Membranes For Proton Exchange Membrane Fuel Cells Research Articles

Assessing the Unique Degradation Mechanisms of Hydrocarbon-Based Membranes in Conventional MEA Design Using 4D in-Situ X-Ray Computed Tomography

The degradation of proton exchange membrane fuel cells (PEMFCs) stands as a critical determinant in evaluating the robustness of fuel cell systems, crucial for the commercial-scale transition to sustainable energy. For zero-emission vehicles, fuel cell stacks need to demonstrate lifespans exceeding 8,000 (light-duty vehicles) and 30,000 hours (heavy-duty vehicles)[1]. For achieving robust PEMFC systems at commercial scale, it is crucial to precisely understand the degradation pathways to effectively pinpoint and mitigate degradation issues. To achieve this, customized small-scale fuel cell fixtures are utilized for accelerated stress testing (AST) and X-ray computed tomography (XCT) in-situ and ex-situ visualization [2,3]. This approach enables comprehensive analysis of membrane electrode assembly (MEA) aging processes. Our group previously employed this approach to identify chemical, mechanical, and chemo-mechanical degradation mechanisms in commonly used perfluorosulfonic acid (PFSA) ionomer membranes[4,5]. In recent years, transitioning from PFSA membranes to hydrocarbon-based (HC) membranes in PEMFCs has gained significant attention. This shift eliminates fluorinated compounds typically found in PFSA membranes, aligning with sustainability goals, and reducing environmental impact. This transition signifies both technological advancement and innovation, driving forward the quest for efficient, cost-effective, and environmentally friendly energy solutions. Despite their promising characteristics, HC membranes are more susceptible to mechanical degradation than PFSA ones[6], presenting unique compatibility challenges due to their distinct chemical composition. Historically, PEMFC systems intentionally developed and optimized for PFSA may face performance issues and premature failure with HC membranes. This research therefore investigates the unique aspects of HC membrane degradation within a conventional fuel cell design with PFSA ionomer catalyst layers, using 4D in-situ XCT to understand chemo-mechanical degradation, enhancing fuel cell technology.Herein, ZEISS Xradia® 520 Versa micro XCT system was used to visualize samples. Repetitive scans were taken at room temperature in a dry state of the MEA. The first set of MEAs consisted of reinforced HC membranes (Pemion-PF1-HLF8-15-X) of 15 µm thickness, spray-coated with PFSA catalyst ink to form catalyst-coated membranes (CCMs), and assembled with gas diffusion layers (Freudenberg H14C15, 190 µm) featuring smooth and crack-free microporous layer. The AST protocol was custom-designed for chemo-mechanical membrane degradation and included open circuit voltage hold for chemical degradation and relative humidity cycling for mechanical degradation, which were applied consecutively. It has been demonstrated that MEAs undergo dimensional changes during wet-dry AST cycles due to alternating conditions of hydration and dehydration[5,7]. It is apparent from the degraded XCT image (Figures 1a-d) that cracks were initiated and propagated between the membrane and catalyst layers, with cracks prominently visible near agglomerated electrode particles. Differential swelling between the membrane and catalyst layer, compounded by varying rates of expansion or contraction, resulted in magnified mechanical stresses at the membrane-catalyst layer interfaces.The second set of cells consisted of the same reinforced HC membrane assembled with commercial gas diffusion electrodes (GDEs; 0.5 mg/cm² 60% Pt on Vulcan, Sigracet 22 BB, 215 µm). The existence of interfacial voids (Figure 1e) was observed in the pristine sample at both anode and cathode membrane-GDE interfaces, likely due to interfacial adhesion fatigue (IAF)[8]. Uneven compression and interfacial incompatibility during fuel cell assembly results in IAF. When these GDE based MEAs were subjected to wet-dry AST cycles, mechanical stress was induced at the membrane-GDE interfaces[9, 10]. The uneven mechanical stress can aggravate creep propagation in the membrane. Due to creep propagation, membrane thinning at the edges was evident from the XCT images, and resulted in electrode shorting, as shown in Figure 1(f and g). It is believed that constraints during creep failure hindered membrane's return to original thickness after swelling, causing permanent dimensional changes. The combined effects of cyclic dimensional changes and membrane thinning due to the creep mechanism contributed to performance degradation and reduced durability of GDE-based MEAs. Acknowledgements This work was supported by the Natural Sciences and Engineering Research Council of Canada, Ionomr Innovations Inc., Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Pacific Economic Development Canada, and Canada Research Chairs. References C.S. Gittleman et al., Joule, 5 (2021) 1660–1677.Y. Singh et al., J Power Sources, 412 (2019) 224–237.D. Ramani et al., Electrochim Acta, 380 (2021) 138194.Y. Chen et al., J Power Sources, 520 (2022) 230674.Y. Chen et al., J Electrochem Soc, 170 (2023) 114526.S.H. Mirfarsi et al., Int J Hydrogen Energy, 47 (2022) 13460–13489.A. Sadeghi Alavijeh et al., J Power Sources, 427 (2019) 207–214.X. Huang et al., J Polym Sci B Polym Phys, 44 (2006) 2346–2357.V.A. Sethuraman et al., J Electrochem Soc, 155 (2008) B50.S.H. Mirfarsi et al., Int J Hydrogen Energy, 50 (2024) 1507–1522. Figure 1

