Two-dimensional ferroelectric heterostructures for overall water-splitting from DFT aspects

Currently, the construction of direct Z-type heterojunctions is an effective way to improve the overall water splitting catalytic efficiency of existing two-dimensional(2D) materials, which can simultaneously combine spatial separation of active sites and enhanced redox ability. In particular, when the internal structure of heterojunction was polarized, the polarization can effectively tune electronic properties and remove band gap (1.23 eV) limitation on water splitting. So far, the effect of polarization on water-splitting reactivity in heterojunctions based on the 2D layered polarized In2Y3 (Y = S, Se) and the nonpolarized 2D beta-Sb monolayer is unclear. Therefore, we constructed a series of such heterojunctions and made theoretical predictions of overall water splitting performance by first-principles calculations. The predictions shown that As/In2Se3(up), Sb/In2Se3(-down) and Sb/In2S3(down) are potential photocatalysts with direct Z-scheme band positions, and hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) will occur on different surfaces of system. It is found that the intrinsic polarization electric field of In2Y3 (Y = S, Se) monolayer effectively enhances photo-generated carrier driving force of reaction. Notably, the promising photocatalysts have a high solar-hydrogen (STH) efficiency of 17.71 %, which has potential commercial applications. Also, Bi/In2S3up (S) and As/ In2Te3up (As) exhibit desirable electrocatalytic HER performance. These insights provide an important strategy for application of ferroelectric heterojunctions in water splitting.