Highly Dispersed Co-B/N Codoped Carbon Nanospheres on Graphene for Synergistic Effects as Bifunctional Oxygen Electrocatalysts.

Oxygen reduction and evolution reactions as two important electrochemical energy conversion processes in metal-air battery devices have aroused widespread concern. However, synthesis of low-cost non-noble metal-based bifunctional high-performance electrocatalysts is still a great challenge. In this work, we report on the design and synthesis of a novel Co-B/N codoped carbon with core-shell-structured nanoparticles aligned on graphene nanosheets (denoted as CoTIB-C/G) derived from cobalt tetrakis(1-imidazolyl)borate (CoTIB) and graphene oxide hybrid template. Compared with pristine CoTIB-derived bulk structure (CoTIB-C), CoTIB-C/G particles with an average size of 25 nm are uniformly dispersed on highly conductive graphene sheets in the hybrid material, thus dramatically increasing the utilization efficiency and activity of the active components upon oxygen reduction and evolution. After all, because of the "barrier effect" of graphene sheets toward CoTIB-C/G and the synergistic effect between Co nanoparticles and carbon shells linked to the graphene sheets, as well as heteroatoms' doping effect, the as-obtained bifunctional electrocatalyst exhibits remarkable oxygen reduction and evolution reaction activities in alkaline media, indicating its feasibility and potential in practical applications.