ZIF-derived carbons as highly efficient and stable ORR catalyst

Abstract

To develop highly efficient none-precious metal catalysts in lieu of Pt/C for catalyzing oxygen reduction reaction (ORR), ZIF-67 derived carbons are fabricated rationally in combination with reduced graphene oxide (rGO) integration and further KOH etching respectively. ZIF-C/rGO presents excellent ORR activity especially in alkali media with onset potential, half-wave potential and limited current density being 1.00 V, 0.87 V and 5.92 mA cm−2, respectively, which are close approaching or superior to those of commercial Pt/C. Although the ORR activity in acid media is still a little inferior to that of the Pt/C, the durability of ZIF-C/rGO is better in both alkali and acid electrolytes. Further KOH etching (ZIF-C/rGO-KOH) reduces active N sites and destroys the micropores with resulting in reduced ORR performances, though more mesopore Brunauer–Emmett–Teller surface and volume are obtained. Through comparable study, huge performance enhancements form rGO integration is attributed to the attained higher charge transfer channels, more micropores with avoiding great losses of N and Co active sites can depress over polarization of electrolyte, aggregation of active components and collapsing of mass transport channels, on which the ORR activity is boosted to the extreme due to the resulted synergistic effect.