Construction Of TiO₂-based Catalyst And Research On Its Electrocatalytic Performance

TiO₂,compared with other transition metal oxides,has good chemical and thermal stability,strong environmental compatibility and multiple functions,so it has been used in photocatalysis and other fields.However,the single active component leads to the low catalytic performance of TiO₂,which inhibits its application in hydrogen evolution from electrolytic water and lithium-sulfur battery at high current density.Therefore,in order to improve the catalytic activity of the active components of TiO₂-based catalysts,this paper takes TiO₂catalysts as the research object,（1）modified TiO₂materials by C-doping and hydrothermal reduction,（2）modified TiO₂/three-dimensional carbon materials by loading TiO₂,on 3D porous carbon materials and carbonization in reduction atmosphere.（3）TiO₂materials were loaded on the surface of 2D flexible MXenes materials,and TiO₂/MXenes composites were prepared by hydrothermal reduction modification to improve the intrinsic activity of TiO₂catalysts.The relationship between the nano-size,morphology,composition and microstructure of TiO₂-based catalysts and the catalytic activity of electrocatalysts was clarified.Based on this,the main research results of this paper are as follows:1.Ti-O hybridization is an effective way to improve the hydrogen evolution performance of TiO₂-based electrocatalysts.TiO₂/C precursors were prepared by mixing tetra-n-butyl titanate and polyethylene glycol-400 by hydrotherma and carbonization method,and then C-doped TiO₂/C-T electrocatalysts were prepared at different carbonization temperatures in reduction atmosphere（H₂/Ar）.The relationship between microstructure and electrocatalytic hydrogen evolution performance was explored.The microstructure analysis of TiO₂/C-T electrocatalyst showed that with the increase of carbonization temperature,anatase TiO₂in TiO₂/C catalyst changes to rutile TiO₂,while C-doping changes the existence environment of Ti,and the TiO₂/C catalyst prepared in reduction atmosphere has abundant oxygen vacancy（Ovs）.The study on the hydrogen evolution performance of TiO₂/C-T catalyst showed that compared with the TiO₂/C samples prepared under 850 ^oC and 1050 ^oC,TiO₂/C-950had higher catalytic activity and excellent stability in electrocatalytic hydrogen evolution.The analysis of the catalytic mechanism of TiO₂/C-T materials showed that the excellent catalytic activity of TiO₂/C-950 comed from the strong Ti-O hybridization in TiO₂/C materials,and the strong Ti-O hybridization reduces the hydrogen adsorption energy.The preparation method provided a strategy for improving Ti-O hybridization in TiO₂/C materials for hydrogen evolution at high current by C-doping.2.Transition metal oxides such as TiO₂loaded on the surface of 3D porous carbon materials can achieve efficient adsorption and catalytic conversion of lithium polysulfide.TiO₂/three-dimensional porous carbon materials（TiO₂/TPC）with different loading amounts were prepared by hydrothermal-thermal reduction method using 1,4-diaminoanthraquinone as carbon source and tetraisopropyl titanate as titanium source.The effect of TiO₂loading on the microstructure and electrochemical properties of carbon materials was studied.The microstructure analysis of TiO₂/TPC materials showed that the prepared TiO₂materials were nano-spherical particles connected with each other,while the TiO₂/TPC materials with different loading were3D porous structure,and with the increase of TiO₂content,the Ti element in the material existed as Ti（IV）.The electrochemical performance tests of TiO₂/TPC materials showed that,compared with 10%TiO₂/TPC and 50%TiO₂/TPC,25%TiO₂/TPC composites,after 200 long cycles at a current density of 1 C,the discharge specific capacity was 704 m Ah g^-1,and the attenuation rate per cycle is only 0.029%,showing good cycle stability.The study on the electrochemical mechanism of TiO₂/TPC materials showed that the addition of TiO₂promotes the catalytic conversion of lithium polysulfide,improved the reaction kinetics of lithium polysulfide,and improved the electrochemical performance of lithium-sulfur battery.The results of this study provided a feasible strategy for reasonably regulating the microstructure of TiO₂/C materials to improve the catalytic conversion of lithium polysulfide.3.2D MXenes materials have excellent physical and chemical properties,but the tendency of reaccumulation leads to the decrease of 2D MXenes active sites and their application in energy storage systems.Based on this,in order to improve the electrochemical performance of MXenes materials,TiO₂/MXenes materials with different loading were prepared by hydrothermal-thermal reduction method,and the effects of TiO₂loading on the micro-morphology and electrochemical properties of2D MXenes materials were studied.The microstructure analysis of TiO₂/MXenes materials showed that the prepared TiO₂/MXenes materials had a 2D flake structure.With the increase of the content of TiO₂,the interlayer spacing of MXenes nanosheets increases,and the Ti elements in the catalyst mainly existed in the form of Ti-C,Ti（II）,Ti（III）and Ti（IV）.Compared with the electrochemical performance of 10%TiO₂/MXenes and 50%TiO₂/MXenes materials,under the current density of 2 C,after200 cycles,the discharge specific capacity of 25%TiO₂/MXenes could still reach687.1 m Ah g^-1,and the attenuation rate of each cycle was only 0.024%,showed excellent electrochemical performance.The results of SEM and UV-vis tests showed that the excellent electrochemical performance comes from the loading of TiO₂,which inhibits the restacking of the lamellar structure,expanded the layer spacing between the sheets,and improved the catalytic conversion of Li₂S.