Search

The search for new and improved materials has led to the discovery and establishment of compositionally complex or high-entropy materials. The work in this thesis is focused on the investigation of new compositionally complex materials based on the refractory metals of groups 4-6. The materials in this work were synthesised using non-reactive dc magnetron sputtering and three material systems have been studied: HfNbTiVZr-C, CrTiTaWNb-C and Nb-Mo-C. In the context of compositionally complex materials, this thesis aims to contribute specifically to questions regarding (i) the prediction of phase formation and stability (ii) the chemical interaction between atoms (iii) the correlation between the material properties and compositional complexity. The prediction of phase formation and stability using calculated phase diagram (CALPHAD) methods was studied in the HfNbTiVZr-C system. The findings suggest that CALPHAD methods are promising predictive tools, although kinetic effects during synthesis need to be taken into consideration. Furthermore, theoretical, and experimental evidence of charge transfer effects was demonstrated within the HfNbTiVZr-C system. The results of ab initio materials simulations and X-ray Photoelectron Spectroscopy (XPS) measurements highlight the importance of understanding and considering the local chemical environment and chemical interactions in compositionally complex materials. The approach of metal alloying according to the valence electron concentration (VEC) to tune the mechanical properties was studied in the Nb-Mo-C system. The findings show the importance of microstructural effects on the mechanical properties in the studied thin film materials, which can overshadow the compositional or VEC variations. The response to Xe heavy-ion irradiation was studied in the CrTiTaWNb-C system using in situ irradiation experiments. This work presents a comparison between three different compositions: a TaW-rich alloy and carbide thin film as well a

Electrolyte additives are indispensable to enhance the performance of Li-ion batteries. Lithium bis(oxalato)borate (LiBOB) has been explored for many years, as it improves both cathode and anode performance. No consensus regarding its reaction mechanisms has, however, been established. A model operando study combining attenuated total reflection infrared spectroscopy (ATR-FTIR), electrochemical quartz crystal microbalance (EQCM), and online electrochemical mass spectrometry (OEMS) is herein presented to elucidate LiBOB reduction and electrode/electrolyte interphases thus formed. Reduction of the BOB– ion sets in at ∼1.8 V with solid lithium oxalate and soluble oxalatoborates as the main products. The reduced BOB– ion also reacts with itself and its environment to evolve CO2, which in turn impacts the interphase formed on the negative electrode. This study provides further insights into the reduction pathways of LiBOB and how they contribute to the interphase formation.

The rising demand for high-performance lithium-ion batteries, pivotal to electric transportation, hinges on key materials like the Ni-rich layered oxide LiNixCoyAlzO2 (NCA) used in cathodes. The present study investigates the redox mechanisms, with particular focus on the role of oxygen in commercial NCA electrodes, both fresh and aged under various conditions (aged cells have performed >900 cycles until a cathode capacity retention of ∼80%). Our findings reveal that oxygen participates in charge compensation during NCA delithiation, both through changes in transition metal (TM)–O bond hybridization and formation of partially reversible O2, the latter occurs already below 3.8 V vs. Li/Li+. Aged NCA material undergoes more significant changes in TM–O bond hybridization when cycling above 50% SoC, while reversible O2 formation is maintained. Nickel is found to be redox active throughout the entire delithiation and shows a more classical oxidation state change during cycling with smaller changes in the Ni–O hybridization. By contrast, Co redox activity relies on a stronger change in Co–O hybridization, with only smaller Co oxidation state changes. The Ni–O bond displays an almost twice as large change in its bond length on cycling as the Co–O bond. The Ni–O6 octahedra are similar in size to the Co–O6 octahedra in the delithiated state, but are larger in the lithiated state, a size difference that increases with battery ageing. These contrasting redox activities are reflected directly in structural changes. The NCA material exhibits the formation of nanopores upon ageing, and a possible connection to oxygen redox activity is discussed. The difference in interaction of Ni and Co with oxygen provides a key understanding of the mechanism and the electrochemical instability of Ni-rich layered transition metal oxide electrodes. Our research specifically highlights the significance of the role of oxygen in the electrochemical performance of electric-vehicle-grade NCA elect

Indoor photovoltaics (IPV) using dye-sensitized solar cells (DSCs) is one among the most promising ambient energy harvesting technologies used to realize self-powered Internet of Things (IoT), consumer electronics and portable devices. The emergence of new generation Cu(II/I) redox electrolytes used with co-sensitized organic dyes enables DSCs to realize higher open circuit photovoltages (Voc) and power conversion efficiencies (PCE) under indoor/ambient illumination. Even though Cu(II/I) electrolytes are promising candidates, the recombination of electrons from the conduction band and sub-bandgap states to the oxidized Cu(II) species and slower regeneration of Cu(II) at the counter electrode limit their performance. Taking inspiration from the asymmetric redox behaviour exhibited by the conventional iodide/triiodide electrolyte, which is efficient in inhibiting the undesirable recombination process, we introduced an alternative strategy of modifying the coordination environment of Cu(II) metal center using the 2,9-dimethyl-1,10-phenanthroline (dmp) ligand. The resulting dual species [Cu(II)(dmp)2Cl]+/[Cu(I)(dmp)2]+ electrolyte exhibited an improved lifetime both under full sun and indoor illumination and better regeneration at the counter electrode. Employing this asymmetric dual species Cu(II)/Cu(I) electrolyte with the co-sensitized D35:XY1 dyes, we realized a record PCE of 35.6% under 1000 lux warm white CFL illumination.

While transition metal carbides (TMCs) exhibit favourable mechanical properties, alloying according to the valence electron concentration (VEC) has the potential to further enhance the properties of these hard but inherently brittle materials. This study investigates the influence of alloying on the microstructure and mechanical properties of (NbxMo1-x)C carbide films, including binary references and ternary compositions with varying metal ratios (x between 0.35 and 0.53). Furthermore, the influence of various substrate materials is studied by comparing films deposited on Al2O3, MgO and SiO2. All films exhibit a NaCl-type carbide structure and X-ray photoelectron spectroscopy revealed the presence of small amounts of an additional amorphous carbon (a-C) phase. Hardness values around 20 ± 2 GPa were obtained for the films on Al2O3 and MgO, whereas a reduced hardness of 11 ± 1 GPa was observed for the films on SiO2 which is attributed to larger crystallite size and more polycrystalline structure. Overall no clear trend as a function of composition can be noted, indicating that microstructure effects dominate the mechanical properties in this study overshadowing the effect of varying the metal content.

This paper investigated the electronic properties and photoresponse of two-dimensional SnX2 (X = Cl, Br, I) monolayer binary materials using computational techniques. The calculated band structure and density of states indicate that these are large band gap semiconducting materials with an indirect band gap. The studied chemical bonding mechanism shows the existence of the hybrid bonding of ionic and covalent bonds in these dihalide materials. The valence band (VB) and conduction band (CB) edge positions are also estimated, using the concept of electronegativity and band gap, to investigate the photocatalytic activity of SnX2. Next, we investigated the polarization and energy-dependent dielectric and optical functions along the crystallographic axes of these materials in the linear response approach of the perturbing incident oscillating light field. These materials exhibit an anisotropic behavior of these functions, especially in the high-energy visible and low-energy ultraviolet (UV) regions. The absorption of incident light photons is very fast in SnI2 than SnBr2 and SnCl2 in the low-energy UV region. It demonstrates the higher absorption coefficient and optical conductivity in Snl2. The obtained average static refractive index of SnCl2 is comparable to that of glass (1.5), showing its application as transparent material. The low reflection coefficient, less than 20%, makes them superior for antireflection coating materials in the infrared and visible regions. The prominent energy loss peaks show the existence of plasmon resonances in these materials. The most of losses occur in the UV region. The investigated electronic and photoresponse properties indicate that these Sn-based dihalide materials are excellent for electronic devices and optoelectronic applications. Also, the calculated VB and CB edge positions with respect to the normal hydrogen electrode show the favorable water-splitting capability of these materials.

