Cobalt-gluconate-derived high-density cobalt sulfides nanocrystals encapsulated within nitrogen and sulfur dual-doped micro/mesoporous carbon spheres for efficient electrocatalysis of oxygen reduction

Abstract

The exploration of an efficient nonprecious electrocatalyst for oxygen reduction reaction (ORR) is critical to the commercialization of various electrochemical energy-conversion devices. Herein, a cobalt-gluconate-derived nitrogen and sulfur dual-doped micro/mesoporous carbon sphere (Co9S8/N, S-MCS) with encapsulated high-density cobalt sulfide (Co9S8) nanocrystals is developed by annealing and subsequent high-temperature vulcanization. Particularly, the vulcanization temperature has a critical impact on the formation of high-density Co9S8 nanocrystals. Benefiting from the favorable material characteristics of large surface area, abundant micro/mesopores and high graphitic nanostructures, as well as the synergistic effects between high-density Co9S8 nanocrystals and N, S-dual doped graphitic carbon shells, the resulting catalyst demonstrates superior ORR catalytic activity and durability compared to platinum/carbon (Pt/C) catalyst. More notably, the proposed approach can be extended potentially to fabricate other transition metal sulfide (or oxide, carbide) based electrocatalysts.