Exploiting Z-scheme charge carrier dynamics in MA2Z4 based van der Waals heterostructures for bias-assisted water splitting applications

Abstract

The MA 2 Z 4 (M = transition metal; A = Si, Ge; Z = N, P, As) monolayers, characterized by exceptional stability and tailorable electronic structures, offer a versatile platform for constructing high-efficiency van der Waals heterostructure photocatalysts. Here, we systematically investigate six MA 2 Z 4 -based heterostructures-specifically MoSi 2 P 4 /MoSi 2 As 4 , MoSi 2 P 4 /WSi 2 P 4 , WSi 2 P 4 /WSi 2 As 4 , CrSi 2 P 4 /CrSi 2 As 4 , CrSi 2 P 4 /WSi 2 P 4 and CrSi 2 P 4 /MoSi 2 P 4 -using first-principles calculations. All candidates exhibit intrinsic direct bandgaps and robust Type-II band alignments. The resultant interfacial built-in electric fields facilitate a Z-scheme migration pathway, which ensures the spatial separation of photogenerated carriers while preserving potent redox potentials essential for overall water splitting. Solar-tohydrogen efficiency (η STH ) estimations reveal that CrSi 2 P 4 /CrSi 2 As 4 achieves a remarkable peak value of 38.65%. However, Gibbs free energy analyses for the