High solar-to-hydrogen efficiency photocatalytic hydrogen evolution reaction with the HfSe2/InSe heterostructure

We identify two configurations of the HfSe2/InSe van der Waals heterostructure that can drive photocatalytic overall water splitting reactions with high solar-to-hydrogen (STH) efficiency after investigating four different configurations (represented by HI, HIx, HIy, and HyI) for the heterostructure. The electronic properties, optical absorption, and mobility are calculated by using the obtained structures. The projected band edges and the interfacial built-in electric fields for the two monolayers demonstrate that the two configurations are type-II heterostructures that can match the conditions for photocatalytic hydrogen generation from water splitting, while the other two configurations have no satisfactory band edge for the overall water splitting. The corrected STH efficiency (η′STH) is calculated based on the obtained overpotentials and bandgaps, which give 25.24% and 25.07% for the two configurations, respectively. The effects of strain engineering on η′STH are also investigated but turn out to be not significant. In addition, the Gibbs free energy changes (ΔGs) are calculated to confirm the thermodynamic feasibilities of the hydrogen/oxygen evolution reactions. The obtained ΔGs in the redox reaction for the two configurations indicate that the hydrogen/oxygen evolution reactions are feasible from the view of thermodynamics. Apparently, the HfSe2/InSe heterostructure is a potential candidate for developing high STH efficiency photocatalysts.