Cation-inhibitor and metal–support synergy for efficient and durable hydrogen evolution in natural seawater

Direct seawater electrolysis holds promise for sustainable green hydrogen production, yet its scalability is hindered by cathode fouling from Mg(OH)2 and Ca(OH)2 precipitates and high energy barriers for the hydrogen evolution reaction. Herein, we present a hybrid electrocatalyst, RuNiMo/MO/MN, integrating Ru single atoms with a NiMo, MoO2, and Mo2N heterostructure (NiMo/MoO2/Mo2N) to address these challenges through strong metal–support interactions and a cation-inhibitor strategy. Self-released NH4+ ions sequester local OH− to suppress precipitate formation, preserving active site accessibility, while Ru single atoms facilitate the injection of electrons to MoO2, optimizing H adsorption and reducing the energy barrier for H2 evolution. RuNiMo/MO/MN cathode achieves a low overpotential of 259.2 mV at 10 mA cm−2 and a high Faradaic efficiency of 99.5 %, with 2,000-h durability at 100 mA cm−2 in natural seawater, surpassing commercial Pt/C. Furthermore, RuNiMo/MO/MN | |RuO2 membrane electrode assembly sustains operation at 200 mA cm−2 for over 250 h, with a hydrogen production cost of $1.36 per kg, below the US Department of Energy target of $2 per kg. Direct seawater electrolysis is promising for green hydrogen production, but is limited by cathode fouling. Here, the authors report an integrated strategy combining strong metal–support interactions with a cation inhibitor to create a local acidic environment, enabling hydrogen evolution in natural seawater.