Computational studies on functionalized Janus MXenes MM′CT₂, (M, M′ = Zr, Ti, Hf, M ≠ M′; T = –O, –F, –OH): photoelectronic properties and potential photocatalytic activities

Abstract

Motivated by the successful synthesis of Janus monolayers of transition metal dichalcogenides (<i>i.e.</i>, MoSSe), we computationally investigated the structural, electronic, optical, and transport properties of functionalized Janus MXenes, namely MM'CT₂ (M, M' = Zr, Ti, Hf, M ≠ M', T = -O, -F, -OH). The results of the calculations demonstrate that five stable O-terminated Janus MXenes (ZrTiCO₂-I, ZrHfCO₂-I, ZrHfCO₂-III, HfTiCO₂-I, and HfTiCO₂-III), exhibit modest bandgaps of 1.37-1.94 eV, visible-light absorption (except for ZrHfCO₂-I), high carrier mobility, and promising oxidization capability of photoinduced holes. Additionally, their indirect-gap, spatially separated electron-hole pairs, and the dramatic difference between the mobilities of electrons and holes could significantly limit the recombination of photoinduced electron-hole pairs. Our results indicate that the functionalized Janus MXene monolayers are ideal and promising materials for application in visible light-driven photocatalysis.