Energy‐Saving Hydrogen Production by Seawater Splitting Coupled with PET Plastic Upcycling

Direct seawater electrolysis presents a promising route for grid‐scale green hydrogen (H2) production without reliance on scarce freshwater. However, it is severely hampered by high energy consumption (> 4.3–5.73 kWh m−3 H2) and harmful chlorine corrosion. Herein, an energy‐saving and chlorine‐free H2 production system by coupling seawater splitting and upcycling of polyethylene terephthalate (PET) waste into value‐added glycolic acid (GA) over a Pd─CuCo2O4 catalyst is reported. An ultra‐low potential of 1.15 V versus RHE is required to achieve an industry‐level current density of 600 mA cm−2, which reduces electricity cost to 2.45 kWh m−3 H2. Notably, this system maintains 1.6 A for longer than 100 h, demonstrating excellent stability. Experimental and theoretical results unveil that 1) the specific adsorption of PET‐derived ethylene glycol (EG) on Pd enhances the catalytic performance, and the downshifted d‐band center of Pd accelerates the desorption of GA to prevent over‐oxidation; 2) the strong adsorption of OH− on CuCo2O4 synergistically promotes EG electrooxidation (EGOR) and forms a negative charge layer that effectively repels Cl− by electrostatic repulsion, thus preventing chlorine corrosion. This work may provide new opportunities for H2 production and value‐added GA from vast marine resources and PET waste. Seawater electrolysis coupled with PET waste upcycling produces value‐added GA and H2 over a Pd─CuCo2O4 catalyst. The system achieves excellent stability at a high current of 1.6 A for longer than 100 h, together with a significant reduction in electricity costs (2.45 kWh m−3 H2) compared to an alkaline seawater electrolyzer (4.79 kWh m−3 H2).