In-situ synthesis of facet-dependent BiVO4/Ag3PO4/PANI photocatalyst with enhanced visible-light-induced photocatalytic degradation performance: Synergism of interfacial coupling and hole-transfer

Considering that the crystal facet is highly correlated with the photocatalytic performance of the semiconductor, a novel BiVO4/Ag3PO4/PANI photocatalyst combined with facet engineering and heterojunction is prepared by depositing Ag3PO4 on the highly active (0 4 0) facet of BiVO4 and then incorporating polymer polyaniline (PANI). The synergistic modification of Ag3PO4 and PANI realizes excellent photocatalytic performance, with the degradation efficiency of 85.92% and the maximum rate constant of 0.00894 L mg(-1) min(-1), which is 10.1, 5.6 and 1.6 times than that of BiVO4, BiVO4/PANI and BiVO4/Ag3PO4, respectively. This enhanced photocatalytic performance is attributed to the following: (i) selective exposure of highly active BiVO4 (0 4 0) facet greatly improves the spatial separation efficiency of charge carriers; (ii) the (0 4 0) facet with preferentially exposed low-coordinated oxygen atoms provides sufficient binding sites for Ag+ anchoring, resulting in strong interfacial coupling between BiVO4 and Ag3PO4, which facilitates charge separation and transfer; (iii) the CB-electrons of Ag3PO4 can be timely consumed by the VB-holes of BiVO4 by the built-in electric field, thus preventing photo-corrosion of Ag3PO4; (iv) PANI acting as hole-transfer material can rapidly migrate holes accumulated in the VB of Ag3PO4 to the catalyst surface by its HOMO orbital, thereby achieving efficient charge separation; (v) the introduction of PANI results in a significant increase in visible light absorption efficiency. This work provides a novel design based on facet engineering and heterojunction, which can also be employed to other semiconductors to improve photocatalytic performance.