Pore-edge graphitic nitride-dominant hierarchically porous carbons for boosting oxygen reduction catalysis

The construction of pore structures at different scales (atomic defect and molecular porous structures) is the most promising method to achieve excellent ORR catalytic activity for carbon-based catalysts. As a proof of concept, a graphitic nitride-doped carbon substrate was chosen as the research model in this study, and we fabricated a delicate pore-edge graphitic-nitride configuration (labeled as P N-C) with hierarchical porosity and abundant vacancy defects via a SiO2-protected shell-mediated template approach. The hole edge carbon defects in the derived porous carbon expose efficient active sites and modulate the electronic environment to be favorable for catalyzing oxygen reduction, while the enriched porosity facilitates charge transfer. All of these features enable considerable catalytic performance, with a half-wave potential of 0.842 V and high extreme current density under alkaline conditions. As expected, the P N-C applied as a cathode in liquid zinc–air batteries (ZABs) delivers a high specific capacity of 779.4 mA h g Zn−1 at 20 mA cm−2, with satisfactory operating stability, proving its practical feasibility. This study highlights that the rational engineering of pore structures is key to achieve kinetic promotion in carbon-based ORR catalysts.