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MXenes are the newest class of two-dimensional nanomaterials characterized by large surface area, high conductivity, and hydrophilicity. To further improve their performance for use in energy storage devices, heteroatoms or functional groups can be inserted into the Mxenes’ structure increasing their stability. This work proposes insertion of lanthanum atoms into niobium-MXene (Nb-MX/La) that was characterized in terms of morphogy, structure, and electrochemical behavior. The addition of La to the Nb-MXene structure was essential to increase the spacing between the layers, improving the interaction with the electrolyte and enabling charge/discharge cycling in a higher potential window and at higher current densities. Nb-MX/La achieved a specific capacitance of up to 157 mF cm–2, a specific capacity of 42 mAh cm–2at 250 mV s–1, a specific power of 37.5 mW cm–2, and a specific energy of 14.1 mWh cm–2after 1000 charge/discharge cycles at 50 mA cm–2.

Pt nanoparticles anchoring on MnV2O6led to electrocatalyst with high performance for the direct borohydride fuel cell anode at low Pt loading along with remarkable stability shown by both experiments and DFT calculations.

The new 2D coordination polymers (CPs) [M(L)2(H2O)2]n[M = CoII(1) and NiII(2); L = 4-(pyridin-3-ylcarbamoyl)benzoate] were synthesized from pyridyl amide-functionalized benzoic acid (HL). They were characterized by elemental, Fourier transform infrared, thermogravimetric, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (XRD) structural analyses. Single-crystal XRD analysis revealed the presence of a 2D polymeric architecture, and topological analyses disclose a 2,4-connected binodal net. A thermochromic effect leads to the production of two new CPs, 1′and 2′, by heating at ca. 220 °C, accompanied by a color change from orange to purple in the case of 1and from blue to green in the case of 2. The transformation of 1to 1′takes place through an intermediate (1a) with a different twist of the L–ligand, leading to the formation of a 1D polymeric architecture, as proven by single-crystal XRD analysis. The addition of water or keeping 1′or 2′in air for several days leads to regeneration of 1or 2, respectively. The thermochromic-triggered structural transformations of 1and 2were further substantiated by PXRD and UV–vis ground-state diffuse-reflectance absorption studies. The supercapacitance ability of the CPs 1and 2and a Ni–Co composite (made from mixing the CPs 1and 2) was investigated by electroanalytical techniques, such as cyclic voltammetry and electrochemical impedance spectroscopy. The CP 2exhibits the highest specific capacity of 273.8 C g–1at an applied current density of 1.5 A g–1. These newly developed CPs further act as electrocatalysts for the water-splitting reaction.

Organic electrosynthesis has received great attention as a powerful green tool for synthesis, affording less waste production, less chemicals spent, and often fewer reaction steps than conventional methods. Functional group interconversion and C–C bond generation by imposition of a proper electrode potential is what lies behind organic electrosynthesis processes. Paired electrochemical reactions, indirect electrosynthesis, electrochemical microreactors, and the use of ionic liquids are some of the highlighted means that contribute to optimization of the overall process. Necessity to use specific organic solvents combined with supporting electrolytes is one of the main limitations to be overcome to make the electrochemical process more economically feasible when compared to nonelectrochemical processes. Numerous examples from the bench scale to industrial routes such as adiponitrile, substituted benzaldehydes, anthraquinone, fluorinated products, and succinic acid production are well described throughout this review.

The corrosion behavior of nickel (Ni)-based alloys used for low-temperature aqueous or condensed systems is reviewed in detail in this paper. Commercially available pure Ni, nickel-copper (Ni-Cu), nickel-molybdenum (Ni-Mo), nickel-chromium-molybdenum (Ni-Cr-Mo), and nickel-chromium-iron (Ni-Cr-Fe) alloys as well as cast Ni-based alloys are addressed. It is shown that Ni-Cr-Mo alloys are multipurpose alloys that can be used in both reducing and oxidizing conditions. Special attention is given to a few Ni alloys, which not only extend the range of usefulness of existing alloys by overcoming their limitations but are also reliable and cost-effective and have opened new areas of applications.

Gold-silver (AuAg) nanoparticles were deposited on reduced graphene oxide (rGO), with Au wt% varying from 34.6 to 46.2 and Ag wt% ranging from 31.7 to 35.3. Three AuAg/rGO samples were characterized by inductively coupled plasma optical emission spectroscopy, transmission and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis. Subsequently, AuAg/rGO materials were studied using the rotating disk electrode as electrocatalysts for oxygen reduction reaction (ORR) for potential application in alkaline fuel cells. AuAg/rGO-3 (with ca. 34.6 wt% Au and 35.3 wt% Ag) showed the most promising performance, with high ORR activity and good stability, as evidenced by the highest current density (−4.45 mA cm−2at 0.5 V), the lowest Tafel slope (103 mV dec−1), and the highest number of electrons exchanged (4.1).

