Controllable Preparation Of Networked Titanium-based Nanowires Composite Structures And Their Performance Of Methanol Oxidation

Direct methanol fuel cell has the characteristics of simple structure,fast start-up,high energy density and no pollution,and has broad application prospects in the field of new energy.Platinum is the most common and most effective precious metal catalyst in direct methanol fuel cells.However,the shortages of platinum resources and the high cost limit its large-scale application.In order to improve the efficiency of platinum use,three-dimensional networked TiO₂nanowires with large specific surface area and corrosion resistance were prepared by hydrothermal and annealing method,and modified by hydrogenation and carbon coating,the precious metal platinum was then loaded.Finally,the methanol oxidation performance of the catalysts was systematically investigated.The main results are as follows:（1）Three-dimensional networked TiO₂nanowires were prepared by hydrothermal method and annealing process.The ratio of anatase TiO₂to TiO₂-B can be controlled by adjusting the annealing temperature.The TiO₂nanowires have a diameter distribution between 50 and 100 nm and a length of about 10μm.（2）Hydrogenated three-dimensional networked TiO₂nanowires（H-TiO₂）were prepared by a combination of hydrothermal method and hydrogenation process.The phase structure of H-TiO₂kept unchanged after hydrogenation in a 2.5%and 5%hydrogen-argon atmosphere compared to the annealed TiO₂nanowires in air.（3）Carbon-coated TiO₂nanowires（TiO₂@C）with controlled carbon layer thickness were obtained by hydrothermal method and high temperature carbonization with glucose as the carbon source.The morphology of the TiO₂nanowires was controlled by adjusting the temperature,and the optimized carbonization temperature was 800°C.（4）Pt was loaded on the TiO₂nanowire by the formic acid reduction method,and the TiO₂nanowire was annealed at 450°C,500°C and 550°C,and the growth of Pt was controlled by adjusting the amount of chloroplatinic acid.When the amount of chloroplatinic acid was reduced from 600μL to 150μL,the uniform dispersion of Pt in the TiO₂nanowires was obtained.At the annealing temperature of 450°C and the amount of chloroplatinic acid of 150μL,the catalyst exhibited the largest electrochemical activity specific surface area and the highest methanol oxidation current density.（5）Pt was loaded on the hydrogenated TiO₂nanowire by a formic acid reduction method,and the deposition of Pt was modulated by changing the amount of chloroplatinic acid.Compared with the TiO₂annealed in air,deposition of Pt on the H-TiO₂is more uniform and well dispersed,and the electrochemically active surface area of Pt/H-TiO₂is 1.5 times that of Pt/TiO₂,and the oxidation current density of methanol is 2.8 times that of Pt/TiO₂.（6）TiO₂@C core/shell nanowires were obtained by thermal decomposition using glucose as the carbon precursor.Three dimensional ultrathin Pt nanowires were obtained by the formic acid reduction method on the TiO₂@C nanowries treated at800°C and 1 mol/L glucose.The diameter of the Pt nanowire was about 3 nm and the hierarchical Pt/TiO₂@C catalyst for methanol oxidation was thereby achieved.And compared with the commercial Pt/C catalyst,the current density of Pt/TiO₂@C-800-1methanol oxidation is 1.6 times that of Pt/C.The methanol oxidation potential（0.657V）of the sample Pt/TiO₂@C-800-1 is lower than the methanol oxidation potential of Pt/C（0.681V）and has superior electrochemical stability.