A hybrid of Co3O4 nanoparticles coupled with B, Co/N-codoped C@B4C as an efficient bifunctional catalyst for oxygen reduction and oxygen evolution reactions

Abstract

The design of novel cost-effective, highly-efficient and highly-durable non-noble-metal bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been an important research subject in the sustainable energy fields such as regenerative fuel cells and rechargeable metal-air batteries. Here, a hybrid of Co3O4 nanoparticles coupled with core-shell structured B, Co/N-codoped carbon on nano-B4C (Co3O4/B4C@CoNBC) was demonstrated to be an effective bifunctional catalyst. For the first time, nano-B4C was used as a catalytic material not only a catalyst support. The B4C@BC prepared by annealing nano-B4C had ORR catalytic activity due to B self-doped carbon shell. Then, we combined B4C@BC and Co3O4 nanoparticles effectively and doped with N in the meanwhile by the hydrothermal method to obtain Co3O4/B4C@CoNBC. Remarkably, the Co3O4/B4C@CoNBC showed the overall oxygen redox activity (OER/ORR) was only 0.70 V in 0.1 M KOH, outperforming the recently reported highly active non-noble metal bifunctional catalysts. The excellent catalytic activities were attributable to the synergetic effects of Co3O4, B self-doped carbon and Co/N-doped carbon in Co3O4/B4C@CoNBC. In addition, the B4C with strong chemical stability could be used as a support through synergistic effect with Co3O4 and CoNBC to effectively improve the stability of the hybrid.