Catalyst Coated Membrane Method Research Articles

Effects of fabrication parameters of membrane–electrode assembly for high-performance anion exchange membrane fuel cells

High-performance membrane–electrode assemblies (MEAs) are required for anion exchange membrane fuel cells (AEMFCs). In this study, we investigated different electrode coating methods and the effect of the ionomer/carbon (I/C) ratio to determine a suitable method for use with different anion exchange membranes (AEMs). The MEAs were manufactured by spray coating using catalyst-coated substrate (CCS) and catalyst-coated membrane (CCM) methods. By controlling the I/C ratio in the electrode, a reduction in the ohmic resistance was possible due to changes in the ionic path at the membrane–electrode interface, which affected the electrode morphology. In particular, for the CCS method, the ohmic resistance can be reduced by increasing the I/C ratio, whereas, for the CCM method, which yields a relatively low ohmic resistance, the I/C ratio has a greater effect on the electrode morphology than the resistance at the membrane/electrode interface, thus improving AEMFC performance. Finally, MEAs were fabricated from four commercially available AEMs using CCS and CCM, and the choice of method was found to be dependent on the properties of the AEMs. Overall, selecting a fabrication method optimized for the MEA requires understanding the electrode and AEM properties.

Double-Layer ePTFE-Reinforced Membrane Electrode Assemblies Prepared by a Reverse Membrane Deposition Process for High-Performance and Durable Proton Exchange Membrane Fuel Cells

To promote further commercialization of proton exchange membrane (PEM) fuel cells, developing a novel preparation method for high-performance and durable membrane electrode assemblies (MEAs) is imperative. In this study, we adopt the reverse membrane deposition process and expanded polytetrafluoroethylene (ePTFE) reinforcing technology to optimize the interface combination and durability of MEAs simultaneously for the preparation of novel MEAs with double-layer ePTFE reinforcement skeletons (DR-MEA). With the wet-contact between the liquid ionomer solution and porous catalyst layers (CLs), a tight 3D PEM/CL interface is formed in the DR-MEA. Based on this enhanced PEM/CL interface combination, the DR-MEA exhibits a significantly increased electrochemical surface area, reduced interfacial resistance, and improved power performance compared with a conventional MEA (C-MEA) based on a catalyst-coated membrane method. Furthermore, with the reinforcement of double-layer ePTFE skeletons and the support of rigid electrodes for the membranes, the DR-MEA demonstrates less mechanical degradation than the C-MEA after wet/dry cycle test, reflected in lower increase in hydrogen crossover current, interfacial resistance, and charge-transfer resistance and reduced power performance attenuation. With less mechanical degradation, the DR-MEA therefore shows less chemical degradation than the C-MEA after an open-circuit voltage durability test.

A Comparative Study of CCM and CCS Membrane Electrode Assemblies for High-Temperature Proton Exchange Membrane Fuel Cells with a CsH5(PO4)2-Doped Polybenzimidazole Membrane.

Membrane electrode assemblies (MEAs) are critical components in influencing the electrochemical performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). MEA manufacturing processes are mainly divided into the catalyst-coated membrane (CCM) and the catalyst-coated substrate (CCS) methods. For conventional HT-PEMFCs based on phosphoric acid-doped polybenzimidazole (PBI) membranes, the wetting surface and extreme swelling of the PA-doped PBI membranes make the CCM method difficult to apply to the fabrication of MEAs. In this study, by taking advantage of the dry surface and low swelling of a CsH5(PO4)2-doped PBI membrane, an MEA fabricated by the CCM method was compared with an MEA made by the CCS method. Under each temperature condition, the peak power density of the CCM-MEA was higher than that of the CCS-MEA. Furthermore, under humidified gas conditions, an enhancement in the peak power densities was observed for both MEAs, which was attributed to the increase in the conductivity of the electrolyte membrane. The CCM-MEA exhibited a peak power density of 647 mW cm-2 at 200 °C, which was ~16% higher than that of the CCS-MEA. Electrochemical impedance spectroscopy results showed that the CCM-MEA had lower ohmic resistance, which implied that it had better contact between the membrane and catalyst layer.

