In this work, we prepared the nafion/montmorillonite/heteropolyacid nanocomposite membranes for direct methanol fuel cells (DMFCs). The analyses, such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM), were conducted to characterize the filler dispersion and membrane structure in prepared nanocomposite membranes. XRD patterns of nafion-CsPW-MMT nanocomposites membranes showed the exfoliated structure of membranes by adding MMT and CsPW. SEM-EDXA results showed proper dispersion of nanoparticles in the membrane matrices. Addition of CsPW-MMT to nafion membranes increases water uptake and IEC due to the increase of hydrophilic groups in membranes. The proton conductivity results showed that proton conductivity increases by increasing amount of CsPW and decreasing of clay content in the membrane. Methanol crossover through polymer electrolyte membranes is a critical issue and causes an important reduction of performance in DMFCs. The developed intercalated nafion/CsPW/MMT nanocomposite membranes have successfully improved the membrane barrier properties due to the unique feature of MMT which contributed to the formation of a longer pathway towards methanol across the membrane. The lowest methanol crossover of the developed membranes in this study was 1. 651×10-6 cm2s-1 Error! Digit expected. which is lower than re-cast nafion membrane (2. 078×10-6 cm2s-1). The methanol permeability was significantly reduced by the incorporation of MMT and increased by addition of CsPW in the nafion membrane. Finally, according to the selectivity results, the nafion-MMT-CsPW nanocomposite membrane with MMT mass fraction of 2. 5 % and CsPW mass fraction of 8 % shows the best membrane selectivity and this nanocomposite membrane could be suitable for application in DMFCs.

Here, we demonstrate the synthesis of Pt nanoparticles integrated on graphene/cobalt oxide (CoO) architecture (Pt/CoO-GNS) through a facile hydrothermal method. The synthesized catalyst was characterized by X-ray diffraction and the morphology of it was studied by scanning electron microscopy. The obtained results indicated that the sample had unique tolerable porous structure. This structure can supply sufficient mass transfer channels and plenty of active sites on Pt/CoO-GNS to assist the catalytic reaction. The synthesized Pt/CoO-GNS was prospected as an electrocatalyst for the oxygen reduction reaction and presented comparable oxygen reduction performance with outstanding methanol resistance. In addition, the astability of this catalyst was improved in comparison with Pt/C.

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.

We reported on a Pd-Co (3: 1) /graphene oxide (Pd3Co /GO) catalyst through a one-step strategy. GO is synthesized from graphite electrodes using ionic liquid-assisted electrochemical exfoliation. Controllable GO-supported Pd3Co electrocatalystis then was reduced by ethylene glycol as a stabilizing agent to prepare highly dispersed PdCo nanoparticles on carbon graphene oxide to be used in an oxygen reduction reaction in passive direct methanol fuel cell (DMFC) catalysts. The performance of these electrodes in the ORR was measured with cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), inductive coupled plasma (ICP), X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive X-ray (SEM–EDX). Since the Pd3Co/GO alloy electrocatalysts are inactive for the adsorption and oxidation of methanol, it can act as a methanol-tolerant ORR catalyst in a direct methanol fuel cell (DMFC). A membrane-electrode assembly (MEA) has been prepared by employing of the Pd3Co/GO as a cathode for a passive direct methanol fuel cell and characterized by polarization curves and impedance diagrams. A better performance was obtained for the cell using Pd3Co/RGO (3.56 mW cm-2) compared to Pd/RGO (1.75 mW cm-2) and Pt/C-Electrochem (1.9 mW cm-2) as a cathode in the DMFC.

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 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.

A novel Nafion®-based nanocomposite membrane was synthesized to be applied as direct methanol fuel cells (DMFCs). Carbon nanotubes (CNTs) were coated with a layer of silica and then reacted by chlorosulfonic acid to produce sulfonate-functionalized silicon dioxide coated carbon nanotubes (CNT@SiO2-SO3H). The functionalized CNTs were then introduced to Nafion® , and subsequently, methanol permeability, proton conductivity, ion exchange capacity (IEC) and water uptake properties of the prepared membranes were investigated. The experimental results showed that the water uptake and IEC of the Nafion® /CNT@SiO2-SO3H (1 wt%) membrane increased in comparison with the recast Nafion® . IEC was enhanced from 0. 9 meq/g for the recast Nafion® to 0. 946 meq/g for Nafion® /CNT@SiO2-SO3H, which could be attributed to the presence of sulfonate groups on the surface of CNTs. In addition, the proton conductivity of the sulfonate modified CNT/Nafion® composite was enhanced in a wide range of temperatures. Selectivity of the fabricated membrane was found to be more than 8-fold higher than that of recast Nafion® 117, demonstrating the promising potential of the produced membranes for DMFC applications.

In this study nanocomposite films of PtW nanoparticles deposited on a poly ethylen dioxy thiophene/graphene nanoplates/gas diffusion layer (PEDOT/GNP/ GDL) electrode are fabricated via an electrochemical route involving a series of electrochemical process. GNPs are in situ reduced on carbon paper covered with 3, 4 ethylen dioxy thiophene during the in situ polymerization of EDOT. PtW nanoparticles 18. 57nm in average size are prepared by electrodeposition on the surface of PEDOT/GNP/GDL. Field emission scanning electronic microscopy (FESEM) images showed spongy aggregates of PEDOT densely cover the surface and edges of the GNP layers, implying the existence of a strong interaction between PEDOT and GNP. Based on electrochemical characterization, it was found that the as prepared electrode exhibited comparable activity for the methanol oxidation (MEOH) reaction with respect to commercial Pt/C/GDL based on the traditional sprayed method. A significant reduction in the potential of the CO electro-oxidation peak from 0. 92V for Pt/C to 0. 75V for the PtW/PEDOT/GNP/GDL electrode indicates that an increase in the activity for CO electro-oxidation is achieved by replacing Pt with PtW. This may be attributed to structural changes caused by alloying and the increased conductivity and high specific surface area of PEDOT and GNPs catalyst support, respectively. CV scanning results showed that the PtW/ PEDOT/GNP/GDL electrode has greater stability than the Pt/C/GDL electrode.