Hydrogen Generation from Direct Z-Scheme for Photocatalytic Overall Water Splitting with the Sise/Snse2 and Sise/Snsse Heterostructures

Abstract

The direct Z-schemes of the photocatalytic overall water splitting with the SiSe/SnSe2, SiSe/SnSSe-I, and SiSe/SnSSe-II heterostructures are constructed according to the electronic properties and carrier transfer from the density functional theory calculations and the nonadiabatic molecular dynamics (NAMD) simulations. The maximum solar-to-hydrogen efficiency (ηʹSTHs) reaches 19.18% and can be enhanced up to 28.71% under tensile biaxial strains. The NAMD simulations indicate the transfer of the electron for hydrogen evolution reaction (HER) and hole for oxidation evolution reaction (OER) for SiSe/SnSe2 are apparently slower than those for other processes, implicating the reduction and oxidation activities of this heterostructure is well-protected. Moreover, the shortest electron-hole recombination time is attributed to SiSe/SnSSe-I, indicating it holds superior photocatalytic performance. Remarkably, the Gibbs free energies (ΔG) apparently indicate that both HER and OER with SiSe/SnSSe-I can spontaneously proceed, while the OER with the other two heterostructures can proceed but cannot drive HER spontaneously. Therefore, the newfound heterostructures, especially the SiSe/SnSSe-I, are promising candidates in photocatalytic overall water splitting.

Keywords: solar-to-hydrogen, direct Z-scheme, Hydrogen evolution reaction, photocatalytic, Gibbs free energy, nonadiabatic molecular dynamics simulation