Coupling Ru-MoS2 Heterostructure with Silicon for Efficient Photoelectrocatalytic Water Splitting

Abstract Photoelectrochemical water splitting for hydrogen evolution reaction (PEC-HER) is always challenged by the low charge-separation efficiency and catalytic hydrogen evolution activity. Herein, we designed a Ru-MoS2 heterostructured catalyst on a titanium (Ti) protecting p-type silicon (n+p-Si) to address these obstacles. The n+p-Si/Ti/Ru-MoS2 delivers the largest reported photocurrent density for the Si-based photocathode (−43 mA cm−2 at 0 V versus a reversible hydrogen electrode (VRHE)). A considerably high half-cell solar-to-hydrogen conversion efficiency (HC-STH) of 7.28% is achieved at 0.2 VRHE. The excellent performance of n+p-Si/Ti/Ru-MoS2 is benefited from the electronic properties of Ru-MoS2 that dramatically decrease charge transfer resistance, and enhance the built-in electric field at the photoelectrode/electrolyte interface for the charge separation. Significantly, the density functional theory (DFT) calculation further reveals that the engineered electronic structure of the Ru-MoS2 contributes to the improvements in catalytic HER efficiency by optimizing electron transportation and Gibbs free energy of hydrogen adsorption (ΔGH*) on hetero-interface sites.