First-principles study on the electronic structure and photocatalytic properties of novel two-dimensional Janus CrXCN4 (X = Si, Ge)

Abundant studies demonstrate the significant role of Janus-structured two dimensional semiconductors as photocatalytic materials, highlighting their substantial advantages and importance in photocatalysis. In this work, CrXCN4 (X = Si, Ge) Janus monolayers were constructed based on CrC2N4, and the thermal stability, thermodynamic stability, mechanical stability, electronic properties, and optical properties of the monolayers were systematically investigated. Furthermore, an investigation was conducted to examine the impact of biaxial strain on their electronic and light absorption properties. The findings reveal that both monolayers exhibit direct band gap characteristics, with high absorption coefficients for visible light owing to their appropriate band gaps (1.44 eV for CrSiCN4 and 1.15 eV for CrGeCN4, respectively). At compressive strains exceeding 3%, the CrSiCN4 monolayer demonstrates an optimal band edge position, suggesting its potential as a photocatalyst for overall water splitting. Furthermore, as the compressive strain increases, the absorption spectra have blue-shifted and the absorption coefficient becomes higher, exceeding 2 x 10(5) cm(-1) under a -3% compressive strain. Our study highlights the potential applications of CrXCN4 monolayers in the field of optoelectronic device, particularly emphasizing the promising candidacy of CrSiCN4 as an efficient photocatalyst.