The Editors-in-Chief for Journal of Materials Chemistry A, B and C look back at the 10th anniversary year and the celebratory activities that took place.

Lithium-sulfur (Li-S) batteries, renowned for their potential high energy density, have attracted attention due to their use of earth-abundant elements. However, a significant challenge lies in developing suitable materials for both lithium-based anodes, which are less prone to lithium dendrite formation, and sulfur-based cathodes. This obstacle has hindered their widespread commercial viability. In this study, we present a novel sulfur host material in the form of a two-dimensional semiconductor boron nitride framework, specifically the 2D orthorhombic diboron dinitride (o-B2N2). The inherent conductivity of o-B2N2 mitigates the insulating nature often observed in sulfur-based electrodes. Notably, the o-B2N2 surface demonstrates a high binding affinity for long-chain Li-polysulfides, leading to a significant reduction in their dissolution into the DME/DOL electrolytes. Furthermore, the preferential deposition of Li2S on the o-B2N2 surface expedites the kinetics of the lithium polysulfide redox reactions. Additionally, our investigations have revealed a catalytic mechanism on the o-B2N2 surface, significantly reducing the free energy barriers for various sulfur reduction reactions. Consequently, the integration of o-B2N2 as a host cathode material for Li-S batteries holds great promise in suppressing the shuttle effect of lithium polysulfides and ultimately enhancing the overall battery performance. This represents a practical advancement for the application of Li-S batteries.

Wustite, Fe1-x O, is a crucial phase for the transition to CO2-free steel manufacturing as well as promising for electrochemical applications such as water splitting and ammonia synthesis. To study the effect of interfaces in these applications, thin-film model systems with defined interfaces are ideal. Previous studies lack a description of the growth mechanism to obtain Fe1-x O thin films. Here, we investigate the phase formation of metastable Fe1-x O during reactive magnetron sputtering while systematically varying the O-2/Ar flow ratio from 1.8% to 7.2% and the pressure-distance product between 3.5 and 7.2 Pa cm. If bulk diffusion is minimized, thin films containing 96 vol.% wustite and 4 vol.% Fe as impurity phase were achieved. Therefore, the wustite phase formation appears to be surface diffusion dominated. To reveal the influence of impurity phases in wustite on the electrical resistivity, systematic electrical resistivity measurements while cooling in situ were performed for the first time. The electrical resistivity was lower than that of single crystals of the respective iron oxides. This is attributed to the formation of Fe-rich layers at the substrate-film interface, which serve as additional conduction paths.

This study reports on the influence of air annealing and Na incorporation into the absorber on the performance of Cu2ZnSnS4 (CZTS) bifacial solar cells with FTO and W/FTO back contacts. Na was incorporated by depositing similar to 12 nm thick NaF on the CZTS precursors prior to the sulfurization process via thermal evaporation. After sulfurization, some of the samples were annealed in air at 300 degrees C for 90 s and subsequently at 200 degrees C for 600 s. Transmission electron microscopy confirmed sulfurization of the W interlayer to form WS2 which improves the FTO ohmicity. Na incorporation improved grain size of the absorber as revealed by scanning electron microscopy. Non-annealed samples had the unwanted SnS2 phase while the air annealed samples, particularly those with both W interlayer and Na incorporation, were exempt from SnS2 phase, as was confirmed through grazing incident X-ray diffraction and Raman spectroscopy. These results suggest that absorber air annealing and Na incorporation enhance absorber crystal growth which is advantageous in reducing bulk carrier recombination. As a result, the efficiency was significantly improved from 3.0% for solar cells fabricated directly on FTO to 5.2% for those whose absorbers were air annealed, incorporated with Na and made on W/FTO. The latter also exhibits the highest external quantum efficiency response and calculated short circuit current density for both sides illumination. This indicates that the air annealing, Na incorporation and W interlayer are enhancing the performance of bifacial CZTS solar cells with FTO back contact for both back side and front side illumination.

Porous organic polymers (POPs) constitute an important class of sorbents studied in various adsorption and separation processes. Their unique properties, including high surface areas, adjustable pore sizes, and surface chemistries make them ideal candidates for CO2 capture. To achieve a high CO2 adsorption capacity and selectivity, particularly at the low partition pressures required for post-combustion CO2 capture or direct capture of CO2 from the atmosphere, incorporating amines onto the polymer frameworks or within the pores has shown much promise. This review provides a comprehensive summary of recent studies on the synthesis and CO2 capture performance of amine-functionalized POPs. The review also provides a detailed discussion of structure-performance relationships, focusing on how the loading amount and amine type influence CO2 capture capacity, CO2/N2 selectivity, heat of adsorption, sorption kinetics, and recyclability of POPs. Additionally, the authors offer their perspective on the challenges associated with the practical implementation of amine-modified POPs for CO2 capture.

An electrolyte destined for use in a dual-ion battery (DIB) must be stable at the inherently high potential required for anion intercalation in the graphite electrode, while also protecting the Al current collector from anodic dissolution. A higher salt concentration is needed in the electrolyte, in comparison to typical battery electrolytes, to maximize energy density, while ensuring acceptable ionic conductivity and operational safety. In recent years, studies have demonstrated that highly concentrated organic electrolytes, ionic liquids, gel polymer electrolytes (GPEs), ionogels, and water-in-salt electrolytes can potentially be used in DIBs. GPEs can help reduce the use of solvents and thus lead to a substantial change in the Coulombic efficiency, energy density, and long-term cycle life of DIBs. Furthermore, GPEs are suited to manufacture compact DIB designs without separators by virtue of their mechanical strength and electrical performance. In this review, we highlight the latest advances in the application of different electrolytes in DIBs, with particular emphasis on GPEs.

In this study, Synchrotron X-ray diffraction (XRD) radiography was utilized to investigate the ageing heterogeneity in 48 Ah prismatic lithium-ion cells with Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) as the positive electrode active material and graphite as the negative electrode active material after ∼2800 cycles. The study revealed that the area closest to the positive electrode tab is most vulnerable to degradation, particularly impacting the NMC material. Application of principal component analysis allowed to differentiate and visualize part of positive electrode material that has a different degradation due to the lithium plating. A comparison of non-destructive X-ray diffraction-based methods and electrochemical characterization method which was performed on the opened cell has shown an importance of a complementary approach. Our results highlight the feasibility of employing non-destructive techniques to study large prismatic cells, thereby presenting extensive opportunities for advancements in battery research and industry.

