Photoelectric/Photothermal Synergy Activation in Floating Aerogel Cathode Breaks Neutral Triphase Reaction Barriers for High‐Efficiency Full‐Spectrum‐Responsive Seawater Batteries

Abstract Harnessing natural resources (solar, seawater) to explore next‐generation sustainable energy storage is an intriguing yet challenging task. Here, we establish a unique floating photoelectric/photothermal dual‐activated catalytic platform based on engineered Janus aerogel that overcomes inherent mass transport/kinetics constraints in neutral triphase oxygen reaction systems to enable a full‐spectrum‐responsive seawater battery with ultrahigh energy efficiency. Our approach employs in situ region‐selective assembly of the rationally designed fluorinated donor–acceptor polymers on carbon‐nanotube aerogel (FMTAPPC), creating a new floatable FMTAPPC photoelectrode with asymmetric wettability, superior photoelectric/photothermal dual‐response, and bifunctional oxygen evolution/reduction (OER/ORR) catalysis. This all‐in‐one integration enables floating FMTAPPC to maximize sunlight utilization for interface micro‐environment regulation and adsorbate binding optimization via photoelectric/photothermal dual‐activation while satisfying paradoxical wetting requirements of OER/ORR, which tunes reaction kinetics and intermediate energetics to remarkably promote both OER/ORR in neutral media. Under sunlight, floating FMTAPPC delivers large current densities for both OER/ORR–3–4 fold‐enhancement over dark conditions. This enables the seawater‐based Zn–air battery to simultaneously improve charge/discharge performance at high rates and deliver ultrahigh round‐trip efficiency of 128.2%—surpassing most photo‐assisted batteries. Mechanistic studies unveil that photoelectric/photothermal effects synergistically boost OER/ORR kinetics, while the photoelectric effect dominates intermediate energetics optimization, substantially lowering reaction energy barriers.