Simultaneous Nitrogen Doping and Reduction of Graphene Oxide

Abstract

We develop a simple chemical method to obtain bulk quantities of N-doped, reduced graphene oxide (GO) sheets through thermal annealing of GO in ammonia. X-ray photoelectron spectroscopy (XPS) study of GO sheets annealed at various reaction temperatures reveals that N-doping occurs at a temperature as low as 300ºC, while the highest doping level of ~5% N is achieved at 500ºC. N-doping is accompanied by the reduction of GO with decreases in oxygen levels from ~28% in as-made GO down to ~2% in 1100ºC NH 3 reacted GO. XPS analysis of the N binding configurations of doped GO finds pyridinic N in the doped samples, with increased quaternary N (N that replaced the carbon atoms in the graphene plane) in GO annealed at higher temperatures (>900ºC). Oxygen groups in GO were found responsible for reactions with NH 3 and C-N bond formation.Pre-reduced GO with fewer oxygen groups by thermal annealing in H 2 exhibits greatly reduced reactivity with NH 3 and lower N-doping level.2 Electrical measurements of individual GO sheet devices demonstrate that GO annealed in NH 3 exhibits higher conductivity than those annealed in H 2 , suggesting more effective reduction of GO by annealing in NH 3 than in H 2 , consistent with XPS data. The N-doped reduced GO shows clearly n-type electron doping behavior with Dirac point (DP) at negative gate voltages in three terminal devices. Our method could lead to the synthesis of bulk amounts of N-doped, reduced GO sheets useful for various practical applications.3

Structure of graphene and its disorders: a review

“…Akada et al [349] found that nitrogen atoms doped at a graphitic site (inside the graphene) lower the work function, while nitrogen atoms at a pyridinic or a pyrrolic site (edge of graphene) increase the work function, and they suggested that the work function of graphene can be tuned from 4.3 eV to 5.4 eV by adjusting plasma treatment time and the amount of initial defects. Further, thermal annealing in ammonia environment allows efficient synthesis of N-doped rGO sheets with fairly high-conductivity [350]. …”

Surface modification of graphene and graphite by nitrogen plasma: Determination of chemical state alterations and assignments by quantitative X-ray photoelectron spectroscopy

“…Annealing of graphene or graphene oxide with NH 3 is also a means of nitrogen doping that can easily be scaled, but it requires elevated temperatures (over 300 °C) [19][20][21].…”

Nanocrystal Growth on Graphene with Various Degrees of Oxidation

“…[7][8][9] The oxygen content in GS (~5%) was much lower than in GO (~20%) as measured by Auger spectroscopy 9 and X-ray photoelectron spectroscopy (XPS). 11 In the first step of Ni(OH) 2 growth on graphene, we deposited precursor materials in the form of small nanoparticles uniformly nucleated onto GS or GO by hydrolysis of Ni(CH 3 COO) 2 at 80℃ in a 10:1 N, N-dimethylformamide (DMF)/water mixture (see Supporting Information). The 10:1 DMF/H 2 O ratio was found important to afford good dispersion of graphene and slow rate of hydrolysis that led to selective and uniform coating of nickel hydroxide on graphene, with little particle growth in free solution.…”