Effective construction of a B and N co-doped 3D porous carbon metal-free oxygen reduction reaction catalyst by a secondary pyrolysis strategy

Controllable development of cost-effective oxygen reduction reaction (ORR) catalysts with a bottom-up method is one of the primary remaining challenges in catalysis due to the complexity and random reaction among ingredient molecules. Herein, a B and N co-doped metal-free carbonaceous (BNC) catalyst with hierarchical porous structure and super high specific surface area was rationally constructed by a secondary pyrolysis method for the ORR. By comparatively analyzing the preparation parameter-structure relationship, the addition time of the B precursor was proved to have a key influence on the B doping content. Meanwhile, the secondary pyrolysis procedure endowed BNC with a large amount of homogeneous exposed N and B active species, abundant mass transfer nanopores, and high conductivity. Consequently, BNC provides an outstanding ORR activity with an onset potential of 0.94 V and a half-wave potential of 0.84 V, which are similar to those of Pt/C. More importantly, a BNC based Zn-air battery delivers high peak power density (115.5 mW cm(-2)) and good discharge stability (45 h).