Optimum compositions of membrane electrode assemblies (MEAs) for direct dimethyl ether fuel cell

We investigated the effects of the compositions of catalyst layers and diffusion layers on performances of the membrane electrode assemblies (MEAs) for direct dimethyl ether fuel cell. The performances of the MEAs with different thicknesses of Nafion membranes were compared in this work. The optimal compositions in the anode are: 20 wt% Nafion content and 3.6 mg cm⁻² Pt loading in the catalyst layer, and 30 wt% PTFE content and 1 mg cm⁻² carbon black loading in the diffusion layer. In the cathode, MEA with 20 wt% Nafion content in the catalyst layer and 30 wt% PTFE content in the diffusion layer presented the optimal performance. The MEA with Nafion 115 membrane displayed the highest maximum power density of 46 mW cm⁻² among the three MEAs with different Nafion membranes. Copyright © 2009 John Wiley & Sons, Ltd.     

Highly efficient,cell reversal resistant PEMFC based on PtNi/C octahedral and OER composite catalyst

In order to obtain a fuel cell with both enhanced power generation performance and cell reversal resistance, the composite catalyst consisting of the self-made PtNi/C octahedral and the oxygen evolution reaction (OER) catalyst IrO₂ and RuO₂ is mixed and applied in the anode, and the only octahedral catalyst is employed as the cathode to prepare the membrane electrode assembly (MEA). The electrochemical activity of the composite catalyst decreases slightly, but its performance retention after the accelerated durability test (ADT) is higher. In the single cell test, the MEA fabricated using the composite catalyst maintains good single cell power generation performance. Compared with the control fabricated with Pt/C (JM), the cell voltage at 1 A cm⁻² and the maximum power density are increased by 23 mV and 119 mW cm⁻², respectively. Especially, its durability under continuous cell reversal condition is also improved significantly, and the holding time is prolonged by 1 h. This work realizes the transformation of the octahedral catalyst from the laboratory research to the actual application, and solves the difficulties in fuel cell application, and promotes its commercialization.     

Enhanced membrane electrode assembly performance by adding PTFE/Carbon black for high temperature polymer electrolyte membrane fuel cell

Phosphoric acid used as a proton-conductive medium in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) poisons the Pt surface and prevents oxygen transport in the cathode catalyst layer. The hydrophobic binders in the catalyst not only maintain the catalyst layer structure but also control the phosphoric acid distribution. In this study, polytetrafluoroethylene (PTFE)/carbon black (Vulcan XC-72R) added to the catalyst layer generates an oxygen transport channel. The catalyst layers coated on the gas diffusion layer by the bar-coating method serve as the cathode. High PTFE content causes hydrophobicity in the catalyst layer. The membrane electrode assembly (MEA) with 6 wt% PTFE/Vulcan results in the highest peak power density (0.347 W cm⁻²) and voltage (0.653 V) at 0.2 A cm⁻². A critical reason for its high performance is having the lowest R_ct + R_mt values measured at 0.6 V and 0.4 V. These results could contribute to improving the MEA performance for HT-PEMFCs.     

The effect of electrode parameters on the performance of anion exchange polymer membrane fuel cells

An investigation of several electrode parameters on performance of an alkaline membrane fuel cell is described. The studied parameters were: ionomer content, anode and cathode catalyst layer thickness, electrode aminating agent and membrane thickness.It was found that an optimum ionomer content depended on a balance between the OH⁻ ion/water mobility and the oxygen solubility/diffusivity through it and which varied with temperature. Thick catalyst layers were necessary for the anode as thin anode catalyst layers suffered from flooding. 40%Pt/C provided the best thickness (with loading of 0.4 mg_Pt cm⁻²) for cathodes operating with air.An aminated low density poly(ethylene-co-vinyl benzyl chloride) (LDPE-VBC) membrane was shown to be a good membrane for an alkaline membrane fuel cell, giving conductivities up to 0.13 S cm⁻¹ at 80 °C. A Membrane Electrode Assembly (MEA) utilizing this membrane with fully hydrated thickness of 57 μm produced good peak power density, at a high potential of 500 mV, of 337 mW cm⁻² with air (1 bar gauge) at 60 °C.     