An ePTFE-reinforced membrane electrode assembly based on a wet-contact interface design strategy for high-performance proton exchange membrane fuel cells

The interfacial bonding between a proton exchange membrane (PEM) and catalyst layers (CLs) is a critical factor that dominates the power performance and durability of the membrane electrode assembly (MEA) in a proton exchange membrane fuel cell and therefore must be designed with considerable attention. On this basis, we present a novel MEA preparation approach by combining a wet-contact interface design strategy and expanded polytetrafluoroethylene (ePTFE) reinforcing technology to optimize the PEM/CL interfacial combination and durability of MEAs simultaneously. With a tight and robust three-dimensional PEM/CL interface, the MEAs based on the wet-contact process exhibit significantly reduced interfacial resistance and charge-transfer resistance and improved electrochemical surface area, resulting in superior power performance compared with conventional MEAs. Simultaneously, intercalating ePTFE reinforcement skeletons into the PFSA membrane obviously reduces the hydrogen crossover of the novel MEAs. Furthermore, due to the tighter PEM/CL interfacial bonding and the support of the rigid electrodes, the novel ePTFE-reinforced MEA shows less mechanical degradation than a conventional MEA based on the catalyst coated membrane method (with a Gore membrane) after a wet/dry cycle test. This is reflected by the lower increase in hydrogen crossover current, interfacial resistance, and charge-transfer resistance, as well as less power performance attenuation.

High-Performance Alkaline Water Electrolysis Using Anion-Exchange Membrane-Electrode Assembly with Catalyst Coated Membrane and Platinum Free Catalysts

Possibility of operation a water electrolysis technology using cost-effective components for current collectors or porous transport layers and non-platinum group metal catalysts with fast response to intermittent loads from renewable energy sources makes membrane alkaline water electrolysis (MAWE) an attractive technology for producing low cost “green” hydrogen. MAWE represents a technology combining the advantages of the already established electrolyser technologies, i.e. proton exchange membrane water electrolysis (PEMWE) and alkaline water electrolysis (AWE). It combines the relatively low-cost materials of AWE with utilisation of the ion-selective polymer electrolyte as separator of the electrode compartments which is commonly used in PEMWE. In the case of the utilisation of the ion-selective polymer electrolyte the electrodes can be pressed directly to its surface thus creating the membrane-electrode assembly (MEA). Reduction of the gap between the electrodes and separator to zero lowers the ohmic drop on the cell. This positively affects the efficiency of the water electrolysis. In MAWE the anion-selective materials are still facing some limitations in terms of poorer chemical stability in high pH environments and at elevated temperatures due to degradation of the anion exchange groups either by Hoffman elimination or nucleophilic attack by OH- ions, or lower ionic conductivity.Primarily two different MEA fabrication methods are recognized in literature [1]: catalyst-coated substrate (CCS) and catalyst-coated membrane (CCM). In the CCS method, catalyst ink, consisting of a binder/ionomer, catalyst particles and solvent, is applied to one side of the porous transport layer whereas in CCM method the catalyst ink is applied to the ion-selective membrane. The CCM approach is established in the PEMWE technology, but in MAWE the above-mentioned problem with stability of anion-selective materials limits the research.From PEMWE we know that CCM approach provides several advantages, including close contact between the catalyst layer and membrane resulting in better utilization of the catalyst compared to CCS. This advantage allows the MEA to maintain the overall performance with lower catalyst loading. Also, the catalyst layer thickness is reduced, which lowers ohmic losses on the MEA. However, the CCM method can also cause poor electrical contact between the MEA and current collector or within the catalyst layer itself.In this work, we first compare the CCS and CCM approaches and study the possibility of catalyst loading reduction. Then, with CCM we further optimize the composition of the catalyst layer, study the effect of method of preparation and compare two different membranes – non-commercial with 2 different thicknesses and commercial oneAs anion-selective material we use chloromethylated block copolymer polystyrene-ethylene-butylene-styrene (PSEBS-CM) functionalized with 1,4-diazabicyclo[2.2.2]octane (DABCO) groups. The solution of PSEBS-CM is used also as a binder of the catalyst layer. This material showed good ionic conductivity, ion exchange capacity and stability at elevated temperature. For comparison reason, Fumapem® FAA-3-50 membrane is tested. NiCo2O4 and NiFe2O4 are used as anode and cathode catalysts, respectively. Air-brush or computer controlled ultrasonic dispersion of catalyst ink are used to prepare MEA. As many operating conditions have been reported to significantly affect MAWE performance, including membrane thickness, electrolyte type, and operating temperature we decided to test the performance of the prepared CCSs and CCMs by mean of the load curves in in the range 1.5 – 2.0 V in different concentrations of KOH (1 – 15 wt.%) at 50 °C. To identify the influence of membrane thickness, we use membrane with thickness of 250 or 60 µm. To have deeper insight on the system, electrochemical impedance spectroscopy is used under the MAWE conditions at voltage of 0, 1.5 and 1.8 V in frequency range 100 kHz – 0.1 Hz with amplitude of 10 mV. Scanning electron microscopy is used to observe the morphology of the layers. The chosen CCMs undergo the stability test measured at 50 °C in 10 wt.% KOH at current density of 250 mA cm-2 for 160 hours.The obtained results show the possibility of: 1) replacing the CCS with CCM, 2) reduction of the catalyst load by 75%, 3) improvement of performance with optimized catalyst/binder ratio and 4) improvement of performance with reduction of the membranes thickness.Acknowledgments:This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 875118. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe research. Financial support by the Technology agency of the Czech Republic within the framework of the project No. TK 02030001 is gratefully acknowledged. Huah, L.B., et al., Chinese Journal of Chemical Engineering, 2020.

