Design And Synthesis Of Bismuth-based Photoanode And Its Photocatalytic Performance

Human society is developing rapidly in economics,humanities,and science and technology,but the ensuing energy shortages and environmental pollution have become major obstacles to the development of human civilization.In order to solve these problems,people have developed a technology that can store and use solar energy to obtain clean energy and manage the environment-semiconductor photocatalysis technology.Among many semiconductor photocatalysts,Bi-based semiconductors have attracted people's attention due to their low cost,suitable band gap and nonpolluting characteristics.Therefore,this thesis takes the concept of sustainable development as the core and conducts research on photocatalysis with Bi-based semiconductors as the core:(1)Construct a chemical bond to bond a heterogeneous structure to suppress the recombination rate of photogenerated carriers.Using zinc oxide quantum dots(ZnO QDs)doped in a bismuth vanadate(BiVO₄)precursor solution and annealed and calcined,the BiVO₄/ZnO QDs heterostructure was constructed.Taking advantage of the surface defects and many dangling bonds of ZnO QDs,chemical bonding interfaces(CBIs)are formed at the interface between BiVO₄ and ZnO QDs.In the photoelectrocatalysis process,CBIs can not only accelerate the migration efficiency of photogenerated electrons,but also act as a trap layer for photogenerated holes to capture photogenerated holes from ZnO and BiVO₄.At the same time,CBIs can also have a synergistic effect with element Bi,using the water oxidation kinetics of element Bi to export holes,thereby avoiding electron-hole recombination,and optimizing the photoelectrocatalysis(PEC)performance of BiVO₄.The photocurrent density under simulated natural light irradiation can reach up to 5.5 m A/cm2.(2)Construct hole transport channels to solve the problem that Type I heterojunction holes are difficult to derive.The BiVO₄/?-Fe₂O₃ heterostructure was constructed by insitu calcination of MOFs in BiVO₄ precursor solution.Taking advantage of the lateral expansion of MIL-53(Fe)in the process of transforming into ?-Fe₂O₃ at high temperature,a special structure of semi-covered ?-Fe₂O₃ spindle is formed in the porous BiVO₄ film.In the photoelectrocatalytic process,?-Fe₂O₃ can be in contact with BiVO₄ and the electrolyte solution at the same time,thereby constructing a unique hole transport channel,inhibiting the secondary recombination rate of electrons and holes,and it simulates the highest photocurrent density under natural light irradiation.Up to5.4 m A/cm2(Na SO3 is used as a hole sacrificial reagent in the test process).The oxidation kinetics of Fex+ on the exposed part of ?-Fe₂O₃ in the electrolyte solution plays an important role in inhibiting the recombination of electrons and holes.(3)A heterojunction(Mo,W: BVO/ ZnO NSs)mixed with Mo,W ion-doped bismuth vanadate(Mo,W: BVO)and zinc oxide nanospheres(ZnO NSs)is obtained by internal doping method.ZnO NSs),expand the transmission channel of photo-generated carriers.In addition to ZnO NSs can increase the charge carrier density in the heterojunction,the larger contact area between Mo,W: BVO and ZnO NSs will also increase the transport channel for the charge carriers.Reducing the size of ZnO NSs will further increase the contact area between the two and make this effect more obvious.The PEC test shows that when the average size of ZnO NSs is 100 nm,the photocurrent density of Mo,W: BVO/ZnO NSs can reach up to 2.5 m A/cm2.Experiments have proved that the PEC performance of the ZnO/Mo,W: BVO heterojunction obtained by the traditional coating method is much lower than that of the Mo,W: BVO/ZnO NSs,which proves that the high charge density and large contact area are important for the improvement of photocatalytic performance.Sex.In summary,this thesis improves the spectral response range of bismuth-based photoanodes and promotes its photo-generated load through a series of unique experimental methods of constructing hole transport channels,chemical bonding heterojunctions,and uniformly mixing heterojunctions.The separation efficiency of currents provides a theoretical and experimental basis for exploring stable and efficient semiconductor photoanodes,has important scientific research value and practical significance.