Upgrading the Properties of Reduced Graphene Oxide and Nitrogen-Doped Reduced Graphene Oxide Produced by Thermal Reduction toward Efficient ORR Electrocatalysts

Abstract

N-doped (NrGO) and non-doped (rGO) graphenic materials are prepared by oxidation and further thermal treatment under ammonia and inert atmospheres, respectively, of natural graphites of different particle sizes. An extensive characterization of graphene materials points out that the physical properties of synthesized materials, as well as the nitrogen species introduced, depend on the particle size of the starting graphite, the reduction atmospheres, and the temperature conditions used during the exfoliation treatment. These findings indicate that it is possible to tailor properties of non-doped and N-doped reduced graphene oxide, such as the number of layers, surface area, and nitrogen content, by using a simple strategy based on selecting adequate graphite sizes and convenient experimental conditions during thermal exfoliation. Additionally, the graphenic materials are successfully applied as electrocatalysts for the demanding oxygen reduction reaction (ORR). Nitrogen doping together with the starting graphite of smaller particle size (NrGO 325 -4) resulted in a more efficient ORR electrocatalyst with more positive onset potentials (E onset = 0.82 V versus RHE), superior diffusion-limiting current density (j L, 0.26V, 1600rpm = −4.05 mA cm −2 ), and selectivity to the direct four-electron pathway. Moreover, all NrGO m -4 show high tolerance to methanol poisoning in comparison with the state-of-the-art ORR electrocatalyst Pt/C and good stability.

Hierarchical Doped Gelatin-Derived Carbon Aerogels: Three Levels of Porosity for Advanced Supercapacitors

“…These values are greater than those reported for traditional carbon aerogels prepared via the pyrolysis of sol–gel-derived resin precursors at 2500 °C (at ∼5 nm [ 44 ]), yet lower than those reported for aerogels produced by subjecting a graphene oxide-based 3D graphene to high-temperature annealing (at crystallite sizes of >40 nm, and as high as 150 nm [ 34 ]). It shows that the crystallite size decreases with respect to the activation temperature which is due to the presence of defects due to doping levels of nitrogen and this is consistent with the earlier reported work [ 45 , 46 ].…”

Investigation of Nitrogen-Doping Influence on the Electrocatalytic Activity of Graphene in Alkaline Oxygen Reduction Reaction

“…After nitrogen-doping, n value increased to 3 (Table 3), indicating that N-graphene promotes oxygen partial and complete reduction pathways simultaneously, with possible formation of HOOand OHspecies. This combined 2 and 4 electrons reduction process has also been reported in other works for nitrogen-doped carbon-based electrocatalysts 28,[37][38][39] .…”

“…For example, Chai et al (2019) reported a b value of 75.4 mV dec -1 for a solid carbon spheres electrocatalyst 49 . Ramirez-Barria et al (2019) prepared a nitrogen-doped reduced graphene oxide electrocatalyst through the thermal annealing of reduced graphene oxide in ammonia-containing atmosphere at 700 °C, which was synthesized from a modified Brodie's method using 100 mesh graphite powder 39 . This electrocatalyst's b value was 99 mV dec -1 .…”

Investigation of and mechanism proposal for solvothermal reaction between sodium and 1-(2-hydroxyethyl)piperidine as the first step towards nitrogen-doped graphenic foam synthesis

“…Recently, nitrogen-doped carbon materials have attracted great attention due to their potential as critical metal-free catalysts, [18][19][20] their semi-conducting properties or their capacity to provide good anchors for metal nanoparticle nucleation. 21,22 Synthesized by arc-discharge-based synthesis, 23 chemical vapor deposition (CVD), 24 thermal treatment, 25,26 metallothermic reduction 27 or plasma treatment, 28 high quality N-doped carbon materials can also be prepared through direct solvothermal-based synthesis. [29][30][31][32] However, only a few examples of solvothermal synthesis of N-doped graphenic materials have been reported so far.…”