Thickness effects of anode catalyst layer on reversal tolerant performance in proton exchange membrane fuel cell

Real-world driving conditions will likely cause hydrogen starvation at the anode chambers of stacks to trigger voltage reversal events, posing a tremendous challenge to the durability of proton exchange membrane fuel cells (PEMFCs). The reversal-tolerant anode (RTA), a material-based solution, that inclusion of oxygen evolution reaction (OER) catalyst into the anode is usually employed to cope with the voltage reversal issue. In this work, we investigate the impact of anode catalyst layer thickness on the voltage reversal performance of the membrane-electrode assemblies (MEAs) with conventional anodes (Pt/C catalyst) and RTAs doped with IrO₂ catalyst, a representative OER catalyst. We find that regardless of how thick the anode catalyst layer is, the conventional MEAs exhibit almost similar voltage reversal behaviors and times, only about 1 min to reach the shutdown voltage (?2.5 V). As for the RTA MEAs, a surprising thickness effect that the thinner RTA with the same IrO₂ loading shows superior voltage reversal tolerance. Notably, an ultra-thin RTA (~2 μm) exhibits the reversal tolerance time of 310 min, which is five times higher reversal tolerance time than most of the reported RTAs. We conclude that this thickness effect mainly results from the ionomer distribution on the OER catalyst. Besides, we observe that the RTA with a higher ionomer content shows the better reversal tolerance performance. Our work highlights the importance of the OER Triple-Phase-Boundary (TPB) and the need for improved electrode designs for robust RTAs.     

Performance of membrane electrode assemblies using PdPt alloy as anode catalysts in polymer electrolyte membrane fuel cell

Pd-based nanoparticles, such as 40 wt.% carbon-supported Pd₅₀Pt₅₀, Pd₇₅Pt₂₅, Pd₉₀Pt₁₀ and Pd₉₅Pt₅, for anode electrocatalyst on polymer electrolyte membrane fuel cells (PEMFCs) were synthesized by the borohydride reduction method. PdPt metal particles with a narrow size distribution were dispersed uniformly on a carbon support. The membrane electrode assembly (MEA) with Pd₉₅Pt₅/C as the anode catalyst exhibited comparable single-cell performance to that of commercial Pt/C at 0.7 V. Although the Pt loading of the anode with Pd₉₅Pt₅/C was as low as 0.02 mg cm⁻², the specific power (power to mass of Pt in the MEA) of Pd₉₅Pt₅/C was higher than that of Pt/C at 0.7 V. Furthermore, the single-cell performance with Pd₅₀Pt₅₀/C and Pd₇₅Pt₂₅/C as the anode catalyst at 0.4 V was approximately 95% that of the MEA with the Pt/C catalyst. This indicated that a Pd-based catalyst that has an extremely small amount of Pt (only 5 or 50 at.%) can be replaced as an anode electrocatalyst in PEMFC.     

Performance of direct methanol fuel cell using carbon nanotube-supported Pt–Ru anode catalyst with controlled composition

The performance of a single-cell direct methanol fuel cell (DMFC) using carbon nanotube-supported Pt–Ru (Pt–Ru/CNT) as an anode catalyst has been investigated. In this study, the Pt–Ru/CNT electrocatalyst was successfully synthesized using a modified polyol approach with a controlled composition very close to 20 wt.%Pt–10 wt.%Ru, and the anode was prepared by coating Pt–Ru/CNT electrocatalyst on a wet-proof carbon cloth substrate with a metal loading of about 4 mg cm⁻². A commercial gas diffusion electrode (GDE) with a platinum black loading of 4 mg cm⁻² obtained from E-TEK was employed as the cathode. The membrane electrode assembly (MEA) was fabricated using Nafion^® 117 membrane and the single-cell DMFC was assembled with graphite endplates as current collectors. Experiments were carried out at moderate low temperatures using 1 M CH₃OH aqueous solution and pure oxygen as reactants. Excellent cell performance was observed. The tested cell significantly outperformed a comparison cell using a commercial anode coated with carbon-supported Pt–Ru (Pt–Ru/C) electrocatalyst of similar composition and loading. High conductivity of carbon nanotube, good catalyst morphology and suitable catalyst composition of the prepared Pt–Ru/CNT electrocatalyst are considered to be some of the key factors leading to enhanced cell performance.     