Utilization of catalyst-coated membrane (CCM) and spraying methods in fabrication membrane electrode assembly (MEA) for direct methanol fuel Cell (DMFC) using Pt-Co / C catalyst

Utilization of Catalyst-Coated Membrane (CCM) and Spraying Methods in fabrication of Membrane Electrode Assembly (MEA) for Direct Methanol Fuel Cell (DMFC) Using a varied Pt-Co/C catalyst has been carried out. The use of Pt-Co/C catalyst is intended to reduce the use of Pt catalysts in the electrode. Electrodes and MEAs of the two methods are characterized and tested for performance, both in open circuit voltage (OCV) and under load conditions. The MEA performance test results with the spraying method show that the best performance MEA is obtained at the ratio of Pt: Co = 60: 40, while with the CCM method, the best MEA is obtained at the ratio of Pt: Co = 40: 60. However, the power density of the spraying method in the best conditions is greater than the CCM method.

Ni@Pd core-shell nanostructure supported on multi-walled carbon nanotubes as efficient anode nanocatalysts for direct methanol fuel cells with membrane electrode assembly prepared by catalyst coated membrane method

Multi-walled carbon nanotubes supported Ni@Pd core-shell nanoparticles (Ni@Pd/MWCNTs) are successfully synthesized by two-step reduction procedure. The Ni@Pd/MWCNTs electrocatalysts are characterized by using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. According to characterization results, nanoparticles (5–10 nm) are spread on carbon support uniformly with high porosity. Moreover, the electrocatalytic performance of Ni@Pd/CNTs towards methanol electro-oxidation are evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry and chronopotentiometry methods in a conventional three-electrode cell. The results show that Ni@Pd/MWCNTs electrocatalysts have a good catalytic activity towards methanol oxidation in alkaline solutions. The performance of direct methanol fuel cell (DMFC) is evaluated in a single fuel cell set-up. The Membrane Electrode Assembly used in fuel cell set-up is prepared by catalyst-coated membrane technique. The catalyst loading is fixed at 0.5 mg Pt/C cm−2 for the cathode and 1.0 mg Ni@Pd/MWCNTs cm−2 for the anode. The used anolyte and catholyte are NaOH + CH3OH and H2SO4 + H2O2, respectively. The results exhibit that the maximum power density is about 67 mW cm−2 at 60 °C. The present paper clearly demonstrates the possibility of Ni@Pd/MWCNTs nanostructure as good performance and less expensive anode catalyst for DMFCs.

