Precise Graphitic Nitrogen-Incorporation by Electrochemical Oxidation

Abstract

Graphitic nitrogen (graphitic-N) plays a very important role in energy conversion and environmental protection. Although various synthesizing methods have been developed, complex devices and harsh conditions are often needed causing difficulty in flexible regulation. Electrochemical approaches are attracting increasing attention due to their mild reaction conditions, controllability, and environmental compatibility. However, precisely incorporating graphitic-N remains a significant challenge. This study designed a synthesis strategy that creating carbon single vacancies via electrochemical oxidation and then incorporating N radicals to construct graphitic-N. Graphite paper doped with exclusive graphitic-N was achieved by using ammonium ions as the nitrogen source. By integrating multiple operando electrochemical characterization techniques and density functional theory calculations, the crucial regulation parameters were clarified and the proposed doping mechanism was validated. Hydroxyl radicals generating from electrochemical water dissociation performed three functions including: evolving (i) carbon single vacancies and (ii) adjacent oxygen-containing functional groups, as well as (iii) activating ammonium ions into N-radicals. Ketone exhibited superior thermodynamic behavior than hydroxyl when assembling N radicals into carbon single vacancies. The findings offer both experimental and theoretical foundations for a deeper understanding of the structure-property relationships of graphitic-N and broaden the application prospects of graphitic-N-doped materials.