Study On The Co-catalyst And Support For PEMFC's Pt-based Catalyst

The catalyst is one of the most significant key materials for Proton Exchange Membrane Fuel Cells(PEMFCs).Presently,the Pt/C plays as the most widely used catalyst for PEMFCs, however,it also possesses several problems,such as high cost,low activity of oxygen reduction reaction(ORR) and stability,which stock the the efficiency and commercializing of PEMFCs. In this thesis,fisrtly,the methods for preparing catalyst were confirmed and the yield of Pt/C was step wisely scaled up,in order to meet the consumation of Pt-based catalyst at laboratory.Then focusing on the co-catalyst and novel support,some promising materials were studied aiming for improving Pt-based catalyst's activity and stability.Firstly,the methods for preparing catalyst were confirmed and the yield of Pt/C was step wisely scaled up.Though comparing the activity and form of Pt/C,the optimum method and support were selected within different preparing methods(constant microwave,pulse microwave and EG refluxing) and carbon materials.The Pt/C with 50%Pt loading was prepared with stepwise yield target.Compared with the commercial Pt/C,the homemade catalyst showed smaller Pt particle size and bigger ECA.The quality of homemade catalyst was stable within repeated preparation.Moreover,it can be found from single cell test that the homemade catalyst is a promising catalyst for PEMFCs.Secondly,the N and Sn doped TiO₂(NTT) was prepared and characterized by XPS,TEM and XRD.The NTT/Pt/C catalyst,constituted by different contents of NTT,were tested by the cyclic voltammetry(CV) and the rotating disk electrode(RDE) method for investigating their electrochemically active surface area as well as their half-wave potential of ORR.The NTT/Pt/C catalysts were also tested within single cells with H₂/O₂ and H₂/Air under different humidity.The results indicated that through the addition of NTT,besides the activity of Pt/C could be improved,the performance of PEMFC under low humidity was also highly promoted mainly due to the water retention characteristic of NTT.Thirdly,TiC and TiN were systematically investigated to apply as the supports of Pt-based catalyst.The supports were characterized by XRD,TEM,BET to analyze their crystal form, profile,specific surface area and pore structure.The electrochemical stabilities of supports were tested by dynamic potential scanning.The Pt/TiC and Pt/TiN with various Pt loading were synthesized and tested by CV and RDE for investigating their electrochemical area(ECA) and activity of ORR;moreover their electrochemical stabilities were also tested by dynamic potential scanning and stepwise potential oxidation.The results indicated that within three kinds of mterials,the electrochemical stability of Vulcan XC-72 carbon particles could be commensurate with TiC,which excelled the TiN material.After Pt being loaded,the Pt/TiN and Pt/C possessed comparative activities for ORR and performed better than Pt/TiC.