Morphology and defect modification on in-situ derived Co9S8-porous nitrogen-doped carbon as a bifunctional electrocatalyst for oxygen evolution and reduction

Abstract

Exploration high-efficient bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance for several renewable energy applications. In this paper, a catalyst composed of Co9S8 and porous carbon (Co9S8–C) is prepared first via the calcination of Co–S–C based precursor coating on carbon-fibre-paper (CFP) substrate under argon atmosphere. Then, the Co9S8–C is modified via the decomposition gas of dicyandiamide, thus Co9S8–N-doped carbon (Co9S8-NC) catalyst is synthesized. As revealed, the morphology and defect features are effectively modulated by the modification, suggesting the reduced particle sizes of Co9S8 component and obviously improved N proportion and various defects. As a result, Co9S8-NC represents excellent activities electrocatalytic performances toward OER and ORR, which surpass those of its three counterparts including Co9S8–C, Co9S8, and NC. A half-wave potential of 0.86 ​V versus RHE for ORR and a low overpotential of 280 ​mV ​at 10 ​mA ​cm-2 current density for OER are achieved, with the ΔE value of 0.64 ​V. Additionally, the catalyst also demonstrates desirable application prospect for Zn-air battery. The post-treatment method reported here might be utilized widespread to promote the synergistic effects between the Co-contained particles and N-doped carbons in composite catalysts.