The electrochemical reduction of nitrate to hydroxyl amine or ammonia is a prominent means to effectively valorize agricultural effluent emissions. We demonstrate that bimetallic electrodes, composed of Ag nanoparticles deposited on Ti metal, exhibit a pronounced synergy in nitrate reduction in acidic electrolyte. This is evidenced by in‐situ electrochemical mass spectrometry (EC‐MS), showing NO evolution in a complex potential‐dependent profile at lower onset potentials compared to single metal Ag or Ti electrodes. Furthermore, liquid phase analysis shows a significant Faradaic efficiency to hydroxylamine for Ag/Ti electrodes, even at potentials above 0 VRHE, i.e., requiring at least a 200–300 mV lower overpotential than necessary for the single metal electrodes. We discuss favorable NO and hydroxylamine formation to be occurring on highly effective Ag/Ti interfaces. This work highlights the importance of interfaces and suggests that optimization of (Ag/Ti) bimetallic electrodes appears to be a valuable means to develop high performance electrodes for the reduction of nitrate in acidic conditions.
Atomic layer deposition (ALD) has emerged as a powerful fabrication strategy for the design of advanced electrocatalysts for water electrolysis. Owing to its sequential self‐limiting surface reactions, ALD enables atomic‐scale control over film thickness, composition, morphology, and interface structure, while simultaneously providing highly conformal coatings on complex and porous substrates. These characteristics make ALD particularly attractive for engineering electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), where catalyst utilization, stability, and interface properties critically influence electrochemical performance. Beyond catalyst synthesis, ALD has also emerged as a powerful platform for disentangling structure‐activity‐stability relationships in electrocatalysis. This review discusses recent advances in ALD‐enabled electrocatalyst fabrication for water electrolysis, with emphasis on noble‐metal and earth‐abundant catalyst systems, including transition‐metal oxides, sulfides, and phosphides. Attention is given to the role of ALD in controlling catalyst dispersion, stabilizing active phases, tuning oxidation states, and engineering catalyst–support interactions. In addition, recent developments in interface engineering, ultrathin overlayers, and phase‐controlled oxide systems are highlighted. Finally, current limitations associated with scalability, throughput, and processing cost are discussed together with future perspectives involving spatial ALD (SALD), plasma‐enhanced ALD (PEALD), and operando characterization approaches for next‐generation water electrolysis technologies.
This work aims to advance the research on microwave (MW)‐assisted hydrometallurgical recycling of Li(Ni/Mn/Co)O2 (NMC) cathode materials, with a special focus on leaching and mixed oxalate precipitation. Traditional (hot plate and magnetic stirring) setup and MW‐assisted one have been systematically compared across different organic‐based leaching recipes. Pristine NMC532 MW‐assisted leaching achieves near quantitative recovery (>99%) for Ni, Mn, Co while reducing the reaction times by up to 75%. Characterization of the obtained oxalates reveals that, while the leaching media do not affect the composition, mechanical stirring plays a major role during the precipitation, ensuring uniform growth and morphology. Consequently, the hybrid setup (MW‐assisted leaching and “standard” precipitation) has been chosen for the best‐performing recipe scale up, followed by cathode recovery and electrochemical testing. Quantitative green chemistry metrics further confirm the process efficiency, demonstrating a 40%–60% reduction in specific energy consumption and 35% reduction in process mass intensity via direct solid‐oxalate addition. The resynthesized cathodes demonstrate electrochemical performance comparable with the pristine commercial benchmark, demonstrating the feasibility of the proposed recycling routes. Finally, the procedure was successfully validated on real NMC622 spent battery black mass, confirming the efficiency and transferability of the proposed method as a sustainable hydrometallurgical recycling route.
Lithium metal battery behavior is strongly influenced by the electrolyte environment from which the solid–electrolyte interphase develops, yet the effects of combining anions in dilute multi‐salt formulations remain incompletely understood. Combinations of LiFSI, LiTFSI, and LiNO3 in DME, at a total Li+ concentration of 1 mol kg−1, were investigated using complementary spectroscopy, electrochemistry, and microscopy. Raman and 1H/7Li NMR spectroscopy reveal composition‐dependent changes in imide‐anion association, DME coordination‐sensitive spectral features, and the average Li+ environment. These changes are accompanied by interfacial impedance responses and lithium deposit morphologies. Most notably, all nitrate‐containing formulations show improved preservation of a lithium reservoir formed on Cu, sustaining 80–86 reversible cycles with average Coulombic efficiencies close to 99%, while displaying limited impedance evolution and more continuous deposits. Within this nitrate‐containing series, FSI and TFSI produce distinct spectroscopic and interfacial responses, even though a ranking in reservoir reversibility cannot be established. TFSI is shifted predominantly toward noncontact environments upon nitrate addition, whereas FSI retains a substantial contribution from contact‐associated configurations. The combined results demonstrate that multi‐salt electrolytes cannot be described as simple superpositions of their single‐salt components and support a working interpretation in which the anion composition modulates the prereduction Li+ solvation ensemble and subsequent interfacial evolution.
Iridium oxide (IrO 2 ) is the benchmark catalyst for the acidic oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE), but its cost and scarcity require improved Ir utilization. Herein, Nb 2 O 5 @IrO 2 core–shell catalysts were developed using ball‐milled Nb 2 O 5 supports with uniform IrO 2 shell formation. Ball‐milling at 300 rpm for 8 h produced a rounded and relatively uniform Nb 2 O 5 morphology with a high defect‐related oxygen contribution, providing favorable support characteristics for homogeneous IrO 2 deposition. Electron microscopy and elemental mapping supported an approximately 3 nm IrO 2 shell on the Nb 2 O 5 core. Among catalysts prepared from supports milled for different durations, BM‐8h‐Nb 2 O 5 @IrO 2 exhibited the best OER performance in 0.1 M HClO 4 , with an overpotential of 307 mV at 10 mA cm −2 and an IrO 2 mass activity of 304.17 A g IrO2 −1 , outperforming unsupported IrO 2 . Although the 18 h ball‐milled catalyst exhibited the largest electrochemically active surface area, its lower OER activity indicates that optimized support morphology and defect structure, rather than surface area alone, govern IrO 2 utilization. These results demonstrate that ball‐milled Nb 2 O 5 support provides an effective platform for Ir‐efficient acidic OER catalysts relevant to PEMWE anodes.