Activity and Stability of Carbide Derived Carbon Supports in PEMFC Application

Polymer electrolyte membrane fuel cells (PEMFCs) are regarded as a promising alternative energy conversion devices for both mobile and stationary applications. Main problems hindering the wide-scale commercialization of PEMFCs are high overpotential for oxygen electroreduction reaction (ORR) at the cathode decreasing the efficiency as well as the instability of porous carbon supports in fuel cell working conditions. Therefore, novel catalyst materials are being sought for PEMFC applications [1, 2]. Hierarchical microporous-mesoporous carbon supports were prepared from molybdenum carbide using the high temperature chlorination method. Prepared materials exhibited high specific surface area and large mesopore volume [3-4]. Thermogravimetric analysis, X-ray diffraction, low temperature nitrogen sorption and high resolution transmission electron microscopy methods were used to characterize the structure of the synthesized catalyst materials. Prepared catalysts were used in the single cell measurements. Catalyst coated membrane method was used to prepare the MEAs using ultrasonic spaying technique. The polarization curves and chronopotentiometric measurements were conducted to evaluate the activity and stability of the catalyst materials synthesized. From cyclic voltammetry the electrochemically active surface area values were calculated and used to estimate the contact surface of platinum nanoparticles and Nafion electrolyte. The series resistance of electrolyte, polarization resistance and activation energy values have been calculated from electrochemical impedance spectroscopy data. It was established that prepared carbon materials with well-defined properties are excellent objects to study the impact of the catalyst support properties on the performance of a PEM fuel cell. It was found that the novel synthesized catalyst materials are very stable and catalytically active towards ORR. Therefore, prepared materials are suitable for PEMFC applications. Acknowledgements. This work was supported by Estonian target research project IUT20-13, Personal Research Grant PUT1033, Estonian Centre of Excellence Project No. 2014-2020.4.01.15-0011. References S. Sepp, K. Vaarmets, J. Nerut, I. Tallo, E. Tee, H. Kurig, J. Aruväli, R. Kanarbik, E. Lust, Electrochim. Acta 2016, 203, 221−229.S. Sepp, K. Vaarmets, J. Nerut, I. Tallo, E. Tee, H. Kurig, J. Aruväli, R. Kanarbik, E. Lust, J. Solid State Electrochem. 2016, 21(4), 1035–1043.S. Sepp, E. Härk, P. Valk, K. Vaarmets, J. Nerut, R. Jäger, E. Lust, J. Solid State Electrochem. 2014, 18(5), 1223 – 1229.E. Lust, K. Vaarmets, J. Nerut, I. Tallo, P. Valk, S. Sepp, E. Härk, Electrochim. Acta 2014, 140, 294-303.

Electrode Configuration of Anion Exchange Membrane Electrolyzer

In the case of proton exchange membrane (PEM) electrolyzer, the material of bipolar plates has been practically limited to titanium (Ti). The material restriction for the bipolar plates should be relieved, when a membrane performing under alkaline (basic) conditions was applied to the electrolyte. In addition, alkaline conditions might enable to use less expensive catalysts. One of the alternative materials for electrolyte is an anion exchange membrane (AEM) that has high internal pH. The potential of AEM electrolysis has been presented by several previous studies [1-3]. However, it is difficult to say that the cell components have been sufficiently optimized, in terms of membrane, catalyst, electrode structure/configuration, and electrolytic solution. In this study, focusing on the electrode structure and configuration, various types of membrane electrode assembly (MEA) were fabricated in house, applying either configuration of catalyst coated membrane (CCM) or catalyst coated substrate (CCS), and then electrolytic cell with those MEAs were operated. Based on the experimental results of electrolysis, an appropriate electrode structure for AEM electrolyzer has been examined.The current density (i) - cell voltage (V) characteristics were measured using various cell set-ups In the cell set-ups, a commercial AEM (A201, Tokuyama) was applied for the membrane electrolyte, and commercially available electrocatalyst was used for hydrogen (cathode) and oxygen (anode) evolution, namely, 4030 and 3030 (Acta SpA), respectively [3]. Cathode catalyst layers (CLs) were commonly prepared by catalyst coating membrane (CCM) method using commercial anion exchange ionomer (AS-4, Tokuyama) as a binder. As for anode, two different arrangements for CL configuration were adopted, namely, CCM and CCS. In the fabrication of CCS, polytetrafluoroethylene (PTFE) was used as a binder. In order to examine the stability of electrode structure, the series of i-V measurement was repeated in 2 days. The observed i-V and i-R_cell characteristics using different cell set-ups are shown in Figure 1. In EL1 cell, the both electrodes were fabricated by CCM. As shown in Fig. 1 (a), the i-V performance of EL1 in 2nd day was definitely degraded from that in 1st day. In particular, the difference in V was relatively large even in small i range (<100 mA cm-2), though the difference in R_cell was negligible. It means that the degradation was mainly caused by the increase of activation overpotential related to catalyst performance. In the case of EL2 cell, CCS was applied for the anode CL, while the cathode CL was fabricated by the CCM method. As shown in Fig. 1 (b), the degradation in 2nd day was significantly decreased. It was clearly suggested that, for the anode, CLs fabricated by CCS must be much stable rather than that of CCM. References L. Xiao et al., Energy Environ. Sci., 5, 7869 (2012). Y. Leng et al., J. Am. Chem. Soc., 134,9054 (2014). 3. C.C. Pavel et al., Angew. Chem. Int. Ed., 53, 1378 (2014). Figure 1

