A Facile Approach to Efficiently Load and Isolate CoN Active Sites for the Preparation of a High-Performance Co-N-C Oxygen Reduction Catalyst

A facile approach is developed for the preparation of an oxygen reduction reaction (ORR) catalyst Co-N-GA-1 by pyrolyzing a well-designed precursor CoTPP/H2TPP@OGA. In the precursor, Co is preanchored into the porphyrinato cobalt CoTPP molecule by Co-N-4 core that is further protected by the metal-free porphyrin H2TPP depending on the intermolecular pi-pi interaction during the self-assembled process on the surface of lipophilic porous original graphene aerogel. The resulted Co-N-GA-1 owns a Co elemental content up to 1.67%, which is approximate to 13 times than that of Co-N-CB-1 originated from a CoTPP/H2TPP precursor absorbed on commercial carbon black. Meanwhile, CoN content accounts for 71.7% of the total Co-based species in the Co-N-GA-1, more than that of CoN-GA-2 (58.9%) originated from the CoTPP@OGA precursor. Consequently, Co-N-GA-1 exhibits the most ORR performance among the present three catalysts with the more positive onset and half-wave potentials of 0.96 and 0.88 V vs reversible hydrogen electrode, respectively, also superior to those of the commercial 20 wt% Pt/C and most of the Co-based catalysts reported so far. Furthermore, Zn-air battery assembled with Co-N-GA-1 exhibits a higher peak power density of 110 mW cm(-2) and excellent durability than that with Pt/C.