Construction Of High Performance Platinum-based Catalyst And Its Electrochemical Oxidation Of Methanol

The methanol oxidation reaction（MOR）of direct methanol fuel cell（DMFC）anode is limited by slow kinetic process and high reaction energy barrier,which greatly reduces the energy conversion efficiency of DMFC.The development of efficient and stable ano de catalyst is very important to promote the industrial application of DMFC.At present,the development of DMFC anode catalysts mainly faces the following problems:（1）catalyst efficiency is low and easy to poison,and methanol oxidation kinetics is slow at room temperature;（2）The catalyst cost is high.The precious metal Pt is the best known active component of methanol electrocatalytic oxidation catalyst,while Pt has low storage,high load rate and high cost.（3）Poor stability.Agglomeration,migrat ion and shedding of nanoparticles will occur in the methanol oxidation process,leading to low utilization rate of precious metals and poor catalytic activity.In view of the above key problems,based on a large number of literature research,this thesis carried out three parts:Pt-Ni alloy performance research,MnO ₂modified CNTs carrier effect research and Pt-Ni alloying synergistic carrier effect research,and obtained the Pt-based electrocatalyst with excellent performance.It has certain theoretical value for rational design and controllable construction of DMFC anode MOR electrocatalyst.Specific research contents are as follows:In this study,a series of Pt_xNi_y/CNTs alloy catalysts were prepared by a one-pot method.The electrochemical test results s howed that the catalytic activity and stability of Pt₃Ni₁/CNTs were the highest,which were 5.89 times and 38.97 times higher than that of commercial Pt/C,respectively,which was significantly superior to that of commercial Pt/C,mainly due to the synergi stic effect of the unique structure of carbon nanotubes and bimetallic alloy.In order to enhance the proton-conductivity of the catalyst,the composite carrier MnO₂-CNTs was prepared by citric acid reduction method,and then a series of Pt/_xMnO₂-CNTs catalysts were prepared by loading Pt nanoparticles on the surface of MnO₂-CNTs by glycol reduction method.The characterization results showed that the Pt nanoparticles were uniformly dispersed on the catalyst surface with an average particle size of 3.69 nm.The electrochemical test results showed that Pt/MnO₂-CNTs catalyst had the best catalytic performance for methanol oxidation when the content of MnO₂ was 20 wt%.The activity and stability of Pt/MnO₂-CNTs catalyst were 4.0 and 5.41 times than that of commercial Pt/C,respectively,which was also better than that of commercial Pt/C catalyst,mainly due to the synergistic effect between the unique structure of modified carbon nanotubes and Pt.Finally,a series of Pt_xNi_y/MnO₂-CNTs alloy catalysts were prepared by a two-step method.The characterization results showed that the nanoparticles were uniformly dispersed on the catalyst surface with an average particle size of 2.46 nm.Electrochemical test results showed that:The activity and stability of Pt₁Ni₁/MnO₂-CNTs catalyst were 8.99 times and 61.22 times higher than that of commercial Pt/C for methanol oxidation,with an electrochemical active area of 121.8 m²/g and an I_f/I_b value of 3.21.The activity and stability of Pt₁Ni₁/MnO₂-CNTs catalyst were superior to that of commercial Pt/C catalyst.It is mainly attributed to the alloy effect and the synergistic action of oxide composite carrier.