Continuous modulation of H* adsorption induced by N-gradient doping to enhance photocatalytic H2 generation

The adsorption strength between the hydrogen intermediate (H*) and the active site has a crucial influence on the interfacial H2-evolution rate. Although numerous studies have reported on optimizing this adsorption strength, achieving continuous regulation to attain near-equilibrium adsorption/desorption kinetics remains a considerable challenge. Herein, we deliberately designed a gradient nitrogen-doped carbon layer (NxC)-supported rhenium disulfide (ReS2) nanosheet, denoted as ReS2@NxC, to facilitate the continuous optimization of H* adsorption strength for enhancing overall H2-evolution activity. Systematic characterization and theoretical simulations demonstrate that the gradient N-doped NxC support can regulate the discharge extent of the ReS2 component by creating a tunable polarization field between ReS2 and NxC. This process further optimizes the adsorption state of H* and achieves near-equilibrium H* adsorption/desorption dynamics over ReS2. Additionally, the well-designed ReS2@NxC cocatalysts provide an efficient pathway for the rapid transfer of photoelectrons from CdS, as examined by in-situ Kelvin probe force microscopy and transient absorption spectroscopy. Consequently, the H2-generation activity of the optimal ReS2@N2.1C/CdS photocatalyst was significantly increased to 17.3 mmol g-1h-1 with an apparent quantum efficiency as high as 38.7 %. The microstructural design strategy and mechanistic insights presented in this work are expected to inform the rational design of high-performance photocatalysts.