科研之友
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摘要
N/S co-doped non-precious metal material for the oxygen reduction reaction(ORR) was prepared with ferrous sulfate heptahydrate(FeSO4 center dot 7H(2)O) pyrrole and p-toluenesulfonic acid(TsOH) as Fe, N and S precursors supported on vulcan XC 72R, and followed by heat treatment in an inert atmosphere at 600 C. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) were employed with the Koutechy-Levich theory to make clear the ORR kinetical constants and the reaction mechanism. It is found that the catalysts dual-doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The overall electron transfer numbers for the catalyzed ORR are determined to be 3. 899 and 3. 098, respectively, for the catalysts with and without TsOH-doping. And these catalysts exhibit superior methanol tolerance to commercial 40% Pt/C catalyst. The XRD results demonstrate the decomposition of the precursors because of pyrolysis and formation of Fe-N-x-C active surface groups and some less active species. XPS analysis indicate that the pyrrolic-N groups are the most active sites and sulfur species are also structurally bonded to carbon in the forms of C-S-n-C and oxidized -SOn- bonds, which are beneficial for ORR.
