Effect of low-energy nitrogen ion treatment of highly ordered pyrolytic graphite on oxygen reduction reaction activity

Abstract

We systematically investigated highly ordered pyrolytic graphite film doped by low-energy atomic nitrogen ion of 20 eV, addressing major issues that include the effect of treatment time on the oxygen reduction reaction activity of highly ordered pyrolytic graphite film, and the influence of treatment time on the chemical and physical structures of highly ordered pyrolytic graphite surface. From the experimental results, it was clarified that the treatment for 60 s or less in nitrogen plasma was effective to modify the highly ordered pyrolytic graphite surface with improved oxygen reduction reaction performance, where the oxygen reduction reaction current increases by about 2 times as compared to that of untreated specimen. Moreover, we discussed the content of various C-N bonds, the strain which derived from the substitution of carbon and nitrogen, and a modification of the highly ordered pyrolytic graphite surface due to treatment, on the basis of the results of Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.

Boosted Electrocatalytic Oxygen Reduction Performance of Porous Co-NC Catalysts by the Coexistence of Abundant Co–N4 and g-N Sites

“…The value obtained by this method may be lower than that obtained by the de visu method . The diffusion-limiting current density ( J L ) of the Co-NC­(Zn12)-900 sample was −5.5 mA cm –2 at 0.4 V, outperforming the other materials, which may be explained by the presence of abundant Co–N 4 and g-N sites in porous structures for effective O 2 reduction, transportation, and diffusion. − The Tafel slope of the Co-NC­(Zn12)-900 sample was determined to be ca. −43.0 mV decade –1 , which was significantly higher than that of 10% Pt/C (−75.6 mV decade –1 ) (Figure D), and it showed better ORR kinetics on the Co-NC­(Zn12)-900 catalyst.…”

Electrocatalytic Activity of Heteroatom-Doped Graphene for Oxidation of Hydroquinones

“…We have also demonstrated that graphiticand pyridinic-nitrogen act as reaction sites for ORR on nitrogendoped high ordered pyrolytic graphite (HOPG) prepared by electron-beam-excited plasma treatment. 61,62 Previous researches suggest that the catalytic activity of doping elements for ORR is dependent on both elemental species and its lattice structure. However, for organic molecules, few studies were reported on the investigation of the catalytic activity using heteroatom-doped graphenes.…”

Dependence on treatment ion energy of nitrogen plasma for oxygen reduction reaction of high ordered pyrolytic graphite

“…12) It has currently been reported that the active sites of oxygen reduction reaction (ORR) are created by the graphite-N and pyridinic-N components, and the mixing of the nitrogen species in the carbon materials. 1,[7][8][9][10]13,16,19,22,23) However, the high energy bombardment in the doping process may cause a significantly damage on the surface morphology of carbon material. In spite of such efforts, the relationship between the nitrogen ion energy and the resultant electronic properties of carbon-based materials, remains far from being completely understood.…”

“…In a previous paper, we have reported that the ORR activity of HOPG film is improved when its surface is modified by a short time treatment with low-energy nitrogen ions of 20 eV. 23) The nitrogen doping into HOPG film was carried out using the electron beam excited plasma (EBEP). [23][24][25][26][27][28][29] Nitrogen plasma using the EBEP system can generate the higher density nitrogen atoms and ions when compared to the conventional plasma system.…”

“…23) The nitrogen doping into HOPG film was carried out using the electron beam excited plasma (EBEP). [23][24][25][26][27][28][29] Nitrogen plasma using the EBEP system can generate the higher density nitrogen atoms and ions when compared to the conventional plasma system. The HOPG films at the treatment time of 60 s using the nitrogen ion of 20 eV, indicated that the ORR current increased by about 2 times as compared with the untreated specimen.…”