Search

Electrolyzers operate over a range of temperatures; hence, it is crucial to design electrocatalysts that do not compromise the product distribution unless temperature can promote selectivity. This work reports a synthetic approach based on electrospinning to produce NiO:SnO2 nanofibers (NFs) for selectively reducing CO2 to formate above room temperature. The NFs comprise compact but disjoined NiO and SnO2 nanocrystals identified with STEM. The results are attributed to the segregation of NiO and SnO2 confirmed with XRD. The NFs are evaluated for the CO2 reduction reaction (CO2RR) over various temperatures (25, 30, 35, and 40 °C). The highest faradaic efficiencies to formate (FEHCOO−) are reached by NiO:SnO2 NFs containing 50% of NiO and 50% SnO2 (NiOSnO50NF), and 25% of NiO and 75% SnO2 (NiOSnO75NF), at an electroreduction temperature of 40 °C. At 40 °C, product distribution is assessed with in situ differential electrochemical mass spectrometry (DEMS), recognizing methane and other species, like formate, hydrogen, and carbon monoxide, identified in an electrochemical flow cell. XPS and EELS unveiled the FEHCOO− variations due to a synergistic effect between Ni and Sn. DFT-based calculations reveal the superior thermodynamic stability of Ni-containing SnO2 systems towards CO2RR over the pure oxide systems. Furthermore, computational surface Pourbaix diagrams showed that the presence of Ni as a surface dopant increases the reduction of the SnO2 surface and enables the production of formate. Our results highlight the synergy between NiO and SnO2, which can promote the electroreduction of CO2 at temperatures above room temperature. [ABSTRACT FROM AUTHOR]

Permanent magnets (PM) play an important role in enabling technologies and modern devices of today [1]. Ba- and Sr-ferrites are most-produced permanent magnetic materials in the world [2]. Although ferrite magnets are inferior in performance to rare-earth magnets, the harmful environmental impact of production, uneven distribution, and increasingly questionable supply chain force us to look for alternatives. One of the possible candidates comes from the group of hexagonal ferrites [3]. M-type ferrite magnets generally do not contain critical raw materials [4]. In our study we tested pressurless spark plasma sintering (PSPS) on strontium hexaferrite using graphite die in spark plasma sintering (SPS) device, that enabled to isolate radiation as a sintering mechanism. Although ceramic magnets and radiation assisted sintering process have been known for some time, this is a less commonly used approach to sintering this widely used magnetic material. This research focuses mostly on analysis of phase evolution during PSPS sintering of Sr-ferrite where we tried to determine newly formed phases in the sample. The samples were extensively analysed on a scanning electron microscope (SEM) where, with the help of energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) techniques, we were able to determine the segregation of the base material and the new arrangement of grains. In addition, we analysed the diffractions with the help of transmission electron microscopy (TEM) and thus tried to determine the crystal phases of the newly formed phases. Additionally, we confirmed our results with X-ray diffraction analysis (XRD) and thermogravimetry differential thermal analysis (TG/DTA) analysis. We found that ferrite reduction occurs in the sample due to a slightly reducing atmosphere, which is caused by a combination of vacuum and carbon sputtering. This causes the appearance of strontium depleted and enriched phases. [ABSTRACT FROM AUTHOR]

Spatially separated palladium nanocubes (Pd NCs) terminated by {100} facets are synthesized using direct micelles approach. The stepwise seed-mediated growth of Pd NCs is applied for the first time. The resulting Pd NCs are thoroughly characterized by HR-TEM, XPS, Raman, ATR-FTIR, TGA, and STEM-EDX spectroscopies. Some traces of residual stabilizer (polyvinylpyrrolidone, PVP) attached to the vertices of Pd NCs are identified after the necessary separation-washing procedure, however, it is vital to avoid aggregation of the NCs. Pd NCs are subsequently and uniformly loaded on Vulcan carbon (≈20 wt.%) for the electrochemical hydrogen cycling. By post-mortem characterizations, it is revealed that their shape and size remained very stable after all electrochemical experiments. However, a strong effect of the NCs size on their hydrogen interaction is revealed. Hydrogen absorption capacity, measured as the H:Pd ratio, ranges from 0.28 to 0.48, while hydrogen evolution and oxidation reactions (HER and HOR) kinetics decrease from 15.5 to 4.6 mA.mg Pd -1 between ≈15 and 34 nm of Pd NCs, respectively. Theoretical calculations further reveal that adsorption of H atoms and their penetration into the Pd lattice tailors the NCs electronic structure, which in turn controls the kinetics of HER, experimentally observed by the electrochemical tests. This work may pave the way to the design of highly active electrocatalysts for efficient HER stable for a long reactive time. In particular, obtained results might be transferred to active Pd-alloy-based NCs terminated by {100} facets., (© 2025 The Author(s). Small published by Wiley‐VCH GmbH.)