Demonstration of a 20 W class high-temperature polymer electrolyte fuel cell stack with novel fabrication of a membrane electrode assembly

Acid-doped polybenzimidazole (PBI) membrane and polytetrafluoroethylene (PTFE)-based electrodes are used for the membrane electrode assembly (MEA) in high-temperature polymer electrolyte fuel cells (HTPEFCs). To find the optimum PTFE content for the catalyst layer, the PTFE ratio in the electrodes is varied from 25 to 50 wt%. To improve the performance of the electrodes, PBI is added to the catalyst layer. With a weight ratio of PTFE to Pt/C of 45:55 (45 wt% PTFE in the catalyst layer), the fuel cell shows good performance at 150 °C under non-humidified conditions. When 5 wt% PBI is added to the electrodes, performance is further improved (250 mA cm⁻² at 0.6 V). Our 20 W class HTPEFC stack is fabricated with a novel MEA. This MEA consists of 8 layers (1 phosphoric acid-doped PBI membrane, 2 electrodes, 1 sub-gasket, 2 gas-diffusion media, 2 gas-sealing gaskets). The sub-gasket mitigates the destruction of a highly acid-doped PBI membrane and provides long-term durability to the fuel cell stack. The stack operates for 1200 h without noticeable cell degradation.     

Characterization methodology for anode starvation in HT-PEM fuel cells

Degradation caused by fuel starvation may be an important reason for limited fuel cell lifetimes. In this work, we present an analytical characterization of the high temperature polymer exchange membrane fuel cell (HT-PEM FC) behavior under cycled anode starvation and subsequent regeneration conditions to investigate the impact of degradation due to H₂ starvation. Two membrane electrode assemblies (MEAs) with an active area of 21 cm² were operated of up to 550 min, which included up to 14 starvation/regeneration cycles. Overall cell voltage as well as current density distribution (S⁺⁺ unit) were measured simultaneously each minute during FC operation. The cyclicity of experiments was used to check the long term durability of the HT-PEM FC. After FC operation, micro-computed tomography (μ-CT) was applied to evaluate the influence of starvation on anode and cathode catalyst layer thicknesses.During starvation, cell voltage and current density distribution over the active area of the MEA significantly differed from nominal conditions. A significant drop in cell voltage from 0.6 to 0.1 V occurred after approx. 20 min for the first starvation step, and after 10 min for all subsequent starvation steps. By contrast, the voltage response is immediately stable at 0.6 V during every regeneration step. During each starvation, the local current density reached up to 0.3 A∙point⁻¹ at the area near the gas inlet (9 cm²) while near the outlet it drops to 0.01 A∙point⁻¹. The deviation from a balanced current density distribution occurred after 10 min for the first starvation step, and after ca. 2 min for the subsequent starvation steps. Hence, compared to the voltage drop, the deviation from a balanced current density distribution always starts earlier. This indicates that the local current density distribution is more sensitive to local changes in the MEA than overal cell voltage drop. This finding may help to prevent undesirable influences of the starvation process.The μ-CT images showed that H₂ starvation lead to thickness decrease of ca. 20–30% in both anode and cathode catalyst layers compared to a fresh MEA. Despite of the 14 starvation steps and the thinning of the catalyst layers the MEA presents stable cell voltage during regeneration.     

Membrane electrode assemblies with low noble metal loadings for hydrogen production from solid polymer electrolyte water electrolysis

High performance membrane electrode assemblies (MEAs) with low noble metal loadings (NMLs) were developed for solid polymer electrolyte (SPE) water electrolysis. The electrochemical and physical characterization of the MEAs was performed by I–V curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Even though the total NML was lowered to 0.38 mg cm⁻², it still reached a high performance of 1.633 V at 2 A cm⁻² and 80 °C, with IrO₂ as anode catalyst. The influences of the ionomer content in the anode catalyst layer (CL) and the cell temperature were investigated with the purpose of optimizing the performance. SEM and EIS measurements revealed that the MEA with low NML has very thin porous cathode and anode CLs that get intimate contact with the electrolyte membrane, which makes a reduced mass transport limitation and lower ohmic resistance of the MEA. A short-term water electrolysis operation at 1 A cm⁻² showed that the MEA has good stability: the cell voltage maintained at ∼1.60 V without distinct degradation after 122 h operation at 80 °C and atmospheric pressure.     

