Consecutive Regulation of H* Adsorption Equilibrium via Selenium-Enriched Engineering for Boosted Photocatalytic Hydrogen Evolution

Balanced hydrogen intermediate (H*) adsorption–desorption dynamics over active sites are one of the most critical factors in achieving high photocatalytic H2-evolution activity; however, controllably and consecutively regulating H* adsorption capacity still remains challenging. In this case, a consecutive manipulation of H* adsorption strength on Rh active sites was achieved on the designed Rh@MoSe2+x heterococatalyst by introducing the MoSe2+x mediator with varying Se-enrichment degrees, and the corresponding correlation between microcomponent design and H* intermediate adsorption was disclosed. Experimental and theoretical results highlight that Se-enriched engineering of the MoSe2+x mediator can alter the charging extent of Rh to controllably regulate the antibonding-orbital occupancy of the Rh–H bond, thereby consecutively optimizing H binding strength and then realizing the balanced H adsorption/desorption for enhanced photocatalytic H2-evolution activity. Moreover, the Se-enriched Rh@MoSe2+x cocatalysts also provide an efficient channel to rapidly transfer the photoelectrons from ZnIn2S4, as revealed by in situ Kelvin probe force microscopy and transient absorption spectroscopy. Encouragingly, the obtained Rh@MoSe2.2/ZnIn2S4 photocatalyst delivers a remarkably boosted H2-evolution activity of 11.5 mmol g–1 h–1 with an apparent quantum efficiency as high as 31.3%. This work uncovers the intrinsic regulation mechanism of microcomponent design on intermediate adsorption and opens up a promising prospect for exploring advanced solar water-splitting systems.