O3-type NaNi 0.8 Mn 0.1 Co 0.1 O 2 (NaNMC811) cathode active materials for sodium-ion batteries (SIBs), with a theoretical high specific capacity (∼ 187 mAh g -1 ), are in the preliminary exploration stage. This study comprehensively investigates NaNMC811 from multiple perspectives. For the first time, the phase evolution ( P 3 ¯ m 1 $P\overline{3}m1$ - F m 3 ¯ m $Fm\overline{3}m$ - R 3 ¯ m $R\overline{3}m$ ) during the solid-state synthesis is systemically investigated, which elucidates in-depth the mechanisms of the thermal sodiation process. Furthermore, an Al-gradient doping of NaNMC811 was successfully implemented through Al 2 O 3 coating on the cathode active material (CAM) precursor. The modified Al-NaNi 0.8 Mn 0.1 Co 0.1 O 2 (Al-NaNMC811) exhibits excellent electrochemical dynamics and performance, maintaining a specific capacity above 100 mAh g -1 after 100 cycles at 0.1 C (1.5-4.1 V) while providing a promising capacity retention of 63%. Additionally, the material demonstrates excellent rate capabilities, retaining a specific capacity of 107 mAh g -1 at 5 C. Compared to pristine NaNMC811, the modified Al-NaNMC811 is proven to have improved electrochemical kinetics with a higher Na + diffusion coefficient due to dilated (003) interplanar spacing, and a more stable structure during the electrochemical charge-discharge processes, which is attributed to stronger Al-O bond energy. Understanding phase formations during the synthesis and comprehensive insight in the gradient doping for O3-type NaNMC811 CAMs guides further development of next-generation SIBs materials., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

Designing electrocatalysts with optimal activity and selectivity relies on a thorough understanding of the surface structure under reaction conditions. In this study, experimental and computational approaches are combined to elucidate reconstruction processes on low-index Pd surfaces during H-insertion following proton electroreduction. While electrochemical scanning tunneling microscopy clearly reveals pronounced surface roughening and morphological changes on Pd(111), Pd(110), and Pd(100) surfaces during cyclic voltammetry, a complementary analysis using inductively coupled plasma mass spectrometry excludes Pd dissolution as the primary cause of the observed restructuring. Large-scale molecular dynamics simulations further show that these surface alterations are related to the creation and propagation of structural defects as well as phase transformations that take place during hydride formation., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising cathode materials for high energy density Li-ion batteries (LiBs). However, NMC811 suffers from capacity fading during electrochemical cycling because of its structure instability at voltages >4.2 V vs Li|Li + due to the known hexagonal H2→H3 phase transition. Zr doping has proven to be effective in enhancing electrochemical performances of the NMC811. In depth investigations are conducted through operando x-ray diffraction (XRD) and ex situ x-ray absorption spectroscopy (XAS) measurements to mechanistically understand the benefits of Zr-doping in a NMC811 material when doped during the co-precipitation step. Herein, Zr-doping in NMC811 reduces the formation of the detrimental H3 phase and mitigates the transition metal dissolution upon cycling., (© 2024 The Author(s). ChemSusChem published by Wiley-VCH GmbH.)

The widespread use of high-capacity Ni-rich layered oxides such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), in lithium-ion batteries is hindered due to practical capacity loss and reduced working voltage during operation. Aging leads to defective NMC811 particles, affecting electrochemical performance. Surface modification offers a promising approach to improve cycle life. Here, we introduce an amorphous lithium titanate (LTO) coating via atomic layer deposition (ALD), not only covering NMC811 surfaces but also penetrating cavities and grain boundaries. As NMC811 electrodes suffer from low structural stability during charge and discharge, We combined electrochemistry, operando X-ray diffraction (XRD), and dilatometry to understand structural changes and the coating protective effects. XRD reveals significant structural evolution during delithiation for uncoated NMC811. The highly reversible phase change in coated NMC811 highlights enhanced bulk structure stability. The LTO coating retards NMC811 degradation, boosting capacity retention from 86 % to 93 % after 140 cycles. This study underscores the importance of grain boundary engineering for Ni-rich layered oxide electrode stability and the interplay of chemical and mechanical factors in battery aging., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

