Elucidating Carrier Dynamics and Interface Engineering in Sb₂S₃: Toward Efficient Photoanode for Water Oxidation

Conjugation of low-cost and high-performance semiconductors is essential in solar-driven photoelectrochemical (PEC) energy conversion. Sb₂S₃ is a wide-bandgap (≈1.7 eV) semiconductor with the potential to deliver a maximum photocurrent density of 24.5 mA cm⁻², making it highly attractive for PEC water splitting applications. However, bulk Sb₂S₃ exhibits intrinsic recombination issues and low electron–hole separation, posing a limit to photocurrent generation. This study clarifies the carrier dynamics by ultrafast spectroscopy measurements and proposes the design of a heterojunction between Sb₂S₃ and SnO₂, with suitable band-edge energy offset. The SnO₂/Sb₂S₃ heterojunction enhances the charge separation efficiency, resulting in improvement of the photocurrent. The SnO₂/Sb₂S₃ photoanode, fabricated entirely by vapor deposition processes, demonstrates photoelectrochemical water oxidation with a photocurrent density up to ≈3 mA cm⁻² at 1.38 V versus RHE.