Abstract
The advantages of direct methanol fuel cells (DMFC) over hydrogen fuel cells include easy storage of the high energy density liquid fuel, direct fuel feeding without reforming and low operating temperature. It is therefore considered by many people the most promising alternative power source for mobile applications and electric vehicles. Despite its advantages over hydrogen fuel cells, a few engineering obstacles of the DMFC remain to be overcame. The sluggish catalysis of the anode, on one hand, makes higher methanol concentration more favorable. The methanol permeation problem, on the other hand, generates a mixed potential at the cathode and adversely lowers the output voltage with high methanol concentration. Motivated by these two issues, we performed a thorough study of different methods of catalyst synthesis. Based on Watanabe et al. and Pattabiraman, we synthesize catalysts of Pt/Ru/C (1:1) by bubbling hydrogen. We then visualize the morphologies and the compositions of them by X-ray diffraction (XRD), transmission electronic microscopy (TEM), and inductively coupled plasma-mass spectrometer (ICP-MS). Their electrochemical behaviors in a half cell are analyzed by cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS) using H2SO4 (1 M) + CH3OH (1 M). Their performances in a single cell at 30 ℃ and 60 ℃ were investigated, using methanol of 1 M and air, by EIS and IV characteristic curves. In the end we compare our home-made catalysts with commercial PtRu/C (1:1) catalysts from Johnson Matthey: As for a half cell, in spite of lower peak current densities, they triumph with lower peak potentials, less carbon monoxide poisoning and lower charge transfer impedance. In terms of power densities of a single cell, they compete well with commercial catalysts. Therefore, in operations of long periods of time, we consider our catalysts a good candidate for the anode of a DMFC.