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Supercritical Deposition Coupled with Ammonia Treatment: A New Route to Co‐Promoted N‐Doped Carbon Aerogels with High Oxygen Reduction Reaction Activity
Author(s) -
Ünsal Seçil,
Yağcı Mustafa Barış,
Bozbağ Selmi Erim,
Deljoo Bahareh,
Aindow Mark,
Erkey Can
Publication year - 2019
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201900450
Subject(s) - aerogel , catalysis , pyrolysis , carbon fibers , supercritical fluid , inorganic chemistry , chemistry , ammonia , cobalt , supercritical drying , oxygen , chemical engineering , materials science , organic chemistry , nanotechnology , composite number , engineering , composite material
A new highly active family of Co‐promoted N‐doped carbon aerogel catalysts is prepared by a supercritical CO 2 ‐assisted technique combined with NH 3 treatment. The active sites are created during the complex transformation of an organic aerogel to a carbon aerogel in the presence of cobalt by NH 3 as the source of nitrogen and pyrolysis medium. The mass activity for oxygen reduction reaction (ORR) is highest for the catalyst pyrolyzed at 800 °C. The catalyst displays similar activity for ORR as a commercial Pt/C catalyst. Moreover, the catalyst exhibits nearly double the mass activity of N‐doped carbon aerogel pyrolyzed at the same temperature. The nature of the active sites for ORR is also investigated by selectively adding or removing various species (i.e., Co–N x and Co–O) via post acid–base treatments. After removing the Co species from the catalyst, the same activity as the parent catalyst is achieved suggesting that the Co species in the catalyst are spectators in ORR catalysis and they serve only to promote the formation of catalytically active graphitic N sites during pyrolysis in NH 3 . A strong correlation is found between the relative distribution of graphitic N species and the mass activity.