Gas diffusion electrodes containing sulfonated poly (arylene ether) ionomer for PEFCs: Part 1. Effect of humidity on the cathode performance

Gas diffusion electrodes (GDEs) containing Pt/C catalyst and sulfonated poly (arylene ether) (SPAE) ionomer as a proton conducting binder (SPAE-GDE) were prepared. The cathode performances were evaluated in a PEFC at 80 °C and relative humidities (RH) from 60 to 100%. The value of the electrochemical active surface area (ECA) of 65 m² g⁻¹ for the SPAE-GDE, which was measured by cyclic voltammetry at 100%-RH and 40 °C, was nearly the same as that for a Nafion-GDE. In contrast, the RH-dependencies of the performance indices (such as mass activity at 0.9 V, Tafel slope, or current density at 0.7 V) at the SPAE-GDE were very large and distinct from those for the conventional Nafion-GDE. With decreasing RH, the mass activity at the Nafion-GDE decreased monotonically, whereas that at the SPAE-GDE reached a maximum at 88%-RH and decreased steeply below 78%-RH, predominantly due to a strong adsorption of functional groups, probably sulfonate groups, in the SPAE on the Pt catalyst surface. However, at 88-100%-RH, the concentration polarization became significant for current densities j > 0.1 A cm⁻² due to excessive swelling of the SPAE ionomer. Strategies to improve the performance of SPAE-GDEs have been elucidated.     

Gas diffusion electrodes containing sulfonated poly (arylene ether) ionomer for polymer electrolyte fuel cells: Part 2. Improvement of the cathode performance

The performances of gas diffusion electrodes (GDEs) containing Pt/C catalyst (48 wt.% and 68 wt.%-Pt) and sulfonated poly (arylene ether) (SPAE) ionomer (ion exchange capacity, IEC = 1.8 and 2.5 meq g⁻¹) as a proton-conducting binder (SPAE-GDE) were examined in a PEFC at 80 °C and relative humidities (RH) from 60% to 100%. Based on our analyses in Part 1, we have succeeded in improving the cathode performance over the whole range of current densities examined by using a high Pt-loading for the catalyst (68 wt.%-Pt/C), in place of the previously used 48 wt.% one, for the reduction of thickness of the catalyst layer, which enabled us to increase the O₂ gas diffusion rate and to suppress the adsorption of the SPAE binder on the Pt surface via an effective utilization of generated water. The performance, especially at low RH, was improved further by employing an SPAE binder with a lower IEC, 1.8 meq g⁻¹ [SPAE(1.8)]. It was demonstrated by cyclic voltammetry that the specific adsorption of the sulfonate or organic moiety on the Pt surface was indeed suppressed for the case of SPAE(1.8). Hence, for the SPAE-GDEs, the use of a high Pt-loading catalyst, together with a binder with an appropriate IEC, is very important.     

Influence of ionomer content on the structure and performance of PEFC membrane electrode assemblies

Nafion^® ionomer content of the cathode catalyst-layer of a polymer electrolyte fuel cell (PEFC), made by the “decal” hot pressing method, has been investigated for its effect on performance and structure of the membrane electrode assembly (MEA). Varying Nafion^® content was shown to have an effect on performance within the entire range of polarization curves (i.e. kinetic, ohmic, and mass-transport regions) as well as on the structure. AFM analysis shows the effect of Nafion on the dispersion of carbon aggregates. Further analysis using TEM demonstrates the effect of Nafion on both the dispersion of carbon aggregates and the distribution and thickness of the Nafion ionomer films surrounding the catalyst/carbon aggregates. The MEA structure change correlates well with the MEA performance on both kinetics and mass-transport region. The determining factors on the performance of MEA are the interfacial zone (between the ionomer and catalyst particle), the dispersion of catalyst/carbon aggregates and the distribution/thickness of Nafion films. An optimized Nafion^® content in the range of 27 ± 6 wt.% for the cathode was determined for an E-TEK 20% Pt₃Cr/C catalyst at a loading of 0.20 mg Pt/cm².     

