In this study, a research technique - Dynamic Electrochemical Impedance Spectroscopy for fuel cell research is presented. The Direct methanol fuel cell was the object of the study. The changes of operational conditions such as temperature, oxidant flow intensity and load on the cell global impedance were examined. The results of these changes on the performance of the cell were observed.

Effect of methanol concentration and channel depth of bipolar plates on the performance of single Direct methanol fuel cell was investigated experimentally. The membrane used in this experiment was Nafion117. Dimension of the single cell were 10cm´10 cm. methanol concentrations of 0.50, 1.0, 1.5, 2.0, 3.0 molar were used. Channel depth of the bipolar plates were chosen to be 1.0, 1.5, 2.0 mm, and in order to investigate the effect of channel depth, anode channel depth and cathode depth were changed simultaneously. Optimized methanol concentration for the single cell were 0.5-1.5 molar. Based on different experiments, as channel depth is decreased, mass transfer is improved and removal of carbone dioxide takes place easier. The results indicate that the best channel depth for this kind of single cell is 1.0 mm.

A two-dimensional, single-phase, isothermal model has been developed for a Direct methanol fuel cell (DMFC). The model considers the anode and cathode electrochemical equations, continuity, momentum and species transport in the entire fuel cell. Then, the equations are coupled together and solved simultaneously using a commercial, Finite element based, COMSOL Multiphysics software. The crossover of methanol is also investigated in the model. This model describes the electrochemical kinetics of methanol oxidation at the anode catalyst layer by nonTafel kinetics. The concentration distribution of methanol, water, and oxygen was predicted by the model. In addition, the changes of methanol crossover and fuel utilization with current density were evaluated for different methanol concentrations (0. 5 M, 1 M, 2 M, 4 M, and 6 M). Furthermore, it was also found that the crossover of methanol decreases at low methanol concentrations and high current densities. The results show that the polarization curve is in agreement with experimental data.

The power density of a Direct methanol fuel cell (DMFC) stack as a function of temperature, methanol concentration, oxygen flow rate, and methanol flow rate was studied using a response surface methodology (RSM) to maximize the power density. The operating variables investigated experimentally include temperature (50-75 ° C), methanol concentration (0. 5-2 M), methanol flow rate (15-30 ml min-1), and oxygen flow rate (900-1800 ml min-1). A new design of the central composite design (CCD) for a wide range of operating variables that optimize the power density was obtained using a quadratic model. The optimum conditions that yield the highest maximum power density of 86. 45 mW cm-2 were provided using 3-cell stack at a fuel cell temperature of 75 ° C with a methanol flow rate of 30 ml min-1, a methanol concentration of 0. 5 M, and an oxygen flow rate of 1800 ml min-1. Results showed that the power density of DMFC increased with an increase in the temperature and methanol flow rate. The experimental data were in good agreement with the model predictions, demonstrating that the regression model was useful in optimizing maximum power density from the independent operating variables of the fuel cell stack.

In this work, Pt, Fe and Co nanoparticles were prepared by chemical reduction of the metal salts in chitosan as the support. NaBH4 was used as the reducing agent Pt-Fe, Pt-Co and Pt-Fe-Co-chitosan nanocomposites were synthesized and characterized by UV–Vis spectra and Transmission electron microscopy images. GC/Pt-chitosan, GC/Pt-Co-chitosan, GC/ Pt-Fe-chitosan and GC/Pt-Co-Fe-chitosan electrodes were prepared.The performances of these electrodes for methanol electrooxidation were investigated through cyclic voltammetric and chronoamperometric curves. The effect of some experimental factors such as the amounts of Fe and Co nanoparticles dispersed in chitosan, methanol concentration and scan rate were studied and the optimum conditions were determined.The effect of temperature was also investigated and the activation energies were calculated. The performance of Pt-Fe-Co-chitosan nanocomposites was determined in a Direct methanol fuel cell in different conditions.The electrochemical and fuel cell measurements showed that Pt-Fe-Cochitosan nanocatalyst has the best activity for electrooxidation of methanol among all different compositions electrodes.

Direct methanol fuel cells, because of their environmental compatibility and relatively high power density, are promising alternative for future energy needs. However they have some disadvantages such as high methanol cross-over through the cell membrane and low performance in lower humidity conditions that limit their applications. Electrically conducting polymers such as polyaniline and polypyrrole have been used for the modification of membrane and catalyst layer in Direct methanol fuel cells. Studies have shown that using of these materials can improve the cell performance by reduction of methanol cross-over through the membrane, improvement of operation at lower humidity conditions and improvement of the mechanical strength and catalyst layer properties. In this paper the studies, made on the application of conducting polymers especially polyaniline and polypyrrole in Direct methanol fuel cells have been reviewed.