The solubility of manganese in mercury was determined electrochemically via amalgamation and stripping in the room temperature ionic liquid n‐hexyltriethylammonium bis(trifluoromethanesulfonyl)imide, [N6,2,2,2][NTf2]. A hemispherical mercury electrode was made by electrodepositing mercury onto a planar platinum microelectrode. Cyclic voltammetry of Mn2+in [N6,2,2,2][NTf2] at the mercury microhemisphere electrode was investigated at temperatures of 298, 303 and 313 K. The solubility of Mn in Hg was determined on the basis of the charge under the reduction peak (Mn2+→Mn0) and the corresponding reoxidation.

Manganese dioxide modified carbon powder was prepared via a wet impregnation method from the solution of permanganate salt. After heating at 120 °C over night in air, the formation of manganese oxide was confirmed by cathodic stripping voltammetry. The synthesized material was used for fabrication of composite electrodes and their potential application in the field of electroanalysis investigated. The composite electrodes based on the manganese dioxide modified carbon powder proved to be useful as electrodes for detection of hydrogen peroxide, ascorbic acid and nitrite ions.

The combinatorial screening of different metallic nanoparticles as electrocatalysts was investigated and efficiently applied for the detection of hydrazine. In a first step, glassy carbon microspheres decorated with metallic nanoparticles (Au, Pd, and Ag) were abrasively attached on the surface of a basal plane pyrolytic electrode giving a ‘multi–metal’ nanoarray. In a second step, electrodes modified with only one type of metallic nanoparticles allowed the identification of Pd as the unique catalytic material. In addition, a carbon‐epoxy composite electrode loaded with the Pd nanoparticles was then constructed for a practical use. The carbon‐epoxy composite nanoarray electrode was found to have excellent characteristics as for the sensing of hydrazine with a limit of detection of 2 μM.

The electrocatalytic oxidation of oxalate at several carbon based electrodes including basal plane (BPPG) and edge plane (EPPG) pyrolytic graphite and glassy carbon (GC) electrode, was studied. The electrodes were examined for the sensing of oxalate ions in aqueous solutions and all three electrodes showed a response to oxalate additions. The peak of oxalate oxidation at BPPG electrode appeared at lower potential, +1.13 V vs. SCE, than at EPPG (+1.20 V vs. SCE) and GC electrode (+1.44 V vs. SCE). Oxalate oxidation at BPPG electrode was studied in more details for response characteristics (potential and current), effects of pH, temporal characteristics of response potential and current. The results indicated that oxalate oxidation proceeds as two‐electron process at the BPPG electrode with a transfer coefficient βand a diffusion coefficient Devaluated to be 0.45 and 1.03 (±0.04)×10−5cm2s−1respectively. The BPPG electrode was found to be suitable for oxalate determination in aqueous media showing linear response to oxalate concentration with a sensitivity of 0.039 AM−1and a limit of detection of 0.7 μM.

The modification of carbon powder with manganese dioxide using a wet impregnation procedure with electrochemical characterisation of the modified powder is described. The process involves saturation of the carbon powder with manganese(II) nitrate followed by thermal treatment at ca. 773 K leading to formation of manganese(IV) oxide on the surface of the carbon powder. The construction of composite electrodes based on manganese dioxide modified carbon powder and epoxy resin is also described, including optimisation of the percentage of the modified carbon powder. Composite electrodes showed attractive performances for electroanalytical applications, proving to be suitable for the electrochemical detection of hydrogen peroxide, ascorbic acid and nitrite ions with limits of detection comparable to the detection limits achieved by other analytical techniques. The results obtained for detection of these analytes, together with composite electrodes flexible design and low cost offers potential application of composite electrodes in biosensors.

A simple method for the modification of carbon powder with copper oxides is presented. Carbon powder is impregnated with copper(II) nitrate by stirring carbon powder in copper(II) nitrate solution for 1 hour and subsequently thermally treated at 823 K. The modified carbon powder was characterized using electrochemical and spectroscopic techniques. The existence of both copper(I) and copper(II) oxides have been established. The copper oxide modified carbon powder was used for preparation of composite electrodes, and the electrochemical and electrocatalytic behavior of the resulting composite electrodes was studied. The copper oxide modified carbon powder – epoxy composite electrodes showed a high electrocatalytic activity for the nitrite detection in aqueous media, with the detection limit comparable or lower than detection limits obtained with other electrochemical sensors.

