ChemElectroChem最新文献

Pure-phase titanate pyrochlores, BIi₂Ti₂O₇ (BTO) and Y₂Ti₂O₇ (YTO), are synthesized via an optimized sol–gel method that effectively suppresses secondary phase formation and produces uniform nanoparticle morphologies. Comprehensive structural and interfacial characterizations reveal that YTO exhibits stronger TiO covalent bonding and a lower density of oxygen vacancies compared to BTO, despite both adopting the same A₂B₂O₇ pyrochlore framework. Electrochemical evaluations in alkaline media demonstrate that this enhanced covalency in YTO promotes improved charge–transfer kinetics and stabilizes key oxygenated intermediates, resulting in superior bifunctional electrocatalytic activity. Notably, YTO achieves a low oxygen evolution reaction overpotential of 350 mV at 10 mA cm⁻² and delivers durable round-trip performance in rechargeable zinc–air flow batteries, surpassing the conventional Pt/C + RuO₂ benchmark. These results underscore that Ti-centered active sites and strong interfacial covalent networks—rather than oxygen-vacancy density alone—play a decisive role in governing oxygen electrocatalysis. Given their structural tunability, cost-effectiveness, and excellent interfacial stability, titanate pyrochlores represent promising alternatives to noble-metal-based catalysts for next-generation metal–air batteries and other surface-sensitive energy applications.

Lithium-ion batteriesface growing limitations for large-scale energy storage due to high cost, resource constraints, and safety concerns. In response, aqueous battery systems have emerged as compelling alternatives, offering intrinsic safety, low cost, and environmental sustainability. Among them, manganese-based aqueous batteries are particularly attractive, owing to manganese's earth abundance, low redox potential (−1.19 V vs. SHE), and high theoretical capacity. Nevertheless, the development of Mn-ion batteries is hindered by the large hydrated ionic radius and high desolvation energy of Mn²⁺, which severely restrict ion insertion kinetics and structural reversibility. This review critically examines recent advances in the design of electrode materials and electrolytes for aqueous Mn-based batteries. Emphasis is placed on interfacial challenges at Mn metal anodes, strategies to suppress side reactions, and criteria for enabling reversible Mn²⁺ storage. A broad range of cathode materials—including vanadium oxides, vanadium bronzes, Fe-based compounds, and organic frameworks—are evaluated with respect to their crystallographic architectures, ion diffusion pathways, and redox mechanisms. Through systematic comparison of structure–property–performance relationships, this review highlights current limitations and outlines promising directions for the development of high-energy, long-cycle-life aqueous Mn-ion batteries.

Electrodeposited Mo-rich NiMo catalysts offer enhanced catalytic activity for the alkaline hydrogen evolution reaction (HER) and provide an electrically conductive, binder-free substrate connection, making them promising catalysts for green hydrogen production. However, creating Mo-rich deposits is challenging, as the codeposition process typically favors Ni. Optimal deposition conditions for Mo-rich NiMo catalysts remain insufficiently explored. This article investigates Mo-rich NiMo electrodeposition from an ammonia-free citrate bath using NaSO₄ as a chlorine-free support electrolyte. The effects of the deposition parameters, 1) sodium molybdate concentration in the electrolyte, 2) deposition current density, and 3) enhanced mass transport via working electrode rotation on the alkaline HER activity, were studied. The electrodeposits, containing 44–66 wt% Mo, exhibited increased surface area due to a rough, cracked morphology and variable oxygen content of the catalyst. The oxygen content was linked to HER activity, revealing an inhibiting effect. The lowest overpotential of 118 mV at −10  mA cm⁻² for the alkaline HER was achieved using an electrolyte with 0.02 mol L⁻¹ sodium molybdate, a deposition current density of 600 mA cm⁻², without electrode rotation. Respective samples combined a favorable Ni:Mo ratio comprising 56 wt% Mo content with increased surface area and low oxygen content.

