Photothermal Effect of Cu NCs on CdS Homojunction Boosting Hydrogen Evolution in Alkaline Seawater

Abstract Developing photocatalysts with desired activity and stability toward hydrogen evolution reaction (HER) in alkaline seawater is of prime significance but still pressingly challenging. Herein, cuprum nanoclusters (CuNCs) are anchored on the surface of cadmium sulphide homojunctions (CdS‐H) with unsaturated edge sulphur (S) by an in situ photoreduction technique, which promotes the stability and hydrogen evolution of photocatalyst in the process of alkaline seawater hydrogen (H₂) evolution (15.5 mmol g⁻¹ h⁻¹) with an apparent quantum yield of 11.0% at 450.0 nm. It is comprehensively confirmed that the unsaturated edge S not only effectively anchored Cu NCs but also promoted the adsorption of chloride ion (Cl⁻) ions, which suppressed the oxidation of lattice S and modulated the stability of the photocatalyst in alkaline seawater. The photothermal effect induced by the anchored Cu NCs accelerated the reaction kinetics, and the directional migration of the photocarrier at the metal‐semiconductor interface is demonstrated via the in situ method. This work affords a new perspective to rational design photocatalysts with high stability and superior performance in alkaline seawater.