Electrocatalyst materials for fuel cells based on the polyoxometalates—K7 or H7[(P2W17O61)Fe(H2O)] and Na12 or H12[(P2W15O56)2Fe4(H2O)2]

Free acids of the iron substituted heteropoly acids (HPA), H₇[(P₂W₁₇O₆₁)Fe^III(H₂O)] (HFe1) and H₁₈[(P₂W₁₅O₅₆)₂Fe^III₂(H₂O)₂] (HFe2) were prepared from the salts K₇[(P₂W₁₇O₆₁)Fe^III(H₂O)] (KFe1) and Na₁₂[(P₂W₁₅O₅₆)₂Fe^III₄(H₂O)₂] (NaFe4), respectively. The iron-substituted HPA were adsorbed on to XC-72 carbon based GDLs to form HPA doped GDEs after water washing with HPA loadings of ca. 1 μmol. The HPA was detected throughout the GDL by EDX. Solution electrochemistry of the free acids are reported for the first time in sulfate buffer, pH 1-3. The hydrogen oxidation reaction was catalyzed by KFe1 at 0.33 V, with an exchange current density of 38 mA/cm². Moderate activity for the oxygen reduction reaction was observed for the iron substituted HPA, which was dramatically improved by selectively removing oxygen atoms from the HPA by cycling the fuel cell cathode under N₂ followed by reoxidation to give a restructured oxide catalyst. The nanostructured oxide achieved an OCV of 0.7 V with a Tafel slope of 115 mV/decade. Cycling the same catalysts in oxygen resulted in an improved catalyst/ionomer/carbon configuration with a slightly higher Tafel slope, 128 mV/decade but a respectable current density of 100 mA/cm² at 0.2 V.     

In situ analysis of oxygen partial pressure at the cathode catalyst layer/membrane interface during PEFC operation

To understand the concentration overpotential in the polymer electrolyte fuel cell (PEFC), we have performed an in situ analysis of the oxygen partial pressure (p[O₂]_CL/PEM) at the interface between the cathode catalyst layer (CL) and the polymer electrolyte membrane (PEM). Diffusion-limited oxygen reduction current was measured, with Pt probes inserted into the PEM, during cell operation by supplying H₂ to the anode and O₂ + N₂ to the cathode at 80 °C. It was found that the p[O₂]_CL/PEM decreased by ca. 20% when the current density was stepped from 0 to 2.0 A cm⁻² at p[O₂]_gas = 54 kPa and 100% RH at the cathode inlet, irrespective of the oxygen utilization UO₂ (from 10% to 50%). Such a change in p[O₂]_CL/PEM might result in a concentration overpotential of ca. 10 mV, based on the Tafel slope of 120 mV decade⁻¹ in the high current density region. It was also found that ohmic losses in the ionomer phase of the CL increased with decreasing humidity, from 100% to 80% RH, and became a dominant factor in the increased total overpotential, while the corresponding concentration overpotential was unchanged. The present results provide new insight into the transport of oxygen and water at the CL/PEM interface, especially at the high current densities required for the electric vehicle application.     

Improved gas diffusion electrodes for hybrid polymer electrolyte fuel cells

In this study, the performance of the anionic electrodes for hybrid polymer electrolyte fuel cells was improved. The anion exchange membrane (AEM) electrodes were initially characterized as the cathode on a proton exchange membrane (PEM) anode/membrane half-assembly (i.e. hybrid polymer electrolyte fuel cell). The electrode performance was improved by tailoring the ionomer distribution within the electrode structure so as to better balance the electronic, ionic, and reactant transport within the catalyst layer. An ionomer impregnation method was used to achieve a non-uniform ionomer distribution and higher performance. Traditional electrode fabrication methods (i.e. thin-film method) lead to a uniform ionomer distribution. The peak power density at 70 °C for a H₂/O₂ hybrid fuel cell was 44 mW cm⁻² using the thin-film electrode, and 120 mW cm⁻² using the ionomer impregnated electrode. A hydrophobic additive used in the catalyst layer further improved the electrode performance, giving a peak power density of 315 mW cm⁻² for H₂/O₂ at 70 °C. Electrochemical impedance spectroscopy was used as an in situ diagnostic tool to help understand the origin of the electrode improvements. The increase in performance was attributed to improved catalyst utilization due to the creation of facile gas transport domains in the AEM electrode structure. Similarly, the AEM anode prepared by ionomer impregnation with polytetrafluoroethylene resulted in a three-fold increase in the peak power density compared to ones made by the thin-film method, which has no polytetrafluoroethylene.     

