Study on the Synthesis of CNTs and the Fabrication of CNTs-Based MEA for DMFC Application
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0963-Q20-14
Study on the Synthesis of CNTs and the Fabrication of CNTs-Based MEA for DMFC Application Chun-Hsi Su1, Chii-Ruey Lin2, and Hsin-Chin Hung2 1 Institute of Mechanical and Electrical Engineering, National Taipei University of Technology, No.1, Sec.3, Chung-Hsiao E. Road, Taipei, 10608, Taiwan 2 Mechanical and Electrical Engineering, Taipei, 10608, Taiwan ABSTRACT A fuel cell (FC) generates electricity by chemical reactions. The catalyst dispersion in Membrane electrode assembly (MEA) is a crucial factor among various factors to affect the performance of a FC. A novel grafting method is adopted in this study to grow secondary carbon nano-tubes (CNTs) on a substrate comprised of primary CNTs, in order to form branchy CNTs with higher specific surface area (SSA). The as-obtained branchy CNTs are then used as catalyst carriers in the MEA of Direct methanol fuel cell (DMFC). An self-assembled DMFC of airbreathing type with active MEA area of 2 x 2 cm2 is used in this study as the standard FC for the electrical performance test. The peak power of DMFC comprised of an MEA with sole primary CNTs is 0.002 watts at 0.15 V. Such peak power can be increased up to 0.01 watts at 0.4 V while replacing the MEA with the new branchy CNTs. The open circuit voltages (OCVs) are 0.4 V and 0.6 V for DMFCs with MEAs of sole primary CNTs and branchy CNTs, respectively. Furthermore, the patterns of CNTs was designed to create micro-channel of fuel. The pattern growth of CNTs have been fabricated by selective area growth method in this research. INTRODUCTION The MEA has been widely studied in view of the practical importance in the field of FC. Because catalyst carriers of MEA are recognized as one of the crucial features of current research, much literature has been performed in studying. Especially, much active research is using CNTs as catalyst carriers to substitute for carbon black [1-7]. Many superior properties of carbon nano-tubes (CNTs) have been studied and applied rapidly on fabricating high performance working electrodes of FC. The branched CNTs structure was used as catalyst carriers seem to promote the activity of MEA just using low concentration of methanol and a little catalyst. EXPERIMENT In this sol-gel method, iron(III) nitrate solution contain Fe (NO3) 3 and isopropanol which were solute and solvent respectively. Titanium n-butoxide mixing with iron(III) nitrate solution caused the reaction of hydrolysis and condensation. The sol-gel solution was stirred under ultrasonically vibrating for five minutes in order to make the solution well mixed. The sol-gel solution was spread homogeneously on CNTs substrates. The precursor gases, H2 (40 sccm), N2 (40 sccm), and CH4 (10 sccm), were introduced into the MPCVD system. After the pressure of chamber was stable at a working pressure of 40 torrs, a microwave power of 1 kilowatt was applied to induce the microwave plasma. The substrate temperature of 800 oC was measured using a pyrometer. After 30 minutes, the carbon nanotubes were grown.
The pattern of CNTs was designed
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