Regulating effect of biaxial strain on electronic, optical and photocatalytic properties in promising X2PAs (X = Si, Ge and Sn) monolayers

TL;DR

This study explores how biaxial strain can tune the electronic, optical, and photocatalytic properties of Janus X2PAs monolayers (X=Si, Ge, Sn), enabling their use as adaptable, piezo-photocatalysts for water splitting.

Contribution

It demonstrates that biaxial strain can effectively modulate the band edges and photocatalytic activity of X2PAs monolayers, offering a new approach for designing tunable piezo-photocatalysts.

Findings

All X2PAs monolayers exhibit suitable band edges for water splitting.

Intrinsic electric fields promote separation of photogenerated carriers.

Biaxial strain can tune band edges and switch between OER and HER.

Abstract

Photocatalytic water splitting is an effective way to obtain renewable clean energy. The challenge is to design tunable photocatalyst to meet the needs in different environments. At the same time, the oxygen and hydrogen evolution reactions (OER and HER) on the photocatalyst should be separated, which will be conducive to the separation of products. The electronic, optical and photocatalytic properties of Janus X2PAs (X = Si, Ge and Sn) monolayers are explored by first-principles calculation. All the strain-free X2PAs monolayers exhibit excellent photocatalytic properties with suitable band edge positions straddling the standard redox potential of water and large visible light absorption coefficients (up to 105 cm-1). Interestingly, the intrinsic internal electric field is favorable for separating photogenerated carriers to different surfaces of the monolayer. It contributes to realize the OER and HER separated on different sides of the monolayer. In particular, the energy band edge positions of X2PAs monolayers can be well adjusted by biaxial strain. Then it can effectively modulate photocatalytic reactions, suggesting X2PAs monolayers can be a piezo-photocatalytic switch between the OER, HER and full-reaction of redox for water splitting. This investigation not only highlights that the photocatalyst X2PAs monolayers with the separated OER and HER can be effectively tuned by the mechanical strain, but also provides a new strategy for designing highly adaptable and tunable piezo-photocatalysts.