High performance membrane electrode assembly with ultra-low platinum loading prepared by a novel multi catalyst layer technique

An ultra-low platinum loading membrane electrode assembly (MEA) with a novel double catalyst layer (DCL) structure was prepared by using two layers of platinum catalysts with different loadings. The inner layer consisted of a high loading platinum catalyst and high Nafion content for keeping good platinum utilization efficiency and the outer layer contained a low loading platinum catalyst with low Nafion content for obtaining a proper thickness thereby enhancing mass transfer in the catalyst layers. Polarization characteristics of MEAs with novel DCL, conventional DCL and single catalyst layer (SCL) were evaluated in a H₂–air single cell system. The results show that the performance of the novel DCL MEA is improved substantially, particularly at high current densities. Although the platinum loadings of the anode and cathode are as low as 0.04 and 0.12 mg cm⁻² respectively, the current density of the novel DCL MEA still reached 0.73 A cm⁻² at a working voltage of 0.65 V, comparable to that of the SCL MEA. In addition, the maximum power density of the novel DCL MEA reached 0.66 W cm⁻² at 1.3 A cm⁻² and 0.51 V, 11.9% higher than that of the SCL MEA, indicative of improved mass transfer for the novel MEA. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) tests revealed that the novel DCL MEA possesses an efficient electrochemical active layer and good platinum utilization efficiency.     

Effect of catalyst layer with zeolite on the performance of a proton exchange membrane fuel cell operated under low-humidity conditions

Proton exchange membrane fuel cells (PEMFCs) employ a proton conductive membrane as the separator to transport a hydrogen proton from the anode to the cathode. The membrane's proton conductivity depends on the water content in the membrane, which is affected by the operating conditions. A membrane electrode assembly (MEA) that can self-sustain water is the key component for developing a light-weight and compact PEMFC system without humidifiers. Hence, zeolite is employed to the anode catalyst layer in this study. The effect of the gas diffusion layer (GDL) materials, catalyst loading, binder loading, and zeolite loading on the MEA performance is investigated. The MEA durability is also investigated through the electrochemical impedance spectroscopy (EIS) method. The results suggest that the MEA with the SGL28BCE carbon paper, Pt loadings of 0.1 and 0.7 mg cm^?2 in the anode and cathode, respectively, Nafion-to-carbon weight ratio of 0.5, and zeolite-to-carbon weight ratio of 0.3 showed the best performance when the cell temperature is 60 °C and supplies with dry hydrogen and air from the environment. According to the impedance variation measured by EIS, the MEA with zeolite in the anode catalyst layer shows higher and more stable performance than those without zeolite.     

Enhanced low-humidity performance of proton exchange membrane fuel cell by incorporating phosphoric acid-loaded covalent organic framework in anode catalyst layer

Developing self-humidifying membrane electrode assembly (MEA) is of great significance for the practical use of proton exchange membrane fuel cell (PEMFC). In this work, a phosphoric acid (PA)-loaded Schiff base networks (SNW)-type covalent organic framework (COF) is proposed as the anode catalyst layer (CL) additive to enhance the PEMFC performance under low humidity conditions. The unique polymer structure and immobilized PA endow the proposed COF network with not only excellent water retention capacity but also proton transfer ability, thus leading to the superior low humidity performance of the PEMFC. The optimization of the additive content, the effect of relative humidity (RH) and PEMFC operating temperature are investigated by means of electrochemical characterization and single cell test. At a normal operation temperature of 60 °C and 38% RH, the MEA with optimized COF content (10 wt%) showes the maximum power density of 582 mW cm^?2, which is almost 7 times higher than that of the routine MEA (85 mW cm^?2). Furthermore, a preliminary durability test demonstrates the potential of the proposed PEMFC for practice operation under low humidity environment.     

Carbon supported Ag nanoparticles with different particle size as cathode catalysts for anion exchange membrane direct glycerol fuel cells

