Study On Control Synthesis And Photocatalytic Water Oxidation Performance Of One-dimensional Transition Metal-based Semiconductor Nanomaterials

The extensive use of fossil fuels has caused serious environmental problems and an increasingly prominent energy crisis.The development of new,efficient and green renewable energy sources has received increasing attention.Photocatalytic water splitting into oxygen and hydrogen is a green technology that uses solar energy to produce hydrogen,which is expected to alleviate energy crisis and environmental problems.However,the oxygen evolution reaction（OER）involves four-electron transfer,the kinetic process is slow,and the formation of O-O bonds has a high energy barrier,which hinders the process of photolysis of water for hydrogen evolution.Promoting the separation of photogenerated electrons and holes is the key to improving the efficiency of the water splitting reaction.To this end,this paper selects transition metal-based oxide semiconductors as the research object,and uses strategies such as doping,constructing heterojunctions,and crystal defects to modify them from various aspects such as composition,morphology,and electronic structure to improve electron-vacancy.The e^-and h⁺separation allows more holes to participate in the water oxidation reaction,thereby improving the performance of water decomposition and oxygen generation.1.Doping Mo into 1D tubular Bi₁₁VO₁₉ enhances the separation of carriers and promotes the photocatalytic oxygen generation performanceThis chapter mainly introduces the synthesis of 1D tubular Bi₁₁VO₁₉ using the Kirkendall effect by synthesizing sodium vanadate nanowires as a template.In the process of synthesizing bismuth vanadate,Mo source is introduced to obtain Mo-doped1D tubular Bi₁₁VO₁₉.Ion doping can introduce impurity energy levels,change the energy band structure of semiconductors,reduce the band gap,and enhance the absorption of visible light.In addition,the introduction of impurity levels can also inhibit the recombination of carriers.The best Mo doping rate is 3.0 wt%,and the average generation rate of O₂ is 789.83μmol·g^-1 h^-1·,which is 12 times higher than that of pure Bi₁₁VO₁₉NTs.The improvement of sample performance benefits from the impurity level introduced by doping and the hollow 1D tubular structure,which provides a larger specific surface area and a large number of surface reaction sites.2.One-step photodeposition constructs a tunableα-Mn O_x/Cd S composite heterojunction to improve the performance of photocatalytic oxygen productionIn this work,we first synthesized manganese dioxide nanowires,and then adjusted the electron flow direction by photo-deposition method to constructα-Mn O_x/Cd S NWs heterojunction while adjusting the oxygen vacancy content ofα-Mn O_x.S powder is reduced to S^2-by the photogenerated electrons of Mn O₂ under light.Due to the existence of Cd²⁺,Cd S immediately formsα-Mn O_x/Cd S NWs on Mn O₂.As we all know,oxides will react as follows under light:MO_n→MO_n-δ+δ/2O₂,thereby increasing the oxygen vacancy content under irradiation.The obtained photocatalystα-Mn O_x/Cd S-0.5 NWs achieves the best photocatalytic water oxidation performance of779μmol g^-1h^-1,which is 3.93 times that of pureα-Mn O₂NWs.3.Synthesis of Cu-doped Bi₂WO₆/Co WO₄ heterojunction to improve the oxygen production activity of the photocatalyst by electrospinning method.This work mainly introduces the synthesis of copper-doped fiber precursors by electrospinning and then ZIF-67 nanosheets grows on the precursors by static method,and finally formed the Cu-doped Bi₂WO₆/Co WO₄ heterojunction by air calcination.Cu doping can adjust the energy band structure of bismuth tungstate,reduce the band gap of bismuth tungstate,and better form type II heterojunction with cobalt tungstate.This work combined two strategies of doping and heterojunction to construct a new photocatalyst Cu-BWO/CWO,improved the performance of pure photocatalyst semiconductors.The material can obtain high visible light catalytic oxygen production performance of 810.6μmol g^-1 h^-1without adding any cocatalysts.