The comparison of direct borohydride-hydrogen peroxide fuel cell performance with membrane electrode assembly prepared by catalyst coated membrane method and catalyst coated gas diffusion layer method using Ni@Pt/C as anodic catalyst

Carbon supported Ni@Pt nanoparticles are synthesized using sodium dodecyl sulphate (SDS) and sodium borohydride (NaBH4) as a structure-directing and reducing agents, respectively. The metal loading in synthesized nanocatalyst is 20 wt% and the ratio of Ni:Pt in the nanocatalyst is 1:1. The structural characterizations and morphologies of Ni@Pt/C nanocatalyst are investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The electrocatalytic activity of Ni@Pt/C catalyst toward borohydride (BH4−) oxidation in alkaline medium is studied by means of cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA). The results show that Ni@Pt/C catalyst has superior catalytic activity toward borohydride oxidation (8825.38 mA mg Pt−1). The Membrane Electrode Assembly (MEA) used in fuel cell set-up is fabricated with catalyst-coated membrane (CCM) and catalyst coated gas diffusion medium (CCG) techniques. The effect of two MEA performances on current–voltage (I–V) and current–power density (I–P) curves in the direct borohydride-hydrogen peroxide fuel cell was investigated using Pt/C 0.5 mg cm−2 as cathode catalyst and Ni@Pt/C 1 mg cm−2 as anode catalyst. The influence of cell temperature, sodium borohydride and hydrogen peroxide concentration on the I–V and I–P is determined. The results show that the maximum power density in MEA prepared using CCM method (CCM-MEA) is 68.64 mW cm−2 at 60 °C, 1 M sodium borohydride and 2 M hydrogen peroxide (H2O2) that is higher than MEA prepared using CCG method (CCG-MEA). The impedance results show that with increasing temperature and discharging current, the overall anodic and cathodic charge transfer resistances reduce.

The Application of Ultrasound to the Coating of Platinum Catalyst on Membrane for Proton Exchange Membrane Fuel Cell

MEA (Membrane Electrode Assembly) consisting of the electrodes coated with a catalyst and the membrane is the most important in fuel cell. In fabricating MEA, there are two ways to coat catalyst depending on a coating substrate, i.e. CCM (Catalyst Coated Membrane, coating on membrane), and CCS (Catalyst Coated Substrate, coating on carbon paper). Generally, CCM is known as a better way than CCS, and spray coating has been widely used for CCM method. In this study, CCM method was also adopted to make MEA, however, catalyst was coated sonochemically to introduce a new catalyst coating method in making MEA.The most convincing and famous mechanism known for a sonochemical metal ion reduction is a reduction of metal precursor by radicals generated by hot spot during ultrasound irradiation1. Thus we introduced ultrasound irradiation for synthesizing and coating of platinum on membrane simultaneously. In applying ultrasound irradiation, we changed experimental conditions such as time of radiation and the intensity of radiation. The amount of platinum loaded on membrane was proportion to the time and the power of ultrasound irradiation as shown in Fig. 1. The solution used for platinum electrode formation includes not only platinum precursor but also a reducing agent and a surfactant to help precursor reduction. After Pt catalyst coating, remaining impurities like a reducing agent and a surfactant were removed by using stirring in pure water.In order to check whether platinum was successfully loaded on membrane, FE-SEM (Field Emission Scanning Electron Microscope) and EDS (Energy Dispersive x-ray Spectroscopy) analyses were carried out as shown in Fig. 2, and it proved the effectiveness of ultrasound irradiation in making platinum electrode on membrane. Furthermore, we looked into the electrochemical characteristics of the MEA using CV (Cyclic Voltammertry) and EIS (Electrochemical Impedance Spectroscopy), and then the result was compared with that of a conventional MEA. MEAs, both new and conventional, were made into single cells for a performance test and a comparison. In making a single cell with the MEA made by ultrasound irradiation, ionomer effect was thoroughly studied to take advantage of thin thickness of platinum catalyst layer. It is known that the mass transfer through thin film catalyst layer is fast without ionomer2.In thus presentation, all the results investigated in the study will be presented with in-depth discussion.

