An asymmetric photothermal platform for coupled seawater splitting and desalination

Abstract

Photocatalytic seawater splitting provides a sustainable route to green hydrogen, but faces barriers of inefficiency and scalability. Graphitic carbon nitride (g-C3N4, CN) offers saline tolerance, yet its catalytic potential requires atomic-level control of structure and charge dynamics. Herein, we design three single-atom Co configurations on CN, including symmetric Co–N4, vacancy-anchored Co–N3, and asymmetric Co–N4. The asymmetric Co–N4 in hierarchically porous carbon nitride (CoSA-hCN) introduces second-shell carbon vacancies that reshape electronic asymmetry and charge dynamics, establishing a robust pathway for effective salinity-mediated charge transfer and in situ Pt photodeposition for H2 evolution. On a scalable 60 cm2 floating photothermal platform under 1 sun, H2 production (47.7 mmol m−2 h−1) and interfacial seawater evaporation (1.88 kg m−2 h−1) are achieved directly from natural seawater. In this work, we offer design principles for a single-atom catalyst on scalable photothermal platform for coupled seawater splitting and desalination.