Graphitic N-C-P configuration of phosphorus and nitrogen co-doped carbon for boosting the oxygen electroreduction

Abstract

The introduction of heteroatoms to carbon-based metal-free electrocatalysts has been verified to be a promising strategy for enhancing catalytic activity in the oxygen reduction reaction (ORR). Nevertheless, it remains a challenge to precisely identify the real active configuration of heteroatoms doped carbon, particularly for dual-heteroatom doping. Herein, a facile strategy is described to synthesize a phosphorus-nitrogen co-doped carbon (PNC) metal-free electrocatalyst. Benefiting from the abundant micropores/mesopores and large surface area of PNC cubes, it delivers a superb ORR activity with a half-wave potential (E_1/2 ∼ 0.870 V). More importantly, the experiment results demonstrate the strong correlation between the content of Graphitic N-C-P structure and kinetic current density. The density functional theory (DFT) calculations further unveil that the Graphitic N-C-P structure is the real active configuration of PNC. Notably, the doping of P atom can make the carbon atom adjacent to the Graphitic N be more positive, thereby optimizing the adsorption/desorption of ORR intermediates. Moreover, the assembled Zn-air battery (ZAB) based on PNC delivers outstanding long-term cycling stability for 420 h without significant decay. This work provides a path for the development of green and low-cost energy storage devices.