Preparation and structural evolution of well aligned-carbon nanotube arrays onto conductive carbon-black layer/carbon paper substrate with enhanced discharge capacity for Li-air batteries

This study demonstrates the preparation of well aligned-carbon nanotube (WA-CNT) arrays onto a carbon paper substrate with a conductive carbon-black layer by the catalyst seed-impregnated chemical vapor deposition method. The prepared WA-CNT arrays were then characterized by scanning electron microscopy for different growth temperatures, standard linear velocities of feed vapors, and ferrocene-toxylene ratios in the feed vapors. Results indicate that the optimal WA-CNT arrays of length 40-50 mu m and diameter 30-40 nm were obtained at the growth temperature range of 750-800 degrees C, standard linear velocity of 1.40 cm s(-1), and ferrocene-to-xylene molar ratio of 1:50-1:30. These results provide new insights into the growth mechanism of CNT arrays, which involves cross-coupling of chemical reaction and mass transfer based on reaction engineering theory. The samples prepared in the study can be used as catalyst supports in air electrodes considering their three-dimensional porous structure, approximately linear channel, controllable length and diameter distribution, and excellent CNT conductivity. Electrochemical measurement indicated that the WA-CNT arrays/carbon-black layer/carbon paper substrate composites achieved relatively high discharge capacity of 2930 mAh g((CNTS))(-1)) at a current density of 0.05 mA cm(-2) in Li-air batteries, which far exceeded other carbonaceous materials in Li-air batteries. (C) 2015 Elsevier B.V. All rights reserved.