Switch effect on controlled water splitting by biaxial strain regulating the promising two-dimensional Janus X2PAs (X = Si, Ge and Sn) photocatalyst

Two-dimensional photocatalytic materials with unique properties have been well-reported in recent decades. However, strategies for controlling the photocatalytic process are still ongoing. Herein, Janus X2PAs (X = Si, Ge and Sn) monolayers have been explored by first-principles calculations to meet this challenge. All strain-free X2PAs monolayers exhibit excellent photocatalytic properties with high carrier mobility (2.39 × 102-1.34 × 104 cm2 V-1 s-1), suitable band edge positions straddling the standard redox potential of water and large visible light absorption coefficients (up to 105 cm-1). Most importantly, a reaction switch effect is proposed for the first time towards controlling the microscopic photocatalytic process of water splitting on X2PAs monolayers through macroscopic mechanical strain. This effect renders the Janus X2PAs photocatalytic switches among the states of only oxygen evolution reaction, only hydrogen evolution reaction and the full redox reaction for controlled water splitting. This work not only provides a new avenue for designing highly tunable photocatalysts but also offers new physical insights into controlling the photocatalytic water-splitting reaction.