Forming mechanism of nitrogen doped graphene prepared by thermal solid-state reaction of graphite oxide and urea

Enhancement of Au/AC acetylene hydrochlorination catalyst activity and stability via nitrogen-modified activated carbon support

“…Moreover, it is shown that the oxidation of AC by HNO 3 that creates various oxygen surface functional groups, however, as the annealing temperature increases to 500°C after disposition of urea, the content of oxygen decreases from 10.39 to 6.19 wt.%. Although it is often omitted that the thermal stability of the labile oxygen-containing functional groups, such as carboxylic groups, is limited to temperatures close to 400°C [36,37], AC can be reduced more easily in the presence of urea has been reported before [38]. Additionally, the Au/C ratio is close to the nominal ratio for Au/AC1 sample (0.98), but for the sample Au/ NAC1, the XPS-detected ratio of Au/C is only 56% of the nominal ratio.…”

Deactivation of carbon electrode for elimination of carbon dioxide evolution from rechargeable lithium–oxygen cells

“…This also implies that the NO x species of the surface layer is used as the source of nitrogen. The nitrogen doping of carbon, which typically takes place by the interaction of N-containing molecules with oxygenated groups on carbon (such as À OOH, ¼ O, À OH) and subsequent transformation into Pyrrolic or Pyridinic structures, leads to the loss of active sites on carbon surface 21,25 . The reaction between the solvate and active sites of carbon cathode in Li-O 2 cells, therefore, deactivates the carbon against parasitic reactions 26 .…”

Study on urea precursor effect on the electroactivities of nitrogen-doped graphene nanosheets electrodes for lithium cells

“…As shown in Table 1, pyrrolic-N was predominant and graphitic-N was not observed for all composites. This was because graphitic-N was probably formed during the thermal solid reaction at 500°C to 700°C [19,23]. The greater amount of nitrogen content in the NGS-3 composite, and the difference in distribution of the nitrogen species, may be dependent on the ratio of urea to GO and would explain the electrochemical performance of the cells [24,25].…”

“…The use of nitrogen atoms in a carbon matrix was expected to prevent dissolution of polysulfide and enhance the cycle performance of cells [18]. Because of its low cost and easy preparation, urea is generally the source of choice for nitrogen doping of graphene-based carbon materials [19,20]. Oxygen-containing functional groups in graphene oxide (GO) and amino-groups of urea are thought to be essential in the formation of C-N bonds in the graphene lattice.…”