Modulation of Fermi level gap and internal electric field over Cs3Bi2Br9@VO-In2O3 S-scheme heterojunction for boosted charge separation and CO2 photoconversion

Abstract

Modulating the internal electric field (IEF) represents a potential strategy to stimulate the photocatalytic activity of heterojunctions, especially S-scheme photocatalysts. Herein, a Cs3Bi2Br9@VO-In2O3 (CBB@VO-In2O3) S-scheme heterojunction, of which Cs3Bi2Br9 perovskite quantum dots (PQDs) are embedded into mesoporous VO-In2O3 hosts, is rationally designed as a cornerstone for further IEF manipulation. Briefly, by introducing oxygen vacancies (VO) into the composed reduction semiconductor (mesoporous In2O3), an enlarged Fermi level (EF) gap between CBB and VO-In2O3 is achieved, yielding an intensified IEF over the CBB@VO-In2O3 heterojunction. Such an enhanced IEF affords a much more robust driving force for directional carrier delivery, leading to accelerated carrier transfer of CBB@VO-In2O3 heterojunction. Consequently, the optimized CBB@VO-In2O3 heterojunction features desirable CO2-to-CO conversion efficiency, and its CO production rate reaches 130.96 μmol g−1 h−1. The reaction intermediates and CO2 photoconversion pathway were unraveled by in-situ diffuse reflectance infrared Fourier transform spectroscopy. Combining with the DFT calculation, it was revealed that oxygen vacancies in VO-In2O3 act as reactive centers, which optimize the coordination modes of the intermediates, thus reducing the activation energy for photocatalytic CO2 reduction. Our work demonstrates that the IEF modulation of S-scheme-based heterojunction could significantly boost the charge separation and then to drive efficient catalytic reaction, achieving high-efficiency solar fuel production.