Effects of hydrophobicity of the cathode catalyst layer on the performance of a PEM fuel cell

The effects of hydrophobicity of the cathode catalyst layer on the performance of a PEM fuel cell are studied. The surface contact angle is measured to understand the changes of the hydrophobicity of the cathode catalyst layer upon the addition of hydrophobic dimethyl silicone oil (DSO). The results show that the contact angle increases with the DSO loadings in the cathode catalyst layer ranging from 0 to 0.65 mg/cm². The subsequent electrochemical measurements of the fuel cells with various cathodes reveal that the addition of DSO in the cathode catalyst layer can effectively prevent the cathode flooding at high current density, thus leading to a much higher limiting current density and the maximum power density when compared to the fuel cell with a normal cathode. An optimal DSO loading in the cathode catalyst layer is found to be around 0.5 mg/cm² under the testing conditions in this work. The fuel cell with cathode loaded with 0.5 mg/cm² can reach the maximum power density of 356 mW/cm² in H₂/air (or 709 mW/cm² in H₂/O₂) at room temperature, which is around 2.5 times in H₂/air (or 1.8 times in H₂/O₂) of that with normal cathode. All of the results indicate that the hydrophobicity of the cathode catalyst layer plays a crucial role in the water management of the fuel cell. The possible function of the DSO on improved oxygen solubility for the oxygen starved cathode during flooding warrants some further investigation.     

Decreasing resistances of membrane-electrode assemblies containing hydrocarbon-based ionomers for improving their anodic performances

To improve methanol-oxidation performances of membrane-electrode assemblies composed of a hydrocarbon-based ionomers, the resistances involved in the reaction were decreased. Electrochemical impedance spectroscopy revealed that the proton-conductive resistance (R_i) in the anode was decreased from 0.54 to 0.40 Ω cm² by increasing a loading ratio of platinum-ruthenium to carbon support of anode catalyst from 54 to 73 wt.%. In addition, R_i was decreased to be 0.25 Ω cm² by increasing ion-exchange capacity (IEC) of the ionomer from 1.4 to 2.9 mequiv. g⁻¹. Consequently, the polarization resistance of the anode was significantly decreased, in turn, increasing current density of methanol oxidation at the potential of 0.45 V from 0.110 to 0.244 A cm⁻².     

New highly proton-conducting membrane poly(vinylpyrrolidone)(PVP) modified poly(vinyl alcohol)/2-acrylamido-2-methyl-1-propanesulfonic acid (PVA-PAMPS) for low temperature direct methanol fuel cells (DMFCs)

A new type of chemically cross-linked polymer blend membranes consisting of poly(vinyl alcohol) (PVA), 2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) and poly(vinylpyrrolidone) (PVP) have been prepared and evaluated as proton conducting polymer electrolytes. The proton conductivity (σ) of the membranes was investigated as a function of cross-linking time, blending composition, water content and ion exchange capacity (IEC). Membranes were also characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), and the differential scanning calorimetry (DSC). Membrane swelling decreased with cross-linking time, accompanied by an improvement in mechanical properties and a small decrease in proton conductivity due to the reduced water absorption. The membranes attained 0.088 S cm⁻¹ of the proton conductivity and 1.63 mequiv g⁻¹ of IEC at 25±2 °C for a polymer composition PVA-PAMPS-PVP being 1:1:0.5 in mass, and a methanol permeability of 6.1×10⁻⁷ cm² s⁻¹, which showed a comparable proton conductivity to Nafion 117, but only one third of Nafion 117 methanol permeability under the same measuring conditions. The membranes displayed a relatively high oxidative durability without weight loss of the membranes (e.g. 100 h in 3% H₂O₂ solution and 20 h in 10% H₂O₂ solution at 60 °C). PVP, as a modifier, was found to play a crucial role in improving the above membrane performances.     

