Enhancing visible-light driven photocatalytic performance of BiOBr by self-doping and in-situ deposition strategy: A synergistic effect between Bi5+ and metallic Bi

A novel composite photocatalyst of Bi/BiOBr-Bi5+ was successfully developed via a facile two-step procedure. The co-existence of self-doped Bi5+ and in-situ deposited Bi(M) was evidenced by X-ray diffraction, field emission transmission electron microscope and X-ray photoelectron spectra. Its photocatalytic performance on the Rhodamine B (RhB) degradation under visible light irradiation displayed a significant improvement compared with that of Bi/BiOBr or BiOBr-Bi5+, which was mainly attributed to the synergistic effect between Bi(M) and Bi5+. For Bi(M), enhancement of visible-light absorption capacity was beneficial from surface plasmon resonance (SPR) effect while the promoted separation of photoinduced charge carriers was attributed to the formation of oxygen vacancies (OVs) and Schottky-barrier. Besides, Bi(M) induced a predominant exposure of (010) facet, further enhancing photocatalytic performance. Differently, Bi5+ brought a narrowed bandgap of BiOBr in increasing the carrier density. A plausible mechanism towards RhB degradation was proposed based on analysis of electron transfer pathway and determination of dominant active species. The work offers new routes to enhance the photocatalytic performance of Bi-based materials without introducing any impurities.