We study the effect of nitrogen on the morphological evolution of thin silver (Ag) films deposited on weakly-interacting amorphous carbon (a-C) and silicon oxide (SiOx) surfaces. Films are synthesized at a deposition rate of 0.1nm·s-1 by direct current magnetron sputtering (DCMS), high power impulse magnetron sputtering (HiPIMS), and electron-beam evaporation (EBE). We monitor growth in situ and in real time by measuring the evolution of film stress and optical properties, complemented by ex situ analyses of discontinuous-layer morphologies, film crystal structure, and film composition. We find that addition of molecular nitrogen (N2) to the plasmagenic gas (Ar) during DCMS and HiPIMS promotes a two-dimensional (2D) morphology. Concurrently, EBE-deposited films exhibit a significantly more pronounced three-dimensional morphological evolution, independently from the gas atmosphere composition. We argue that the 2D morphology in DCMS- and HiPIMS-grown films is enhanced due to incorporation of atomic nitrogen (N)—result of plasma-induced N2 dissociation—that hinders island reshaping during coalescence. This mechanism is not active during EBE due to the absence of energetic plasma electrons driving N2 dissociation. The overall results of the study show that accurate control of vapor-phase chemistry is of paramount importance when using gaseous species as agents for manipulating growth in weakly-interacting film-substrate systems., QC 20240326

To further our understanding of a thermoplastic arabinoxylan (AX) material obtained through an oxidation-reduction-etherification pathway, the role of the initial arabinose:xylose ratio on the material properties was investigated. Compression molded films with one molar substitution of butyl glycidyl ether (BGE) showed markedly different tensile behaviors. Films made from low arabinose AX were less ductile, while those made from high arabinose AX exhibited elastomer-like behaviors. X-ray scattering confirmed the presence of nanostructure formation resulting in nano-domains rich in either AX or BGE, from side chain grafting. The scattering data showed variations in the presence of ordered structures, nano-domain sizes and their temperature response between AX with different arabinose contents. In dynamic mechanical testing, three transitions were observed at approximately −90 °C, −50 °C and 80 °C, with a correlation between samples with more structured nano-domains and those with higher onset transition temperatures and lower storage modulus decrease. The mechanical properties of the final thermoplastic AX material can therefore be tuned by controlling the composition of the starting material., QC 20240318

One often proposed route to improved energy density for lithium-ion batteries is to use alloy anodes, such as silicon, able to store large amounts of lithium. Mechanical instability caused by the large expansion and contraction associated with (de)lithiation, and hence bad cyclability, has, however, so far hindered progress. As proof-of-concept of a remedy, we here present BiSbSe1.5Te1.5, a medium high-entropy alloy with improved cycling stability for conversion-alloying (de)lithiation reactions. We attain five to twenty times more stable cycles than previously reported for comparable metal-Se and -Te-based anodes, with a very good reversible capacity (464 mAh g−1) for up to 110 cycles- and this without using any carbonaceous materials to create a composite. Altogether, this highlights how alloy engineering and increased entropy materials can stabilize conversion-alloying electrodes., Validerad;2024;Nivå 2;2024-05-22 (joosat);For funding information, see: https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/batt.202300585;Full text license: CC BY-NC-ND

MoS2 is widely praised as a promising replacement for Pt as an electrocatalyst for the hydrogen evolution reaction (HER), but even today, it still suffers from low performance. This issue is tackled by using Mn3+ as a surface modifier to trigger sulfur vacancy formation and enhance electron transport in few-layered 2H MoS2. Only 10% of Mn is sufficient to transform the semiconductive MoS2 into an active HER electrocatalyst. The insertion of Mn reduces both HER onset potential and Tafel slope which allows reaching 100 mA/cm2 at an overpotential of 206 mV, ten times larger of what undoped MoS2 can achieve. The enhanced activity arises because Mn3+ introduces electronic states near the conduction band, promotes sulfur vacancies, and increases the hydrogen adsorption. In addition to its facile production and extended shelf-life, Mn–MoS2 exhibits an efficiency of 73% at 800 mA/cm2 and 2.0 V when used in proton exchange membrane water electrolyzers.

This study reports on the first all-printed vertically stacked organic electrochemical transistors (OECTs) operating in accumulation mode; the devices, relying on poly([4,4?-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2?-bithiophen-5,5?-diyl]-alt-[thieno[3,2-b]thiophene-2,5-diyl]) (pgBTTT) as the active channel material, are fabricated via a combination of screen and inkjet printing technologies. The resulting OECTs (W/L ≈5) demonstrate good switching performance; gm, norm ≈13 mS cm?1, µC* ≈21 F cm?1 V?1 s?1, ON?OFF ratio > 104 and good cycling stability upon continuous operation for 2 h. The inkjet printing process of pgBTTT is established by first solubilizing the polymer in dihydrolevoglucosenone (Cyrene), a non-toxic, cellulose-derived, and biodegradable solvent. The resulting ink formulations exhibit good jettability, thereby providing reproducible and stable p-type accumulation mode all-printed OECTs with high performance. Besides the environmental and safety benefits of this solvent, this study also demonstrates the assessment of how the solvent affects the performance of spin-coated OECTs, which justifies the choice of Cyrene as an alternative to commonly used harmful solvents such as chloroform, also from a device perspective. Hence, this approach shows a new possibility of obtaining more sustainable printed electronic devices, which will eventually result in all-printed OECT-based logic circuits operating in complementary mode., This project received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 964677 (MITICS). The authors would like to thank Jessica Åhlin for valuable electrolyte discussions. A.M. and P.A.E. thank Vinnova for financial support (grant agreement no. 2023-01337). W.M., L.B., and A.G. thank the FWO Vlaanderen for financial support (WEAVE project G025922N and Ph.D. grant 1S70122N)

Mitigation of greenhouse gas emissions, especially CO2, highlights the critical demand for efficient CO2 capture technologies. This is due to their essential role in climate change and their profound impact on global ecosystems and human well-being. Activated carbons have emerged as promising candidates for CO2 capture due to their availability, cost-effectiveness, and tunable properties. In this study, activated carbons were synthesized from sawdust carbonized at various temperatures within the 700–1100 °C range and subsequently activated using CO2. Comprehensive characterization was conducted through SEM, FESEM, XRD, TGA, and FTIR techniques to assess the properties. The results reveal that carbonization at 1000 °C yielded an activated carbon with a hierarchical and microporous structure, featuring surface area, pore volume, and pore size of 1651.34 m2/g, 0.69 cm³/g, and <1.76 nm, respectively. Remarkably, this activated carbon exhibited promising CO2 uptake of 9.2 mmol/g at 25 °C and 1 bar. Moreover, a remarkable recyclability over 10 cycles demonstrates its potential for practical CO2 capture applications. Furthermore, the synthesized activated carbon exhibited high selectivity for CO2 over N2 (85/15 v/v), reaching 40.2 at 1 bar and 25 °C. These findings underscore the viability of the as-prepared activated carbon as a desired candidate for efficient and selective CO2 capture, contributing to the ongoing efforts to mitigate the impact of anthropogenic CO2 emissions to the environment., Validerad;2024;Nivå 2;2024-04-05 (marisr);Full text license: CC BY

