Zn and N co-doped carbon (Zn-N-C) shows encouraging catalytic stability for oxygen reduction reaction (ORR) because of the fulfilled d orbital of Zn, but its catalytic activity is not satisfactory. Herein, hierarchically porous Zn, S and N co-doped carbon (Zn-S-N-C) with large specific surface area (2433 m2 g-1) and pore volume (3.007 cm3 g-1) is synthesized by using NaCl/ZnCl2-assisted pyrolysis of sucrose and thiourea. The Zn-S-N-C catalyst exhibits superior ORR activity with half-wave potentials (E1/2) up to 0.774 V in 0.1 M HClO4 and 0.894 V in 0.1 M KOH, good ORR stability with 19- and 4-mV loss in E1/2 values after 10,000 potential cycles in 0.1 M HClO4 and 0.1 M KOH, respectively, and excellent methanol tolerance. The good ORR performance of Zn-S-N-C can be attributed to its enhanced intrinsic ORR activity resulting from the formation of S, N doped carbon and ZnS in Zn-S-N-C, its hierarchically porous structure resulting from the pore-forming roles played by ZnCl2, NaCl and thiourea, and its improved graphitization degree resulting from the added ZnCl2 during Zn-S-N-C synthesis. This work will provide a novel strategy for the synthesis of hierarchically porous Zn, S and N co-doped carbon materials for ORR.
Keywords: Oxygen reduction reaction; Salt-assisted pyrolysis; Zn-S-N-C catalyst.
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