A Low‐carbon Space‐Isolated Zinc Hydrolysis for Harvesting Hydrogen and Salts from Seawater and Wastewater

The direct use of seawater/wastewater for H₂ production remains a challenge because impurities in the water compromise electrolyzer stability. Here, we propose a two-step approach that uses seawater/wastewater for H₂ generation, salt recovery, and pollutant degradation. First, Zn hydrolysis occurs at 250 °C in a space-isolated system, where vapor reacts with solid Zn to generate porous ZnO and H₂ at the Zn/vapor interface, achieving up to 99.8% H₂ production efficiency. The physical isolation ensures automatic separation of ZnO, salts, and H₂ while facilitating in situ hydrogenation that degrades 96.9% of organic phenol, demonstrating pollutant remediation. To close the materials-loop, the produced ZnO is electrochemically reduced back to Zn with a 99.3% Faradaic efficiency. We validate scalability using a 72 Ah Zn electrolyzer coupled with a 1000 mL reactor, achieving batch production of 2.32 g H₂ and 0.92 g seasalt. LCA confirms this combined electrolysis-hydrolysis approach has fewer carbon emissions and environmental footprints. Beyond H₂ production, this system leverages Zn as both an energy carrier to mitigate renewable energy intermittency and a versatile agent for salt recovery and wastewater treatment.