Role of intrinsic dipole on photocatalytic water splitting for Janus MoSSe/nitrides heterostructure: A first-principles study

Abstract

Searching for visible-infrared solar utilization for photocatalytic water splitting is highly desirable, since most of solar energy is distributed the visible-infrared region. However, it is difficult for a pure system to satisfy both band gap and band edge conditions for water splitting in visible-infrared region. Herein, heterostructure consisting of Janus MoSSe and nitrides XN (X = Al, Ga) is proposed, and the structural and electronic properties are systematically studied by the first-principles calculations. It shows that the AA-stacking heterostructure is more stable than other stacking. The calculated electronic property shows that MoSSe/AlN heterostructures have indirect band gaps in the range of 1.00 eV–1.68 eV, while MoSSe/GaN heterostructures are always direct semiconductors with band gaps of 0.8 eV–1.51 eV. Interestingly, despite the band gaps of MoSSe/XN heterostructures being smaller than 1.23 eV, the band edge positions are always suitable for water splitting, suggesting good activity of these heterostructures in visible-infrared region. This special behavior mainly originates from the intrinsic dipole with the electrons of VBM and CBM distributed on two opposite layers, producing an electrostatic potential difference between the layers. This electrostatic potential difference, acting as an auxiliary booster for photoinduced carriers, can effectively reduce the band gap required for water splitting in visible-infrared region. In addition, the band edge position can be further adjusted by strains, leading to higher reactivity for water splitting. Our findings strongly suggest that this novel Janus MoSSe/XN heterostructure can offer exciting opportunities for designing visible-infrared photocatalysis for water splitting.