Enhancing Electron Transfer and Electrocatalytic Activity on Crystalline Carbon-Conjugated g-C₃N₄

Abstract

Carbon nitride (g-C 3 N 4 ) materials are electro-activated for oxygen reduction (ORR) and oxygen evolution (OER) reactions when they are supported by conductive carbons. However, the electrocatalytic process on semiconductor-based heterostructures such as carbon-supported g-C 3 N 4 still suffers from a huge energy loss because of poor electron mobility. Here, we demonstrated a concept that the conjugation of g-C 3 N 4 with crystalline carbon can improve the in-plane electron mobility and make interior triazine units more electro-active for ORR and OER. As a result, the Co metal coordinated g-C 3 N 4 with crystalline carbons (Co–C 3 N 4 /C) showed a remarkable electrocatalytic performance toward both ORR and OER. For example, it displayed an onset potential of 0.95 V for ORR and an overpotential of 1.65 V for OER at 10 mA cm –2, which are comparable and even better than those of benchmark Pt, RuO 2, and other carbon nitride-based electrocatalysts. As a proof-of-concept application, we employed this catalyst as an air electrode in the rechargeable aluminum-air battery, which showed more rechargeable and practicable than those of Pt/C and RuO 2 catalysts in two-electrode coin battery. The characterization results identified that the good performance of Co–C 3 N 4 /C was primarily attributed to the enhanced in-plane electron mobility by crystalline carbon conjugation and the Co-coordinated g-C 3 N 4 along with nitrogen-doped carbons.