Hydrogen peroxide (H 2 O 2 ) is a powerful industrial oxidant and potential carbon-neutral liquid energy carrier. Sunlight-driven synthesis of H 2 O 2 from the most earth-abundant O 2 and seawater is highly desirable. However, the solar-to-chemical efficiency of H 2 O 2 synthesis in particulate photocatalysis systems is low. Here, we present a cooperative sunlight-driven photothermal-photocatalytic system based on cobalt single-atom supported on sulfur doped graphitic carbon nitride/reduced graphene oxide heterostructure (Co-CN@G) to boost H 2 O 2 photosynthesis from natural seawater. By virtue of the photothermal effect and synergy between Co single atoms and the heterostructure, Co-CN@G enables a solar-to-chemical efficiency of more than 0.7% under simulated sunlight irradiation. Theoretical calculations verify that the single atoms combined with heterostructure significantly promote the charge separation, facilitate O 2 absorption and reduce the energy barriers for O 2 reduction and water oxidation, eventually boosting H 2 O 2 photoproduction. The single-atom photothermal-photocatalytic materials may provide possibility of large-scale H 2 O 2 production from inexhaustible seawater in a sustainable way.