CVD grown CNTs within iron modified and graphitized carbon aerogel as durable oxygen reduction catalysts in acidic medium

• Published in: Carbon (New York) Vol. 79; pp. 518 - 528
• Main Authors: Kolla, Praveen, Lai, Chuilin, Mishra, Srujan, Fong, Hao, Rhine, Wendell, Smirnova, Alevtina
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2014; Elsevier
• Subjects: Carbon; Catalysis; Catalysts; Chemical vapor deposition; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Chemistry; Colloidal state and disperse state; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Durability; Electron states; Exact sciences and technology; Formations; General and physical chemistry; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Methods of electronic structure calculations; Morphology; Nanostructure; Physics; Porous materials; Reduction; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Oxygen; Catalysts; Porous materials; Potential difference; Iron; Carbon; Mesoporosity; Aerogels; CVD; Chemical reduction; Generalized gradient approximation; Microstructure; Methanol
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2014.08.010

CNTs were grown on iron-modified mesoporous graphitized carbon aerogel (GCA) at 700°C, 800°C and 900°C using catalytic CVD method. Resultant CNT/GCA materials composition, morphology and structure were studied to understand their electrochemical stability and performance for oxygen reduction reaction (ORR) in acidic medium. CNT growth was increased from 700°C to 800°C, dominated by MWCNTs formation. In the temperature range from 800°C to 900°C, the growth was reduced by forming nanofiber/nanoribbon structures accompanied by MWCNTs. Mesoporosity of CNT/GCA composites declined at 700°C and 800°C due to MWCNT formation. However, CNT/GCA growth at 900°C improved mesoporosity with substantial increase in pore volume (∼3 times of GCA) due to formation of nanofibers and nanoribbons. The structure of CNT/GCA materials revealed nitrogen doping and dispersion of FeNx phase. A synergistic contribution of CNT/GCA material structure and morphology to ORR activity was noticed. Among CNT/GCA materials, CNT-800°C/GCA material showed ORR activity at lowest onset potential of 0.5V. However, CNT-900°C/GCA exhibits the highest ORR mass activity, with a half-wave onset potential difference of 120mV with Pt (40wt.%)/C. Moreover, CNT-900°C/GCA demonstrates high selectivity (>3.97) to 4 electron ORR path, excellent methanol tolerance and electrochemical durability which makes it a potential DMFC cathode candidate.