MOFs-derived S-scheme ZnO/BiOBr heterojunction with rich oxygen vacancy for boosting photocatalytic CO2 reduction

Abstract

In this paper, a MOFs-derived S-scheme ZnO/BiOBr heterojunction photocatalyst was constructed by a one-step calcination method. It was found that the dodecahedral ZnO was well attached to the BiOBr hollow rods in ZnO/BiOBr composites, which could simultaneously introduce oxygen vacancies and enhance interfacial interactions. The photocatalytic CO2 reduction results exhibited that ZnO/BiOBr, without adding any sacrificial agent and photosensitiser, produced CO and CH4 at rates of 21.13 μmol·g−1·h−1 and 2.2 μmol·g−1·h−1 under simulated sunlight, with a CO selectivity of 74.34 %, which was 6.35 and 4.07 times higher than that of the original BiOBr as well as the original ZnO 4.14 and 1.98 times, respectively. The optimised ZnO/BiOBr has excellent photocatalytic CO2 reduction performance. The ZnO/BiOBr photocatalyst has excellent stability after 5 cycles. The unique heterostructures and matched energy band potentials between ZnO and BiOBr provided close interfacial contacts, a large number of active sites and effective charge transferred for photocatalytic CO2 reduction. Furthermore, the mechanism of photocatalytic CO2 reduction for S-scheme ZnO/BiOBr heterojunction was also proposed. Therefore, the MOFs-derived ZnO/BiOBr composites had the potential to be used as photocatalyst for CO2 reduction, providing a rational design idea for solar energy-driven CO2 conversion of MOFs-structured photocatalysts.