Activation and Stabilization of Nitrogen-Doped Carbon Nanotubes as Electrocatalysts in the Oxygen Reduction Reaction at Strongly Alkaline Conditions
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- 作者：Anqi Zhao ; Justus Masa ; Wolfgang Schuhmann ; Wei Xia
- 刊名：Journal of Physical Chemistry C
- 出版年：2013
- 出版时间：November 21, 2013
- 年：2013
- 卷：117
- 期：46
- 页码：24283-24291
- 全文大小：488K
- 年卷期：v.117,no.46(November 21, 2013)
- ISSN：1932-7455
文摘
Nitrogen-doped carbon nanotubes (NCNTs) are highly active electrocatalysts in the oxygen reduction reaction (ORR) at alkaline conditions. However, the initial activation and stabilization of NCNTs have rarely been investigated at industrially relevant conditions. Three types of NCNTs were synthesized by catalytic growth (NCNT-growth) or posttreatment of oxygen-functionalized CNTs with NH3 (NCNT-NH3) or aniline (NCNT-aniline). The obtained NCNTs were treated in 10 M KOH at 80 掳C for 5 h, and the formation of oxygen groups by alkaline treatment and their interaction with existing nitrogen groups was analyzed. X-ray photoelectron spectroscopy showed that the concentrations of pyridinic and quaternary nitrogen increased in NCNT-growth due to the KOH treatment accompanied by the decrease of pyrrolic nitrogen, whereas the nitrogen groups changed differently in NCNT-NH3 and NCNT-aniline. NCNT-NH3 showed the highest ORR activity before alkaline treatment. After the treatment, the activity of NCNT-growth was higher, whereas those of NCNT-NH3 and NCNT-aniline were lower. These results were found to be correlated with changes in the nitrogen groups caused by alkaline treatment. Furthermore, NCNTs showed different C鈺怬/C鈥揙 ratios after alkaline treatment as compared to a strong increase of C鈥揙 in CNTs, indicating that the presence of nitrogen in NCNTs influences the formation of oxygen groups on carbon and surface oxidation.