Interplay between Nitrogen Dopants and Native Point Defects in Graphene

TL;DR

This study uses density functional theory to explore how nitrogen dopants interact with native point defects in graphene, revealing that defects influence dopant stability and promote their aggregation, with implications for material modification.

Contribution

It provides new insights into the energetic preferences and cooperative effects of nitrogen dopants and native defects in graphene, supported by theoretical calculations and experimental correlation.

Findings

N prefers to substitute near defect sites with larger bond shortening.

Doping becomes exothermic in defective graphene, unlike in defect-free graphene.

Native defects and N dopants attract each other, promoting defect and dopant aggregation.

Abstract

To understand the interaction between nitrogen dopants and native point defects in graphene, we have studied the energetic stability of N-doped graphene with vacancies and Stone-Wales (SW) defect by performing the density functional theory calculations. Our results show that N substitution energetically prefers to occur at the carbon atoms near the defects, especially for those sites with larger bond shortening, indicating that the defect-induced strain plays an important role in the stability of N dopants in defective graphene. In the presence of monovacancy, the most stable position for N dopant is the pyridinelike configuration, while for other point defects studied (SW defect and divacancies) N prefers a site in the pentagonal ring. The effect of native point defects on N dopants is quite strong: While the N doping is endothermic in defect-free graphene, it becomes exothermic for defective graphene. Our results imply that the native point defect and N dopant attract each other, i.e., cooperative effect, which means that substitutional N dopants would increase the probability of point defect generation and vice versa. Our findings are supported by recent experimental studies on the N doping of graphene. Furthermore we point out possibilities of aggregation of multiple N dopants near native point defects. Finally we make brief comments on the effect of Fe adsorption on the stability of N dopant aggregation.