Cobalt, sulfur, nitrogen co-doped carbon as highly active electrocatalysts towards oxygen reduction reaction
Rational design of efficient, cost-effective electrocatalyst towards oxygen reduction reaction (ORR) is of vital importance to the wide application of polymer electrolyte membrane fuel cells. In this work, a novel and simple Na 2 SO 4 -assisted pyrolysis strategy with ZIF-12 as the precursor is reported for the synthesis of cobalt, sulfur, nitrogen, co-doped carbon (termed as CoSNC- x Na 2 SO 4 -T) materials towards ORR. Different from CoNC-800 derived from pure ZIF-12, with the presence of Na 2 SO 4 , the derived CoSNC-0.5Na 2 SO 4 -800 material exhibits layered flake morphology with hierarchical meso-microporous structure. Besides, CoSNC-0.5Na 2 SO 4 -800 material shows higher content of pyridinic-N and graphitic-N, higher relative intensity of Co-N x , higher content of carbon defect, as well as larger specific surface area in comparison with CoNC-800, which results in higher activity of CoSNC-0.5Na 2 SO 4 -800. The CoSNC-0.5Na 2 SO 4 -800 material displays a half-wave potential of 0.88 V, which is superior to that of commercial Pt/C (half-wave potential being 0.86 V). Moreover, CoSNC-0.5Na 2 SO 4 -800 demonstrates a better durability compared with Pt/C. The pyrolysis temperature and the amount of Na 2 SO 4 are found to affect the physiochemical properties and electrochemical performance of the CoSNC- x Na 2 SO 4 -T materials. This work not only provides a facile and novel synthesis approach for the preparation of highly active Co, S, N co-doped carbon materials for ORR, but also disclosing the key structure properties for enhancing the performance of these catalysts.
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