Composite electrodes based on iron(III) oxide, Fe2O3, carbon powder and epoxy resin have been prepared and characterized using electrochemical methods and X‐ray photoelectron spectroscopy (XPS). Initially composite electrodes were made by mixing micron sized carbon powder surface with iron(III) oxide. However, the voltammetric responses were unsatisfactory. Therefore, a new type of composite electrodes was made using carbon powder modified with iron(III) oxide via a wet impregnation procedure. This technique involves saturation of the carbon powder with iron(III) nitrate followed by thermal treatment at ca. 623 K forming iron(III) oxide on the surface of the carbon powder.

The synergy of power ultrasound with screen printed electrodes and screen printed modified electrodes is shown to be possible and beneficial. Proof‐of‐concept is shown for the anodic stripping voltammetry of lead at screen printed electrodes and screen printed calomel modified electrodes offering shorter deposition times and increased sensitivity.

Two bromide-based ionic liquids (ILs), 1-butyl-3-ethylimidazolium bromide [Beim][Br] and 1,3-diethylimidazolium bromide [Eeim][Br], were prepared and their effect as alkaline electrolyte additives investigated for the hydrogen evolution reaction (HER). Electrochemical characterization was performed using platinum electrodes in IL-free 8 M KOH electrolyte and after addition of 1 or 2 vol.% of each ionic liquid. The addition of 2 vol.% of [Beim][Br] led to higher current densities. The home-made bromide-based additives changed the HER kinetics, with slightly higher Tafel slopes and small changes on the charge transfer coefficient and exchange current density being among the observed effects. Impedance measurements showed a strong decrease of the overall impedance of the system in the ionic liquid-added alkaline electrolytes, with the Nyquist plots being dominated by the intermediate frequency relaxation related with the adsorbed H. The bromide-based ionic liquids are shown to improve the electrolyte properties and to enhance the alkaline electrolysis efficiency.

Heteropoly acid (HPA) was supported on BEA zeolite by optimized synthesis method yielding samples containing different amounts (20 to 50 wt%) of 12-phosphotungstic acid (HPW). The prepared supported HPW samples were subjected to different post-synthesis procedures including calcination and ultrasonication resulting in BEA-HPW (BPW) hybrid materials. These BPW samples were characterized using SEM, N2-sorption and electrical conductivity measurements. They were subsequently used for the preparation of composites with carbonized polyaniline synthesized in the presence of 5–sulfosalicylic acid, and studied as electrode materials for phenols sensing in acidic, neutral and alkaline media. Linear dependence of current on p–nitrophenol concentration in acidic media was obtained enabling evaluation of limit of detection. Composite electrode gave response to p–nitrophenol presence in alkaline media as well, while no response was recorded in neutral media. The work demonstrates benefits of using novel composite based on BPW hybrid materials and carbonized polyaniline for sensing of phenols in aqueous environmental samples.

Four TiO2electrodes have been investigated for the oxygen reduction reaction (ORR) in 2 M NaOH. Anodic oxidation of Ti-foil was used as the final or the first step in the preparation of four electrodes based on TiO2: amorphous (Ti/AM-TiO2), two anatase forms (Ti/A400-TiO2and Ti/A550-TiO2), and, finally, lithium-anatase form (Ti/A-Li0.25TiO2), all of them obtained as TiO2nanotube arrays. The electrodes’ structure was examined by Raman spectroscopy. Cyclic voltammetry and chronoamperometry were employed for the study of kinetics of ORR. Ti/A-Li0.25TiO2and Ti/A400-TiO2electrodes showed the highest catalytic activity for ORR with the highest cathodic peak current density and the lowest Tafel slope values. Number of electrons exchanged during ORR at TiO2electrodes was in the range from 2.3 to 2.8. Additionally, TiO2electrodes showed good stability as well as acceptable selectivity in the presence of borohydride, methanol or ethanol as typical fuels for fuel cells. Thus this study introduces a simple, low-cost preparation route of TiO2-based electrodes with high efficiency for ORR for energy conversion and storage applications.

Nickel and nickel-cerium (Ni-Ce) alloys with different amounts of Ce (5 and 10 at.% Ce) have been prepared by arc melting and characterized by scanning electron microscopy and electron probe microanalysis based on energy dispersive X-ray spectroscopy, to investigate microstructure and to determine phase composition. Subsequently, Ni and Ni alloy-based electrodes were fabricated and studied for borohydride (BH4-) oxidation in alkaline media by cyclic voltammetry and chronoamperometry in the temperature range 25 – 45 ºC. Preliminary results showed comparable BH4-oxidation peak current densities obtained at three electrodes, with Ni95Ce5electrode giving the highest current densities. Electrochemical data are modelled to obtain relevant kinetic parameters of BH4-oxidation at these electrodes. Effect of electrolyte temperature on the evaluated parameters has been investigated as well.