How Much N-Doping Can Graphene Sustain?

Abstract

Doped, substituted, or alloyed graphene is an attractive candidate for use as a tunable element of future nanomechanical and optoelectronic devices. Here we use the density functional theory, density functional tight binding, cluster expansion, and molecular dynamics to investigate the thermal stability and electronic properties of a binary 2D alloy of graphitic carbon and nitrogen (C(1-x)N(x)). The stability range naturally begins from graphene and must end before x = 1, where pure nitrogen rather forms molecular gas. This poses a compelling question of what highest x < 1 still permits stable 2D hexagonal lattice. Such upper limit on the nitrogen concentration that is achievable in a stable alloy can be found based on the phonon and molecular dynamics calculations. The stability switchover is predicted to between x = 1/3 (33.3%) and x = 3/8 (37.5%), and no stable hexagonal lattice two-dimensional CN alloys can exist at the N concentration of x = 3/8 (37.5%) and higher.

High-temperature superconductivity in heavily N- or B-doped graphene

“…2(b)] shows two branches having imaginary frequency modes (following conventional notation, we plot imaginary frequency as negative values), consistent with previous results [12]. The lower soft branch corresponds to out-of-plane acoustic (ZA) mode, and the upper branch is out-of-plane optic (ZO) mode.…”

“…This result demonstrates that the N uptake concentration in graphene can be as high as 50% by applying both hole-doping and tensile strain, simultaneously. This concentration is much higher than that reported previously [11,12]. …”

“…The maximum N content that has been achieved experimentally thus far is 21.66 wt%, corresponding to honeycomb-(h-) C 1-x N x composition of x = 19.1% [11]. Yakobson and oworkers used a cluster expansion model to explore the structure and stability of h-C 1-x N x with different x and concluded that when x exceeds 37.5%, the 2D alloy structure will be dynamically 3 unstable [12]. Similarly, in B-doped graphene (h-C 1-x B x ), the highest B uptake is x = 25%, namely, BC 3 sheet [13,14].…”

Tuning the nature of nitrogen atoms in N-containing reduced graphene oxide

“…The amount of nitrogen and level of reduction achieved by each particular method determines the electrical and conducting properties of the resulting material, [6] depending not only on the chosen technique but also on the experimental conditions employed. In the continuous race to achieve the highest possible amount of N-doping, [22] the nature of the resulting N atoms is sometimes M A N U S C R I P T…”

Materials design for electrocatalytic carbon capture

“…Substitutional N-doped graphene is conductive and is herein predicted to have electro-responsive switchable binding capacity for CO 2 , via the C sites adjacent to the N dopant atoms. Given that there is a limit to the fraction of N that can be doped into graphene of around 1/3, 49 it is also significant to consider the binding capacity for CO 2 around the N site. There are three adjacent carbons that could potentially bind.…”