The Studies Of The Electrocatalysts For Oxygen Reduction For Fuel Cells

The application of fuel cells have important significance to release the enviroment pressure and energy crisis.Oxygen reduction reaction（ORR）plays a key role for fuel cells,and the reduction of the oxygen depends on the quality of electrocatalysts.Here methods of electrodeposition and chemical oxidative polymerization were developed to prepare the carbon support metal nanoparticles and polymer composites.What’s more,physical characterization（SEM,XPS）and electrochemical measurements（CV,RDE,RRDE,EIS）were used to get some imformation about the surface chemical composition,the metallic state,the electrocatalytic activity and stability of the electrocatalysts.（1）Cyclic voltammetry was used to fabricate Pt-Cu/C,Pt/C and Cu/C for oxygen reduction reaction at ambient temperature.A flowerlike structure of Pt-Cu nanoparticles were occurred with a variety of neutral metallic bonding.Compared with Pt/C and Cu/C electrocatalysts,Pt-Cu/C exhibits the highest efficient catalytic activity for ORR.Measurements results show that the novel material Pt-Cu/C has excellent electrocatalytic activity and the ORR is a four-electron dominant reduction pathway,which reduced the O₂ to H₂O.（2）Indole-5-carboxylic acid monomer was electropolymerized on carbon modified glass carbon electrode,followed by covalent bonding with pyridine-2,4-diamine by using EDAC,NHS catalyst,and then was complexed with copper ions to obtain the composite（Cu INPD/C）.All physical characterization and electrochemical measurements demonstrate that Cu INPD/C is the best electrocatalyst among Cu INPD,INPD,INPD/C with excellent stability and electrocatalytic activity due to the copper ions doping and carbon modification,which play key roles in increasing the current density and enhancing the charge transfer kinetics.Moreover,the average electron transfer number is about 3.1,indicating the ORR of Cu INPD/C may takes a coexisting pathway involving both the two-electron and four-electron transfers.（3）At room temperature,organic compound with high N content and good symmetry were used as raw material to prepare Cu PPy Phen/C and Fe PPy Phen/C catalysts with a developed method of chemical oxidative polymerization,these catalysts possess excellent stability and electrocatalytic activity.XPS was applied to confirm the synthetic method was feasible.Analytical testing suggest the Cu PPy Phen/C catalyst exhibits better electrocatalytic activity and stability than the Fe PPy Phen/C.Moreover,the calculated electron transfer number is almost 4,suggesting a predominant four-electron catalyzed by the Cu PPy Phen/C catalyst for reduction of oxygen.Compared with the results of other research group,our results are more competitive and satisfactory in terms of ORR activities.In this case,both of the two catalysts,especially the Cu PPy Phen/C catalyst are good candidates for non-noble metal ORR catalysts with excellent performances among the reported catalysts of the same kind up to date.In a word,low cost,feasible synthetic method,high electrocatalytic activity of Pt-Cu/C,Cu INPD/C and Cu PPy Phen/C catalysts will make them have a bright future in theoretical research and practical application for energy,fuel cells and electrocatalysis.