NH3 Post‐Treatment Induces High Activity of Co‐Based Electrocatalysts Supported 
on Carbon Nanotubes for the Oxygen Evolution Reaction

Yang, Fengkai; Xia, Wei; Maljusch, Artjom; Masa, Justus; Hollmann, Dirk; Sinev, Ilya; Roldan Cuenya, Beatriz; Schuhmann, Wolfgang; Muhler, Martin

doi:10.1002/celc.201700109

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NH₃ Post‐Treatment Induces High Activity of Co‐Based Electrocatalysts Supported on Carbon Nanotubes for the Oxygen Evolution Reaction

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Yang, F., Xia, W., Maljusch, A., Masa, J., Hollmann, D., Sinev, I., et al. (2017). NH₃ Post‐Treatment Induces High Activity of Co‐Based Electrocatalysts Supported on Carbon Nanotubes for the Oxygen Evolution Reaction. ChemElectroChem, 4(8), 2091-2098. doi:10.1002/celc.201700109.

Cite as: https://hdl.handle.net/21.11116/0000-0006-B131-A

Abstract

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 Co₃O₄ 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 Co₃O₄ 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.