Metal Doped Porous Carbon As Fuel Cell Cathode Catalyst

Green energy is the key to the development of sustainable society. Low temperature fuel cells work with high efficiency, low operating temperature and benign to the environment, and thus could be used to provide power for vehicles, portable devices and small stationary power. However, the performance and cost of the fuel cells, in which the platinum-based materials account for about 49% of their costs, hinder its commercialization process. Researching for high activity, stability, and low-cost fuel cell cathode non-noble metal catalysts has important theoretical significance and application value. We designed and prepared a series of transition metal doped porous carbon materials by using the biomorphic materials to improve the poor activity of non-precious metal catalyst. Furthermore, the modern spectroscopy microscopy and electrochemical methods were carried out to characterize the physical properties and electrochemical performance of the catalysts in order to study the relationship between the microstructure and catalytic behavior. The main research results are as follows.(1) The one-pot method was used to prepare three-dimensional porous lung-like Fe-N-C materials as high efficient catalysts for oxygen reduction reaction. The template of SiO2 microspheres, carbon source, nitrogen source and iron source were mixed directly, the Fe-N-C precursor was prepared self-assembly with the inducement of solvent evaporation. We optimized and prepared three-dimensional linked mesoporous-macroporous spherical structure Fe-N-C materials by the way of pyrolysis. The pore distribution of Fe-N-C materials prepared by different raw materials was between 10-100nm, and analyzed the effects of different pyrolysis temperature on the structure morphology. The onset potential of the electrocatalyst for the ORR is around 0 V (vs. Ag/AgCl), half-wave potential is around-0.15 V (vs. Ag/AgCl), activity which was comparable to that of commercial Pt/C catalyst (half-wave potential is around-0.147 V). The durability of the Fe-N-C catalyst was assessed through chronoamperometric measurements at-0.4 V (vs. Ag/AgCl), and the current density of the Fe-N-C catalyst decreases by 7% during the 1800 s test, which is better than that of the commercial Pt/C catalyst (decrease by 18%). According to CV tests for the methanol tolerance, its capacity for the methanol tolerance is higher than commercial Pt/C catalyst.(2) Citrus peel was used as carbon sources, and supported the Mn precursor by impregnation method using its own pore structure. Meanwhile, carbon supported MnOx electrocatalyst with a face-centered cubic structure was prepared by pyrolysis method. MnOx nanoparticles with a diameter of 10-20 nm supproted on the porous citrus peel-carbon surface uniformly. The ORR oneset potential of the MnOx/C is around-0.09 V (vs. Ag/AgCl), the half-wave potential is around-0.175 V (vs. Ag/AgCl), and the limiting current density is 6 mA cm-2. Furthermore, through chronoamperometric measurements at-0.4 V, the current density decreases by 3.3% after 1800 s. These are better than that of the commercial Pt/C catalysts (current density decrease by 18% in chronoamperometric measurements). According CV tests for the methanol tolerance, its capacity for the methanol tolerance is higher than commercial Pt/C catalyst.