Nitrogen and Phosphate Co‐doped Graphene as Efficient Bifunctional Electrocatalysts by Precursor Modulation Strategy for Oxygen Reduction and Evolution Reactions

Abstract

AbstractHeteroatoms doped carbon‐based metal‐free catalysts are important candidates as alternatives for precious group metal (PGM) catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) – two of the most important reactions in electrochemical energy conversion and storage areas. Despite the significant efforts in developing heteroatoms doped metal‐free electrocatalysts with enhanced electrocatalytic activity, few studies focus on their bifunctional activities for ORR and OER due to the unclear catalytic mechanism and complicated active sites configurations. Herein, a series of nitrogen and phosphate co‐doped carbon‐based catalysts (NP/C) are successfully synthesized via a precursor modulation strategy. In this method, 5‐aminouracil, 2, 6‐diaminopyridine and 1, 3‐diaminobenzene are selected to modulate pyridinic N (NP), graphitic N (NG) and pyrrolic N (NPY) sites, respectively, while phytic acid is used as P sites. The results demonstrate that the N and P co‐doped graphene with NP+NG+P configuration shows increased ORR performance, and on the other hand, the NP+NPY+P configuration enhances OER. Density functional theory (DFT) calculation demonstrates that different NP configurations formed by precursor modulation induce different electronic structure on surrounding carbon atoms, providing a possibility to manipulate intermediates energy in reaction pathway for ORR and OER. This study sheds new light on revealing the intrinsic correlation between active site configurations and catalytic bifunctional activity and selectivity of graphene based electrocatalysts for oxygen redox reactions.