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Abstract Seawater electrolysis using renewable electricity offers an attractive route to sustainable hydrogen production, but the sluggish electrode kinetics and poor durability are two major challenges. We report a molybdenum nitride (Mo2N) catalyst for the hydrogen evolution reaction with activity comparable to commercial platinum on carbon (Pt/C) catalyst in natural seawater. The catalyst operates more than 1000 hours of continuous testing at 100 mA cm−2 without degradation, whereas massive precipitate (mainly magnesium hydroxide) forms on the Pt/C counterpart after 36 hours of operation at 10 mA cm−2. Our investigation reveals that ammonium groups generate in situ at the catalyst surface, which not only improve the connectivity of hydrogen-bond networks but also suppress the local pH increase, enabling the enhanced performances. Moreover, a zero-gap membrane flow electrolyser assembled by this catalyst exhibits a current density of 1 A cm−2 at 1.87 V and 60 oC in simulated seawater and runs steadily over 900 hours.

Developing durable catalysts for carbon dioxide reduction to formate at commercial-scale current densities is challenging. This work reports that indium sulfide stabilized through zinc incorporation can produce formate efficiently and quickly at high current densities over long timescales.