Ab initio calculation of the effect of phosphorus substitution on MgAl2S4 monolayer for electrocatalytic and water-splitting applications

Abstract

Identifying efficient catalysts for photoelectrochemical water splitting is crucial to reducing our reliance on fossil fuels. Strategies such as doping are commonly employed to enhance catalytic activity. In this work, we investigate the effect of substituting one aluminum atom with a phosphorus atom in a single-layer MgAl${}_2$S${}_4$ structure. We also analyze the active sites for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) using density functional theory (DFT). Our results reveal that the Pourbaix diagram indicates the P@MgAl${}_2$S${}_4$ structure is stable in acidic media for HER and in alkaline media for OER. Moreover, the presence of the phosphorus atom significantly enhances both reactions by modifying the local electronic structure. This substitution not only improves catalytic performance but also yields an optimal band gap and band alignment suitable for water splitting. Overall, our findings suggest that phosphorus-doped MgAl${}_2$S${}_4$ is a promising candidate for photoelectrochemical water splitting applications.