Sputtered Ni and NiMo catalysts at low loadings for the alkaline hydrogen evolution reaction in AEM water electrolyzers

Low catalyst loading and process-integrated electrode fabrication are important for reducing material demand and manufacturing complexity in anion-exchange membrane water electrolysis (AEMWE). Here, Ni and NiMo hydrogen-evolution cathodes are fabricated by direct-current magnetron sputtering, enabling direct catalyst deposition onto the electrode substrate without separate catalyst-powder synthesis, ink formulation, or post-deposition thermal treatment. On planar substrates, decreasing sputter power and increasing Ar pressure shifts film growth toward a rougher, more open columnar morphology and increases the electrochemically accessible surface area. Transfer of the optimized process to porous carbon paper yields catalyst loadings of 0.03–0.13 mg/cm 2 for Ni and 0.04–0.21 mg/cm 2 for NiMo, with cross-sectional SEM-EDX showing preferential catalyst localization in the membrane-facing region of the substrate. The NiMo200 cathode, containing only 0.14 ± 0.02 mg NiMo /cm 2 , reaches 1 A/cm 2 at 1.95 V and 60 °C and 1.88 V at 80 °C in a fully PGM-free AEM electrolyzer with an uncoated stainless-steel anode. This corresponds to a cathode-mass-specific current density of 7.1 ± 1 A/mg NiMo . During 500 h operation at 1 A/cm 2 , the cell reaches 2.00 V and a late-stage degradation rate of 10 ± 7 μV/h. A Pt-cathode control with the same stainless-steel anode exhibits a similar degradation profile and late-stage rate, suggesting that NiMo-specific degradation is comparable to that of Pt and is largely masked by degradation contributions from other components of the assembly. The results demonstrate magnetron sputtering as a material-efficient, solvent- and ionomer-free route to low-loading AEMWE cathodes while highlighting electrode cross-contamination and long-term catalyst evolution as remaining challenges.