A Sustainable and Eco-Friendly Membrane for PEM Fuel Cells Using Bacterial Cellulose.

Bacterial cellulose (BC) is an advantageous polymer due to its renewable nature, low cost, environmental compatibility, biocompatibility, biodegradability, chemical stability, and ease of modification. With these advantages, BC is an interesting candidate for the development of novel eco-friendly materials for proton-exchange membrane (PEM) applications. However, its practical applications have been limited by its relatively high dispersion in water, which usually occurs during the operation of proton-exchange membrane fuel cells (PEMFCs). In addition, the proton conductivity of bacterial cellulose is poor. In this study, functionalized BC modified with 3-aminopropyltriethoxysilane (APTES) was prepared using a solvent casting method to enhance its performance. The results showed that the water stability of the modified BC membrane was significantly improved, with the contact angle increasing from 54.9° to 103.3°. Furthermore, the optimum ratio of BC and APTES was used to prepare a proton-exchange membrane with a maximum proton conductivity of 62.2 mS/cm, which exhibited a power generation performance of 4.85 mW/cm2 in PEMFCs. It is worth mentioning that modified BC membranes obtained by combining an alkaline proton carrier (-NH2) with BC have rarely been reported. As fully bio-based conductive membranes for PEMFCs, they have the potential to be a low-cost, eco-friendly, and degradable alternative to expensive, ecologically problematic fluoric ionomers in short-term or disposable applications, such as biodegradable electronics and portable power supplies.

Advances in the Application of Sulfonated Poly(Ether Ether Ketone) (SPEEK) and Its Organic Composite Membranes for Proton Exchange Membrane Fuel Cells (PEMFCs)

This review discusses the progress of research on sulfonated poly(ether ether ketone) (SPEEK) and its composite membranes in proton exchange membrane fuel cells (PEMFCs). SPEEK is a promising material for replacing traditional perfluorosulfonic acid membranes due to its excellent thermal stability, mechanical property, and tunable proton conductivity. By adjusting the degree of sulfonation (DS) of SPEEK, the hydrophilicity and proton conductivity of the membrane can be controlled, while also balancing its mechanical, thermal, and chemical stability. Researchers have developed various composite membranes by combining SPEEK with a range of organic and inorganic materials, such as polybenzimidazole (PBI), fluoropolymers, and silica, to enhance the mechanical, chemical, and thermal stability of the membranes, while reducing fuel permeability and improving the overall performance of the fuel cell. Despite the significant potential of SPEEK and its composite membranes in PEMFCs, there are still challenges and room for improvement, including proton conductivity, chemical stability, cost-effectiveness, and environmental impact assessments.

High Temperature Studies of Graphene Nanoplatelets-MOFs Membranes for PEM Fuel Cells Applications

The wide applicability of proton exchange membrane fuel cells (PEMFCs) is hindered by their dependency on the Nafion membrane as a state-of-the-art electrolyte. Nafion membranes can only operate at relatively low temperatures, up to 80°C. Therefore, any application of the fuel cell above this temperature would cause the PEMFC to lose its proton conductivity and mechanical integrity. For this reason, the development of Nafion-free membranes for PEMFCs has been studied extensively through the corporation of several additives over polymer substrates. The charge transfer abilities of metal-organic frameworks (MOFs), among other properties, make them one of the possible additives. The objective of this work is to synthesize Nafion-free membranes based on graphene oxide, MOFs, ionic liquids, polyethylene glycol, and zirconium phosphate over PTTFE membrane as an alternative to Nafion membranes. The preliminary results gave proton conductivities in the range of 10-4 S/cm up to 150°C with graphene oxide MOF addition to all samples.

