Fabrication of monodispersed B, N co-doped hierarchical porous carbon nanocages through confined etching to boost electrocatalytic oxygen reduction

Dual heteroatom-doped carbons have attracted widespread research attention as catalysts in the field of energy storage and conversion due to their unique electronic structures and chemical tunability. In particular, boron and nitrogen co-doped carbon (B,N@C) has shown great potential for photo/electrocatalytic applications. However, more needs to be done for rational designing and regulating the structure of these materials to improve their catalytic performance. Herein, monodispersed hierarchical porous B,N@C nanocages were fabricated by pyrolyzing zeolite imidazole framework (ZIF) which was treated with ammonia borane or boric acid via an integrated double-solvent impregnation and nanocofined-etching method. The treated ZIF-8 provided an essential structural template to achieve B, N co-doped hierarchical structures with micro/meso/macro multimodal pore size distributions. The resultant B,N@C nanocages displayed high catalytic activities for electrochemical oxygen reduction reaction (ORR) in alkaline media, outperforming most carbon-based catalysts, particularly from the perspective of the half-wave potentials. Such high catalytic performance is due to the enhanced activity by the coexistence of B and N and the mass transfer promoted by the unique hierarchical porous structure.