The Study On The Electrocatalysts For Oxygen Reduction Reaction Prepared By Pyrolysis Of Milk And Graphite Oxide

The fuel cell has become the major object of study in the field of energy and environment due to a series of advantages, but the oxygen reduction reaction(ORR) in cathode has restricted its commercial use. The traditional Pt/C catalyst has strong catalytic activity, but it has the disadvantages of high price, scare resource, poor stability and low methanol tolerance. Therefore, the development of cheap and efficient electrocatalyst for ORR has become a hot topic now.In this paper, a series of N/C catalysts were prepared by choosing the cheap biomass milk as nitrogen resource and graphite oxide as carbon resource through hightemperature pyrolysis. Then the influence of nitrogen contents, heat treatment temperature and time, the doping of metal and two-step pyrolysis on catalytic activity was investigated. The experimental results show that the obtained N/C catalysts prepared by one-step pyrolysis has catalytic activity for ORR. In 0.1 mol/L KOH solution, the onset and peak potential of optimal N/C catalyst for ORR is Eonset = 0.020 V, Ep =-0.115 V vs(Hg/Hg O),respectively. The electron transfer numbers(n) for ORR at N/C is 2.5. Besides, the doping of metal and two-step pyrolysis can all significantly improve the catalytic activity of N/C catalyst. In order to identify the role of metal Co in catalysts, the obtained Co-N/C catalyst after the addition of Co Cl2·6H2O was treated with acid solution and labed as Co-N/C-A hereafter. The results of electrochemical tests show that the potential of Co-N/C-A catalyst for ORR is Eonset = 0.037 V, Ep =-0.082 V vs(Hg/Hg O) in 0.1 mol/L KOH solution, respectively. The electron transfer numbers(n) for ORR at Co-N/C-A is 3.8. Compared to N/C, the CoN/C-A catalyst exhibits stronger catalytic activity which may be associated with high contens of pyridinic and pyrrolic-N. In addition, the onset and peak potential of optimal N/C? catalyst for ORR prepared by two-step pyrolysis is more positive 15 m V and 25 m V than that of N/C, respectively. The electron transfer numbers(n) for ORR at N/C? is 3.7. The reason for this result may be that the first step pyrolysis help the protein in milk decompose thoroughly, where the carbon will be graphitized as mucn as possible and then make the doping of N in carbon material easier for two-step pyrolysis. Finally, a series of N/C catalysts prepared in this paper have superior stability and tolerance to methanol than Pt/C catalyst in 0.1 mol/L KOH solution.