Decay behaviour of ultrathin reinforced membranes in PEMFCs subjected to the combination of mechanical/chemical accelerated stress testing

To improve the performance of proton exchange membrane fuel cells (PEMFCs), proton exchange membranes (PEMs) have been made much thinner. However, the thinner the PEM, the more challenging its durability. In this paper, the degradation of ultrathin reinforced PEMs with two thicknesses, 8 μm and 12 μm, under the combination of mechanical/chemical accelerated stress testing (AST) is researched. The results show that the cycle numbers of the two ultrathin reinforced PEMs are equivalent and meet the target proposed by the United States Department of Energy (DOE). They present very different trends from those of changes in the durability of traditional homogeneous PEMs with thickness. The growth of the hydrogen crossover current follows an exponential function, which is the same as that of traditional homogeneous PEMs but with an order of magnitude smaller characteristic parameter k, which might be the key reason that the cycle numbers of ultrathin reinforced PEMs far exceed those of other PEMs. The failure analysis shows that the fracture of the two ultrathin reinforced PEMs is located at the edge of the membrane electrode assembly (MEA) frame. These failures could be attributed to the stress concentration at the edge of the frame and contribute to the similar lifetime and decay regulations. More details are observed that the edge failure points of the two PEMs at the gas inlet or outlet region. In addition, the effects of thinner PEMs at the gas inlet and outlet are more obvious than that at other parts. It is concluded that the durability of ultrathin reinforced PEMs is almost independent of thickness, while the stress concentration caused by the MEA structure and the condition control at the location of the gas inlet and outlet are mainly responsible for the failure of the PEM. The results in this work will provide a new perspective for the development of ultrathin reinforced PEMs.

A Critical Review of Electrolytes for Advanced Low- and High-Temperature Polymer Electrolyte Membrane Fuel Cells

In the 21st century, proton exchange membrane fuel cells (PEMFCs) represent a promising source of power generation due to their high efficiency compared with coal combustion engines and eco-friendly design. Proton exchange membranes (PEMs), being the critical component of PEMFCs, determine their overall performance. Perfluorosulfonic acid (PFSA) based Nafion and nonfluorinated-based polybenzimidazole (PBI) membranes are commonly used for low- and high-temperature PEMFCs, respectively. However, these membranes have some drawbacks such as high cost, fuel crossover, and reduction in proton conductivity at high temperatures for commercialization. Here, we report the requirements of functional properties of PEMs for PEMFCs, the proton conduction mechanism, and the challenges which hinder their commercial adaptation. Recent research efforts have been focused on the modifications of PEMs by composite materials to overcome their drawbacks such as stability and proton conductivity. We discuss some current developments in membranes for PEMFCs with special emphasis on hybrid membranes based on Nafion, PBI, and other nonfluorinated proton conducting membranes prepared through the incorporation of different inorganic, organic, and hybrid fillers.

Quantitative diagnosis of PEMFC membrane humidity with a vector-distance based characteristic mapping approach

Membrane dehydration or flooding fault is one of the main causes of performance degradation for Proton Exchange Membrane Fuel Cell (PEMFC). Effective and accurate diagnosis of membrane humidity faults is necessary to ensure the optimal operation of PEMFC. However, the research gap lies in the quantitative diagnosis of membrane humidity values under complex working conditions of vehicle application. In this paper, characteristic spaces describing membrane humidity are established as multi-matrices consisting of the amplitude spectrum extracted from output voltage and pressure drop in PEMFC under different vehicle working conditions. In the multi-matrix, the relationship between the membrane humidity fault levels and the amplitude spectrum can be described as characteristic vectors. Then, a vector-distance based mapping approach under multi-information characteristic vectors is developed to describe the relationship between characteristic vectors and humidity values. Consequently, the membrane humidity of the PEMFC can be quantitatively evaluated with the projection length between characteristic vector and humidity-change vector, with which the humidity value of PEMFC membrane can be obtained under different working conditions in real-time. The performance of the proposed a vector-distance based characteristic mapping approach is verified by New European Driving Cycle (NEDC) and World Light Vehicle Test Procedure (WLTP) working conditions. The diagnostic results show that the quantitative humidity diagnosis strategy can achieve diagnostic accuracy of 98.16% and 92.24% under NEDC and WLTP working conditions, compared with the single information of output voltage-based and pressure drop-based diagnosis strategy, the accuracy is improved by 4.37% and 4.08% respectively.

