The Synthesis And Electrocatalytic Performance Of TiO₂ Based Materials Supported Noble Metal Catalysts

Carbon-based supports are widely used in fuel cells and other electrocatalytic systems because of their good conductivity and large specific surface area.However,during the electrochemical cycles,the supported noble metal nanoparticles can catalyze and accelerate the corrosion of the carbon support,resulting in rapid degradation of the catalytic performance.Therefore,it is of great significance to study the catalyst support with high efficiency,low cost and excellent stability for the long-term operation of energy conversion devices such as fuel cell and hydrogen production by electrolysis of water.This paper choose the excellent stability of titanium dioxide as a substitute for carbon support,doping,composite method are adopted to solve the problem of poor conductivity of titanium dioxide,then precious metal catalysts are loaded for application in catalytic reaction.The activity and stability differences between titanium dioxide supported noble metal catalyst and carbon supported catalyst are discussed in depth.The main research contents and results of this paper are listed as follows:（1）Elemental doping method is applied to modify titanium dioxide.Mo element is doped into the lattice of titanium dioxide by solvothermal method to improve the electrical conductivity of titanium dioxide.The electrochemical hydrogen evolution performance of the catalyst is studied after loading Pt with mass fraction of 5 wt%by impregnation-reduction method.The overpotential at current density of 10 m A cm^-2 of Pt/Ti_0.9Mo_0.1O₂catalyst is only 26 m V,and the mass activity at overpotential of 50 m V for Pt/Ti_0.9Mo_0.1O₂catalyst reaches 1.72 A mg^-1.Compared with the traditional 20%Pt/C catalyst,the mass activity is increased by 4.4 times.The decay rate of mass activity after 10 000 cycles is far less than that of Pt/C catalyst.（2）Ti O₂ and carbon nanotubes are composited and precious metal Ir is loaded onto it to prepare Ir/CNT@Ti O_2-x catalyst.The uniform growth of Ti O₂ particles on the surface of CNTs is controlled by adjusting the feeding ratio of the precursors,which not only enables the CNT@Ti O_2-x composite support possess good electrical conductivity,but also larger specific surface area.The HOR performance of Ir/CNT@Ti O_2-x catalyst is studied,and the resistance to CO poisoning is emphasized.The HOR performance of Ir/CNT@Ti O_2-xcatalyst is tested in electrolyte saturated with H₂ and H₂/1 000 ppm CO,respectively.The limited current density attenuation of Ir/CNT@Ti O_2-x catalyst is only 3.4%,which is significantly better than that of Ir/C and Pt/C catalysts.（3）The alloying strategy is adopted to optimize the supporting metal.By alloying with cheap transition metal,the amount of precious metal is reduced and the cost of catalyst is further lowered.The Pt Co/Ti O₂-C catalyst was prepared by adding 3d-transition metal Co into Pt catalyst and Ti O₂-C composite material is selected as catalyst support.The ORR performance of Pt Co/Ti O₂-C catalyst is excellent and the mass activity of Pt Co/Ti O₂-C catalyst reaches 0.47 A mg^-1 at 0.9 V,which is 3.9 times and 1.5 times higher than that of Pt/C and Pt Co/C catalysts,respectively.The stability performance of different catalysts is studied by using low voltage cycling and high voltage cycling.The performance attenuation of Pt Co/Ti O₂-C catalysts after cycling was higher than that of Pt/C and Pt Co/C catalysts.