High Mobility and Low Exciton Binding Energy in Monolayer Cd2Cl2 for Efficient Photocatalytic Water Splitting

Abstract

Two-dimensional (2D) materials generally suffer from high exciton binding energies and low carrier mobilities, limiting their applications in optoelectronics and photocatalysis. In this study, we systematically investigate the properties of monolayer Cd 2 Cl 2 using first-principles calculations. The results reveal that this material exhibits a low exciton binding energy of 0.27 eV, which is highly favorable for efficient carrier charge separation. Notably, the electron mobility reaches up to 5.31×10 4 cm 2 V -1 s -1 , approximately six times higher than that of holes, demonstrating excellent carrier transport performance. Additionally, monolayer Cd 2 Cl 2 possesses an indirect bandgap of 2.46 eV and strong near-ultraviolet light absorption. These outstanding intrinsic properties make it a promising candidate for photocatalytic water splitting. Further theoretical calculations indicate that, in the presence of Cl vacancies, the HER reaction can proceed spontaneously, with a STH efficiency of 18.35%, significantly exceeding the practical application threshold. This work not only reveals the exceptional performance of monolayer Cd 2 Cl 2 in exciton binding energy and carrier mobility but also provides crucial theoretical guidance for designing efficient 2D photocatalysts, thereby advancing the development and application prospects of solar-driven clean energy technologies.