Study On Photocatalytic Water Splitting For Titanium Oxide Oxygen Vacancy Regulation And Oxygen Conversion Of Carbon-containing Catalyst

Photocatalytic water splitting is one of the effective methods to simultaneously obtain hydrogen and oxygen.Not only often used as the adsorption and active center of heterogeneous catalysis,oxygen vacancy is also closely related to the electronic structure,charge transport and optical properties.But the technology on how to accurately control the concentration of oxygen vacancy is still lacking.The research on the conversion process of oxygen on the surface of carbon containing catalysts tends to be ignored.The previous work results show a single half reaction for hydrogen production,without specific explanation for the conversion process of oxygen.Based on the importance of the two issues,this paper mainly focuses on the following two parts:the control of oxygen vacancies in the classical titanium oxide system for photocatalytic water splitting and the oxygen conversion on the reduced graphene oxide surface.（1）Atomic layer deposition（ALD）technology was used to control oxygen vacancies in titanium oxides.Ti O₂nanotubes without oxygen defects were prepared by hydrothermal method,and then titanium oxide layers with different oxygen vacancy concentrations（0.04-0.18 mol%）were deposited on its surface by ALD technology.Through the analysis of its performance,it was found that when the oxygen vacancy concentration reached the maximum of 0.18 mol%,the visible-light photocatalytic hydrogen production activity reached the maximum of 230.9μmol·g^-1·h^-1.Meanwhile,we found that all the Ti O_Xmaterials with different oxygen vacancy concentrations accelerated the separation ability of electron and hole,and broadened the optical absorption range in visible light.The transient photocurrent density of the sample peaked at(1.25μA·cm^-2),four times higher than that of pure Ti O₂(0.31μA·cm^-2).Therefore,the control of oxygen vacancy concentration is the key to improve the efficiency of hydrogen production from photocatalytic water splitting.（2）Photocatalytic oxygen corrosion study of reduced graphene oxide and Zn Sn O₃composites.An only 3 layered graphene exposed photocatalyst（hollow perovskite Zn Sn O₃-reduced graphene oxide（r GO）nanocube）is skillfully constructed,in which～3 nm Zn Sn O₃nanoparticle aggregates are closely wrapped up by r GO with a C-O-Zn（Sn）chemical bond connection.Assisted by this ideal robust model without the effect of the externally exposed metal oxide,the oxygen’s transformation process in water splitting is performed at C vacancy defect in graphene,which is clarified through in-situ Raman spectrum and gas chromatography analysis.It is also found that the oxygen of H₂O on r GO undergoes a step-by-step dehydrogenation process with the intermediate OH-C and O-C,and finally CO₂.Also,it was found that Zn Sn O₃-r GO nanocomposites possessed superior carrier separation capability,and their optical absorption in the visible region was significantly increased,achieving about 3.8 times higher light current compared with pure Zn Sn O₃samples.