Dynamic Creation of a Local Acid-like Environment for Hydrogen Evolution Reaction in Natural Seawater

Electrolysis of natural seawater driven by renewable energy is practically attractive for green hydrogen production. However, because precipitation initiated by an increase in local pH near to the cathode deactivates catalysts or blocks electrolyzer channels, limited catalysts are capable of operating with untreated, natural seawater (<i>viz</i>., pH 8.2 to 8.3 and <i>ca</i>. 35 g salts L^-1); most are used in strongly alkaline or acidic seawater. Here, we report a new natural seawater electrolysis cathode with precipitation-suppression via a Pt/WO₂ catalyst to create a dynamically local acid-like environment. The <i>in situ</i> formed hydrogen tungsten bronze (H_<i>x</i>WO_<i>y</i>) phase via continuous hydrogen insertion from water acts as a proton reservoir. As a result, dynamically stored protons create a local acid-like environment near the Pt active sites. We evidence that this tailored acid-like environment boosts the hydrogen evolution reaction in natural seawater splitting and neutralizes generated OH^- species to restrict precipitation formations. Consequently, a long-term stability of >500 h at 100 mA cm^-2 was exhibited in direct seawater electrolysis.