A Value‐Added Solar‐Mediated Rechargeable Battery Integrating Efficient Photoelectrochemical Energy Storage with Sunlight‐Boosted Self‐Powered H ₂ O ₂ Production from Natural Seawater

Developing sustainable functional batteries capable of generating valuable chemicals during electricity storage/release represents challenging frontiers. Here, we present a new battery chemistry that enables the first value-added solar-mediated rechargeable seawater battery integrating photoelectrochemical energy storage with sunlight-boosted self-powered H₂O₂ production from seawater without external power/O₂ supply. This system is enabled by rationally-designed bifunctional S-scheme heterojunction photocathodes (MP-COP@TiO₂) comprising A3-(D-core) polymer (MP-COP) encapsulated TiO₂. A3-(D-core) topology induces favorable electronic modulation that optimizes oxygen specie adsorption and steering oxygen reduction reaction (ORR) toward one-step 2e^- pathway-while facilitating electronic coupling with oxygen evolution reaction (OER)-active TiO₂ to establish S-scheme charge transfer mechanism alongside strengthened built-in electric field. These endow MP-COP@TiO₂ with sunlight-boosted 4e^- OER for in situ O₂-generation during photo-charge and 2e^- ORR for on-site H₂O₂ synthesis during photo-discharge, establishing solar-mediated self-sustaining value-added reaction cycles. Integrating MP-COP@TiO₂ with sodium anodes and seawater creates previously-unexplored functional battery, yielding remarkable H₂O₂ yield of 5.47 mmol g^-1 h^-1 during photo-discharge-9.4 times those in dark and exceeding most reported seawater systems while delivering near-zero charge/discharge voltage gap under illumination. Mechanistic studies reveal promoting effect of A3-(D-core) modulation and its synergistic role with S-scheme charge transfer that promotes Yeager-type O₂ adsorption and facilitates one-step 2e^- ORR toward H₂O₂.