Effect of cathode binder IEC on kinetic and transport losses in all-SPEEK MEAs

The effect of ion exchange capacity (IEC) and loading of sulfonated polyether ether ketone (SPEEK) binder on PEFC cathode performance was studied. MEAs were prepared by decal transfer onto a SPEEK membrane (IEC-1.75 mequiv./g). The IEC of SPEEK binder in the MEA cathode was varied between 1.3 and 2.1 mequiv./g. Cathodes prepared with 30 wt.% SPEEK loading had an electrochemically active surface area (ECA) that was 25% lower than a Nafion^® bonded electrode with similar loading. Polarization curves were obtained at 80 °C and 75% RH with hydrogen as fuel and air and oxygen (O₂) as oxidants. Polarization data was analyzed to determine the relative contributions of different sources of polarization, namely membrane ohmic losses, electrode ohmic losses, and mass transport losses in the gas diffusion layer, binder film and electrodes. The electrode ohmic and mass transport losses decreased with increase in SPEEK IEC. However, even for the highest SPEEK IEC, these losses were higher than those obtained in a Nafion^® bonded electrode. This was attributed to the lower proton activity and O₂ permeability in SPEEK. The loading of SPEEK in the electrode was found to influence performance in the activation controlled region, with a loading of 7.5 wt.% giving the highest performance. However, gains in this region were negated at higher current densities due to enhanced ohmic and transport losses and MEAs with all binder loadings between 7.5 and 30 wt.% had similar limiting currents.     

Studies of the performance of PEM fuel cell cathodes with the catalyst layer directly applied on Nafion membranes

The performance of a proton exchange membrane fuel cell (PEMFC) with gas diffusion cathodes having the catalyst layer applied directly onto Nafion membranes is investigated with the aim at characterizing the effects of the Nafion content, the catalyst loading in the electrode and also of the membrane thickness and gases pressures. At high current densities the best fuel cell performance was found for the electrode with 0.35 mg Nafion cm⁻² (15 wt.%), while at low current densities the cell performance is better for higher Nafion contents. It is also observed that a decrease of the usual Pt loading in the catalyst layer from 0.4 to ca. 0.1 mg Pt cm⁻² is possible, without introducing serious problems to the fuel cell performance. A decrease of the membrane thickness favors the fuel cell performance at all ranges of current densities. When pure oxygen is supplied to the cathode and for the thinner membranes there is a positive effect of the increase of the O₂ pressure, which raises the fuel cell current densities to very high values (>4.0A cm⁻², for Nafion 112—50 μm). This trend is not apparent for thicker membranes, for which there is a negligible effect of pressure at high current densities. For H₂/air PEMFCs, the positive effect of pressure is seen even for thick membranes.     

Characterisation of a re-cast composite Nafion 1100 series of proton exchange membranes incorporating inert inorganic oxide particles

A series of cation exchange membranes was produced by impregnating and coating both sides of a quartz web with a Nafion^® solution (1100 EW, 10%wt in water). Inert filler particles (SiO₂, ZrO₂ or TiO₂; 5-20%wt) were incorporated into the aqueous Nafion^® solution to produce robust, composite membranes. Ion-exchange capacity/equivalent weight, water take-up, thickness change on hydration and ionic and electrical conductivity were measured in 1 mol dm⁻³ sulfuric acid at 298 K. The TiO₂ filler significantly impacted on these properties, producing higher water take-up and increased conductivity. Such membranes may be beneficial for proton exchange membrane (PEM) fuel cell operation at low humidification. The PEM fuel cell performance of the composite membranes containing SiO₂ fillers was examined in a Ballard Mark 5E unit cell. While the use of composite membranes offers a cost reduction, the unit cell performance was reduced, in practice, due to drying of the ionomer at the cathode.     

Synthesis of Pt nanocatalyst with micelle-encapsulated multi-walled carbon nanotubes as support for proton exchange membrane fuel cells

Micelle-encapsulated multi-walled carbon nanotubes (MWCNTs) with sodium dodecyl sulfate (SDS) were used as catalyst support to deposit platinum nanoparticles. High resolution transmission electron microscopy (HRTEM) images reveal the crystalline nature of Pt nanoparticles with a diameter of ∼4 nm on the surface of MWCNTs. A single proton exchange membrane fuel cell (PEMFC) with total catalyst loading of 0.2 mg Pt cm⁻² (anode 0.1 and cathode 0.1 mg Pt cm⁻², respectively) has been evaluated at 80 °C with H₂ and O₂ gases using Nafion-212 electrolyte. Pt/MWCNTs synthesized by using modified SDS-MWCNTs with high temperature treatment (250 °C) showed a peak power density of 950 mW cm⁻². Accelerated durability evaluation was carried out by conducting 1500 potential cycles between 0.1 and 1.2 V with 50 mV s⁻¹ scan rate, H₂/N₂ at 80 °C. The membrane electrode assembly (MEA) with Pt/MWCNTs showed superior performance stability with a power density degradation of only ∼30% compared to commercial Pt/C (70%) after potential cycles.     

