High mobility and low exciton binding energy in monolayer Cd₂Cl₂ for efficient photocatalytic water splitting

We investigate the intrinsic properties of monolayer Cd₂Cl₂ using first-principles calculations. The material exhibits an exciton binding energy of 0.27 eV, which is significantly lower than that of many well-known 2D semiconductors. This low excitonic effect favors efficient charge separation. In addition, monolayer Cd₂Cl₂ shows high electron mobility (1.10 × 10⁵ cm² V^-1 s^-1) and strong near-ultraviolet absorption (4.64 × 10⁵ cm^-1), indicating excellent optoelectronic characteristics. These features suggest excellent optoelectronic performance and potential photocatalytic activity. Motivated by these findings, we further assess its photocatalytic water-splitting ability. The band edge positions meet water redox conditions, and Cl vacancies enable spontaneous hydrogen evolution. The solar-to-hydrogen efficiency reaches 18.35%, surpassing the commercial threshold. The electronic and structural stability of monolayer Cd₂Cl₂ in aqueous environments further supports its practical applicability. This work provides insights into the structure-property relationships in monolayer Cd₂Cl₂ and demonstrates its promise as a 2D photocatalyst for solar hydrogen production.