PEDOT functionalized ZIF-67 derived Co-N-S triple-doped porous carbon for high-efficiency oxygen reduction

Highlights: • PEDOT/ZIF-67 was used as precursor to prepare Co, N and S tri-doped porous carbon. • PEDOT functionalization inhibits the aggregation of the final carbon catalyst. • Acid etching leads to exposure of more active sites and transport channels for ORR. • The tri-doped porous carbon exhibits superior ORR activity and methanol-tolerance. Herein, we report the use of poly(3,4-ethylenedioxythiophene) functionalized ZIF-67 (PEDOT/ZIF-67) as a precursor for preparing an efficient and precious metal-free oxygen reduction reaction (ORR) catalyst. The PEDOT/ZIF-67 precursor is subjected to pyrolysis at 800 °C and subsequent acidic etching with 1 M HCl to form Co-N-S triple-doped porous carbon (Co-N-S-PC), in which PEDOT functionalization inhibits the aggregation of the product, while the etching removes the excess Co metal and Co oxides, leading to exposure of more active sites and increase of transport channels. Electrochemical measurements reveal that the Co-N-S-PC catalyst obtained this way has outstanding activity, improved methanol-tolerance and high stability for ORR. Specifically, the limited current density (J_L) and half-wave potential (E_1/2) of the Co-N-S-PC are ~5.183 mA cm⁻² and ~0.845 V, respectively, higher than those of commercial Pt/C (~5.049 mA cm⁻² and 0.824 V). In addition, Co-N-S-PC is insensitive to methanol, without any responses to the injected 2 M CH₃OH solution. Furthermore, the Co-N-S-PC displays better long-term stability, identified by its high activity retention (97.87%) and half-wave potential after chronoamperometry test for 5 h.