Enhanced interfacial charge transfer on Bi metal@defective Bi2Sn2O7 quantum dots towards improved full-spectrum photocatalysis: A combined experimental and theoretical investigation

To mitigate the water pollution problem by photocatalytic degradation of typical antibiotics of tetracycline (TC), we prepared defective Bi2Sn2O7 (BSO) quantum dots (QDs) with a full spectral response due to Bi metal deposition, using a one-pot hydrothermal method, labeled as Bi@BSO-OV. The optimized Bi@BSO-OV showed 73.4% removal of TC in 1 h under irradiation with a 50 W LED lamp in the wavelength band in the visible-near-infrared (Vis-NIR) light, a rate that is substantially greater than that of pure BSO (14.7%). The synergistic interaction of Bi metal and oxygen vacancies (OVs) is crucial to boosting photocatalytic performance. The near-infrared region of the photo-response is extended by the surface plasmon resonance (SPR) effect of Bi metal, enhancing the photocatalytic performance and dramatically raising the efficiency of solar energy utilization. In addition to inducing defect levels in BSO, the OVs also activate the surface adsorbed O2 to promote the production of •O2− and 1O2. DFT calculations reveal that Bi metal and OVs can mutually tune the charge transfer pathways. On the one hand, Bi metal can act as both a charge transfer bridge and an electron donor to assist charge separation. On the other hand, OVs-induced defect levels allow electrons that leap to the conduction band (CB) to first leap from the valence band (VB) to the defect levels, notably improving interfacial charge separation and transfer. The concept of design executed in this study for altering the catalyst by introducing both OVs and Bi metal can provide a rational design idea and potential insight for improving the photocatalytic activity for environmental applications.