Electronic Structures of N-doped Graphene with Native Point Defects

TL;DR

This study uses density functional theory to analyze how nitrogen doping affects the electronic properties of graphene with native point defects, revealing complex interactions that influence free carrier generation and potential catalytic activity.

Contribution

It provides new insights into the electronic structures of N-doped graphene with vacancies and Stone-Wales defects, highlighting defect-dopant interactions and their effects on electronic and magnetic properties.

Findings

Monovacancies act as hole dopants in graphene.

Two N dopants are needed to compensate for vacancy-induced holes.

N dopants at divacancies can act as acceptors rather than donors.

Abstract

Nitrogen doping in graphene has important implications in graphene-based devices and catalysts. We have performed the density functional theory calculations to study the electronic structures of N-doped graphene with vacancies and Stone-Wales defect. Our results show that monovacancies in graphene act as hole dopants and that two substitutional N dopants are needed to compensate for the hole introduced by a monovacancy. On the other hand, divacancy does not produce any free carriers. Interestingly, a single N dopant at divacancy acts as an acceptor rather than a donor. The interference between native point defect and N dopant strongly modifies the role of N doping regarding the free carrier production in the bulk pi bands. For some of the defects and N dopant-defect complexes, localized defect pi states are partially occupied. Discussion on the possibility of spin polarization in such cases is given. We also present qualitative arguments on the electronic structures based on the local bond picture. We have analyzed the 1s-related x-ray photoemission and adsorption spectroscopy spectra of N dopants at vacancies and Stone-Wales defect in connection with the experimental ones. We also discuss characteristic scanning tunneling microscope (STM) images originating from the electronic and structural modifications by the N dopant-defect complexes. STM imaging for small negative bias voltage will provide important information about possible active sites for oxygen reduction reaction.