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Role of Nitrogen Doping on the Performance of Carbon Nanotube Catalysts: A Catalytic Wet Peroxide Oxidation Application
Author(s) -
MartinMartinez Maria,
Ribeiro Rui S.,
Machado Bruno F.,
Serp Philippe,
MoralesTorres Sergio,
Silva Adrián M. T.,
Figueiredo José L.,
Faria Joaquim L.,
Gomes Helder T.
Publication year - 2016
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201600123
Subject(s) - catalysis , peroxide , mineralization (soil science) , decomposition , radical , carbon nanotube , chemistry , doping , nitrogen , chemical decomposition , inorganic chemistry , materials science , organic chemistry , nanotechnology , optoelectronics
Four magnetic carbon nanotube (CNT) samples (undoped, completely N‐doped, and two selectively N‐doped) were synthesized by chemical vapor deposition. The materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4‐nitrophenol solutions (4‐NP, 5 g L −1 ). Relatively mild operating conditions were considered (atmospheric pressure, T =50 °C, pH 3), using a catalyst load of 2.5 g L −1 and the stoichiometric amount of H 2 O 2 needed for the complete mineralization of 4‐NP. N‐doping was identified to influence considerably the CWPO performance of the materials. In particular, undoped CNTs, with a moderate hydrophobicity, favor the controllable and efficient decomposition of H 2 O 2 into highly reactive hydroxyl radicals (HO . ), thus showing high catalytic activity for 4‐NP degradation. On the other hand, the completely N‐doped catalyst, fully hydrophilic, favors a quick decomposition of H 2 O 2 into nonreactive O 2 and H 2 O species. The selectively N‐doped amphiphilic catalysts, that is, hybrid structures containing undoped sections followed by N‐doped ones, provided intermediate results, namely, a higher N content favored H 2 O 2 decomposition towards nonreactive H 2 O and O 2 species, whereas a lower N content resulted in the formation of HO . , increasing 4‐NP mineralization. Catalyst stability and reusability were also investigated by consecutive CWPO runs.