It is still unclear which role space charge layers (SCLs) play within an all-solid-state battery during operation with high current densities, as well as to which extent they form. Herein, we use a solid electrolyte with a known SCL formation and investigate it in a symmetric cell under non-blocking conditions with Li metal electrodes. Since the used LICGC™ electrolyte is known for its instability against lithium, it is protected from rapid degradation by nanometer-thin layers of TiO x deployed by atomic layer deposition. Close attention is given to the interfacial properties, as now additional Li + can traverse through the interface depending on the applied bias potential. The interlayer's impedance response shows efficient lithium-ion conduction for low bias potentials and a diffusion-limiting effect towards high positive and negative potentials. SCLs grow up to a thickness of 5.1 μm. Additionally, estimating the apparent rate constant of the charge transfer across the interface indicates that the potentials where kinetics are hindered coincide with the widest SCLs. In conclusion, the investigation under higher steady-state currents was only possible because of the improved stability due to the interlayer. No chemo-physical failure could be observed after 800+ hours of cycling. However, an ex-situ SEM study shows a new phase at the interface, which grows into the electrolyte., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The development of new encapsulating coatings for flexible solar cells (SCs) can help address the complex problem of the short lifespan of these devices, as well as optimize the technological process of their production. In this study, new laminate-type protective composite coatings were prepared using a silicon oxynitride thin-film matrix obtained by curing the pre-ceramic polymer perhydropolysilazane (PHPS) through two low-temperature methods: (i) thermal annealing at 180 °C and (ii) exposure to UV radiation at wavelengths of 185 and 254 nm. Single-walled carbon nanotubes (SWCNTs) were used as fillers via dry transfer, facilitating their horizontal orientation within the matrix. The optical, adhesive, and structural properties of the matrix films and SiO x N y /SWCNT composite coatings, along with their long-term stability, were studied using Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, HR-SEM, spectral ellipsometry, and a progressive-load scratch test. In this work, the optical constants of PHPS-derived films were systematically studied for the first time. An antireflection effect was observed in the composites revealing their two-component nature associated with (i) the refractive index of the SiO x N y matrix film and (ii) the embedding of a SWCNT filler into the SiO x N y matrix. The curing method of PHPS was shown to significantly affect the resulting properties of the films. In addition to being used as protective multifunctional coatings for SCs, both SiO x N y /SWCNT composites and SiO x N y matrix films also function as broadband optical antireflective coatings. Furthermore, due to the very low friction coefficients observed in the mechanical tests, they show potential as scratch resistant coatings for mechanical applications.

SnO x has received great attention as an electrocatalyst for CO 2 reduction reaction (CO 2 RR), however; it still suffers from low activity. Moreover, the atomic-level SnO x structure and the nature of the active sites are still ambiguous due to the dynamism of surface structure and difficulty in structure characterization under electrochemical conditions. Herein, CO 2 RR performance is enhanced by supporting SnO 2 nanoparticles on two common supports, vulcan carbon and TiO 2 . Then, electrolysis of CO 2 at various temperatures in a neutral electrolyte reveals that the application window for this catalyst is between 12 and 30 °C. Furthermore, this study introduces a machine learning interatomic potential method for the atomistic simulation to investigate SnO 2 reduction and establish a correlation between SnO x structures and their CO 2 RR performance. In addition, selectivity is analyzed computationally with density functional theory simulations to identify the key differences between the binding energies of * H and * CO 2 - , where both are correlated with the presence of oxygen on the nanoparticle surface. This study offers in-depth insights into the rational design and application of SnO x -based electrocatalysts for CO 2 RR., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

Electrolyzers operate over a range of temperatures; hence, it is crucial to design electrocatalysts that do not compromise the product distribution unless temperature can promote selectivity. This work reports a synthetic approach based on electrospinning to produce NiO:SnO 2 nanofibers (NFs) for selectively reducing CO 2 to formate above room temperature. The NFs comprise compact but disjoined NiO and SnO 2 nanocrystals identified with STEM. The results are attributed to the segregation of NiO and SnO 2 confirmed with XRD. The NFs are evaluated for the CO 2 reduction reaction (CO 2 RR) over various temperatures (25, 30, 35, and 40 °C). The highest faradaic efficiencies to formate (FE HCOO - ) are reached by NiO:SnO 2 NFs containing 50% of NiO and 50% SnO 2 (NiOSnO50NF), and 25% of NiO and 75% SnO 2 (NiOSnO75NF), at an electroreduction temperature of 40 °C. At 40 °C, product distribution is assessed with in situ differential electrochemical mass spectrometry (DEMS), recognizing methane and other species, like formate, hydrogen, and carbon monoxide, identified in an electrochemical flow cell. XPS and EELS unveiled the FE HCOO - variations due to a synergistic effect between Ni and Sn. DFT-based calculations reveal the superior thermodynamic stability of Ni-containing SnO 2 systems towards CO 2 RR over the pure oxide systems. Furthermore, computational surface Pourbaix diagrams showed that the presence of Ni as a surface dopant increases the reduction of the SnO 2 surface and enables the production of formate. Our results highlight the synergy between NiO and SnO 2 , which can promote the electroreduction of CO 2 at temperatures above room temperature., Competing Interests: The authors declare no competing interests., (This journal is © The Royal Society of Chemistry.)

