Preparation And Characterisation Of Porphyrin Catalyst Used In DMFC Cathode

Direct methanol fuel cells(DMFC)have attracted considerable attention as an alternative to the present power sources,since they offer numerous benefits,including high efficiency, high power density,low or zero emissions and easy fuel carriage.However,at present,two major technology problems in DMFC still restrict their performances and applications.One problem is the crossover of methanol through the electrolyte membrane.The other is catalyst. Macrocycle compound catalyst as a non-platinum catalyst has good methanol-tolerant performance,but so far,such a catalyst,its oxygen reduction activity and stability need to be improved.Five kinds metallporphyrin were synthesized by the method of mixed solvents (propionic acid,acetic acid and nitrobenzene)and one pot method of mixed solvents(propionic acid,acetic acid and nitrobenzene)using metal ion as template.They were meso-5,10,15,20-tetra (N,N-dimethylaminophenyl)porphyrin Fe(â…¡),meso-5,10,15,20-tetra(N, N-diethylphenyl)porphyrin Fe(â…¡),meso-5,10,15,20-tetra(2-thienyl)porphyrin Fe(â…¡)/Co(â…¡),meso-5,10,15,20-tetra(4-bromine-2-thienyl)porphyrin Fe(â…¡)/Co(â…¡)and meso-5,10,15,20-tetra(3-methyl-2-thienyl)porphyrin Fe(â…¡),which was connected with a strong electron-donating group to strengthen the electron-donating capability of central metal ion,with a view to improving the catalytic performance and the achievement of 4e-reduction. Element analyse,Uv-Vis,IR,¹HNMR were used to characterize these porphyrin compound. The results indicate that the production get from experiment was the aid compound. Metalloporphyrins were adsorbed on carbon black(Vulcan XC-72)with different metal content(2%,4%,6%,8%,10%and 15%),and heat-treated at diferent temperatures(400℃, 600℃,800℃and 1050℃)in Ar atmosphere.TEM method was used to characterize the micromechanism of the catalyst;the result showed metalloporphyrin was adsorbed on the surface of activated carbon uniformly.XRD graph show that metalloporphyrin was amorphous when heat-treated at 600℃,and metal-cluster appeared when activated temperature was higher than 950℃.Rotating disk electrode(RDE)method was used to inspect the catalystic capability of the metallporphyrin catalyst influenced by metal-loadings and activitied temperature in different electrolyte.The results show that 600℃,800℃was the best activation temperature for Fe(â…¡)metal catalyst and 4%,6%was the best Fe(â…¡)loadings. Co(â…¡)metal catalyst showed good catalystic capability when activated at 800℃and with 10%Co(â…¡)loadings.Compare two central metal catalyst in the same amount of metal loadings,and the result showed that Fe(â…¡)metal catalyst has better catalytic performangce, and more inclined to 4e-reduction.The catalystic capability of metallporphyrin catalyst was better in alkaline electrolyte than in acid electrolyte.Compare the metallporphyrin catalyst with Pt/C(ω=30%)catalyst produced by E-Tek,the result is that TDENPPFe(â…¡)catalyst shows analogical catalystic capability with 30%Pt/C in NaHCO₃ electrolyte.DMFC test show that TDMNPPFe(â…¡)and T(2-Th)PFe(â…¡)catalyst has good catalytic performance in the DMFC.