CdS/SiI2: A promising two-dimensional materials for photocatalytic water splitting

Hydrogen production using photocatalyst for water splitting is considered to be one of the most promising methods to solve the energy challenge. The feasibility of CdS/SiI2 heterostructure as a photocatalyst is systematically investigated in geometrical, electronic, optical and transport properties based on the density functional theory (DFT) calculations. The calculated results demonstrate different configurations of CdS/SiI2 heterostructure have a typical type-II direct bandgap with bandgap values ranging from 2.08 to 2.21 eV, which are closer to the ideal bandgap for water-splitting. Not only the band alignment of type-II heterostructures, but also the built-in electric field generated between the two monolayers can effectively drive carriers spatial separation, thus reducing the carrier recombination rate. At the same time, the light absorption of the heterostructures has been substantially enhanced. The biaxial strain can modulate the bandgap values and the band alignment to match different application requirements, and it can also modulate the light absorption intensity and range. At last, the calculated carrier mobility of the heterostructure is up to 103 cm2 V−1 s−1. Such ultrahigh carrier mobility implies a further reduction in the carrier recombination rate and an excellent performance in photocatalyst. To sum up, these calculated results all indicate that the CdS/SiI2 heterostructure with low carrier recombination and ideal bandgap is a particularly promising photocatalyst.