Hydrogen evolution reaction (HER) performance of selenium‐rich multicomponent pentlandites was investigated using the Co 9 −x −y Fe x Ni y S 4 Se 4 series prepared as powders, as‐cast ingots, and induction‐hot‐pressed pellets. Structural, electrochemical, spectroscopic, and density functional theory analyses were combined to establish composition‐structure–activity relationships. Selenium extends the single‐phase range after synthesis but promotes partial phase separation during processing, particularly in Fe‐rich compositions. Although the effect of cationic composition on HER performance is comparatively weak within the investigated Se‐rich series, making the catalytic response increasingly dependent on electrode architecture and phase stability, the best HER performance across all material forms is consistently near the equimolar composition but shifted toward the Fe─Co‐rich region, whereas Ni‐rich compositions remain less active. Fe‐rich pellets show the highest activity ( η 20 = 200 mV) together with pronounced surface reconstruction and preferential iron dissolution, while compositions closer to the equimolar region exhibit higher overpotentials ( η 20 = 251–256 mV) with greater stability, revealing a composition‐dependent balance between activity and structural stability. Calculations indicate that selenium shifts the d‐band center toward the Fermi level and strengthens hydrogen adsorption, contributing to sluggish HER kinetics. Overall, selenium suppresses the beneficial activation characteristic of sulfur‐rich systems and fundamentally changes the factors governing HER performance, making it increasingly dependent on phase stability and electrode architecture.
To realize efficient CO 2 electroreduction, it is important to regulate “beyond catalyst” factors, including the diffusional contribution, which reflects local partial pressures of the CO 2 reactant and the key intermediate, CO, at the three‐dimensional porous electrode under industrially relevant conditions (e.g., at current density exceeding 200 mA cm −2 ). Structural parameters of the catalyst layers, such as porosity, thickness, and pore size, play a decisive role in determining selectivity and CO 2 conversion rates, as they directly control mass transport within the electrode. This study systematically investigates the impact of the mesostructure of Cu catalyst layers originating from CuO x precursor nanoparticles with flake‐, leaf‐, and sphere‐like morphologies, as well as their combinatorial assemblies. The maximum CO 2 conversion rate and CO 2 electroreduction selectivity varied greatly with catalyst particle morphology and mesoscopic catalyst‐layer properties, including void architectures and pathways for gaseous molecules. Even with Cu alone, variations in electrode mesostructure substantially modulate CO 2 mass transfer and local CO concentration, highlighting the critical role of mesoscale architecture in determining CO 2 reduction kinetics and selectivity. Based on these insights, we developed a tandem catalyst layer to improve ethylene productivity.
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.
