Surfactant-Mediated Synthesis of Nickel Oxide Catalysts Combined with Semi-Interpenetrating Network-Type PEMs for Water Electrolyzers

The high cost and inadequacy of platinum-group metals (PGMs) in proton exchange membrane water electrolysis (PEMWE) necessitate the development of earth-abundant HER catalysts persistant in highly acidic environments. Here, we report a surfactant-assisted synthesis of Ni-based oxide (NCT) catalysts using cetyltrimethylammonium bromide (CTAB), followed by controlled calcination to tailor crystallinity, defect chemistry, and electronic structure. Systematic thermal treatment induces a structural evolution from Ni(OH)2 to phase-pure cubic NiO, accompanied by oxygen vacancy modulation and partial Ni valence redistribution. Among all samples, NCT-700 exhibits the most optimized surface and electronic features, enabling efficient reconstruction into Ni-rich active states under HER bias. In 0.5 M H2SO4, NCT-700 delivers an overpotential of 58 mV at 50 mA cm−2 and 150 mV at 100 mA cm−2, with a Tafel slope of 175 mV dec−1, indicating favorable HER kinetics. The membrane used for MEA preparation, In-CEM, shows 4.9 × 10−2 S cm−1 proton conductivity and 1.10 meq g−1 proton exchange capacity. When both the In-CEM and NCT-700 catalyst are integrated in a PEMWE single cell, it achieves 539 mA cm−2 at 1.80 V and maintains excellent operational stability for 80 h at 500 mA cm−2 (80 °C). The results demonstrate that the combination of stable PEM, rational precursor design and thermally guided reconstruction pathways can enable PGM-free catalysts with competitive activity and robustness for acidic water electrolysis and therefore offers an economically compelling alternative to commercial PEM and Pt/C cathodes.