Graphene Quantum Dots as Electron Acceptor Tailoring S-Scheme Heterojunction Bi(2)MoO(6)@Cu(2)O for Highly Efficient Photocatalytic H(2) Evolution.

Hydrogen (H) energy is a clean, renewable energy carrier with a high energy density and zero carbon emissions. Photocatalytic water splitting offers a promising route to H production by utilizing abundant solar energy; yet, it is often limited by sluggish charge carrier kinetics and low quantum efficiency. Herein, we incorporate graphene quantum dots (GQDs) as cocatalysts into the S-scheme heterojunction inorganic semiconductor BiMoO@CuO (BMO@CuO) to boost photocatalytic H evolution. Under simulated sunlight, the GQDs/BMO@CuO composite achieves an exceptional H production rate of 16.1 mmol·g·h and an apparent quantum yield of 33.6% at 420 nm. The built-in electric field (IEF) between BMO and CuO promotes S-scheme charge transfer, enhancing carrier separation. GQDs function as electron acceptors and active sites, where their delocalized π-electron cloud in the sp-hybridized carbon skeleton shortens charge migration paths and lowers the energy barrier for surface H evolution. In situ X-ray photoelectron spectroscopy, Kelvin probe force microscopy, and density functional theory calculations collectively confirm the IEF and S-scheme electron transfer. This work presents a strategic design of GQDs-mediated heterojunctions with efficient charge separation and strong redox capacity, advancing solar-driven H production technology.