0D ultrafine ruthenium quantum dot decorated 3D porous graphitic carbon nitride with efficient charge separation and appropriate hydrogen adsorption capacity for superior photocatalytic hydrogen evolution

Designing a Pt-alternative cocatalyst capable of dissociating HO-H bonds is of great significance yet challenging for the development of high-efficiency and cost-effective water splitting photocatalytic systems. In this study, we designed and constructed a 0D ultrafine ruthenium (U-Ru) quantum dot decorated 3D porous g-C3N4 (3DpCN) nanohybrid (U-Ru/3DpCN) for photocatalytic hydrogen evolution, in which the U-Ru quantum dots act as cocatalysts accelerating the surface proton reduction reaction, and the 3D porous architecture assembled by 2D ultrathin nanosheets inherits a short charge diffusion distance and has a large specific surface area. Owing to these structural and physicochemical merits, the optimal photocatalyst U-1Ru/3DpCN achieves a superior hydrogen evolution performance of 2945.47 mu mol g(-1) h(-1) under visible light with a high apparent quantum efficiency (AQE) of 9.5% at 420 nm, which is close to Pt-cocatalyst/3DpCN and better than most reported co-catalysts/g-C3N4 photocatalytic systems. Experimental results indicate that the formed Schottky junction between U-Ru and 3DpCN contributes to efficient charge separation, and DFT calculations show that the Ru-cocatalyst/g-C3N4 system has an appropriate hydrogen adsorption Gibbs free energy (Delta G(H*)) of 0.24 eV, which are both responsible to improve the photocatalytic performance. This study provides a new way to develop excellent photocatalysts for hydrogen evolution by the integration of cost-effective Ru quantum dot cocatalysts with nanostructured semiconductors.