Enhanced interfacial charge transfer on Bi metal@defective Bi_(2)Sn_(2)O_(7) 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 Bi_(2)Sn_(2)O_7(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@BSOOV 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 O_(2) to promote the production of·O_(2)^(-)and ^(1)O_(2).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.

A short review on recent progress of Bi/semiconductor photocatalysts:The role of Bi metal

Bi/semiconductor photocatalysts have extensively been applied in the production of hydrogen,CO_(2) reduction and environmental remediation in recent years.This short review summarizes the role of Bi metal as a plasma photocatalyst and cocatalyst.As a cocatalyst,Bi metal can be electron/hole trappers,charge transfer mediators,or oxygen vacancy coordinators.In addition,the preparation methods of the Bi/semiconductor photocatalysts are also reviewed.Challenges and future research directions related to Bi/semiconductor photocatalysts are discussed and summarized,including the use of advanced characterization techniques to refine the reaction mechanism,the difficulties of preparing Bi single atom catalyst,and the improvement of the reduction ability of Bi-based photocatalysts.This review helps understand the reaction mechanisms of the composite photocatalytic systems containing Bi metal and proposes new perspectives for designing the photocatalysts which can control air pollution via a reductive process.

Enhancement of solar-driven photocatalytic activity of oxygen vacancy-rich Bi/BiOBr/Sr_(2)LaF_(7)∶Yb^(3+),Er^(3+)composites through synergetic strategy of upconversion function and plasmonic effect

For better use of solar energy,the development of efficient broadband photocatalyst has attracted extraordinary attention.In this study,a ternary composite consisting of Sr_(2)LaF_(7)∶Yb^(3+),Er^(3+)upconversion(UC)nanocrystals and Bi nanoparticles loaded BiOBr nanosheets with oxygen vacancies(OVs,SLFBB)was designed and synthesized by multi-step solvent-thermal method.Mechanisms of in-situ formation of Bi nanoparticles and OVs in BiOBr/Sr_(2)LaF_(7)∶Yb^(3+),Er^(3+)composites(SFLB)are clarified.The Bi metal and OVs enhanced the light-harvesting capacity in the region of visible-near-infrared(Vis-NIR),and promoted the separation of electron-hole(e-/h+)pairs.Furthermore,the surface plasmon resonance(SPR)effect of Bi metal can improve the energy transfer from Sr_(2)LaF_(7)∶Yb^(3+),Er^(3+)to BiOBr via nonradiative energy transfer process,resulting in enhancing the light utilization from up-converting NIR into Vis light.Due to the synergistic effects of UC function,SPR and OVs,the SFLBB exhibited obviously enhanced photocatalytic ability for the degradation of BPA with a rate of 8.9×10^(-3) min^(-1),which is about 2.78 times higher than 3.2×10^(-3) min^(-1) of BiOBr(BOB)under UV-Vis-NIR light irradiation.This work provides a novel strategy for the project of high-efficiency Bismuth-based broadband photocatalysts,which is helpful to fur-ther understand the mechanism of enhanced photocatalysis by UC function and plasmonic effect.

In situ construction of oxygen-vacancy-rich Bi^(0)@Bi_(2)WO_(6)-x microspheres with enhanced visible light photocatalytic for NO removal

Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facile ethylene glycol-assisted solvothermal method.Bi0 nanoparticles were reduced by in situ thermaltreatment on Bi_(2)WO_(6)microspheres to obtain Bi^(0)@Bi_(2)WO_(6)-x as well as maintaining the oxygen vacancies(OVs)under N_(2)atmosphere.Afterwards,photocatalytic NO oxidation removal activities of these photocatalysts were investigated under visible light irradiation and Bi^(0)@Bi_(2)WO_(6)-x shows the best NO removal activity than other samples.The photogenerated cha rge separation and trans fe r are promoted by Bi0 nanoparticles deposited on the surface of semiconductor catalysts.OVs defects promote the activation of reactants(H_(2)O and O_(2)),thereby enhancing the formation of the active substance.Moreover,both OVs defects and Bi0 metal have the characteristics of extending light absorption and enhancing the efficient utilization of solar energy.Besides,the photocatalytic NO oxidation mechanism of Bi^(0)@Bi_(2)WO_(6)-xwas investigated by in situ FTIR spectroscopy for reaction intermediates and final products.This work furnishes insight into the synthesis strategy and the underlying photocatalytic mecha nism of the surfacemodified Bi^(0)@Bi_(2)WO_(6)-x composite for pollutants removal.