Nanostructured materials and nanocomposites have shown great promise for improving the efficiency of thermoelectric materials. Herein, Fe nanoparticles were imbedded into a CrN matrix by combining two physical vapor deposition approaches, namely, high-power impulse magnetron sputtering and a nanoparticle gun. The combination of these techniques allowed the formation of nanocomposites in which the Fe nanoparticles remained intact without intermixing with the matrix. The electrical and thermal transport properties of the nanocomposites were investigated and compared to those of a monolithic CrN film. The measured thermoelectric properties revealed an increase in the Seebeck coefficient, with a decrease of hall carrier concentration and an increase of the electron mobility, which could be explained by energy filtering by internal phases created at the NP/matrix interface. The thermal conductivity of the final nanocomposite was reduced from 4.8 W m-1 K-1 to a minimum of 3.0 W m-1 K-1. This study shows prospects for the nanocomposite synthesis process using nanoparticles and its use in improving the thermoelectric properties of coatings., Validerad;2024;Nivå 2;2024-04-04 (joosat);Funder: Swedish Research Council VR-RFI (2019-00191); Swedish Foundation for Strategic Research (RIF14-0053); Knut and Alice Wallenberg Foundation (KAW 2016.0346); VR (2021-03826);Full text license: CC BY

Cellulose has shown great potential in the development of green triboelectric nanogenerators. Particularly, regenerated cellulose (R-cellulose) has shown remarkably high output power density but the structural features and key parameters that explain such superior performance remain unexplored. In this work, wood cellulose fibers were dissolved in a LiOH(aq)-based solvent to produce a series of R-cellulose films. Regeneration in different alcohols (from methanol to n-pentanol) was performed and the films’ structural features and triboelectric performance were assessed. Nonsolvents of increased hydrophobicity led to R-cellulose films with a more pronounced (1–10) diffraction peak. An open-circuit voltage (VOC) of up to ca. 260 V and a short-circuit current (ISC) of up to ca. 150 µA were measured for R-cellulose against polytetrafluoroethylene (as negative counter-layer). However, R-cellulose showed an increased VOC of 175% (from 88.1 V) against polydimethylsiloxane when increasing the alcohol hydrocarbon chain length from methanol to n-pentanol. The corresponding ISC and output power also increased by 76% (from 89.9 µA) and by 382% (from 8.8 W m–2), respectively. The higher R-cellulose hydrophilicity, combined with soft counter-tribolayer that follow the surface structures increasing the effective contact area, are the leading reasons for a superior triboelectric performance.

The electrochemical and charge storage performance of a fluorine-free structurally flexible hybrid pyrrolidinium-based ionic liquid electrolyte (HILE) in a symmetric graphite-based supercapacitor is thoroughly investigated. The HILE revealed thermal decomposition at above 230°C, a glass transition (Tg) temperature of below −70°C, and ionic conductivity of 0.16 mS cm−1 at 30°C. The chemical and electrochemical properties are investigated using a systematic variable temperature 1H and 31P NMR spectroscopy and diffusometry, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD). The supercapacitor demonstrated a notable specific capacitance of 186 F g−1 at a scan rate of 1 mV s−1 and a specific capacitance of 122 F g−1 at a current density of 0.5 A g−1. The maximum energy density of 48.8 Wh kg−1, a power density of 450 W kg−1 at a current density of 0.5 A g−1, and a potential window of 4 V were obtained. Altogether, this study demonstrates that the new HILE can be used in symmetric graphite-based supercapacitors over a wide potential window of 4 V and a temperature range from −20°C to 90°C., Validerad;2024;Nivå 1;2024-04-04 (signyg)License full text: CC BY-NC-ND 4.0

Electrochemical water oxidation reaction (WOR) lies among the most forthcoming approaches toward eco-conscious manufacturing of green hydrogen owing to its environmental favors and high energy density values. Its vast commoditization is restricted by high-efficiency and inexpensive catalysts that are extensively under constant research. Herein, calcium, magnesium, and yttrium doped lithium nickel phosphate olivines (LiNi1-xMxPO, LNMP; x = 0.1-0.9; M = Ca2+, Mg2+, and Y3+) were synthesized via non-aqueous sol-gel method and explored for catalytic WOR. Lithium nickel phosphates (LNP) and compositions were characterized via Fourier transform infrared, scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray diffraction techniques for the structural and morphological analyses. Glassy carbon electrode altered with the LNMPs when studied in a standard redox system of 5 mM KMnO4, displayed that yttrium doped LNP, i.e. LNYP-3 exhibits the highest active surface area (0.0050 cm(2)) displaying the lowest average crystallite size (D-avg) i.e. similar to 7 nm. Electrocatalytic behavior monitored in KOH showed that LNMP-2 offers the highest rate constant "k(o)," value, i.e. 3.9 10(-2) cm s(-1) and the largest diffusion coefficient "D-o," i.e. 5.2 x 10(-5) cm(2) s(-1). Kinetic and thermodynamic parameters demonstrated the facilitated electron transfer and electrocatalytic properties of proposed nanomaterials. Water oxidation peak current density values were indicative of the robust catalysis and facilitated water oxidation process besides lowering the Faradic onset potential signifying the transformation of less LNP into more conducive LNMP toward water oxidation.

Very strong difference in many properties is well documented for graphite oxides (GtO) synthesized by Brodie (BGO) and Hummers (HGO) methods. The difference is typically assigned to the type of oxidant (chlorates or KMnO4, respectively). However, not only oxidants but also acids used in these methods are different. It is still unclear which of the different properties of GtO are dependent on the oxidant or acid used in the synthesis. Here we synthesized a new type of graphite oxide using an oxidation agent typical for the Brodie method (KClO3) in combination with acids so far used only in modified Hummers' method (H2SO4+H3PO4). The GtO synthesized by this method (MGO) demonstrates some properties similar to BGO (higher temperature of exfoliation and less defected structure) but also similarity to some other properties of HGO (absence of sharp swelling transitions). Comparing MGO, BGO, and HGO allows us to distinguish the effects of acids and oxidants on the properties of graphite oxides. The new procedure proposed in this study allows preparation of GtO nearly free from hole/vacancy defects (similarly to BGO) but avoids dangerous HNO3. MGO is suggested as a favorable precursor for the preparation of graphene films by thermal or chemical reduction methods.

Environmental pollution is a complex problem that threatens the health and life of animal and plant ecosystems on the planet. In this respect, the scientific community faces increasingly challenging tasks in designing novel materials with beneficial properties to address this issue. This study describes a simple yet effective synthetic protocol to obtain nickel hexacyanoferrate (Ni-HCF) nanocubes as a suitable photocatalyst, which can enable an efficient photodegradation of hazardous anthropogenic organic contaminants in water, such as antibiotics. Ni-HCF nanocubes are fully characterized and their optical and electrochemical properties are investigated. Preliminary tests are also carried out to photocatalytically remove metronidazole (MDZ), an antibiotic that is difficult to degrade and has become a common contaminant as it is widely used to treat infections caused by anaerobic microorganisms. Under simulated solar light, Ni-HCF displays substantial photocatalytic activity, degrading 94.3% of MDZ in 6 h. The remarkable performance of Ni-HCF nanocubes is attributeto a higher ability to separate charge carriers and to a lower resistance toward charge transfer, as confirmed by the electrochemical characterization. These achievements highlight the possibility of combining the performance of earth-abundant catalysts with a renewable energy source for environmental remediation, thus meeting the requirements for sustainable development., Funder: Italian Ministry of University and Research (PE0000021); Ca’ Foscari University of Venice, Italy (SPIN2019, SPIN2021); European Union Next Generation EU/PRTR (TED2021-130756B-C31 MCIN/AEI/10.13039/501100011033 );Full text license: CC BY