The electrochemical ammonia oxidation reaction (AOR) shows considerable potential for its applications in waste removal and the production of clean energy. While Pt remains the most investigated catalyst for this reaction, its limitations have prompted research into Pt-based bimetallic alloys. This study investigates both uniform and mixed PtM (M = Au, Ir, Pd, Rh, and Ru) alloys as catalysts for the AOR using density functional theory (DFT). A systematic selection method is used to choose suitable surfaces for testing. The findings indicate that the Oswin–Salomon mechanism is preferred across all surfaces for N₂ (g) formation. Additionally, the results demonstrate that mixed alloys exhibit superior catalytic activity compared to uniform alloys for the AOR. It is found that the atoms in the topmost layer of the alloy are the most significant factor in influencing catalytic activity. Furthermore, the linear relationship between the $$-band center and adsorption energy of key intermediate *NH₂ is confirmed in this work, highlighting the effect of the secondary metal on the electronic structure of the catalyst. The findings provide theoretical insights for the design of high-performance Pt alloys for AOR and serve as a general guideline for modulating the reactivity of binary alloys for electrocatalysis.

A common approach to test electrocatalyst nanoparticles (NPs) for electrolyzers and fuel cells is to deposit catalyst particles (e.g., Pt/carbon) onto standard disk electrodes (e.g., glassy carbon) by making use of inks based on binders (ionomers such as Nafion). In recent years, physical and chemical vapor deposition have garnered interest to deposit catalyst films or particles on electrode surfaces, to circumvent the complications associated with the use of inks. Samples prepared this way might be incompatible with standard equipment, e.g., rotating disk electrodes (RDEs) to assess the effect of mass transport on the electrode performance. Herein, a custom-built adapter is presented to test samples prepared by physical deposition methods in a RDE setup. Using an outer-sphere redox probe (K₄Fe(CN)₆), it is demonstrated that the custom-built adapter provides mass transport conditions comparable to those obtained with a standard disk electrode in a classic RDE setup. Theadapter is used to investigate the hydrogen evolution reaction (HER) activity of model Pt electrodes, that is, sputter-deposited Pt thin films and thermally “dewetted” Pt NPs, in acid electrolytes. Under both hydrostatic and hydrodynamic conditions, the Pt NPs show significantly higher HER kinetics compared to Pt thin films. The results indicate that the enhanced HER activity observed for dewetted Pt NPs is intrinsic and of a kinetic nature, likely linked to catalyst/support interactions, and is not a consequence of mass transport effects.

Iron–nitrogen–carbon materials are still the most promising alternative to platinum group materials for the electrochemical reduction of O₂. Doping with a secondary metal center is a possible way to further enhance the activity, and Sn seems to be a valuable choice. Here, SnFe–N–C materials featuring both Fe and Sn single-site atoms were prepared from Sn precursors to study the effect on physical-chemical and electrochemical properties. Sn could act as a structural promoter for iron, regulate charge distribution, and favor the formation of more chemically stable sites. Here, we show that oxygen-containing ligands favor the fixation of Sn and Sn/Fe alloy, while others do not. Interestingly, the presence of nitrogen is not fundamental in the Sn precursor. Indeed, SnCl₂ is a valuable precursor. At the same time, (NH₄)₂SnCl₆ is a valid and cheaper alternative to Sn(phen)Cl₂ to fix a higher amount of Fe-N_x single-site. Even if the amount of Sn remains low in all samples (as a single site), all the bimetallic catalysts outperform the sole iron one (the best catalysts show a 3-fold increment). In addition, in situ electrochemical XAS confirms the redox behavior of Fe, while Sn does not show any oxidation or coordination changes under operating conditions.

Membranes are essential for an efficient and stable long-term operation of the vanadium redox flow battery (VRFB). Membrane degradation is one of the main limiting factors for VRFB lifetime because of the resulting increase in electrolyte crossover and self-discharge. Understanding membrane degradation is crucial for the lifetime extension of VRFBs. Most studies concerning membrane degradation are based on artificial ageing. In contrast to that, this study examines membrane samples from commercial stacks and compares them to pristine and artificially aged membranes. Performance tests are conducted to determine the membrane resistivity, ion-exchange capacity, and vanadium permeability. The influence of ageing on characteristic cell parameters, like coulombic and voltaic efficiency, is determined in battery cell tests. Furthermore, the membrane materials are compared by light microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. In summary, this study reveals that artificial ageing and real-world ageing lead to similar changes in the physical properties of the membranes. However, it is shown that membranes in large-scale battery systems age inhomogeneously while artificial ageing leads to more evenly degraded membranes.

