds the two electrochemical events were expected, but only one simultaneous process was observed. In order to examine the tendency of ferrocene-nucleobase conjugates to produce reactive oxygen species (ROS), we carried out an acellular screening with DCFH assay in DMSO. We found that the nucleobases coupled with ferrocene generate ROS, while neither ferrocene itself nor the nucleobases were active. By changing the substituents on the purine ring, one can significantly influence the ROS generation of ferrocene-substituted nucleobases. References: [1] K. Kowalski, Coord. Chem. Rev. 2016, 317, 132. [2] M. Patra, G. Gasser, Nat. Rev. Chem. 2017, 1, 1. [3] J. Lapić, V. Havaić, D. Šakić, K. Sanković, S. Djaković, V. Vrček, Eur. J. Org. Chem. 2015, 5424. [4] M. Toma, L. Božičević, J. Lapić, S. Djaković, D. Šakić, T. Tandarić, R. Vianello, V. Vrček, J. Org. Chem. 2019, 84, 19, 12471.

Od utemeljenja Zavoda, akademske godine 1961./62., njegova znanstveno-istraživačka djelatnost bila je usmjerena na elektrokemijska istraživanja metala, pojavu pasiviteta i inhibiciju korozije. Kasnije, ponajprije primjenom elektrokemijskih metoda, proučavaju se fenomeni na granici faza metal│anodni sloj│elektrolitna otopina koji su od značaja za kemijske izvore struje i poluvodičke sustave. Tijekom posljednjih deset godina istraživanja se usmjeravaju u dva smjera: i) ispitivanje utjecaja legirajućih elemenata na dizajn otpornih materijala i biofunkcionalizacija površine biorazgradljivih i biokompatibilnih metalnih implantata; ii) modifikaciju elektroda i njihovih površina u svrhu razvoja novih elektroanalitičkih metoda za određivanje teških metala i biomolekula. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., Since the establishment of the Department of General and Inorganic Chemistry in 1961, at the Faculty of Chemistry and Technology, University of Split, its scientific interest and investigations were focused toward electrochemical research. Consequently, electrochemistry became the backbone of the scientific research and development of the Department. In the last 10 years, scientific interest has been focused on the influence of alloying elements on design of corrosion resistance materials, as well as biofunctionalisation of biodegradable and biocompatible metal-based implants. In addition, development of various electroanalytical methods based on modified electrodes as sensing part of sensors, have been in focus in the recent period. The developed sensors were used for determination of heavy metals or biomolecules. This work is licensed under a Creative Commons Attribution 4.0 International License.

Microporous triclinic AlPO4-34, known as APO-Tric, serves as an excellent water adsorbent in thermal energy storage, especially for low temperature thermochemical energy storage. Increased water adsorption capacity of thermochemical material usually leads to higher thermal energy storage capacity, thus offering improved performance of the adsorbent. The main disadvantage of aluminophosphate-based TCM materials is their high cost due to the use of expensive organic templates acting as structure directing agents. Using ionic liquids as low cost solvents with associated structure directing role can increase the availability of these water adsorbents for TES applications. Here, a green synthesis of APO-Tric crystals at elevated and ambient pressure by using 1-ethyl-3-methyl imidazolium bromide ionic liquid is presented. Large 200 µm romboid shaped monocrystals were obtained at 200 °C after 6 days. The structure of APO-Tric and the presence of 1,3-dimetylimidazolium cation in the micropores were determined by single crystal XRD at room temperature and 150 K. Water sorption capacity of APO-Tric prepared by ionothermal synthesis at elevated pressure increased in comparison to the material obtained at hydrothermal synthesis most probably due to additional structural defects obtained after calcination. The reuse of exhausted ionic liquid was also confirmed, which adds to the reduction of toxicity and cost production of the aluminophosphate synthesis.

The research of battery materials is becoming an increasingly important scientific field due to the growing demand for the electric energy. Magnesium batteries represent one of the promising multivalent battery architectures. To optimize the Mg battery for commercial use, a potential dependent interfacial processes should be understood. Yet, due to great complexity of the interface, there is a lack of theoretical approaches that would enable facing this challenge. A computationally affordable, fully unparameterized, and widely applicable theoretical methodology based on density functional theory and grand canonical approach is extended to investigate the electrochemical stability of Mg-metal/electrolyte interfaces, and to predict their thermodynamic behaviour. The calculated Mg$^{2+}$/Mg$^{0}$ redox potential differs by less than 3% from the experimental value, demonstrating that the methodology provides physically meaningful and reliable results. The methodology is used to study two different Mg electrolytes, based on ethylene carbonate (EC) and dimethylether (DME) solvents. Experiments have shown that the Mg battery fails with the EC electrolyte, while it works fairly well with the DME electrolyte. Our results successfully elucidate atomistic mechanisms that explain the experimental observations. Moreover, our theoretical insights provides valuable guidelines for designing electrolytes with favourable properties. To broaden the theoretical understanding from atomistic to meso-scale, the dependence of morphology evolution on surface orientation is investigated. We found that the surface with the highest area fraction is not necessarily the one with the lowest surface energy, which is usually the only one considered in literature. Morphology evolution should thus be studied on all commonly present surface orientations. Our results show that diffusion of Mg atoms on the Mg anode is slow on some commonly present Mg surface orientations, indicating that Mg could exhibit uneven deposition. Zaradi naraščajoče potrebe po električni energiji postaja raziskovanje baterijskih materialov vedno bolj pomembno znanstveno področje. Magnezijevi akumulatorji predstavljajo obetaven sistem na področju multivalentnih akumulatorjev, vendar je za njihovo optimizacijo in komercializacijo potrebno razumeti procese na medfazni površini elektroda/elektrolit v odvisnosti od napetosti. Kompleksnost teh procesov je privedla v pomanjkanje teoretičnih pristopov, ki bi omogočili njihovo razumevanje. Računsko dostopno, popolnoma neparametrizirano in široko uporabno teoretično metodologijo, ki temelji na teoriji gostotnega funkcionala in velekanonskem ansamblu, smo razširili z namenom raziskovanja elektrokemijske stabilnosti in termodinamskega obnašanja medfazne površine med elektrolitom in Mg elektrodo. Izračunani Mg$^{2+}$/Mg$^0$ redoks potentical se razlikuje za manj kot 3% od eksperimentalne vrednosti, kar dokazuje, da metodologija zagotavlja fizikalno smiselne in zanesljive rezultate. Metodologija je uporabljena za študij dveh različnih elektrolitov baziranih na etilen karbonatu (EC) in dimetil etru (DME). Eksperimenti so pokazali, da Mg akumulator z EC elektrolitom ne deluje, med tem ko z DME elektrolitom deluje dokaj dobro. Naši rezultati pojasnijo atomistične mehanizme, ki teoretično razložijo eksperimentalno opaženo razliko v obnašanju sistemov. Pridobljeni teoretični vpogledi prispevajo tudi smernice za načrtovanje elektrolitov z optimiziranimi lastnostmi. Da bi razširili razumevanje iz atomistične na mezo-skalo, smo raziskali spreminjanje morfologije različnih Mg površin. Pokazali smo, da najbolj zastopana površina ni nujno najbolj stabilna, čeprav je ponavadi edina obravnavana v literaturi. Spreminjanje morfologije mora zato biti raziskano na vseh pogosto prisotnih orientacijah površine. Naši rezultati so pokazali, da je difuzija Mg atomov na Mg anodi počasna na nekaterih pogosto prisotnih orientacijah površine, kar kaže na možnost neenakomernega odlaganja magnezija.