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NH 3 Post‐Treatment Induces High Activity of Co‐Based Electrocatalysts Supported on Carbon Nanotubes for the Oxygen Evolution Reaction
Author(s) -
Yang Fengkai,
Xia Wei,
Maljusch Artjom,
Masa Justus,
Hollmann Dirk,
Sinev Ilya,
Cuenya Beatriz Roldan,
Schuhmann Wolfgang,
Muhler Martin
Publication year - 2017
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201700109
Subject(s) - calcination , materials science , cobalt , thermal treatment , inorganic chemistry , oxygen evolution , catalysis , ammonia , carbon nanotube , chemical engineering , spinel , oxygen , hydrogen , carbon fibers , chemistry , electrochemistry , nanotechnology , composite number , electrode , metallurgy , organic chemistry , composite material , engineering
Cobalt oxide nanoparticles were deposited on nitrogen‐doped carbon nanotubes (NCNTs) through impregnation by using cobalt nitrate as a precursor and subsequent drying and calcination. Co loadings were prepared in the range from 4 to 40 wt%, and hydrogen and ammonia were applied in the thermal post‐treatment of the CoO x /NCNT samples. The Co 3 O 4 spinel structure was detected in all samples, while the thermal treatment in ammonia and hydrogen led to the formation of CoO and metallic Co in addition. Treatment in ammonia resulted in the partial reduction of Co 3 O 4 to CoO and nitrogen doping of the oxides, leading to excellent electrocatalytic activity in the oxygen evolution reaction (OER) and stability despite of the lower Co oxidation states compared with the sample calcined in air. In contrast, the sample reduced in hydrogen showed a lower activity and stability in the OER. The high activity of the ammonia‐treated sample can be assigned to improved conductivity, favorable surface properties with surface nitrogen improving the hydrophilicity of the catalysts, and the more facile transformation to the OER‐active layered cobalt oxyhydroxide phase under anodic conditions.