Preparation And Characterization Of Defective Metallic Oxides Through Laser-melting Method

Metallic oxides have extensive applications,including photocatalysis,biological medicine,solar battery and many other fields.In literature,element doping and morphological control are conventional methods to modify metallic oxide.However,element doping has its own drawback because it can introduce impurities.Self-doping is an effective way to solve this problem.Thus,this method was used in this article to improve the performance of metallic oxides.In this dissertation,a laser-melting method is used to obtain defective Ti O₂,Fe₃O₄ and SrTiO₃.After thorough investigation,it was found that:?1?In the laser-melted TiO₂,new phase(Ti₈O₁₅)was induced during laser-melting process,and the band gap of the materials was decreased from 3.03 eV to 2.52 eV,indicating that laser-melting method has induced oxygen vacancies and Ti³⁺ inside TiO₂.And its ability to absorb light in the visible light range was improved.The defective TiO₂ as photocatalyst has excellent ability of degrading organic dye and hydrogen evolution,and maintains great stability during these processes.The hydrogen production of the laser-melted TiO₂ is 8.54 mmol/?h·g?,which is eight times higher than that of TiO₂ sold in the market?P25?.?2?While the laser-melting method was used to treat Fe₂O₃ and Fe₃O₄,both resulted in Fe₃O₄.During the laser-melting process,the phase was transformed from Fe₂O₃ to Fe₃O₄,indicating that the defects were implanted inside Fe₃O₄.The defective Fe₃O₄ is a superparamagnetic material which means high saturation magnetization,low coercivity?6.6 Oe?and low remanence?0.4 emu/g?.Meanwhile,the saturation magnetization of the laser-melted Fe₂O₃ was slightly increased at a temperature of 5 K,because the magnetocrystalline anisotropy is sensitive to temperature.?3?The phase of SrTiO₃ was not changed after the laser-melting treatment,but the band gap was reduced from 3.20 to 3.05 eV,indicating that defects were induced into SrTiO₃.As a result,its ability to absorb light in the visible light range was improved.Compared to the pristine SrTiO₃,the ability of hydrogen evolution was enhanced and it has great stability during the process.The hydrogen production of the laser-melted Sr TiO₃ is 2.46 ?mol/?h·g?,which is 3.5 times higher than that of the pristine SrTiO₃.