Synthesis of amorphous and graphitized porous nitrogen-doped carbon spheres as oxygen reduction reaction catalysts

Abstract

Amorphous and graphitized nitrogen-doped (N-doped) carbon spheres are investigated as structurally well-defined model systems to gain a deeper understanding of the relationship between synthesis, structure, and their activity in the oxygen reduction reaction (ORR). N-doped carbon spheres were synthesized by hydrothermal treatment of a glucose solution yielding carbon spheres with sizes of 330 ± 50 nm, followed by nitrogen doping via heat treatment in ammonia atmosphere. The influence of a) varying the nitrogen doping temperature (550–1000 °C) and b) of a catalytic graphitization prior to nitrogen doping on the carbon sphere morphology, structure, elemental composition, N bonding configuration as well as porosity is investigated in detail. For the N-doped carbon spheres, the maximum nitrogen content was found at a doping temperature of 700 °C, with a decrease of the N content for higher temperatures. The overall nitrogen content of the graphitized N-doped carbon spheres is lower than that of the amorphous carbon spheres, however, also the microporosity decreases strongly with graphitization. Comparison with the electrocatalytic behavior in the ORR shows that in addition to the N-doping, the microporosity of the materials is critical for an efficient ORR.

Active learning-driven quantitative synthesis–structure–property relations for improving performance and revealing active sites of nitrogen-doped carbon for the hydrogen evolution reaction

“…9, we clearly observe the multivariate contributions of various features on the observed electrochemical performance. Contrary to prior research attributing electrochemical performance to one or the other N species, all N species 21,68,69 affect the electrochemical performance, a fact that may explain the conflicting reports in the literature. However, their effect is not the same: pyrrolic 54 and graphitic 17,53,54 Ns cooperate, whereas pyridinic 20,53 is antagonistic to the other two.…”

Tannin-Based Nanoscale Carbon Spherogels as Electrodes for Electrochemical Applications

“…Each of the spectra shows the distinct D-band at about 1337 cm –1 and G-band at roughly 1588 cm –1 , which correspond to the sp 2 -hybridized disordered carbon (A 1g in-plane breathing vibration mode) and ordered graphite (E 2g in-plane vibration mode), respectively. 43 In general, the D-band is not visible in pure graphitic structure but becomes more visible with a more disordered carbon structure. Hence, the ratio between the areas of the D- and G-bands ( A D / A G ratio) characterizes the relative degree of graphitization of the carbon material, with a higher ratio indicating a more disordered structure.…”

A Unique Synthesis of Macroporous N-Doped Carbon Composite Catalyst for Oxygen Reduction Reaction

“…5000 Wm −1 K −1 ) [ 25 ] has provided mechanical stability and increased charge transfer that can also increase catalytic reaction efficacy [ 26 , 27 ]. N-doped macroporous carbon materials have been synthesised by adopting several approaches, including pyrolysis of biomass [ 28 ], hydrothermal treatment of glucose [ 29 ], ternary doping of carbon fibres [ 30 ], and template methods [ 18 ]. Incorporation of graphene in MCMs is commonly achieved by thermal reduction of graphene oxide (GO) to reduced graphene oxide (rGO) [ 31 ].…”