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.