Multilayer composite solid electrolytes (CSEs) exhibit many advantages over uniform monolayer CSEs but are hindered by high interlayer resistance and complex preparation methods. Herein, for the first time, a natural sedimentation strategy was developed to construct concentration gradient CSEs (GCSEs) for lithium-metal batteries (LMBs). This method utilizes intrinsic gravity and photopolymerization to achieve multiple functions in the monolayer, avoiding additional interlayer resistance and reducing preparation time. Owning to the concentration gradient structure, the Li+ transport on the PolyIL-rich side relies on the weak solvation of Li+ with EMIMTFSI, while the Li+ transport on the LLZTO-rich side follows the 'vehicular diffusion' mechanism with the aid of TFSI−, improving the Li+ transport and enhances the Li+ transference number, leading to the high stability to 2300 h for the Li//Li cell and stable operation at 4.3 V with 89.6 % capacity retention after 100 cycles for the assembled LMB. Moreover, compared with the monolayer uniform hybrid CSEs, the gradient structure alleviates uncoordinated thermal expansion between LLZTO and PolyIL, avoiding stress increase during cycling and battery capacity fade. This gradient strategy mitigates high interlayer resistance and offers a universal path to address the sluggish Li+ transportation in multilayer CSEs and improves compatibility between the electrolyte and electrodes in fabricating solid-state batteries., Validerad;2024;Nivå 2;2024-03-07 (hanlid);Funder: J. Gust Richert Foundation; National Key Research and Development Program of China (2022YFA1504103); Major Program of National Nature Science Foundation of China (21890762);Full text license: CC BY

Producing sustainable anode materials for lithium-ion batteries (LIBs) through catalytic graphitization of renewable biomass has gained significant attention. However, the technology is in its early stages due to the bio-graphite's comparatively low electrochemical performance in LIBs. This study aims to develop a process for producing LIB anode materials using a hybrid catalyst to enhance battery performance, along with readily available market biochar as the raw material. Results indicate that a trimetallic hybrid catalyst (Ni, Fe, and Mn in a 1:1:1 ratio) is superior to single or bimetallic catalysts in converting biochar to bio-graphite. The bio-graphite produced under this catalyst exhibits an 89.28% degree of graphitization and a 73.95% conversion rate. High-resolution transmission electron microscopy (HRTEM) reveals the dissolution–precipitation mechanism involved in catalytic graphitization. Electrochemical performance evaluation showed that the trimetallic hybrid catalyst yielded bio-graphite with better electrochemical performances than those obtained through single or bimetallic hybrid catalysts, including a good reversible capacity of about 293 mAh g−1 at a current density of 20 mA/g and a stable cycle performance with a capacity retention of over 98% after 100 cycles. This study proves the synergistic efficacy of different metals in catalytic graphitization, impacting both graphite crystalline structure and electrochemical performance., QC 20240229

Rationalizing material features according to the adopted synthetic strategy, aiming then to tune them on demand, is among the most relevant purposes of investigation in materials science. Herein, the systematic analysis of the dependence of graphitic carbon nitride (g-C3N4) physical characteristics on the decomposition temperature of urea, rationalizing the impact of synthetic temperature on several characteristics of the materials (degree of N–H condensation, carbon vs nitrogen content, structural parameters, photoluminescence lifetime, surface area, pores volume), is discussed. g-C3N4 nanostructures are fabricated by thermal decomposition of urea at different temperatures under ambient atmosphere, obtaining an almost ideal stoichiometry (C/N = 0.72) when setting the temperature at 600 °C. The samples show structural, textural, compositional, and optical differences directly depending on the fabrication temperature: specific surface area, pore volume and size, intralayer distance, and speed of radiative recombination of photogenerated charges are proportionally enhanced by increasing the synthesis temperature. The role played by all the physicochemical features of the prepared samples in promoting the catalytic degradation of Rhodamine B is investigated, highlighting their synergistic role in enhancing the catalytic efficiency. Significant differences in the dye degradation are recorded when using either UV or solar simulated light, demonstrating that Rhodamine B photosensitization rules the process., Validerad;2024;Nivå 2;2024-04-23 (joosat);Full text license: CC BY-NC-ND

Polyacrylic acid (PAA) is here studied as a binder material for LiNi0.5Mn1.5O4 (LNMO) cathodes for lithium-ion batteries. When the LNMO electrodes are fabricated with an active mass loading of similar to 10 mg cm-2 (similar to 1.5 mA h cm-2), poor discharge capacity and short cycle life is obtained in full-cells with graphite electrodes. The electrochemical results with PAA are compared with a commonly used water-based binder, sodium carboxymethyl cellulose (CMC), which shows better electrochemical performance. The main cause for these problems in PAA based cells is identified to be the high internal resistance in the initial cycles, caused by factors such as contact resistance, inhomogeneous binder distribution and poor electrolyte wetting of the active material.

Emulsion wastewater contain substantial amounts of oil and various additives, which pose threats to the environment and human health. Demulsification is a crucial pretreatment stage for wastewater. This study aims to identify a novel electro-demulsification method with high oil removal efficiency and low energy consumption. Modified carbonized birch wood with a unique isotropic multiscale pore structure is used as a self-standing electrode to treat a toluene oil-in-water (O/W) emulsion. The electrode must have a highly porous structure to facilitate efficient water diffusion and oil adsorption. It must also have high electronic conductivity to expedite polarized molecular electrophoresis to realize penetration into the pores and, subsequently, demulsification. Guided by an applied electric field force, polarized O/W droplets are drawn toward the electrode, revealing electrical characteristics distinct from those of polarized organic molecules. This electric field force augments the capture and adhesion of droplets by the electric double layer at the electrode interface. Consequently, adsorbed droplets in close proximity to the electrode rupture due to the combined influence of the electric field force and the electrostatic effects stemming from the electrode's multiscale porous structure. This synergistic action enables demulsification to occur efficiently at low energy consumption levels. This study has revealed that electro-demulsification can effectively treat toluene emulsions stabilized by various surfactants and microemulsion containing toluene. Therefore, this electro-demulsification technology can be further developed for various types of water pollution., QC 20240229

Solid-state composite electrolytes have arisen as one of the most promising materials classes for next-generation Li-ion battery technology. These composites mix ceramic and solid-polymer ion conductors with the aim of combining the advantages of each material. The ion-transport mechanisms within such materials, however, remain elusive. This knowledge gap can to a large part be attributed to difficulties in studying processes at the ceramic-polymer interface, which are expected to play a major role in the overall ion transport through the electrolyte. Computational efforts have the potential of providing significant insight into these processes. One of the main challenges to overcome is then to understand how a sufficiently robust model can be constructed in order to provide reliable results. To this end, a series of molecular dynamics simulations are here carried out with a variation of certain structural (surface termination and polymer length) and pair potential (van der Waals parameters and partial charges) models of the Li7La3Zr2O12 (LLZO) poly(ethylene oxide) (PEO) system, in order to test how sensitive the outcome is to each variation. The study shows that the static and dynamic properties of Li-ion are significantly affected by van der Waals parameters as well as the surface terminations, while the thickness of the interfacial region - where the structure-dynamic properties are different as compared to the bulk-like regime - is the same irrespective of the simulation setup.

