A ZnO-002/amorphous Bi2WO6 heterojunction with enhanced electron-hole separation for high-performance Cr(VI) photoreduction

Abstract

The difference in bandgap structure results in better charge separation performance of crystalline/amorphous heterojunctions compared to a single component. Considering that the catalytic activity of metal oxides is often accompanied by differences in facets, it has become an interesting topic to further improve the charge separation performance of such heterojunctions by adjusting the facets at the material contact interface. This article synthesized three novels ZnO/amorphous Bi2WO6 heterojunctions with specific facets (ZnO-101/aBi2WO6, ZnO-100/aBi2WO6 and ZnO-002/aBi2WO6) by adding ZnO with different facets to bismuth tungstate precursors through hydrothermal methods. Photoelectric testing shows that compared to a single component, all three heterojunctions display efficient carrier separation characteristics. Among them, the ZnO/aBi2WO6 heterojunction with the 002 facet exhibits more excellent performance, such as photocatalytic reduction of 150 mg·L−1 Cr(VI) without hole scavenger. The system spectral and energy spectrum characterization shows that the matched band structure induces a strong built-in electric field, which accelerates the separation of bulk carriers. And meanwhile, many oxygen vacancies, high specific surface area, low interface resistance and high concentration of carriers also provide help for the treatment of pollutants. In addition, 94.49 % of the photocatalytic activity was retained after 5 cycles, which proved the excellent photo cycling stability of the heterojunction.