Enhanced Thermal Oxidation Stability of Reduced Graphene Oxide by Nitrogen Doping

Abstract

Nitrogen-doped reduced graphene oxide (N-doped RGO) samples with a high level of doping, up to 13 wt. %, have been prepared by annealing graphene oxide under a flow of pure ammonia. The presence of nitrogen within the structure of RGO induces a remarkable increase in the thermal stability against oxidation by air. The thermal stability is closely related with the temperature of synthesis and the nitrogen content. The combustion reaction of nitrogen in different coordination environments (pyridinic, pyrrolic, and graphitic) is analyzed against a graphene fragment (undoped) from a thermodynamic point of view. In agreement with the experimental observations, the combustion of undoped graphene turns out to be more spontaneous than when nitrogen atoms are present.

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

“…[26] As previously reported, both the treatment time and NH 3 flow rate do not play a significant role in the final N content of the samples. [13] Therefore, in the present study these parameters are kept constant for all the treatments (1 h, 300 mL min -1 ). Figure 1 summarizes the N content of the prepared samples, as determined by elemental analyses.…”

“…[13] Concentrated H 2 SO 4 (115 mL) and NaNO 3 (2.5 g) were added slowly to graphite powder (5g) (< 20 µm, Sigma-Aldrich), and the mixture was cooled down to 0 ºC. with an operational range of 200-nm was used.…”

“…Chemical functionalization and doping are an efficient way to tailor the physical and chemical behaviour of materials. [4,5] In this context, N-doping is an interesting approach since this not only allows n-type doping [6] and improves its performance in electrocatalysis, [7,8] supercapacitors, [9] sensors [10] or as magnetic material, [11,12] but also confers enhanced thermal stability; [13] thus extending its potential in fuel cell applications and other fields where high temperatures are required. [4, 14, 15] Different methods have been explored to introduce nitrogen either (i) during the synthesis of the graphene sheets via chemical vapour deposition (CVD) [16] and arc discharge, [17] or (ii) via a post synthesis modification.…”

“…For comparison, data on a sample of previously reduced GO (RGO) subsequently treated with ammonia at 500 ºC is also included (empty rhombus). The employed RGO was prepared by annealing GO at 1050 ºC under Ar/H 2 atmosphere [13]. Elemental analysis confirms the absence of nitrogen in the ammonia treated RGO…”

Preparation, characterization, and physical properties of graphene nanosheets and films obtained from low-temperature expandable graphite

“…The related weight loss (28.3 %) is considerably lower than that of as-prepared graphene. In the later case, the oxygenated groups were involved in the oxidation of the graphitic layers [51].…”