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

The direct use of seawater/wastewater for H 2 production remains a challenge because impurities in the water compromise electrolyzer stability. Here, we propose a two‐step approach that uses seawater/wastewater for H 2 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 H 2 at the Zn/vapor interface, achieving up to 99.8% H 2 production efficiency. The physical isolation ensures automatic separation of ZnO, salts, and H 2 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 H 2 and 0.92 g seasalt. LCA confirms this combined electrolysis–hydrolysis approach has fewer carbon emissions and environmental footprints. Beyond H 2 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.