This work details the synthesis of paramagnetic upconversion nanoparticles doped with Fe3+ in various morphologies via the thermal decomposition method, followed by comprehensive characterization of their structures, optical properties and magnetism using diverse analytical techniques. Our findings demonstrate that by precisely modulating the ratio of oleic acid to octadecene in the solvent, one can successfully obtain hexagonal nanodiscs with a consistent and well-defined morphology. Further adjustments in the oleic acid to octadecene ratio, coupled with fine-tuning of the Na+/F− ratio, led to the production of small-sized nanorods with uniform morphology. Significantly, all Fe3+-doped nanoparticles displayed pronounced paramagnetism, with magnetic susceptibility measurements at 1 T and room temperature of 0.15 emu g−1 and 0.14 emu g−1 for the nanodiscs and nanorods, respectively. To further enhance their magnetic properties, we replaced the Y-matrix with a Gd-matrix, and by fine-tuning the oleic acid/octadecene and Na+/F− ratios, we achieved nanoparticles with uniform morphology. The magnetic susceptibility was 0.82 emu g−1 at 1 T and room temperature. Simultaneously, we could control the nanoparticle size by altering the synthesis temperature. These upconversion nanostructures, characterized by both paramagnetic properties and regular morphology, represent promising dual-mode nanoprobe candidates for optical biological imaging and magnetic resonance imaging., QC 20240223

Porous cellular foams, combining lightweight, high strength, and compressibility, hold great promise in a wide range of advanced applications. Here, the native structure of pine wood was modified by in-situ lignin sulfonation and unidirectional freezing, resulting in an alveolate structure inside the wood cell wall with arrays of sub-100 nm channels. The obtained wood foam exhibited highly enhanced permeability while retaining the native cellular arrangement and high lignin and hemicellulose content. Such engineered cellular foam contributed to superior mechanical performance with compressive strength of 9 MPa and Young's modulus of 344 MPa in the longitudinal direction. The high porosity allowed homogeneous infiltration of conductive polymer PEDOT:PSS inside the wood cell wall. The resulting composite exhibited high conductivity, sponge-like compressibility and the ability to modulate electrical resistance in a reversible manner in the radial direction. This rationally designed conductive wood demonstrated potential in durable and ultrasensitive pressure-responsive devices and strain sensors., Not duplicate with DiVA 1789673QC 20240122

Polydopamine (PDA) is a widely used anchoring layer for multiple purposes. While simple to prepare, PDA is characterized by high chemical and topological diversity, which can limit its versatility. Unraveling the formation mechanism and physicochemical properties of continuous confluent layer and adherent nanoparticles on the nanoscale is crucial to further extend the prospective applications of PDA. Utilizing nano-FTIR spectroscopy, we investigate layers of PDA on three different substrates (silicon/silicon dioxide, nitrogen-doped titanium oxide, and gold substrates) at varying times of deposition (ToD). We observed a good correlation between the nano-FTIR and macroscopic FTIR spectra that reflected the changes in the relative abundance of PDA and polymerization intermediates as ToD increased. To gain analytical power, we utilized the principal component analysis (PCA) and extracted additional information from the resulting loadings spectral curves and data distribution in the score plots. We revealed a higher variability of the spectra of ultrathin surface confluent layers compared to the adherent nanoparticles. While the spectra of nanoparticles showed no apparent dependency on either ToD or the substrate material, the spectra of layers were highly affected by the increasing ToD and exhibited a rise in the absorption of PDA. Concomitantly, the spectra of layers grouped according to the substrate material at the lowest ToD point to the fact that the substrate material affects the PDA's initial physicochemical structure. The observed separation gradually diminished with the increasing ToD as the PDA physicochemical structure became less influenced by the substrate material., QC 20240215

Coarse columnar grains and heterogeneously distributed phases commonly form in metallic alloys produced by three-dimensional (3D) printing and are often considered undesirable because they can impart nonuniform and inferior mechanical properties. We demonstrate a design strategy to unlock consistent and enhanced properties directly from 3D printing. Using Ti−5Al−5Mo−5V−3Cr as a model alloy, we show that adding molybdenum (Mo) nanoparticles promotes grain refinement during solidification and suppresses the formation of phase heterogeneities during solid-state thermal cycling. The microstructural change because of the bifunctional additive results in uniform mechanical properties and simultaneous enhancement of both strength and ductility. We demonstrate how this alloy can be modified by a single component to address unfavorable microstructures, providing a pathway to achieve desirable mechanical characteristics directly from 3D printing., QC 20240222

Hypothesis: The stabilization and isolation to dryness of drug nanoparticles has always been a challenge for nano-medicine production. In the past, the use of montmorillonite (MMT) clay carrier particles to adsorb drug nanoparticles and maintain their high surface area to volume ratio after isolation to dryness has proven to be effective. We hypothesise that the distribution of hydrophilic and hydrophobic patches on the clay's surface as well as its porosity/roughness, hinder the agglomeration of the drug nanoparticles to the extent that they retain their high surface area to volume ratio and display fast dissolution profiles. Experiments: In this work, the distribution of hydrophobicity and hydrophilicity, and the porosity/roughness, of the surface of selected silica carrier particles were varied and the impact of these variations on drug nanoparticle attachment to the carrier particle and subsequent dissolution profiles was studied. Findings: The fastest dissolution profiles at the highest drug nanoparticle loadings were obtained with a periodic mesoporous organosilane carrier particle which had a homogeneous distribution of hydrophobic and hydrophilic surface properties. Carrier particles with rough/porous surfaces and a combination of hydrophobic and hydrophilic patches resulted in nanocomposite powders with faster dissolution behaviour than carrier particles with predominantly either a hydrophobic or hydrophilic surface, or with non-porous/smoother surfaces., QC 20240125

Bismuth telluride-Bi2Te3 is the most promising material for harvesting thermal energy near room temperature. There are numerous works on Bi2Te3 reporting significantly different transport properties, with no clear connection to the synthetic routes used and the resultant surface chemistry of the synthesized materials. It is of utmost importance to characterize the constituent particles’ surface and interfaces to get a better understanding of their influence on the transport properties, that will significantly improve the material design starting from the synthesis step. Electrophoretic deposition (EPD) is a promising technique, enabling the formation of thick films using colloidally stabilized suspensions of pre-made nanoparticles, which can enable the study of the effect of surface chemistry, in connection to the synthetic route, on the material's transport properties. In order to explore the differences in surface chemistry and the resultant transport properties in relation to the synthetic scheme used, here we report on Bi2Te3 synthesised through two wet-chemical routes in water (Hydro-) and oil (Thermo-) as the solvents. XRD analysis showed a high phase purity of the synthesized materials. SEM analysis revealed hexagonal platelet morphology of the synthesized materials, which were then used to fabricate EPD films. Characterization of the EPD films reveal significant differences between the Hydro- and Thermo-Bi2Te3 samples, leading to about 8 times better electrical conductivity values in the Thermo-Bi2Te3. XPS analysis revealed a higher metal oxides content in the Hydro-Bi2Te3 sample, contributing to the formation of a resistive layer, thus lowering the electrical conductivity. Arrhenius plots of electrical conductivity vs inverse temperature was used for the estimation of the activation energy for conduction, revealing a higher activation energy need for the Hydro-Bi2Te3 film, in agreement with the resistive barrier oxide content. Both the samples exhibited neg, QC 20231227

Gadolinium oxyhydride GdHO is a photochromic material that darkens under illumination and bleaches back by thermal relaxation. As an inorganic photochromic material that can be easily deposited by magnetron sputtering, GdHO has very interesting potential applications as a functional material, specially for smart glazing applications. However, the underlying reasons behind the photochromic mechanism - which can be instrumental for the correct optimisation of GdHO for different applications - are not completely understood. In this paper, we rely on the well-established magnetic properties of Gd3+ to shed light on this matter. GdHO thin films present paramagnetic behaviour similar to other Gd3+ compounds such as Gd2O3. Illumination of the films result in a reversible increase of the Curie-Weiss temperature pointing to Ruderman-Kittel-Kasuya-Yosida RKKY interactions, which is consistent with the resistivity decrease observed in the photodarkened films.

