Facile synthesis of three-dimensional Co/N co-doped carbon nanocuboids for an enhanced oxygen reduction reaction

Abstract

The design of metal nitrogen carbon (M–N–C) nanocatalysts with increased durability and activity in the oxygen reduction reaction of fuel cells and metal–air batteries still remains a challenge. Herein, a highly efficient three-dimensional Co–N–C nanocuboids (CoN/CNCs) catalyst synthesized through co-pyrolysis of cobalt benzimidazole frameworks and graphitic carbon nitride (g-C₃N₄) is reported. The distinct porous nanocuboids and g-C₃N₄ play a vital role in improving the ORR performance by fully exposing Co–N active sites, increasing the electron-transfer efficiency, and facilitating the mass transport. Additionally, Co atoms anchored on the highly graphitized carbon matrix are conducive to inhibit the aggregation of metal and carbon corrosion, thereby boosting the activity and stability of catalyst. The optimal CoN/CNCs-800 nanohybrid exhibits superior catalytic performance towards the ORR, with values for E_1/2 of 0.852 V and for J_L of 5.18 mA cm⁻², close to the standard of commercial Pt/C (0.860 V and 5.29 mA cm⁻²). Based on the Koutecky–Levich plots, the number of electrons transferred for CoN/CNCs-800 is calculated to be 4.0, indicating that the ORR over CoN/CNCs-800 follows a 4e⁻ pathway. Meanwhile, the CoN/CNCs-800 catalyst displays excellent methanol tolerance and long-term stability. This work presents a universal strategy for rationally designing and preparing three-dimensional Co–N–C nanocuboids towards boosting the catalytic ORR performance.