Preparation And Electrochemical Properties Of Carbon-based Non-precious Metal Catalysts

With the high efficiency, low temperature of operation, and zero emission, the proton exchange membrane fuel cells (PEMFCs) have been considered as one of the most promising energy conversion technologies. It is well known that platinum is still regarded as an ideal cathode in PEMFCs for its excellent catalytic activity for ORR. However, the issues of limited resources, high price and low tolerance to CO poisoning limit its application. In order to decrease the cost of catalysts and eliminate their dependence on precious metal, developing non-precious metal catalysts (NPMCs) is essential for the commercialization of PEMFCs technology.Among the non-precious metal catalysts, carbon-based catalyst is considered the most promising catalyst, therefore, it is important to the designing and studying of the novel carbon-based catalyst. In this paper, the eigenstate PANI, HC1doping PANI, HF doping PANI, H2SO4doping PANI and H3PO4doping PANI had been synthesized via in-situ polymerization method, then the CNx catalysts were pyrolyzed at a tempreture. The effect of inorganic acid doping for structure and ORR activity was evaluated by XRD, Raman, TEM and RDE.The PANI-WC was synthesized via in-situ polymerization method, then the W-N-C catalysts were obtained via pyrolyzing from700℃to1100℃. The effect of heat treatment tempreture for structure and ORR activity was evaluated by XRD, Raman, TEM and RDE.The results show that CNx catalyst’s performance is closely related to the choice of inorganic acid. The ORR activity improves via inorganic acid doping. The results also show the volcanic type change of ORR activity of W-N-C catalysts with increasing pyrolysis temperature. With increasing pyrolysis temperature up to1000℃, the current density increases correspondingly. However, the current density decreases at1100℃. Further study indicates that WC phase partially transforms into metallic W. After pyrolysis the W-N-C catalyst has structures of nanoshells and a high ratio of the graphitic N, which are responsible for high ORR activity and stability.