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

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.