Electrodeposited Ni–S cathodes on stainless steel nonwovens for PGM-free anion exchange membrane water electrolysis at high current density

Developing cost-effective and scalable cathodes is critical for industrial anion exchange membrane water electrolysis (AEM-WE). This work proposes that Ni-S catalyst layers, electrodeposited directly onto stainless steel nonwovens, enable simultaneous catalyst synthesis and integration into a three-dimensional porous transport layer. Without using platinum group metals (PGMs), the tested membrane-electrode assemblies (MEAs) achieved current densities of 2.5 A cm −2 at 2.0 V in 1 M KOH at 60 °C, demonstrating competitive performance under industry-relevant conditions. Characterization indicated an amorphous Ni-S coating with homogeneous sulfur distribution throughout the porous substrate. Electrochemical impedance spectroscopy revealed a lower apparent charge-transfer resistance than Pt/C on identical substrates, indicating improved interfacial coupling. During operation, partial sulfur leaching was accompanied by formation of nickel-enriched (oxy)hydroxide species. Extended operation at 1 A cm −2 showed that the strongest voltage increase occurs during the initial MEA restructuring period, whereas later operation intervals exhibit apparent voltage increase rates below 1 mV h −1 . Impedance measurements and anode-exchange experiments further indicated that the observed voltage increase represents a full-MEA response rather than direct evidence of irreversible cathode degradation. Our results demonstrate that electrodeposited Ni-S cathodes on stainless steel nonwovens provide a scalable, PGM-free approach for high-current AEM-WE, combining manufacturability, performance, and durability.