High-efficiency solar water splitting and tunable excitons in the 2D RhTeCl monolayer

Photocatalytic water splitting is a pivotal pathway for sustainable hydrogen production, where 2D materials are highly promising due to their exceptional properties. Here, we systematically investigate the potential of monolayer RhTeCl for photocatalytic water splitting through first-principles calculations. Our results reveal that the monolayer exhibits remarkable stability, with a high predicted thermodynamic stability up to 1000 K. It possesses a direct bandgap of 2.26 eV, whose band edges align ideally with the redox potentials for water splitting. Notably, the monolayer demonstrates carrier mobilities ranging from 101.12 to 774.61 cm² V^-1 s^-1, and a superior predicted solar-to-hydrogen conversion efficiency of up to 12%, surpassing the current experimental records. Furthermore, we uncover intriguing tunable excitonic properties in this monolayer. Both external strain and electric fields can effectively modulate the exciton binding energy, with the electric field exerting a more pronounced influence. Importantly, under these external perturbations, the exciton binding energy (E_b) and the direct quasiparticle bandgap (EQPg) are found to approximately adhere to the empirical relationship E_b ≈ 0.25EQPg. These findings position 2D RhTeCl as a compelling and multifunctional platform for high-efficiency solar-driven water splitting and optoelectronic applications.