Janus XMoAZ2 (X = S, Se, Te; A = Si, Ge; Z = N, P, As) monolayers: First-principles insight into electronic structures, optical and photocatalytic properties

With regards to the asymmetry in its structure, two-dimensional Janus materials exhibit distinctive properties when compared to symmetric structures, which endows them with vast potential for application. In this work, we conducted theoretical investigations on the electronic structure, optical and photocatalytic properties of Janus XMoAZ2 (X = S, Se, Te; A = Si, Ge; Z = N, P, As) materials using first principle calculations. The results indicate that the internal electric field effect of Janus XMoAZ2 (X = S, Se, Te; A = Si, Ge; Z = N, P, As) structure leads to a reduction in the likelihood of recombination of photo-generated electron-hole pair. Furthermore, Janus XMoAZ2 (X = S, Se, Te; A = Si, Ge; Z = N, P, As) demonstrate a favorable band gap and possess band edge position that align with the water oxidation reduction potential, thereby encompassing the relevant band gap region. This property bestows them with significant potential as highly efficient photocatalysts for water splitting. Notably, in both acidic (pH = 0) and neutral (pH = 7) environments, Janus XMoAZ2 (X = S, Se, Te; A = Si, Ge; Z = N, P, As) materials holds significant potential as exceptional photocatalysts for water cracking reactions. Moreover, by using biaxial strain, the band gap of the structure can be finely tuned by applying biaxial strain, allowing for further adjustment of their photocatalytic and light absorption capabilities. These findings not only provide valuable experimental guidelines for the application of Janus XMoAZ2 (X = S, Se, Te; A = Si, Ge; Z = N, P, As) in water decomposition, but also contribute to the enriching the MA2Z4 family.