Functional and Environmental Performances of Novel Electrolytic Membranes for PEM Fuel Cells: A Lab-Scale Case Study

Despite being the most employed polymer electrolyte for proton exchange membrane fuel cells (PEMFCs), Nafion® has several limitations: expensiveness, poor performance when exposed to temperatures higher than 80 °C, and its potential as a source of environmentally persistent and toxic compounds (i.e., per- and polyfluoroalkyl substances, known as PFASs) when disposed of. This work explores the functional and environmental performances of three potential PFAS-free alternatives to Nafion® as electrolytic membranes in PEMFCs: sulfonated graphene oxide (SGO), graphene oxide-naphthalene sulfonate (GONS), and borate-reinforced sulfonated graphene oxide (BSGO). Investigated via ATR-FTIR spectroscopy, TGA, and cross-sectional SEM, the membranes show an effective functionalization of GO and good thermal stability. Functional properties are determined via Ion Exchange Capacity (IEC) evaluation, Electrochemical Impedance Spectroscopy, and tensile tests. In terms of IEC, the innovative materials outperform Nafion® 212. Proton conductivities at 80 °C of SGO (1.15 S cm−1) and GONS (1.71 S cm−1) are higher than that of the commercial electrolyte (0.56 S cm−1). At the same time, the membranes are investigated via Life Cycle Assessment (LCA) to uncover potential environmental hotspots. Results show that energy consumption during manufacture is the main environmental concern for the three membranes. A sensitivity analysis demonstrates that the impact could be significantly reduced if the production procedures were scaled up. Among the three alternatives, SGO shows the best trade-off between proton conductivity and environmental impact, even though performance results from real-life applications are needed to determine the actual environmental consequences of replacing Nafion® in PEMFCs.

Review: Modeling and Simulation of Membrane Electrode Material Structure for Proton Exchange Membrane Fuel Cells

Hydrogen energy is recognized as the clean energy with the most development potential, and hydrogen fuel cell technology is considered the ultimate solution utilizing hydrogen energy. The proton exchange membrane fuel cell (PEMFC) has the merits of high energy efficiency, high energy density, low operating temperature, is clean, and affords environmental protection. Improving the structure of each functional layer could play a significant role in improving PEMFC performance. In addition, membrane electrode assemblies (MEAs) are the core components of a PEMFC, and their structure includes three main parts, namely, the gas diffusion layer (GDL), catalytic layer (CL), and proton exchange membrane (PEM). Therefore, this review focuses on progress in the modeling and simulation of the material structure in MEAs. First, the GDL simulation models are critically reviewed, including two-phase calculation models and microscopic simulation models. Second, CL microstructure models are comprehensively evaluated, involving power density enhancement, catalyst loading distribution, electrochemical reaction and its performance optimization. Third, the PEM simulation model, relating to molecular dynamics (MD) simulation techniques, 3D numerical techniques, and multiphysics simulation, are reviewed. Finally, the three aspects of similarity, individuality, and complementarity of these simulation models are discussed, and necessary outlooks, including the current limitations and challenges, are suggested, providing a reference for low-cost, high-performing PEMFC membrane electrodes for the future.

Diagnosing Improper Membrane Water Content in Proton Exchange Membrane Fuel Cell Using Two-Dimensional Convolutional Neural Network

In existing proton exchange membrane fuel cell (PEMFC) applications, improper membrane water management will cause PEMFC performance decay, which restricts the reliability and durability of PEMFC systems. Therefore, diagnosing improper water content in the PEMFC membrane is the key to taking appropriate mitigations to guarantee its operating safety. This paper proposes a novel approach for diagnosing improper PEMFC water content using a two-dimensional convolutional neural network (2D-CNN). In the analysis, the collected PEMFC voltage signal is transformed into 2D image data, which is then used to train the 2D-CNN. Data enhancement and pre-processing techniques are applied to PEMFC voltage data before the training. Results demonstrate that with the trained model, the diagnostic accuracy for PEMFC membrane improper water content can reach 97.5%. Moreover, by comparing it with a one-dimensional convolutional neural network (1D-CNN), the noise robustness of the proposed method can be better highlighted. Furthermore, t-distributed Stochastic Neighbor Embedding (t-SNE) is used to visualize the feature separability with different methods. With the findings, the effectiveness of using 2D-CNN for diagnosing PEMFC membrane improper water content is explored.

Modifications on Promoting the Proton Conductivity of Polybenzimidazole-Based Polymer Electrolyte Membranes in Fuel Cells.

