Preparation And Characterization Of ZnTiO₃-based Photocatalytic Materials

Since the beginning of the new century,with the rapid growth of population,rapid economic development and the rapid rise of modern industry,the accompanying problems of lack of resources and environmental damage have become increasingly serious.Researchers are gradually shifting their research focus to environmental governance and the development of sustainable new energy.Photocatalytic technology is an energy-saving,inexpensive,temperature-conditioned technology,which is considered to be the most ideal way to solve the problem of energy crisis and environmental pollution.Therefore,finding an efficient,stable and practicable semiconductor catalytic material has become the key.Zinc titanate is a new metal oxygenate catalyst with good performance.However,due to the shortcomings of too wide band gap,low solar utilization rate and too high photogenerated carrier recombination rate,ZnTiO₃,a semiconductor photocatalyst,needs to be modified to improve the photocatalytic performance.In this paper,zinc titanate was used as the base to carry out the research,and the performance was optimized by introducing oxygen defects,constructing heterojunctions,etc.,and the prepared materials were applied to experiments such as degradation of organic pollutants and photocatalytic nitrogen fixation.The detailed study is as follows:1.Preparation,characterization and performance testing of oxygen-deficient ZnTiO₃ photocatalytic materials.In the experiment,zinc nitrate hexahydrate was used as zinc source and tetra-n-butyl titanate as titanium source,and the aerosol-gel method was used to prepare zinc titanate photocatalyst in an inert gas environment.The influence of calcination temperature on the photocatalytic performance of semiconductor materials was explored,and the characterization tests of XRD,FT-IR,BET,UV-vis,PL,photoelectrochemistry,photocatalytic degradation of isopropanol and photocatalytic nitrogen fixation were carried out.The experimental data show that 500°C is the optimal calcination temperature,indicating that the appropriate oxygen deficiency concentration requires the appropriate calcination temperature.By introducing oxygen defects,more active sites can be obtained on the surface of the semiconductor material,increasing the adsorption capacity of the sample.According to the results of photocurrent density and electrochemical impedance（EIS）test results of semiconductor samples,the photocurrent density of zinc titanate samples containing oxygen defects was higher than that of single-component samples,among which the photocurrent density of ZTO-500 catalyst was 6.4 times that of pure samples,and the introduction of oxygen defects could effectively improve the separation efficiency of photogenerated carriers.In the photocatalytic degradation of isopropanol experiment,the acetone production of oxygen-containing vacancy ZTO-500 sample reached the highest value,which was 3.34 times that of pure sample ZTO.At the same time,the sample ZTO-500 also has excellent photocatalytic nitrogen fixation and ammonia production activity,and its nitrogen fixation amount is 199.67μmol/L.It reflects that the introduction of oxygen defects can improve the activity of the photocatalyst,which is consistent with the results of sample characterization analysis.2.Preparation,characterization and performance testing of ZnTiO₃/g-C₃N₄heterojunction materials.In the experiment,ZnTiO₃ semiconductor catalyst and g-C₃N₄ semiconductor catalyst were composited,and ZnTiO₃/g-C₃N₄ heterojunction materials were synthesized by simple calcination method with ultrasound assistance.The effect of ZnTiO₃/g-C₃N₄ composite samples containing monomers with different mass ratios on photocatalytic activity was studied.According to the results of XRD,EDS and XPS,ZnTiO₃/g-C₃N₄ nanomaterials were successfully prepared,and the samples were composed of five elements,C,N,O,Zn and Ti,and were evenly distributed.The specific surface area test results show that the composite sample ZTCN-5 has a mesoporous structure and a large specific surface area,which provides more active sites for the photocatalytic reaction.The UV-Vis spectral data were converted into2.92 e V and 3.25 e V for g-C₃N₄ and ZnTiO₃,respectively,and the conduction band positions of the semiconductor materials were-0.7 e V and-1.34 e V,respectively,from the Mott-Schottky data.Further analysis and calculation show that the g-C₃N₄and ZnTiO₃ band structures of semiconductor materials are matched,and the heterojunction of the two can effectively improve the separation efficiency of photogenerated carriers,thereby improving the photocatalytic performance of ZnTiO₃/g-C₃N₄ nanomaterials.In the photocatalytic nitrogen fixation experiment,the hole trap methanol was replaced with rhodamine B,which not only saved the experimental cost but also protected the environment,and realized the photocatalytic reduction of nitrogen and the synergistic degradation of rhodamine B.This experimental design provides a new way to improve the photocatalytic performance.