Polarization properties of La0.6Sr0.4Co0.2Fe0.8O3-based double layer-type oxygen electrodes for reversible SOFCs

We have developed double layer-type (catalyst layer/current collecting layer) oxygen electrodes (DLE) for reversible SOFCs. As the catalyst layer (cathode for SOFC and anode for steam electrolysis) interfaced with a samaria-doped ceria [(CeO₂)_0.8(SmO_1.5)_0.2, SDC] interlayer/YSZ solid electrolyte, mixed conducting La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) and SDC particles were employed. The current collecting porous LSCF layer was formed on the catalyst layer. By controlling the SDC content, as well as the thickness and porosity of the catalyst layer, the gas diffusion rate and the conduction networks for electrons and oxide ions were optimized, resulting in a marked reduction of the overpotential. The LSCF + SDC/LSCF DLE exhibited higher performance than single-layer electrodes of LSCF + SDC or LSCF; the IR-free anode potential vs. an air reference electrode was 0.12 V (corresponding to an overpotential of 0.08 V) at 0.5 A cm⁻² and 900 °C under an atmosphere of O₂ (1 atm).     

PEMFC electrode preparation by electrospray: Optimization of catalyst load and ionomer content

Electrodes for proton exchange membrane fuel cell (PEMFC) have been prepared by means of electrospray deposition, using different ionomer contents and catalyst loads. The electrodes have been mounted in single PEMFC, and tested as cathode. The electroactive platinum area of electrosprayed electrodes has been measured by the hydrogen underpotential deposition method. Polarization curves have been measured to determine the optimal concentration for the platinum catalyst (Pt/C, 20 wt.%) and the ionomer (Nafion^®). Best performance is observed with 15% ionomer content in the electrosprayed cathode due to minimal cell internal resistance. This optimal concentration is lower than that found for electrodes prepared by other standard methods, like airbrushing or impregnation, which is attributed to the improved ionomer distribution within the electrospray deposited catalyst layer. On the other hand, the optimum value for catalyst load is similar to that encountered for electrodes prepared by the other methods, which reflects that electrospray has little or no effect neither on the catalyst nor on the electronic resistance of the catalyst layer.     

PEM fuel cell reaction kinetics in the temperature range of 23-120 °C

The performance of a Nafion 112 based proton exchange membrane (PEM) fuel cell was tested at a temperature range from 23 °C to 120 °C. The fuel cell polarization curves were divided into two different ranges based on current density, namely, <0.4 A/cm² and >0.4 A/cm², respectively. These two ranges were treated separately with respect to electrode kinetics and mass transfer. In the high current density range, a linear increase in membrane electrode assembly (MEA) power density with increasing temperature was observed, indicating the advantages of high temperature operation.Simulation based on electrode reaction kinetic theory, experimental polarization curves, and measured cathodic apparent exchange current densities all gave temperature dependent apparent exchange current densities. Both the calculated partial pressures of O₂ and H₂ gas in the feed streams and the measured electrochemical Pt surface areas (EPSAs) decrease with increasing temperature. They were also used to obtain the intrinsic exchange current densities. A monotonic increase of the intrinsic exchange current densities with increasing temperature in the range of 23-120 °C was observed, suggesting that increasing the temperature does promote intrinsic kinetics of fuel cell reactions.There are two sets of cathode apparent exchange current densities obtained, one set is for the low current density range, and the other is for the high current density range. The different values of cathode current densities in the two current density ranges can be attributed to the different states of the cathode Pt catalyst surface. In the low current density range, the cathode catalyst surface is a Pt/PtO, and in the high current density range, the catalyst surface becomes pure Pt.     

