Preparation Of Modified Carbon-lanthanide Hybrid Metal Oxides And Study Of Their Electrochemical Properties

It is of significance to develop a new catalyst with low cost, high catalytic activity and corrosion resistance for oxygen reduction reaction for the reason that the catalysts of platinum and its alloys applied in the cathodes of various fuel cells and metal-air batteries have drawbacks of high-costing and scarcity, in recent years. A perovskite type composite metal oxide was prepared in this article by co-precipitation and a series of composite catalyst was prepared with the pre-treated carbon support and the composite metal oxide via low temperature calcined blending and loading processes. The activity of LaNiO3, Mn-doped LaNiO3and LaMnO3catalytic for ORR and the paths was investigated in this article, and the effects of covalent complexes of LaMnO3in the composites with carbon catalyst supported to activity of ORR were analyzed as well.The first is pre-pretreating of carbon support. The degree of graphitization for Vulcan XC-72carbon black had been greatly improved and the surface had been grafted on the hydrophilic oxygen-containing functional groups through the procedure of graphitization treatmenting in high temperature, acidified with concentrated nitric acid and concentrated ammonia treatment. The particle sizes are larger when the calcination temperature is too high or too low in the preparation of LaNiO3, while when the temperature is700℃, the smallest particles were achieved, and the dispersion was the best as well. The particles tend to aggregate with the increase of Mn doped contents. The oxygen reduction performance were tested after the mechanical mixing of modified GCB with those oxides and LaMnO3showed the highest oxygen reduction activity, whereby Mn doped during the reaction contributed to reducing the overpotential, the resistance of ORR as well as the yield of H2O2byproducts in a four-electron path.Secondly, LaMnO3nanoparticles were prepared by adjusting the pH of the reaction solution, and heat treating them with modified GCB at low temperature. The combination action were obtained after300℃heat treatment of LaMnO3nanoparticles with aqueous ammonia treatmented acidification GCB, and the more intense complex role of C-O-M was formed with the highest content when the blend ratio is2to3between those two sides. The composite catalyst with blend ratio of2:3after300℃heat treatment had the higher activity by comparing oxygen reduction onset potential, H2O2yield of9.9%-14.2%and the oxygen reduction reaction in a four-electron reaction path with commercial Pt/C catalyst as a function of the oxygen reduction performance testing.Finally, the LaMnO3/C supported catalyst was prepared by a further change of the reaction system and modulating the pH of the reaction solution. The covalent complex role of different loadings LaMnO3/C with aqueous ammonia treatmented acidification GCB was investigated by Raman spectroscopy, FTIR and XPS, whereby it found that when the loading is100%not only the role of electron transfer between LaMnO3and aqueous ammonia treatmented acidification GCB was at most intense, but the formation of a large number of covalent bond C-O-M was achieved as well. The electrochemical tests showed that the100%loading LaMnO3/C has the largest electrochemical specific surface area and the highest activity of ORR in the path of four-electron reaction, with lower content of the hydrogen peroxide byproducts from17%to25%.