The effect of Ag particle size on oxygen reduction reaction (ORR) at the cathode was investigated in anion exchange membrane direct glycerol fuel cells (AEM-DGFC) with oxygen as an oxidant. At the anode, high purity glycerol (99.8 wt%) or crude glycerol (88 wt%, from soybean biodiesel) was used as fuel, and commercial Pt/C served as the anode catalyst. A solution phase-based nanocapsule synthesis method was successfully developed to prepare the non-precious Ag/C cathode catalyst, with LiBEt₃H as a reducing agent. XRD and TEM characterizations show that as-synthesized Ag nanoparticles (NP) with a size of 2–9 nm are well dispersed on the Vulcan XC-72 carbon black support. Commercial Ag nanoparticles with a size of 20–40 nm were also supported on carbon black as a control sample. The results show that higher peak power density was obtained in AEM-DGFC employing an Ag-NP catalyst with smaller particle size: nanocapsule made Ag-NP > commercial Ag-NP (Alfa Aesar, 99.9%). With the nanocapsule Ag-NP cathode catalyst, the peak power density and open circuit voltage (OCV) of AEM-DGFC with high-purity glycerol at 80 °C are 86 mW cm⁻² and 0.73 V, respectively. These are much higher than 45 mW cm⁻² and 0.68 V for the AEM-DGFC with the commercial Ag/C cathode catalyst, which can be attributed to the enhanced kinetics and reduced internal resistance. Directly fed with crude glycerol, the AEM-DGFC with the nanocapsule Ag-NP cathode catalyst shows an encouraging peak power density of 66 mW cm⁻², which shows great potential of direct use of biodiesel waste fuel for electricity generation.     

Synthesis and electrochemical properties of nano-composite IrO2/TiO2 anode catalyst for SPE electrolysis cell

A composite catalyst of nano-grade IrO₂/TiO₂ powder is synthesized by Adams’ fusion method for reducing overvoltage of solid polymer electrolyte (SPE) cell and cost-down of noble metal catalyst, simultaneously. The IrO₂/TiO₂ catalysts, which has a porous composite nanostructure, are prepared according to molar ratio of Ir and Ti element with a specific surface area of 34.1–55.3 m² g^?1. It is found that crystal structure of TiO₂ is more dominated by the rutile phase than by Anatase. For a SPE system, total catalyst loading of anode which made of TiO₂ and IrO₂ is prepared as low as 0.77 mg cm^?2 or less, in which the loading amount of the IrO₂ only is set to 0.6 mg cm^?2 or less. The anode catalyst layer of about 10 ? thickness is coated on the membrane (Nafion 212) for the membrane electrode assembly (MEA) by the decal method. The strong adhesion between the catalyst electrode the membrane is observed by Scanning electron microscopy (SEM). Linear sweep voltammetry (LSV) results shows that the nano-composite IrO₂/TiO₂ catalysts has better oxygen evolution reaction (OER) than that of the synthesis IrO₂ only. Finally, the IrO₂/TiO₂ catalysts is applied as anode electrode for SPE cells and it is observed that in spite of the lower loading amount of the IrO₂ less than 0.5 mg cm^?2, working voltage of 1.68 V is observed at a current density of 1 A cm^?2 and operating temperature of 80 °C.     

Effect of platinum amount in carbon supported platinum catalyst on performance of polymer electrolyte membrane fuel cell

The performance of polymer electrolyte membrane fuel cells fabricated with different catalyst loadings (20, 40 and 60 wt.% on a carbon support) was examined. The membrane electrode assembly (MEA) of the catalyst coated membrane (CCM) type was fabricated without a hot-pressing process using a spray coating method with a Pt loading of 0.2 mg cm⁻². The surface was examined using scanning electron microscopy. The catalysts with different loadings were characterized by X-ray diffraction and cyclic voltammetry. The single cell performance with the fabricated MEAs was evaluated and electrochemical impedance spectroscopy was used to characterize the fuel cell. The best performance of 742 mA cm⁻² at a cell voltage of 0.6 V was obtained using 40 wt.% Pt/C in both the anode and cathode.     

Study of catalyst sprayed membrane under irradiation method to prepare high performance membrane electrode assemblies for solid polymer electrolyte water electrolysis

In this work, a catalyst sprayed membrane under irradiation (CSMUI) method was investigated to develop high performance membrane electrode assembly (MEA) for solid polymer electrolyte (SPE) water electrolysis. The water electrolysis performance and properties of the prepared MEA were evaluated and analyzed by polarization curves, electrochemistry impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The characterizations revealed that the CSMUI method is very effective for preparing high performance MEA for SPE water electrolysis: the cell voltage can be as low as 1.564 V at 1 A cm⁻² and the terminal voltage is only 1.669 V at 2 A cm⁻², which are among the best results yet reported for SPE water electrolysis with IrO₂ catalyst. Also, it is found that the noble metal catalysts loadings of the MEA prepared by this method can be greatly decreased without significant performance degradation. At a current density of 1 A cm⁻², the MEA showed good stability for water electrolysis operating: the cell voltage remained at 1.60 V without obvious deterioration after 105 h operation under atmosphere pressure and 80 °C.     

