Synthesis Of Bi-based Semiconductors With Enhanced Photocatalytic Oxygen Evolution

Currently,a series of efficient and clean new energy resources have been researched and applied to settle the increasingly serious energy crisis.Solar energy,as one of the most important renewable and endless sources of clean energy,is growing concern of researchers.The photocatalytic technology have made a figure in the degradation of pollutants.Likewise,there are also promising prospects to solve the energy crisis by photocatalysis,to convert solar energy into clean and storable hydrogen and hydrocarbon fuels.As a optimal way,the photocatalytic overall water splitting might produce directly hydrogen and oxygen from water.However,it also faces a series of challenges such as low conversion efficiency and unstable.The photocatalytic oxygen evolution reaction,as rate-determining step of overall water splitting,encounters the fundamental scientific challenge of slow kinetics of water oxidation,owing to the more complicated four-electron oxidation process and huge activation energy barrier for O-O bond formation.The photocatalytic oxygen evolution have been studied independently,to further explore the oxygen evolution mechanism.Bi-based photocatalysts,due to low cost,easy synthesis,structure stabilization and outstanding photocatalytic activity,have been a remarkable photocatalyst.In this paper,we present a series of Bi-based semiconductors preparation and their performance studies,including the following three parts:1.Electrospinning preparation of Sn4+-doped BiFeO3 nanofibers as efficient visible-light-driven photocatalysts for O2 evolutionIn this chapter,we here in report a facile electrospinning technique together with subsequent controllable annealing treatment for the fabrication of uniform one-dimensional(1D)Sn4+-doped BiFeo3 nanofibers(Sn-BFO NFs).Benefiting from the unique metal ion doped 1D structure,the as-prepared Sn-BFO NF catalysts exhibit significantly enhanced photocatalytic performance on o2 evolution as well as improved photo stability under visible-light illumination.Revealed by the experimental investigation as well as the density functional theory(DFT)calculation,the doped Sn ions were incorporated into the BFO lattice which results in the modification of the band structure accounting for the boosted light absorption and the production of defect-related energy levels,leading to the improved charge transfer and separation efficiency.Additionally,an optimal Sn4+ doping percentage of 1.0%was discovered to have an average O2 evolution rate of 516.4 ?mol-h-1·g-1,which is nearly two-fold as much as the non-doped BFO samples.2.Synthesis of Co-E cocatalyst and Bi2WO6 composite with visible-light-driven photocatalysts for O2 evolutionIn the work,Bi2WO6/Co-E composite from Bi2WO6 and mixture with cobalt nitrate and ethylenediamine tetraacetic acid disodium have been successfully prepared through an air annealing process.The effects of different synthesis conditions had been investigated for the photocatalytic oxygen evolution.Various characterization methods reveal that the Co-E in Bi2WO6/Co-E is the pyrolysis residual body of ethylene diamine tetraacetate cobalt.And Co-Eis distributed uniformly on the surface of Bi2WO6 with amorphous form.Bi2WO6/Co-E shows the best photocatalytic oxygen evolution and stability at the 300 ?heating and 3.0%Co-E loading.It can be attributed to the synergistic effect of Co-E and Bi2WO6.The results reveal it is a promising research method to find new cocatalyst in the photocatalytic oxygen evolution.3.Electrospinning preparation of Mo-doped BiFeO3 porous nanotubes and coated carbon with visible-light-driven photocatalytic O2 evolutionIn the chapter,electrospinning technology had been further applied in the synthesis of metal oxide semiconductor.The preparation of nanofibers precursor by electrospinning,together with subsequent annealing treatment for the fabrication of uniform one-dimensional(1D)Mo-doped BiFeO3(Mo-BFO)porous nanotubes(PNTs).In order to inhibit the agglomeration of micromagnetic Mo-BFO,hydrothermal coated carbon process was carried out.The photocatalytic activity enhancement with Mo-doped BiFeO3,can be attributed to the effect of Mo doping on the tuning of BiFeO3 band structure and the acceleration of electron hole separation.The carbon coating apparently inhibit the agglomeration of Mo-BFO,and improving the photocatalytic activity and stability.Apparently,electrospinning technology has unique advantages in the synthesis of one-dimensional semiconductor photocatalysts.