Highly efficient photocatalytic water splitting and enhanced piezoelectric properties of 2D Janus group-III chalcogenides†

Recently, Janus two-dimensional (2D) materials have received considerable interest due to their intrinsic vertical dipole, and hence they have great potential in photocatalytic and piezoelectric applications. Here, a new series of Janus 2D structures MM ' XX ' (M, M ' = Ga, In; X, X ' = S, Se, Te) are investigated by means of first-principles calculations. It is found that 2D Janus MM ' XX ' exhibit high dynamical stability and have band gaps in the range of 0.89-2.03 eV. Most outstandingly, these MM ' XX ' monolayers exhibit appropriate band edge positions, strong light absorption (1 x 10(4) cm(-1)) in the visible light region, high energy conversion efficiencies (up to 18.51%), effective spatial separation and fast transfer of carriers (at least 10(3) cm(2) V-1 s(-1)), which make them promising candidates for photocatalytic water splitting (except InGaSTe which has a small band gap of 0.89 eV). What is more, the in-plane piezoelectric coefficients of these MM ' XX ' monolayers (2.62-6.21 pm V-1) are comparable to those of the common bulk materials such as alpha-quartz (2.3 pm V-1), wurtzite GaN (3.1 pm V-1) and AlN (5.1 pm V-1), and the out-of-plane piezoelectric coefficients (0.28-0.41 pm V-1) are higher than those of the Janus MXY (M = Mo, W; X, Y = S, Se, Te) monolayers (0.007-0.030 pm V-1). Our findings reveal the potential applications of these monolayers as efficient photocatalysts and piezoelectric materials.

Automated summary

This study investigates a new series of Janus 2D structures MM'XX' and finds that they exhibit high dynamical stability, suitable band gaps, strong light absorption in the visible light region, and high energy conversion efficiencies, making them promising candidates for photocatalytic water splitting. Additionally, the in-plane piezoelectric coefficients of these monolayers are comparable to common bulk materials, while the out-of-plane piezoelectric coefficients are higher than those of other Janus monolayers.