Electroreduction of oxygen on nitrogen-doped carbon nanotube modified glassy carbon electrodes in acid and alkaline solutions (original) (raw)
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Carbon, 2011
The oxygen reduction reaction has been investigated on acid-treated single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT) modified glassy carbon (GC) electrodes in acid media using the rotating disk electrode (RDE) method. Different acids were used for the carbon nanotube (CNT) purification. A systematic study was carried out to elucidate whether the metal catalyst impurities of CNTs play a role in the electroreduction of oxygen on the CNT modified GC electrodes. The surface morphology of the carbon nanotube samples was examined by transmission electron microscopy and the concentration of metal catalysts in the CNT materials was determined by energy dispersive X-ray spectroscopy. The acid-treated MWCNTs were also characterised by Raman and X-ray photoelectron spectroscopies. Aqueous suspensions of SWCNTs and MWCNTs used for GC surface modification were prepared in the presence of Nafion. The RDE results indicated that the acid-treated CNT modified GC electrodes are less active catalysts for oxygen reduction than as-received CNTs which could be explained by the absence of metal catalysts on the surface of purified CNTs.
Nitrogen doped Carbon Nanotubes as Electrocatalyst for Oxygen Reduction Reaction
International Journal of Electrochemical Science, 2019
The oxygen reduction reaction on nitrogen doped multiwalled carbon nanotubes (N-MCNTs) is studied for its application for deoxygenation of seawater. N-MCNTs were synthesized using commercial MCNTs and polyaniline as nitrogen precursor and annealing at a high temperature. The ORR was studied on N-MCNTs in 0.5 M sodium chloride solution using a rotating disk electrode, and physical characterization of the electrocatalysts was performed using X-ray diffraction, mass spectroscopy and transmission electron microscope techniques. The material showed high activity for the ORR in the chloride electrolyte. The onset potential for N-MCNTs was 0.94 V vs RHE. Koutecky-Levich analysis showed that the electrons transfer mainly followed the four-electron pathway, and the electrocatalyst showed good stability during a 15-h stability test.
Electrochemistry Communications, 2010
A new approach to synthesize nitrogen-doped carbon nanotubes (NCNTs) as catalysts for oxygen reduction by treating oxidized CNTs with ammonia is presented. The surface properties and oxygen reduction activities were characterized by cyclic voltammetry, rotating disk electrode and X-ray photoelectron spectroscopy. NCNTs treated at 800°C show improved electrocatalytic activity for oxygen reduction as compared with commercially available Pt/C catalysts.
Electrochemistry Communications, 2010
The oxygen reduction reaction has been investigated on double-walled carbon nanotube (DWCNT) modified glassy carbon (GC) electrodes in acid and alkaline media using the rotating disk electrode (RDE) method. The surface morphology and composition of DWCNT samples was examined by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Aqueous suspensions of DWCNTs were prepared using Nafion and non-ionic surfactant Triton X-100 as dispersing agents. The RDE results indicated that the DWCNT modified GC electrodes are active catalysts for oxygen reduction in alkaline solution. In acid media DWCNT/GC electrodes possess poor electrocatalytic properties for O 2 reduction which indicates lack of metal catalyst impurities in the DWCNT material studied. The oxygen reduction behaviour of DWCNTs was similar to that of multi-walled carbon nanotubes (MWCNTs) observed in our previous studies.
Electrochimica Acta, 2014
Metal-free nitrogen-doped carbon nanotube (NCNT) catalysts were synthesised via chemical vapour deposition with ethylenediamine and iron phthalocyanine. The electrochemically active NCNT was studied via thin-film rotating-ring disk voltamogram analysis to elucidate the optimum loading of catalysts for oxygen reduction reaction (ORR) in 0.1 M KOH electrolyte. In this study, the activity and stability of NCNT at elevated temperature were investigated. The current limiting plateau was achieved with loading above 500 g/cm 2 on glassy carbon tip with insignificant change in onset potential (c.a. +0.9 V vs RHE). The highest electron transfer number of 3.90 was obtained and it was found comparable to n = 3.95 on 130 g/cm 2 Pt/C catalysts. The subjection to cell's temperature from 298 K to 343 K showed improved activity and was found stable above 323 K.
