Cobalt and nitrogen-doped carbon with enlarged pore size derived from ZIF-67 by a NaCl-assisted pyrolysis strategy towards oxygen reduction reaction

In this work, a facile method is reported for the synthesis of ZIF-67-derived cobalt and nitrogen-doped carbon (Co-N-C) materials with enlarged average pore sizes as electrocatalysts towards oxygen reduction reaction (ORR). The pore diameters of the Co-N-C can be greatly enlarged using NaCl as an additive during the pyrolyzing process. Thermo-gravimetry (TG) results suggest that NaCl could facilitate the structural decomposition of ZIF-67, resulting in the adjusted physiochemical properties of the obtained Co-N-C materials. The CoNC-1NaCl-700 and CoNC-1NaCl-800 materials derived from ZIF-67 in the presence of NaCl at relatively high pyrolyzing temperatures (i.e., 700 °C, 800 °C) exhibit superior catalytic activity compared with the CoNC materials derived from pure ZIF-67, which could be due to their unique structures of larger average pore sizes, higher surface areas, higher contents of pyridinic-N and graphitic-N. The onset potential of the CoNC-1NaCl-800 towards ORR is 0.94 V (vs. RHE) and the half-wave potential is 0.84 V (vs. RHE), which are comparable with that of commercial Pt/C.