Membrane electrode assembly with Pt/SiO2/C anode catalyst for proton exchange membrane fuel cell operation under low humidity conditions

In this work, a novel self-humidifying membrane electrode assembly (MEA) with Pt/SiO₂/C as anode catalyst was developed to improve the performance of proton exchange membrane fuel cell (PEMFC) operating at low humidity conditions. The characteristics of the composite catalysts were investigated by XRD, TEM and water uptake measurement. The optimal performance of the MEA was obtained with the 10 wt.% of silica in the composite catalyst by single cell tests under both high and low humidity conditions. The low humidity performance of the novel self-humidifying MEA was evaluated in a H₂/air PEMFC at ambient pressure under different relative humidity (RH) and cell temperature conditions. The results show that the MEA performance was hardly changed even if the RHs of both the anode and cathode decreased from 100% to 28%. However, the low humidity performance of the MEA was quite susceptible to the cell temperature, which decreased steeply as the cell temperature increased. At a cell temperature of 50 °C, the MEA shows good stability for low humidity operating: the current density remained at 0.65 A cm⁻² at a usual work voltage of 0.6 V without any degradation after 120 h operation under 28% RH for both the anode and cathode.     

Analysis of proton exchange membrane fuel cell polarization losses at elevated temperature 120 °C and reduced relative humidity

Polarization losses of proton exchange membrane (PEM) fuel cells at 120 °C and reduced relative humidity (RH) were analyzed. Reduced RH affects membrane and electrode ionic resistance, catalytic activity and oxygen transport. For a cell made of Nafion^® 112 membrane and electrodes that have 35 wt.% Nafion^® and 0.3 mg/cm² platinum supported on carbon, membrane resistance at 20%RH was 0.407 Ω cm² and electrode resistance 0.203 Ω cm², significantly higher than 0.092 and 0.041 Ω cm² at 100%RH, respectively. In the kinetically controlled region, 20%RH resulted in 96 mV more cathode activation loss than 100%RH. Compared to 100%, 20%RH also produced significant oxygen transport loss across the ionomer film in the electrode, 105 mV at 600 mA/cm². The significant increase in polarization losses at elevated temperature and reduced RH indicates the extreme importance of designing electrodes for high temperature PEM fuel cells since membrane development has always taken most emphasis.     

Kinetics and PEMFC performance of RuxMoySez nanoparticles as a cathode catalyst

Kinetics of Ru_xMo_ySe_z nanoparticles dispersed on carbon powder was studied in 0.5 M H₂SO₄ electrolyte towards the oxygen reduction reaction (ORR) and as cathode catalysts for a proton exchange membrane fuel cell (PEMFC). Ru_xMo_ySe_z catalyst was synthesized by decarbonylation of transition-metal carbonyl compounds for 3 h in organic solvent. The powder was characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. Catalyst is composed of uniform agglomerates of nanocrystalline particles with an estimated composition of Ru₆Mo₁Se₃, embedded in an amorphous phase. The electrochemical activity was studied by rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. Tafel slopes for the ORR remain invariant with temperature at −0.116 V dec⁻¹ with an increase of the charge transfer coefficient in dα/dT = 1.6 × 10⁻³, attributed to an entropy turnover contribution to the electrocatalytic reaction. The effect of temperature on the ORR kinetics was analyzed resulting in an apparent activation energy of 45.6 ± 0.5 kJ mol⁻¹. The catalyst generates less than 2.5% hydrogen peroxide during oxygen reduction. The Ru_xMo_ySe_z nanoparticles dispersed on a carbon powder were tested as cathode electrocatalyst in a single fuel cell. The membrane-electrode assembly (MEA), included Nafion^® 112 as polymer electrolyte membrane and commercial carbon supported Pt (10 wt%Pt/C-Etek) as anode catalyst. It was found that the maximum performance achieved for the electro-reduction of oxygen was with a loading of 1.0 mg cm⁻² Ru_xMo_ySe_z 20 wt%/C, arriving to a power density of 240 mW cm⁻² at 0.3 V and 80 °C.     

The improved methanol tolerance using Pt/C in cathode of direct methanol fuel cell

Membrane electrode assemblies (MEA) were prepared using PtRu black and 60 wt.% carbon-supported platinum (Pt/C) as their anode and cathode catalysts, respectively. The cathode catalyst layers were fabricated using various amounts of Pt (0.5 mg cm⁻², 1.0 mg cm⁻², 2.0 mg cm⁻², and 3.0 mg cm⁻²). To study the effect of carbon support on performance, a MEA in which Pt black was used as the cathode catalyst was fabricated. In addition, the effect of methanol crossover on the Pt/C on the cathode side of a direct methanol fuel cell (DMFC) was investigated. The performance of the single cell that used Pt/C as the cathode catalyst was higher than single cell that used Pt black and this result was pronounced when highly concentrated methanol (above 2.0 M) was used as the fuel.