Performance improvement by a glue-functioned Nafion layer coating on gas diffusion electrodes in PEM fuel cells

To reduce the performance difference of membrane electrode assembles (MEAs) between catalyst coated membrane (CCM) and gas diffusion electrode (GDE) methods, this study presents a novel structure of a glue-functioned Nafion layer coating on the catalyst layer of GDEs to enhance performance. The process of hot pressing is omitted from the membrane electrode assembly (MEA) fabrication in this study. In exploring the effect of the glue-functioned Nafion layer, five MEAs are compared, including one made by the CCM method and four by the GDE method. Loadings of 0, 0.1, 0.3 and 0.5 mg cm−2 of glue-functioned Nafion layer are coated on the surface of the catalyst layer at room temperature with a condensed Nafion solution (20 wt%). The performance of the 0.3 mg cm−2 Nafion layer coating improves 55% compared with that without an extra Nafion layer for the peak power density, and the performance difference reduces from 61.2% to 39.4% when compared with the one using the CCM method. However, the performance of the 0.5 mg cm−2 Nafion layer coating is almost the same as without the Nafion layer. This indicates that increased Nafion cannot guarantee higher performance.

Fabrication and electrochemical performance of Poly (2,5-benzimidazole) (ABPBI)-based MEA by catalyst coated membrane (CCM) method for high-temperature polymer electrolyte fuel cells

The interfacial impedance between membrane and catalyst layer in membrane electrode assembly (MEA) is of great critical for the electrochemical performances of a proton exchange membrane fuel cell. To minimize the interfacial impedance, a series of Poly (2, 5-benzimidazole) (ABPBI)-based MEA were fabricated by catalyst coated membrane (CCM) method. Two kinds of proton exchange resin solution were used in the CCM process and the H3PO4 loading in the CCM catalyst layer was varied. The electrochemical performances such as polarization curve, AC impedance, cyclic voltammetry and stability of the obtained MEAs were studied and compared with the MEA fabricated by gas diffusion electrode (GDE) method. The results indicated that the impedance can be decreased through CCM method compared with GDE method and the MEA fabricated by CCM method with ABPBI as proton exchange agent and 10 mg/cm2 H3PO4 dosages exhibited the optimal electrochemical performances.

Effects of hot pressing conditions on the performance of Nafion membranes coated by ink-jet printing of Pt/MWCNTs electrocatalyst for PEMFCs

In our previous work, a hydrothermal method was employed to prepare Pt/MWCNTs nanocomposites with 20 wt.% Pt, a low mean Pt nanoparticles size (2.8 nm) and a specific surface area of 99 m2 g−1. In this work, the membrane electrode assemblies (MEAs) with hydrothermally synthesized Pt/MWCNTs nanocatalysts were fabricated by catalyst-coated membrane (CCM) method. For this purpose, a commercial HP inkjet printer was used to deposit Pt/MWCNTs ink (as catalyst ink) directly on to the substrate (Nafion membrane or decal substrate) with a loading of 0.2 mg cm−2 Pt for both the anode and cathode. The effects of hot-pressing conditions on the performance of MEAs were investigated through Taguchi design of experiments method using temperature (100 and 130 °C), pressure (800 and 1000 psi) and time (3 and 5 min) as effective experimental parameters. The compression ratios of MEAs were determined by testing the thicknesses before and after hot-pressing process. The performance of MEAs was characterized by the polarization curves and cyclic voltammetry (CV) and the surface morphologies of the electrodes were observed by scanning electron microscopy (SEM). The results showed that the most appropriate hot-pressing conditions were 800 psi, 100 °C, and 3 min. Electrochemical analysis and physical property examination revealed that the MEA fabricated by CCM method has a better performance compared to the one prepared by conventional decal transfer (DT) method.

