Preparation And Electrocatalytic Performance Of Aromatic Nitrogen-containing Transition Metal Complexes Catalysts

Direct methanol fuel cell (DMFC) has become a research hotspot for high efficiency, high energy density, low emissions, and the convenience of the fuel storage and transportation. Commonly, platinum-base metals are used for the catalyst of fuel cells, but the resource is limited, easily poisoned by CO, these prblems limit the commercialization of fuel cells. So people are struggling to find non-noble metal compounds to replace the platinum, nitrogen-containing transition metal compounds as cathode catalyst have been paid more and more attention.In this work, three categories of aromatic nitrogen-containing transition metal compounds are prepared, the first category is the phenanthroline compounds, dipyrido [3,2-a:2’,3’-c ]phenazine (DPPZ) is synthesized, by changing the experimental conditions, the yield is improved; The second category is pyridine compounds, a new kind of compound is synthesized,4’-pyridine-methoxy-phenyl-2,2’:6’,2 "-terpyridine (MPTP); The third category is the carbon and nitrogen compounds, carbon and nitrogen compound C3N4 is prepared by two methods. Analysis the composition and structure of the compounds using infrared spectroscopy and ultraviolet spectroscopy, experimental results show that the target compounds are synthesised. Nitrogen-containing transition metal (cobalt or iron) compounds are prepared by phenanthroline and the aromatic compounds above, transition metal compounds as catalyst precursor, by adding activated carbon, immobilization, activation with the inert gas protection, prepare catalysts of aromatic nitrogen-containing transition metal complexes.Change the activation temperature and the ratio of compounds with activated carbon (cobalt or iron load) of the catalysts of the above, in 0.5mol/L H2SO4 solution, with a rotating disk electrode (RDE) the best of the catalyst preparation conditions and found that the best preparation of catalyst activation temperature is 1050℃, the best ratio of aromatic nitrogen compounds plus metal salts with activated carbon is 1:1, The oxygen reduction potential is about 0.74 of the two kinds of catalysts with central metal ion (cobalt or iron), the catalytic transfer of electrons for oxygen reduction is 3.5 or more. The prepared catalysts for oxygen reduction catalytic activity compared well, the electrode reaction process tend to 4e. Scanning electron microscopy SEM-EDS, X-ray powder diffraction XRD characterize the microstructure of the catalyst and detection the catalyst surface micro region detection elements, found the catalyst distributed uniformly in the activated carbon surface, and prove the existence of the transition metal Co or Fe, the contents of each element are agree with the calculated values. By linear sweep voltammetry, cyclic voltammetry, I-t curves tested the stability of the catalysts, the results prove that the catalysts of aromatic nitrogen-containing transition metal compounds huve good catalytic performance and stability for oxygen reduction.To prove the stability of the catalyst, use electrochemical methods to scan, obtain lth, 100th and 150th polarization curves, 1th,1000th and 2000th cyclic voltammetry curves, and the I-t curve of 50h in strengthening the fuel cell cathode environment, that is, in O2 saturated 0.5M H2SO4 solution. Analyze the stability of the catalyst, the polarization curve attenuate 0.2mAcm-2, cyclic voltammetry curve of 2000th circle attenuate 0.25mAcm-2, I-t curves of 50h minimum attenuation is 28.6%, compared with the simple porphyrin, the results show that aromatic nitrogen-containing catalysts of transition metal compounds have good catalytic performance and stability for oxygen reduction reaction..