Study of the influence of Nafion/C composition on electrochemical performance of PEM single cells with ultra-low platinum load

The electrochemical performance of membrane electrode assemblies (MEAs) with ultra-low platinum load (0.02 mg_Pt cm^?2) and different compositions of Nafion/C in the catalytic layer have been investigated. The electrodes were fabricated depositing the catalytic ink, prepared with commercial catalyst (HiSPEC 2000), onto the gas diffusion layers by wet powder spraying. The MEAs were electrochemically tested using current-voltage curves and electrochemical impedance spectroscopy measurements. The experiments were carried out at 70 °C in H₂/O₂ and H₂/air as reactant gases at 1 and 2 bar pressure and 100% of relative humidity. For all MEAs tested, power density increases when the gasses pressure is increased from 1 to 2 bar. On the other hand, power density also increased when oxygen is used instead of air as oxidant gas in cathode. The lower power density (34 mW cm^?2) and power per Pt loading (0.86 kW g_Pt^?1) corresponds to the MEA prepared without Nafion in anode and cathode catalytic layers working with hydrogen and air at 1 bar pressure as reactants gas. The MEA with 30% wt Nafion/C reached the highest power density (422 mW cm^?2) and power per Pt loading (10.60 kW g_Pt^?1) using hydrogen and oxygen at 2 bar pressure. Finally, electrode surface microstructure and cross sections of MEAs were analyzed by Scanning Electron Microscopy (SEM). Examination of the electrodes, revealed that the most uniform ionomer network surface corresponds to the electrode with 40 wt% Nafion/C, and MEA ionomer-free catalytic layer shows delamination, it leads to low electrochemical performance.     

Self-humidifying membrane electrode assembly prepared by adding PVA as hygroscopic agent in anode catalyst layer

In this work, a novel self-humidifying membrane electrode assembly (MEA) with addition of polyvinyl alcohol (PVA) as the hygroscopic agent into anode catalyst layer was developed for proton exchange membrane fuel cell (PEMFC). The MEA shows good self humidification performance, for the sample with PVA addition of 5 wt.% (MEA PVA5), the maximum power density can reach up to 623.3 mW·cm⁻², with current densities of 1000 mA·cm⁻² at 0.6 V and 600 mA·cm⁻² at 0.7 V respectively, at 50 °C and 34% of relative humidity (RH). It is interesting that the performance of MEA PVA5 hardly changes even if the relative humidity of both the anode and cathode decreased from 100% to 34%. The MEA PVA5 also shows good stability at low humidity operating conditions: keeping the MEA discharged at constant voltage of 0.6 V for 60 h at 34% of RH, the attenuation of the current density is less than 10%, whilst for the MEA without addition of PVA, the attenuation is high up to 80% within 5 h.     

Dependence of high-temperature PEM fuel cell performance on Nafion® content

Operating a proton exchange membrane (PEM) fuel cell at elevated temperatures (above 100 °C) has significant advantages, such as reduced CO poisoning, increased reaction rates, faster heat rejection, easier and more efficient water management and more useful waste heat. Catalyst materials and membrane electrode assembly (MEA) structure must be considered to improve PEM fuel cell performance. As one of the most important electrode design parameters, Nafion^® content was optimized in the high-temperature electrodes in order to achieve high performance. The effect of Nafion^® content on the electrode performance in H₂/air or H₂/O₂ operation was studied under three different operation conditions (cell temperature (°C)/anode (%RH)/cathode (%RH)): 80/100/75, 100/70/70 and 120/35/35, all at atmospheric pressure. Different Nafion^® contents in the cathode catalyst layers, 15–40 wt%, were evaluated. For electrodes with 0.5 mg cm⁻² Pt loading, cell voltages of 0.70, 0.68 and 0.60 V at a current density of 400 mA cm⁻² were obtained at 35 wt% Nafion^® ionomer loading, when the cells were operated at the three test conditions, respectively. Cyclic voltammetry was conducted to evaluate the electrochemical surface area. The experimental polarization curves were analyzed by Tafel slope, catalyst activity and diffusion capability to determine the influence of the Nafion^® loading, mainly associated with the cathode.