Optimizing Electronic Density at Active W Sites for Boosting Photocatalytic H2 Evolution

It is highly desirable but challenging to optimize the electronic structure of an active site to realize moderate active site-H_ads bond energies for boosting photocatalytic H₂ evolution. Herein, an interfacial engineering strategy is developed to simultaneously concentrate hydrogen species and accelerate the combination of an H_ads intermediate to generate free H₂ by constructing W-WC-W₂C (WCC) cocatalysts. Systematic investigations reveal that hybridizing with W₂C creates electron-rich W active sites and effectively induces the downshift of the d-band center of W in WC. Consequently, the strong W-H_ads bonds on the surface of WC are weakened, thus promoting the desorption of H_ads to rapidly produce free H₂. The optimized 40-WCC/CdS photocatalyst exhibits a high hydrogen evolution rate of 63.6 mmol g^-1 h^-1 under visible light (≥420 nm) with an apparent quantum efficiency of 39.5% at 425 nm monochromatic light, which is about 40-fold of the pristine CdS. This work offers insights into the design of cocatalyst for high-efficiency photocatalytic H₂ production.