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

Abstract Direct seawater electrolysis presents a promising route for grid‐scale green hydrogen (H 2 ) production without reliance on scarce freshwater. However, it is severely hampered by high energy consumption (> 4.3–5.73 kWh m −3 H 2 ) and harmful chlorine corrosion. Herein, an energy‐saving and chlorine‐free H 2 production system by coupling seawater splitting and upcycling of polyethylene terephthalate (PET) waste into value‐added glycolic acid (GA) over a Pd─CuCo 2 O 4 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 H 2 . 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 CuCo 2 O 4 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 H 2 production and value‐added GA from vast marine resources and PET waste.