Hydrogen-air proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are excellent fuel cells with high limits of energy density. However, the low carbon monoxide (CO) tolerance of the Pt electrode catalyst in hydrogen-air PEMFCs and methanol permanent in DMFCs greatly hindered their extensive use. Applying polybenzimidazole (PBI) membranes can avoid these problems. The high thermal stability allows PBI membranes to work at elevated temperatures when the CO tolerance can be significantly improved; the excellent methanol resistance also makes it suitable for DMFCs. However, the poor proton conductivity of pristine PBI makes it hard to be directly applied in fuel cells. In the past decades, researchers have made great efforts to promote the proton conductivity of PBI membranes, and various effective modification methods have been proposed. To provide engineers and researchers with a basis to further promote the properties of fuel cells with PBI membranes, this paper reviews critical researches on the modification of PBI membranes in both hydrogen-air PEMFCs and DMFCs aiming at promoting the proton conductivity. The modification methods have been classified and the obtained properties have been included. A guide for designing modifications on PBI membranes for high-performance fuel cells is provided.

Atomically Dispersed Single Metal Site Catalysts for Oxygen Reduction in Acidic Media

Proton exchange membrane fuel cells (PEMFCs) are leading candidates in utilizing clean energy resources for application in transportation, stationary, and portable devices. In PEMFCs, cathode catalysts are crucial for overall performance and durability due to kinetically slow oxygen reduction reactions (ORR). Because platinum (Pt), a state-of-the-art ORR catalyst, is rare and expensive, the development of high-performance platinum metal group (PGM)-free catalysts is highly desirable for future fuel cell technologies. Among various PGM-free catalyst formulations, metal and nitrogen co-doped carbon (M-N-C, M: Fe, Co, or Mn) catalysts have exhibited encouraging activity and stability in acidic media for the ORR, which possess great potential to replace Pt in the future. Therefore, based on our extensive experience in the field of ORR catalysis, the talk will comprehensively summarize the basic principles in the design and synthesis of M-N-C catalysts for durable, inexpensive, and high-performance PEMFCs with an emphasis on Co- and Mn-N-C catalysts to avoid Fenton reactions between Fe2+ and H2O2, which can generate free radicals and lead to the degradation of catalysts, ionomers, and membranes in PEMFCs. Furthermore, template-free 3D hydrocarbon frameworks as attractive precursors to advanced M-N-C catalysts will be discussed to enhance intrinsic ORR activities in acidic media significantly. Also, the long-term performance durability of M-N-C cathodes will be discussed extensively to provide potential solutions to enhance catalyst stability in PEMFCs. Finally, this talk will provide an overall perspective on the progress, challenges, and solutions of PGM-free catalysts for future PEMFC technologies.

High-Performance Nafion Membrane Modified Using a 1,2,4-Triazole Derivative

Proton exchange membrane fuel cells (PEMFCs) are promising power generating devices due to their high energy densities and clean energy emission. Perfluorosulfonic acid (PFSA) based proton exchange membranes, such as Nafion membranes, which have high hydrolytic and oxidative stabilities and excellent proton conductivities are the most commonly used membranes in PEMFCs [1]. Recently, PFSA research has been focused on improving chemical and mechanical stabilities and degradations in the membranes and ionomers. PFSA membranes need to be thinner, lower cost and higher glass transition temperature (T g) materials and have higher conductivities at high temperature under low humidity conditions [2]. We studied Nafion composite membranes using various base additives [3–10]. Base additives were well incorporated into the nanostructure of the sulfonic acid phase in the Nafion polymers. Some base additives showed strong interactions among the hydrophilic terminal sulfonic acid functional groups on the nanoscale, which can be exploited to change the morphology in a nanostructure. From these results, we developed a new method for controlling the conduction path. Modifying the polymer structure of a Nafion membrane by adding a 1,2,4-triazole derivative and then removing it led to higher performance. The ion cluster size of the modified Nafion membrane was larger than that of the original Nafion membrane. The ion exchange capacity (IEC) was the same as that of the Nafion ionomer, but the conductivity was higher due to the modified membrane structure, which has a higher proton mobility. The cell performance of the modified Nafion membrane was better than that of Nafion 212, and in particular, the performance under low relative humidity (RH) conditions was improved. Our simple method using a 1,2,4-triazole derivative as an additive can be applied to the modification of other perfluorosulfonic acid (PFSA) and hydrocarbon polymer electrolytes and will contribute to the improvement of cell performances under high and low RH conditions. Acknowledgements This work was partially supported by the MEXT program for development of environmental technology using nanotechnology.

