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

CNTs were grown on iron-modified mesoporous graphitized carbon aerogel (GCA) at 700 degrees C, 800 degrees C and 900 degrees 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 degrees C to 800 degrees C, dominated by MWCNTs formation. In the temperature range from 800 degrees C to 900 C, the growth was reduced by forming nanofiber/nanoribbon structures accompanied by MWCNTs. Mesoporosity of CNT/GCA composites declined at 700 degrees C and 800 degrees C due to MWCNT formation. However, CNT/GCA growth at 900 degrees C improved mesoporosity with substantial increase in pore volume (similar to 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 degrees C/GCA material showed ORR activity at lowest onset potential of 0.5 V. However, CNT-900 degrees C/GCA exhibits the highest ORR mass activity, with a half-wave onset potential difference of 120 mV with Pt (40 wt.%)/C. Moreover, CNT-900 degrees 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. Published by Elsevier Ltd.