All-inorganic CsPbIBr2 perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability. However, the deposition of high-quality solution-processed CsPbIBr2 perovskite films with large thicknesses remains challenging. Here, we develop a triple-component precursor (TCP) by employing lead bromide, lead iodide, and cesium bromide, to replace the most commonly used double-component precursor (DCP) consisting of lead bromide and cesium iodide. Remarkably, the TCP system significantly increases the solution concentration to 1.3 M, leading to a larger film thickness (∼390 nm) and enhanced light absorption. The resultant CsPbIBr2 films were evaluated in planar n-i-p structured solar cells, which exhibit a considerably higher optimal photocurrent density of 11.50 mA cm−2 in comparison to that of DCP-based devices (10.69 mA cm−2). By adopting an organic surface passivator, the maximum device efficiency using TCP is further boosted to a record efficiency of 12.8% for CsPbIBr2 perovskite solar cells., QC 20231227

Light-induced degradation in metal halide perovskites is a major concern that can potentially hamper the commercialization of perovskite optoelectronic devices. The phenomena viz. ion migration, phase segregation, and defect intolerance are believed to be the factors behind the degradation. However, a detailed mechanistic understanding of how and why light reduces the long-term stability of perovskites is still lacking. Here, by combining multiscale characterization techniques and computational studies, we uncover the role of white light in the surface degradation of state-of-the-art FAPbI3-rich perovskite absorbers (reaching up to 22% PCE in solar cells). We unravel the degradation kinetics and found that white light triggers the chemical degradation of perovskite into secondary phases with higher work function and metallic I–V characteristics. Furthermore, we demonstrate that perovskite degradation is triggered by a combined mechanism involving both light and the presence of defects. We employ surface passivation to understand the role of defect intolerance in the degradation process. Moreover, by using filtered light we uncover the wavelength dependency of the light-induced perovskite degradation. Based on our findings, we infer some strategies for material engineering and device design that can expedite the path toward stable perovskite optoelectronic devices.

Anodic dissolution of aluminum (commonly called aluminum corrosion) is a potential issue in sodium-ion batteries. Herein, it is demonstrated how different sodium-ion battery electrolyte solutions affect this phenomenon. The type of electrolyte was critical for the presence of anodic dissolution, while the solvent appeared to alter the dissolution process.

We present first-principles insights into the electrical and electrochemical properties of Cu2N, a newly synthesized two-dimensional material that features a planar, checkerboard lattice structure [Hu et al., Nano Lett. 2023, 23 (12), 5610–5616]. We evaluate the suitability of monolayer Cu2N as an anode material for Li and Na-ion batteries by examining its storage capacity, diffusion barrier, open-circuit voltage (OCV), volume expansion, and the impact of defects on its electrochemical performance. The monolayer Cu2N demonstrates a storage capacity of 379.88 mAh.g−1 for both Li and Na, comparable to that of commercial graphite for Li (372 mAh.g−1) and significantly higher for Na (less than 35 mAh.g−1). The migration barriers for Li and Na are found to be 0.1 eV and 0.01 eV, respectively, substantially lower than those theoretically reported for commercial anodes TiO2 (0.4–1.0 eV) and graphite (∼0.4 eV), which imply that monolayer Cu2N demonstrates excellent charge/discharge capabilities. Moreover, the volume growth of monolayer Cu2N is 4.14 % with maximal Li adsorption, which is 2.4 times less than graphite. The analysis of vacancy defects reveals a significant enhancement in the binding energies of Li and Na atoms, accompanied by minimal changes in diffusion barriers. Since monolayer Cu2N has already been successfully synthesized, these findings would pave the way for large-scale experimental fabrication of monolayer Cu2N as a battery anode., Validerad;2024;Nivå 2;2024-04-03 (hanlid);Full text license: CC BY

Understanding “efficiency roll-off” (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed. Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, this in situ doping transformation renders a meaningful efficiency analysis challenging. Herein, a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching, is presented. Specifically, the position of the emissive p-n junction in common singlet-exciton emitting LECs is measured to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency is quantified. It is further verified that the LEC-characteristic high electrochemical-doping concentration renders singlet-polaron quenching (SPQ) significant already at low drive current density, but also that SPQ increases super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This results in that SPQ dominates singlet-singlet quenching for relevant current densities, and significantly contributes to the efficiency roll-off. This method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at highluminance.

Three short-alkyl-chain-modified [DBU][TFSI] ionic liquids (ILs) were synthesized and utilized in electrets. The electrets were prepared by mixing a UV-curable polymer with the ionic liquids followed by polymerization while applying an external electric field, thus forming spatially separated anions and cations in the proximity of opposing surfaces of the composite slabs. The immobilized surplus surface charge was measured by periodically engaging the electret with a metal counter electrode plate and detecting the displacement current using a charge amplifier. The results show that electrets based on polymerized [DBU][TFSI] ILs have a separated surface charge density of up to 64 nC × cm−2, which equals an energy harvesting density of 7.0 nJ × cm−2. Control measurements repeated after a few days to assess the stability and reproducibility of the systems showed that while charge separation reverses over time to some extent, the polymerized ionic liquid samples are resilient to exposure to atmospheric conditions and could be utilized in this type of energy harvesting scheme.

Pressure-induced swelling has been reported earlier for several hydrophilic layered materials. MXene Ti3C2Tx is also a hydrophilic layered material composed by 2D sheets but so far pressure-induced swelling is reported for this material only under conditions of shear stress at MPa pressures. Here, high-pressure experiments are performed with MXenes prepared by two methods known to provide “clay-like” materials. MXene synthesized by etching MAX phase with HCl+LiF demonstrates the effect of pressure-induced swelling at 0.2 GPa with the insertion of additional water layer. The transition is incomplete with two swollen phases (ambient with d(001) = 16.7Å and pressure-induced with d(001) = 19.2Å at 0.2 GPa) co-existing up to the pressure point of water solidification. Therefore, the swelling transition corresponds to change from two-layer water intercalation (2L-phase) to a never previously observed three-layer water intercalation (3L-phase) of MXene. Experiments with MXene prepared by LiCl+HF etching have not revealed pressure-induced swelling in liquid water. Both MXenes also show no anomalous compressibility in liquid methanol. The presence of pressure-induced swelling only in one of the MXenes indicates that the HCl+LiF synthesis method is likely to result in higher abundance of hydrophilic functional groups terminating 2D titanium carbide.

