Investigations On The Construction And Durability Of Ordered Oxygen Electrode Structure Of PEMFC

Proton exchange membrane fuel cells as one of the clean energy sources which can directly convert chemical energy into electrical energy.However,the cathodes of proton exchange membrane fuel cell show poor stability and the difficult mass transfer at high overpotentials serious affects cell performance,which limits the development of fuel cells.The problem of poor stability of proton exchange membrane fuel cell cathodes over a long period of time is mainly caused by the oxidation of the catalyst and the corrosion of the support.Oxidation,dissolution,and redeposition of the catalyst on the support surface affects stability.On the other hand,the corrosion of the carbon support caused the surface catalyst to fall off,which also seriously affected the stability of the electrode.However,the difficulty of mass transfer at high overpotential is due to the slow transport of the material caused by the disordered arrangement of the material inside the electrode.In view of the above problems,this paper mainly studies the cathode Pt catalyst and Pt catalyst support with the goal of improving the stability of the cathode of the proton exchange membrane fuel cell and accelerating mass transfer.The electrode stability was improved by optimizing the catalyst support,and strengthening the binding force between the Pt catalyst and the support,improving the anti-oxidant capacity of the catalyst.By rationalizing the structure of the catalyst or the electrode,an orderly mass transfer channel is formed to improve the mass transfer capability of the electrode.The main conclusions are as follows:(1)Through the lamellar graphite oxide and ordered porous carbon-graphite array to replace the traditional carbon support to improve the anticorrosion under long-term operation at high potential.The experimental results show that,the constructed porous carbon-graphite ordered array support can provide rapid water and gas transmission compared to the graphite oxide.After accelerated CV testing,the stability is improved by 30%compared with commercial Pt/C.Although the carbon support is optimized,the presence of this amorphous carbon still affects the stability of the electrode.(2)The corrosion of the carbon support causes the stability to decay rapidly.In this part,by removing the unstable carbon layer,the catalyst is directly loaded on the surface of the stable carbon fiber to improve the stability of the electrode.The rapid mass transfer is achieved by orderly Pt catalyst.The Pt catalyst was supported on the surface of carbon fiber by room temperature reduction method and electrodeposition.The studies have shown that the direct loading of Pt catalyst on carbon paper has higher stability(increased by 40%),and the ordered catalyst array can improve the mass transfer ability of the electrode,but the electrochemically active area is low.Then sheet-shaped nickel-based support is built on the basis of carbon fiber to increase the specific surface area of the support.The sheet-like array realizes the orderly transmission of substances,and the stability can be increased by 50%compared with Pt/C electrodes.(3)Use metal oxide supports instead of carbon as catalyst supports to build ordered array structures with different morphologies.The introduction of the metal oxide array can increase the specific surface area of the support and the stability of the catalyst support,and form a good mass transfer channel.The interaction between the catalyst and the metal oxide support can also enhance the catalytic activity of the catalyst.The rod-shaped and porous TiO2@C,flake,SnO2@C and porous SnO2 supports were constructed,the synthesis conditions were explored,and through the three-electrode system to evaluate the performance.Finally,after a single cell test,the cell performance and mass transfer of porous support was affected by the hydrophilic;and the performance and mass transfer ability of the Pt-SnO2@C ordered array cathode shows better than that of commercial Pt electrode.(4)Prepare-Ni alloy nanoparticles with different morphologies were prepared by controlling the reaction temperature.The electrocatalytic activity of nanoparticles with different morphologies was tested,and the octahedral alloy nanoparticles had the highest electrocatalytic activity.The electrochemically active area was partially improved compared to commercial Pt/C,and the mass specific activity and area specific activity were 8.5 and 7.1 times than that of commercial Pt/C,respectively.The stability test was conducted with octahedral Pt-Ni alloy.The electrode stability has a 25%improvement over the commercial Pt/C.Through XPS analysis,the Pt-Ni alloy reduces the adsorption of oxygen-containing species on the surface of the Pt catalyst,reduces the oxidation of the Pt catalyst and improves the electrode stability.