Effect Of Heat-Treatment Conditions And Metal Precursors On The Structure And Activity Of Co-PPy-TsOH/C As Oxygen Reduction Catalysts

Cathode catalyst is one of the most important factors restricting the commercialization of PEMFC, because of the slow kinetics of oxygen reduction reaction, high cost of the noble metal catalyst and its low utilization. Therefore, it is very important to find a kind of low-cost and high-efficiency ORR catalysts. M-N/C catalysts have been considered as the most likely alternative non-noble ORR catalysts, which have drawn more and more attention. Among various M-N/C catalysts, Co-PPy-TsOH/C has been proved to have a better activity than other similar catalysts.The effects of preparation process of Co-PPy-TsOH/C catalysts including heat-treatment conditions (calcination temperatures and calcination hours) and cobalt precursors on the electrocatalytic properties have been systematically studied in this paper, and the results have been analyzed with physicochemical techniques of TG, IR, Raman, XRD, TEM, XPS, ICP, EA and EXANES.It was found that Co-PPy-TsOH/C catalyst prepared with cobalt acetate as metal precursor and calcined at 800℃for 2 hours exhibited best ORR activity following four-electron transfer mechanism. The calculated electron transfer number is 3.99 and the peak potential for ORR is 0.71V. XRD pattern showed the crystalling phase in this catalyst was primarily in form of metallic Co, except a faint CoO characteristic peak; small, uniform distributed metal particles was found in TEM diagram; XPS spectrum showed that most of the surface N elements in this catalyst was pyrrolic N.In the obtained catalyst Co-PPy-TsOH/C, C acts mainly as catalyst support, no C-N bond created, and N content is not the determining factor of catalytic ORR activity.