Electrochimica Acta, 2016
Iron-and cobalt-containing nitrogen-doped carbon catalysts based on multi-walled carbon nanotubes are prepared using pyrolysis of dicyandiamide and CoCl 2 or FeCl 3 at 800 C. The electroreduction of oxygen is studied in 0.5 M H 2 SO 4 solution by the rotating disk electrode method and the surface morphology and composition of the catalysts are characterised by scanning and transmission electron microscopies and X-ray photoelectron spectroscopy. The as-prepared catalysts show mediocre electrocatalytic activity for oxygen reduction reaction (ORR), which increases as a result of acid treatment and second pyrolysis. The electrocatalytic activity of Fe-containing catalyst towards the ORR surpasses that of Co-based material and it supports a 4-electron reduction of O 2. Co-containing catalyst, in turn, shows higher stability. Both catalysts are highly methanol tolerant in acid media. The transition metal-containing N-doped carbon materials are promising cathode catalysts for low-temperature fuel cells.
Activity and active sites of nitrogen-doped carbon nanotubes for oxygen reduction reaction
Journal of Applied Electrochemistry, 2013
Nitrogen-doped carbon (CNx) nanotubes were synthesized by thermal decomposition of ferrocene/ethylenediamine mixture at 600-900°C. The effect of the temperature on the growth and structure of CNx nanotubes was studied by transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. With increasing growth temperature, the total nitrogen content of CNx nanotubes was decreased from 8.93 to 6.01 at.%. The N configurations were changed from pyrrolic-N to quaternary-N when increasing the temperature. Examination of the catalytic activities of the nanotubes for oxygen reduction reaction by rotating disk electrode measurements and single-cell tests shows that the onset potential for oxygen reduction in 0.5 M H 2 SO 4 of the most effective catalyst (CNx nanotubes synthesized at 900°C) was 0.83 V versus the normal hydrogen electrode. A current density of 0.07 A cm-2 at 0.6 V was obtained in an H 2 /O 2 proton-exchange membrane fuel cell at a cathode catalyst loading of 2 mg cm-2. Keywords Nitrogen-doped carbon nanotubes Á Thermal decomposition Á Oxygen reduction reaction Á Non-precious metal catalysts
Catalysis Today, 2015
Nitrogen-doped carbon nanotubes (N-CNT) were synthesized at 700 • C via the chemical vapour deposition (CVD) method and were used as catalysts in the oxygen reduction reaction (ORR) in 0.1 M KOH. The activity toward the ORR and the stability of these N-CNTs in alkaline solution were studied as a function of the reaction temperature and of the chemical treatment applied to the catalyst. The kinetic analysis of these catalysts was also carried out and compared to the ORR performance of the commercial Pt/C Vulcan XC72 catalyst. N-CNT-700BW catalyst without any chemical treatment after the CVD synthesis, possesses a half-wave potential E 1/2 of approximately 0.82 V vs. RHE, 50 mV lower than the E 1/2 value of Pt/C catalyst and a specific current density J k at 0.9 V = 5.46 mA/mg at T = 25 • C. Removal of the major part of the iron growth catalyst by a chemical treatment resulted in a strongly decreased but still measurable activity. The activation energy of the N-CNT-based catalyst was calculated and is around 38 kJ mol −1 at an ORR overpotential of 300 mV. Increasing the temperature of the electrolyte up to 75 • C leads to a positive shift of the half-wave potential of the reaction as well as an increase of the H 2 O 2 escape. The long-term stability test has also been conducted and indicates a good stability of the activity of the N-CNT-based catalysts under operation in alkaline media.
Carbon, 2014
In this work the electrocatalysis of oxygen reduction on nitrogen-doped few-layer graphene/multi-walled carbon nanotube (FLG/MWCNT) composite catalyst has been investigated. These composite materials were prepared from different nitrogen precursors, acid-treated MWCNTs and graphene oxide (GO), which was synthesised from graphite by the modified Hummers' method. Urea and dicyandiamide were used as nitrogen precursors and the doping was achieved by pyrolysing the mixture of GO and MWCNTs in the presence of these nitrogen-containing compounds at 800°C. The N-doped composite catalyst samples were characterised by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, the latter method revealed successful nitrogen doping. The oxygen reduction reaction (ORR) was studied in 0.1 M KOH on glassy carbon electrodes modified with N-doped FLG/MWCNT electrocatalysts employing the rotating disk electrode (RDE) method. The RDE results indicated that these metal-free nitrogen-doped nanocarbon catalysts possess remarkable electrocatalytic activity towards the ORR in alkaline media similar to that of commercial Pt/C catalyst. The results obtained in this work are particularly important for the development of non-Pt cathode catalysts for alkaline membrane fuel cells.