The concept of confining ionic liquids (ILs) in developing quasi-solid-state electrolytes (QSSEs) has been proposed, where ILs are dispersed in polymer networks/backbones and/or filler/host pores, forming the so-called confinement, and great research progress and promising research results have been achieved. In this review, the progress and achievement in developing QSSEs using IL-confinement for lithium metal batteries (LMBs), together with advanced characterizations and simulations, were surveyed, summarized, and analyzed, where the influence of specific parameters, such as IL (type, content, etc.), substrate (type, structure, surface properties, etc.), confinement methods, and so on, was discussed. The confinement concept was further compared with the conventional one in other research areas. It indicates that the IL-confinement in QSSEs improves the performance of electrolytes, for example, increasing the ionic conductivity, widening the electrochemical window, and enhancing the cycle performance of the assembled cells, and being different from those in other areas, i.e., the IL-confinement concept in the battery area is in a broad extent. Finally, insights into developing QSSEs in LMBs with the confinement strategy were provided to promote the development and application of QSSE LMBs., Validerad;2024;Nivå 2;2024-04-03 (hanlid);Full text license: CC BY-NC

The use of graphene as an additive in materials is often challenging due to the agglomeration of the two-dimensional graphene sheets. An alternative additive is graphene oxide (GO), an oxidized form of graphene, which is easily dispersed in water. In this thesis, a method based on electrostatic interactions has been developed to coat powder particles with GO. The GO surface has a negative charge at most pH values, while most inorganic materials form a thin oxide surface layer with a pH-dependent surface charge. Below a certain pH, a powder surface can have a positively charged surface oxide, which can interact with the negatively charged GO sheets and form a coated particle. The pH range for a successful coating process can be predicted based on the ionic potential (z/r) of the surface oxides and the oxide stability regions seen in Pourbaix diagrams. In the thesis, GO-coatings were obtained on powders of Cu, Fe, 316L stainless steel, MnAl(C) and AlSi7Mg. The coated powders showed reduced reflectance, long-term oxidation stability and in most cases improved flowability. The effect of the GO-coating on the processability of Cu, MnAl(C), 316L stainless steel and AlSi7Mg in laser powder bed fusion (L-PBF) was also investigated. For Cu, the reduced reflectance at the wavelength of the laser led to printing of fully dense parts compared to a 10 % porosity of the printed uncoated Cu powder using the same printing parameters. L-PBF printing of MnAl(C) has a problem with cracking but printing with the GO-coated powder resulted in a 35 % crack reduction. Fully dense parts could also be printed with GO-coated AlSi7Mg and 316L stainless steel powders. Significant changes in texture compared to the uncoated reference as well as moderately improved mechanical properties were observed. TiB2-SiC composites can be formed by reactive hot pressing of a TiC-Si-B4C powder mixture. In agreement with predictions, it was very difficult to coat powders of Si and B4C due to their acidic surf

Lithium-ion batteries constitute a leading technology that plays a major role in the transition towards sustainable transportation and power generation. The stability of modern batteries relies on a passivation layer formed on the negative electrode known as the solid electrolyte interphase (SEI). Despite concerted efforts to comprehend the various processes taking place during SEI formation, monitoring the reaction pathways in real-time is still very challenging. This is due to the complex interactions within the multicomponent electrochemical system, aggravated by the wide range of electrolyte compositions, electrode materials, and operating conditions. In this thesis, operando surface enhanced Raman spectroscopy is explored to elucidate the progressive formation of the SEI on the negative electrode surface when the electrode is negatively polarised in a spectro-electrochemical cell. Complementary online-electrochemical mass spectrometry is employed to identify the associated gaseous products formed during the process. The work illustrates that the electrolyte as well as contaminants, such as O2, CO2, and H2O, contribute in electro-/chemical processes that build up the SEI. The thesis then explores reaction pathways involving a SEI-forming electrolyte additive, namely vinylene carbonate (VC), emphasizing its role as a H2O scavenging agent. In comparison to the conventional electrolyte solvent ethylene carbonate, VC exhibits a faster reaction with water impurities, particularly in presence of hydroxide ions. This results in the formation of products that are less likely to impact cell performance. In the later part, the thesis delves into understanding the stability of electrolyte in an environment of Lewis bases (LB) typically found in the SEI. For that, individual LB (e.g., OH- and OCH3-) are mixed with typical carbonate-based solvents and the products formed as a result of the reaction are analysed. Furthermore, tris(trimethylsilyl)phosphate (TMSPa), a represent

The reliance on Li-ion batteries is increasing as we transition from fossil fuels to renewable energy sources. Despite their widespread use, a gap remains in understanding certain processes within these batteries, especially regarding the solid electrolyte interphase (SEI) and the impact of side reactions on Li-ion batteries. A custom-made Online Electrochemical Mass Spectrometry (OEMS) instrument was designed to explore these aspects. The OEMS instrument was validated through the study of gas-evolving reactions in the classic LiCoO2 | Graphite system. In-depth studies focusing on the reaction pathways of ethylene carbonate, the archetype Li-ion battery electrolyte solvent, identified the specific reaction pathways contributing to SEI formation. Moreover, ethylene carbonate’s interaction with residual contaminants like OH– from H2O reduction was explored. It was revealed that the integrity of the SEI can be compromised by minor amounts of contaminants, establishing a competitive dynamic at the negative electrode surface between ethylene carbonate and residual contaminants such as H2O and HF. Additionally, the roles of additives like vinylene carbonate and lithium bis(oxolato) borate in SEI formation were explored. Vinylene carbonate was shown to form a layer on the negative electrode, but also scavenge protons and H2O, revealing that it is a multi-functional additive. Lithium bis(oxolato) borate on the other hand formed an SEI layer before H2O reduction, blocking the residual contaminant and ethylene carbonate from reaching the electrode surface. By providing insights into the negative electrode’s interphase and SEI formation through a custom-made OEMS instrument, this research underscores the complexity of reaction pathways and the necessity of considering both major and minor, as well as, primary and secondary reactions for a holistic understanding of Li-ion batteries.

The surface of SBA-15 mesoporous silica was modified by N-hydroxyphthalimide (NHPI) moieties acting as immobilized active species for aerobic oxidation of alkylaromatic hydrocarbons. The incorporation was carried out by four original approaches: the grafting-from and grafting-onto techniques, using the presence of surface silanols enabling the formation of particularly stable O−Si−C bonds between the silica support and the organic modifier. The strategies involving the Heck coupling led to the formation of NHPI groups separated from the SiO2 surface by a vinyl linker, while one of the developed modification paths based on the grafting of an appropriate organosilane coupling agent resulted in the active phase devoid of this structural element. The successful course of the synthesis was verified by FTIR and 1H NMR measurements. Furthermore, the formed materials were examined in terms of their chemical composition (elemental analysis, thermal analysis), structure of surface groups (13C NMR, XPS), porosity (low-temperature N2 adsorption), and tested as catalysts in the aerobic oxidation of p-xylene at atmospheric pressure. The highest conversion and selectivity to p-toluic acid were achieved using the catalyst with enhanced availability of non-hydrolyzed NHPI groups in the pore system. The catalytic stability of the material was additionally confirmed in several subsequent reaction cycles.