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.