Ni-rich layered oxides LiNi 1- x - y Mn x Co y O 2 (NMC811, x = 0.1 and y = 0.1) are considered promising cathode materials in lithium-ion batteries (LiBs) due to their high energy density. However, those suffer a severe capacity loss upon cycling at high delithiated states. The loss of performance over time can be retarded by Zr doping. Herein, a small amount of Zr is added to NMC811 material via two alternative pathways: during the formation of the transition metal (TM) hydroxide precursor at the co-precipitation step (0.1%-Zr-cp) and during the lithiation at the solid-state synthesis step (0.1%-Zr-ss). In this work, the crystallographic Zr uptake in both 0.1%-Zr-ss and 0.1%-Zr-cp is determined and quantified through synchrotron X-ray diffraction and X-ray absorption spectroscopy. We prove that the inclusion of Zr in the TM site for 0.1%-Zr-cp leads to an improvement of both specific capacity (156 vs 149 mAh/g) and capacity retention (85 vs 82%) upon 100 cycles compared to 0.1%-Zr-ss where the Zr does not diffuse into the active material and forms only an extra phase separated from the NMC811 particles.

The conversion of biomass and natural wastes into carbon-based materials for various applications such as catalysts and energy-related materials is a fascinating and sustainable approach emerged during recent years. Precursor nature and characteristics are complex, hence, their effect on the properties of resulting materials is still unclear. In this work, we have investigated the effect of different precursors and pyrolysis temperature on the properties of produced carbon materials and their potential application as negative electrode materials in Li-ion batteries. Three biomasses, lignocellulosic brewery spent grain from a local brewery, catechol-rich lignin and tannins, were selected for investigations. We show that such end-product carbon characteristic as functional and elemental composition, porosity, specific surface area, defectiveness level, and morphology strictly depend on the precursor composition, chemical structure, and pyrolysis temperature. The electrochemical characteristics of produced carbon materials correlate with the characteristics of the produced materials. A higher pyrolysis temperature is shown to be favourable for production of carbon material for the Li-ion battery application in terms of both specific capacity and long-term cycling stability., (© 2023 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Electrocatalytic hydrogenation (ECH) approaches under ambient temperature and pressure offer significant potential advantages over thermal hydrogenation processes but require highly active and efficient hydrogenation electrocatalysts. The performance of such hydrogenation electrocatalysts strongly depends not only on the active phase but also on the architecture and surface chemistry of the support material. Herein, Pd nanoparticles supported on a nickel metal-organic framework (MOF), Ni-MOF-74, are prepared, and their activity toward the ECH of benzaldehyde (BZH) in a 3 M acetate (pH 5.2) aqueous electrolyte is explored. An outstanding ECH rate up to 283 μmol cm -2 h -1 with a Faradaic efficiency (FE) of 76% is reached. Besides, higher FEs of up to 96% are achieved using a step-function voltage. Materials Studio and density functional theory calculations show these outstanding performances to be associated with the Ni-MOF support that promotes H-bond formation, facilitates water desorption, and induces favorable tilted BZH adsorption on the surface of the Pd nanoparticles. In this configuration, BZH is bonded to the Pd surface by the carbonyl group rather than through the aromatic ring, thus reducing the energy barriers of the elemental reaction steps and increasing the overall reaction efficiency.