Fuel cell performances at optimized Nafion and Ru 85Se 15 loadings in cathode catalyst layer

The citric acid treated carbon supported Ru 85Se 15 catalysts are synthesized by microwave assisted polyol method at the optimal solution pH = 7. The catalyst coated membrane method with ultrasonic-spray technique is employed to prepare electrodes without hot press step. The cell performances with different Nafion contents and Ru loads in the cathode catalyst layer are systematically examined in both H 2/air and H 2/O 2 fuel cells at 65 °C under ambient pressure. The surface morphologies of membrane electrode assemblies and the interfacial characteristics of single cells are studied using scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The Nafion content is optimized to be 33% when the catalyst loadings are lower than 0.8 and 0.6 mg Ru cm −2 in the H 2/air and H 2/O 2 fuel cells, respectively, but reduced to 20% at the higher Ru loads. The maximum peak power densities of 190 mW cm −2 at 620 mA cm −2 and 400 mW cm −2 at 1430 mA cm −2 are achieved in the H 2/air and H 2/O 2 fuel cells, respectively, with 0.27 mg Ru cm −2 and 33% Nafion. The best catalyst utilizations are obtained at 0.14 mg Ru cm −2 with 33% Nafion, resulting in the maximum peak power densities per unit mass Ru of 917 and 2460 mW mg −1 in the H 2/air and H 2/O 2 fuel cells, respectively.

Fabrication and Performance of Membrane Electrode Assembly Prepared by a Catalyst-Coated Membrane Method: Effect of Solvents Used in a Catalyst Ink Mixture

The effect of solvent types used to prepare catalyst-coated membrane (CCM) electrodes on the coating ink, applied coating process, interaction of catalyst ink and Nafion membrane and, thus, on the performance and power density of the proton exchange membrane fuel cells (PEM fuel cells) was investigated. Among seven types of solvents studied, the catalyst ink prepared using the isopropanol solvent showed the highest cell performance, followed in descending order by ethanol, acetone, water−ethylene glycol, ethylene glycol dimethyl ether (EGDME), and ethylene glycol diethyl ether (EGDEE). The superior performance was due to the good attachment of catalyst layer to membrane and the good surface coverage revealed by the results from the scanning electron microscope (SEM) of the CCMs, optical transmittance of the CCMs, and solvent absorption capacity of membrane. In electrode preparation by the CCM method, the solvent−ionomer mixture in solution form was more favorable than that in colloid form, as it gave high...

Investigation of a Novel Catalyst Coated Membrane Method to Prepare Low‐Platinum‐Loading Membrane Electrode Assemblies for PEMFCs

AbstractIn this work, a novel catalyst coated membrane (CCM) approach–a catalyst‐sprayed membrane under irradiation (CSMUI)–was developed to prepare MEAs for proton exchange membrane fuel cell (PEMFC) application. Catalyst ink was sprayed directly onto the membrane and an infrared light was used simultaneously to evaporate the solvents. The resultant MEAs prepared by this method yielded very high performance. Based on this approach, the preparation of low‐platinum‐content MEAs was investigated. It was found that for the anode, even if the platinum loading was decreased from 0.2 to 0.03 mg cm–2, only a very small performance decrease was observed; for the cathode, when the platinum loading was decreased from 0.3 to 0.15 mg cm–2, just a 5% decrease was detected at 0.7 V, but a 35% decrease was observed when the loading was decreased from 0.15 to 0.06 mg cm–2. These results indicate that this approach is much better than the catalyst coated gas diffusion layer (GDL) method, especially for the preparation of low‐platinum‐content MEAs. SEM and EIS measurements indicated ample interfacial contact between the catalyst layer and the membrane.

A 10 kW class PEM fuel cell stack based on the catalyst-coated membrane (CCM) method

A 60-cell 10 kW class PEM fuel cell stack has been developed and tested. By using the catalyst-coated membrane (CCM) method, a power density of 0.36 W / cm 2 was reached for a single cell with a 600 cm 2 active area. The total Pt loading was 0.6 mg / cm 2 for the anode and cathode catalyst layers. Cyclic voltammogram (CV) tests revealed that the CCM method had a higher Pt utilization when compared to the hydrophobic method. Furthermore, a maximum power of 10.9 kW was reached at an air utilization of 30%. A 400-h performance test showed a ± 2 V fluctuation of the stack voltages. Coupling the 10 kW class stack with an external humidifier gave a relatively poor result of 6 kW.