SiI2 monolayer as a promising photocatalyst for water splitting hydrogen production under the irradiation of solar light

Abstract

The feasibility of SiI2 monolayer as the candidate for photocatalytic water splitting for hydrogen generation under the irradiation of the solar light is explored. The geometrical structure, the electronic and optical properties, the mobility of carrier and strain engineering of the monolayer are investigated based on the first-principles calculations. The results demonstrate SiI2 monolayer possesses an indirect gap of 2.33 eV (HSE06), and both the band edge and the bandgap match the redox potential conditions of the water splitting for hydrogen generation. There is an obvious optical absorption in the visible light and near-ultraviolet region and can be enhanced by the compressive strain. Moreover, the mobility of the electron is significantly different from that of the hole, implicating that the effective spatial charge separation is expectable and the ratio of the recombination of the photogenerated charge pairs is low. The primary adsorption site of the water molecule is identified. The Gibbs free energy and the adsorption energies are calculated to demonstrate the H2 generation from the water molecule splitting on the monolayer. All the considered properties support that SiI2 monolayer can be achieved as a promising candidate for the photocatalytic water splitting for hydrogen production under the irradiation of the solar light.