Composites comprising vanadium-pentoxide (V 2 O 5 ) and single-walled carbon nanotubes (SWCNTs) are promising components for emerging applications in optoelectronics, solar cells, chemical and electrochemical sensors, etc . We propose a novel, simple, and facile approach for SWCNT covering with V 2 O 5 by spin coating under ambient conditions. With the hydrolysis-polycondensation of the precursor (vanadyl triisopropoxide) directly on the surface of SWCNTs, the nm-thick layer of oxide is amorphous with a work function of 4.8 eV. The material recrystallizes after thermal treatment at 600 °C, achieving the work function of 5.8 eV. The key advantages of the method are that the obtained coating is uniform with a tunable thickness and does not require vacuuming or heating during processing. We demonstrate the groundbreaking results for two V 2 O 5 /SWCNT applications: transparent electrode and cathode for Li-ion batteries. As a transparent electrode, the composite shows stable sheet resistance of 160 Ω sq -1 at a 90% transmittance (550 nm) - the best performance reported for SWCNTs doped by metal oxides. As a cathode material, the obtained specific capacity (330 mA h g -1 ) is the highest among all the other V 2 O 5 /SWCNT cathodes reported so far. This approach opens new horizons for the creation of the next generation of metal oxide composites for various applications, including optoelectronics and electrochemistry., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Hydrogen evolution reaction (HER), as an effective method to produce green hydrogen, is greatly impeded by inefficient mass transfer, i.e., bubble adhesion on electrode, bubble dispersion in the vicinity of electrode, and poor dissolved H 2 diffusion, which results in blocked electrocatalytic area and large H 2 concentration overpotential. Here, we report a superaerophilic/superaerophobic (SAL/SAB) cooperative electrode to efficiently promote bubble transfer by asymmetric Laplace pressure and accelerate dissolved H 2 diffusion through reducing diffusion distance. Benefiting from the enhanced mass transfer, the overpotential for the SAL/SAB cooperative electrode at -10 mA cm -2 is only -19 mV, compared to -61 mV on the flat Pt electrode. By optimizing H 2 SO 4 concentration, the SAL/SAB cooperative electrode can achieve ultrahigh current density (-1867 mA cm -2 ) at an overpotential of -500 mV. We can envision that the SAL/SAB cooperative strategy is an effective method to improve HER efficiency and stimulate the understanding of various gas-involved processes.

The mixture of CO and H 2 , known as syngas, is a building block for many substantial chemicals and fuels. Electrochemical reduction of CO 2 and H 2 O to syngas would be a promising alternative approach for its synthesis due to negative carbon emission footprint when using renewable energy to power the reaction. Herein, we present temperature-controlled syngas production by electrochemical CO 2 and H 2 O reduction on a cobalt tetraphenylporphyrin/multiwalled carbon nanotube (CoTPP/MWCNT) composite in a flow cell in the temperature range of 20-50 °C. The experimental results show that for all the applied potentials the ratio of H 2 /CO increases with increasing temperature. Interestingly, at -0.6 V RHE and 40 °C, the H 2 /CO ratio reaches a value of 1.2 which is essential for the synthesis of oxo-alcohols. In addition, at -1.0 V RHE and 20 °C, the composite shows very high selectivity toward CO formation, reaching a Faradaic efficiency of ca. 98%. This high selectivity of CO formation is investigated by density functional theory modeling which underlines that the potential-induced oxidation states of the CoTPP catalyst play a vital role in the high selectivity of CO production. Furthermore, the stability of the formed intermediate species is evaluated in terms of the p K a value for further reactions. These experimental and theoretical findings would provide an alternative way for syngas production and help us to understand the mechanism of molecular catalysts in dynamic conditions., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Stretchable and flexible electronics has attracted broad attention over the last years. Nanocomposites based on elastomers and carbon nanotubes are a promising material for soft electronic applications. Despite the fact that single-walled carbon nanotube (SWCNT) based nanocomposites often demonstrate superior properties, the vast majority of the studies were devoted to those based on multiwalled carbon nanotubes (MWCNTs) mainly because of their higher availability and easier processing procedures. Moreover, high weight concentrations of MWCNTs are often required for high performance of the nanocomposites in electronic applications. Inspired by the recent drop in the SWCNT price, we have focused on fabrication of elastic nanocomposites with very low concentrations of SWCNTs to reduce the cost of nanocomposites further. In this work, we use a fast method of coagulation (antisolvent) precipitation to fabricate elastic composites based on thermoplastic polyurethane (TPU) and SWCNTs with a homogeneous distribution of SWCNTs in bulk TPU. Applicability of the approach is confirmed by extra low percolation threshold of 0.006 wt % and, as a consequence, by the state-of-the-art performance of fabricated elastic nanocomposites at very low SWCNT concentrations for strain sensing (gauge factor of 82 at 0.05 wt %) and EMI shielding (efficiency of 30 dB mm -1 at 0.01 wt %).