Understanding the effect of interface on the charge separation in Bi2S3@Sn: α-Fe2O3 heterojunction for photoelectrochemical water oxidation

The heterojunction based on α-Fe2O3 has been widely explored for enhancing the charge separation efficiency towards photoelectrochemical (PEC) water oxidation, but the serious carrier recombination still impends its solar-to-hydrogen efficiency. Herein, the Bi2S3@α-Fe2O3 is designed and implemented to perform the PEC water oxidation with a modulated interface by Sn doping in α-Fe2O3. Initially, the photocurrent of Bi2S3@α-Fe2O3 is 3.40 mA/cm2 at 1.23 VRHE. After interface regulated, the photocurrent of Bi2S3@(Sn)α-Fe2O3 is up to 4.0 mA/cm2, which is 6.7 times higher than the primary α-Fe2O3. The photocurrent enhancement can be attributed to the broadening light-harvesting, enhanced charge separation efficiency, and abundant oxygen vacancies. The electrochemical impedance measurements reveal that the PEC performance of heterojunction would still be boosted by Sn doping even the energy gaps between the conduction bands, valence bands of two semiconductors are slightly reduced. This work provides an alternative understanding of the effect of interface on the PEC water splitting in the heterojunction.