Co/NC-Gr composite derived from ZIF-67: Effects of preparation method on the structure and electrocatalytic performance for oxygen reduction reaction

Co/NC-Gr catalyst is prepared by in-situ growth of porous ZIF-67 on graphene (Gr) sheets followed by calcination. The effect of preparation method on the structure and catalytic performance of Co/NC-Gr for oxygen reduction reaction is studied. By optimizing the preparation process, the large Gr sheets are wrapped around the surfaces of the Co-incorporated polyhedral N-doped carbon skeleton. This structure plays a great role in connecting different Co/NC rhombic dodecahedron (RD), leading to high conductivity and fast mass transportation. The higher-content of pydinic-N and graphitic-N in Co/NC-Gr-A than those in Co/NC make it have enhanced catalytic activity. The porous Co/NC-Gr-A shows the highest ORR activity and stability through a dominant 4e(-) process. The Co/NC-Gr-A exhibits much higher methanol-tolerant ability than Pt/C. The yield of H2O2 during ORR on Co/NC-Gr-A is very close to that on commercial Pt/C. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.