Polyoxometalates (POMs) are redox-active metal–oxide clusters with well-defined electron transfer properties that make them promising candidates for electrocatalysis and energy conversion. Examples include dinitrogen reduction to ammonia, carbon dioxide reduction to carbon monoxide and cathodic oxygenation of alkanes with dioxygen. While the intrinsic redox behavior of POMs has been extensively studied, the role of interfacial interactions at electrode surfaces remains poorly understood. Herein, the electron transfer kinetics of Keggin-type POMs is investigated, using rotating disk electrode voltammetry to systematically decouple mass transport from interfacial kinetics. Both the redox thermodynamics and kinetics are demonstrated that are sensitive to structural variables, including the identity of the heteroatom (X = Al³⁺, Si⁴⁺, P⁵⁺) and the nature of the addenda metal (Mo vs. W) in plenary compounds, and the substitution with first-row transition metals (Cu²⁺, Ni²⁺, Fe³⁺). Cu-substituted analogs exhibit quasireversible, multielectron behavior marked by electrodeposition at more negative potentials and higher charge transfer coefficients (α), while Fe and Ni substitutions preserve diffusion-limited kinetics. Using rotating disk electrode–linear sweep voltammetry analysis, this study provides a mechanistic basis for the rational tuning of POM and enables clear differentiation between competing interfacial processes.

Dimethyl sulfoxide is a suitable solvent for reversible oxygen reduction in the presence of Ca²⁺, but not sufficiently stable towards the anode. Solvents suitable as anolytes tend to underperform in the context of oxygen reduction. Thus, a combined approach using different electrolytes at the cathode and anode promises superior performance. However, due to the electroosmotic drag, a cross-contamination of both electrolytes is expected. In this work, the influence of solvent mixtures of dimehtyl sulfoxide as an excellent electrolyte is investigated for the cathode with tetraglymeor tetrahydrofuran for oxygen reduction in the presence of Ca²⁺ at gold and glassy carbon electrodes using the rotating ring disc electrode assembly and oxygen solubilities and diffusivities are determined. While a high share of tetraglyme and tetrahydrofuran leads to a quick deactivation of the electrodes products, intermediate shares (1:1 mixture by volume), are beneficial for the oxygen reduction. This is due to the increased solubility of oxygen in those solvent. Even more interesting is the fact that the re-oxidizability of soluble peroxide species is eased by the addition of the ethers. While the reasons for this behavior remain elusive, the beneficial effect of other solvents is an encouraging starting point for a dual electrolyte Ca²⁺-battery.

La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) perovskites, in the form of in–house electrospun nanofibers and commercial powders, have been tested through synchrotron x–ray diffraction and electrochemical impedance spectroscopy in the 800–1200 K range. The former analyses make it possible to evaluate the oxygen vacancies (OV) concentration, and the latter allows to assess the electrokinetics of the oxygen reduction/evolution reaction. Equivalent circuit modeling is carried out to identify the basic electrochemical processes and evaluate the associated polarization resistance R_p. One high-frequency process and two intermediate-frequency processes are recognized. For all electrochemical processes, OV concentration and R_p behave similarly with temperature in both nanofiber and granular electrodes. This led to the proposal of a new equation. For each electrochemical process, it was shown that the activation energy is the sum of an intrinsic electrochemical activation energy, plus the formation energy of OVs. For the LSCF perovskites tested in this work, the intrinsic electrochemical activation energy was found to be independent of the preparation procedure and crystal structure. In contrast, the OV formation energy was found to be strongly dependent on the preparation procedure and crystal structure, with values ranging between 0.5 and 24.1 kJ mol⁻¹. A complete set of data is provided, which can be useful for future simulation studies.