Visible-light-driven Z-scheme protonated g-C3N4/wood flour biochar/BiVO4 photocatalyst with biochar as charge-transfer channel for enhanced RhB degradation and Cr(VI) reduction

Abstract

For the simultaneous photocatalytic reduction of hexavalent chromium (Cr(VI)) and the degradation of rhodamine B (RhB), directional charge-transfer channels and efficient separation of photogenerated holes and electrons are important. Herein, a Z-scheme heterojunction photocatalyst, protonated g-C3N4/BiVO4 decorated with wood flour biochar (pCN/WFB/BiVO4), was prepared through a hydrothermal reaction and electrostatic self-assembly for Cr(VI) photoreduction and RhB photodegradation. The morphological features, crystalline structure, chemical composition, optical properties, specific surface area, and photoelectrochemical properties of the prepared samples were investigated. The pCN/WFB/BiVO4 photocatalyst exhibited superior removal performance when used to remove Cr(VI) and RhB separately or RhB-Cr(VI) system. The biochar bridge served as a charge-transfer channel between two semiconductors, and the electrons in protonated g-C3N4 (pCN) and BiVO4 achieved a charge balance. This led to the formation of a Z-scheme heterojunction, fast photogenerated charge separation, and a powerful redox ability. The pCN/WFB/BiVO4 photocatalyst provides new insight into the mechanisms responsible for boosting multicomponent photocatalytic reactions, while constituting a promising candidate for wastewater treatment.