Silica/montmorillonite nanoarchitectures and layered double hydroxide-SPEEK based composite membranes for fuel cells applications

Anionic and cationic clays were here evaluated as nanofillers of low sulfonated polyetheretherketone (SPEEK, DS = 56%) for preparation of nanocomposite electrolyte membranes for PEMFC (Proton Exchange Membrane Fuel Cells) applications. A synthetic MgAl layered double hydroxide (LDH) exchanged with sulfate anions and a porous SiO2-montmorillonite heterostructured material containing delaminated clay particles, were added to SPEEK polymer for preparation of composite membranes with different nanofiller content (3, 6 and 9%). The resulting membranes were characterized concerning their structure, morphology and electrical conductivity performance. The incorporation of the MgAl LDH and the SiO2-motmorillonite fillers into the SPEEK seems to enhance water retention and the thermal stability of the resulting composite electrolyte membranes. Moreover, the composite electrolyte membranes show higher proton conductivity than the neat SPEEK membrane (0.023 S cm−1) after incorporation of the LDH and the SiO2-motmorillonite fillers (0.070 and 0.158 S cm−1 respectively) at 120 °C and 100% relative humidity, which can be relevant for increasing the performance at high temperature of this type of membranes in fuel cell applications.

Metal-Nitrogen-Carbon Catalysts for Oxygen Reduction in PEM Fuel Cells: Self-Template Synthesis Approach to Enhancing Catalytic Activity and Stability

Proton exchange membrane fuel cells (PEMFCs) are leading candidates in the utilization of clean energy resources for application in transportation, stationary, and portable devices. In PEMFCs, cathode catalysts are crucial for overall performance and durability due to kinetically slow oxygen reduction reactions (ORR). Because platinum (Pt), a state-of-the-art ORR catalyst, is rare and expensive, the development of high-performance platinum metal group (PGM)-free catalysts is highly desirable for future fuel cell technologies. Among the various PGM-free catalyst formulations, metal and nitrogen co-doped carbon (M-N-C, M: Fe, Co, or Mn) catalysts have exhibited encouraging activity and stability in acidic media for ORR and possess great potential to replace Pt in the future. Therefore, based on our extensive experience in the field of ORR catalysis, this review will comprehensively summarize the basic principles in the design and synthesis of M-N-C catalysts for durable, inexpensive, and high-performance PEMFCs with an emphasis on Co- and Mn-N-C catalysts to avoid Fenton reactions between Fe2+ and H2O2, which can generate free radicals and lead to the degradation of catalysts, ionomers, and membranes in PEMFCs. Furthermore, template-free 3D hydrocarbon frameworks as attractive precursors to advanced M-N-C catalysts will be discussed to significantly enhance intrinsic ORR activities in acidic media. In addition, long-term performance durability of M-N-C cathodes will be discussed extensively to provide potential solutions to enhance catalyst stability in PEMFCs. Finally, this review will provide an overall perspective on the progress, challenges, and solutions of PGM-free catalysts for future PEMFC technologies.

Multiphysics-Based Statistical Model for Investigating the Mechanics of Carbon Nanotubes Membranes for Proton-Exchange Membrane Fuel Cell Applications

The filter membrane made up of carbon nanostructure is one of the important components in proton exchange membrane fuel cell (PEMFC). The membrane while under operating conditions of a PEMFC is subjected to various dynamical loads due to the imposition of several input operating factors of the PEMFC. Hence, it is important to estimate optimal process parameters, which can maximize the strength of the membrane. Current studies in PEMFC focus on adsorption and transport-related properties of PEMFC membrane, without adequately investigating the mechanical strength of the membrane. This study proposes a multiphysics model of the membrane, which is used to extract the mechanical properties of the membrane by systematically varying various input factors of PEMFC. The extracted data are then fed into a neural search machine learning cluster to obtain optimal design parameters for maximizing the strength of the membrane. It is expected that the findings from this study will provide critical design data for manufacturing PEMFC membranes with high strength and durability.

Multidimensional nanostructured membrane electrode assemblies for proton exchange membrane fuel cell applications

This review highlights the recent progress in multidimensional nanostructured membrane electrode assemblies for PEMFCs and DMFCs.

Highly active PtxPdy/SnO2/C catalyst for dimethyl ether oxidation in fuel cells

Dimethyl ether (DME) is a nontoxic gas that is considered a potential fuel for direct-feed proton exchange membrane fuel cells (PEMFCs). DME has several advantages over other fuels, including high energy density, pumpless fuel delivery, liquefied storage, low toxicity and minimal crossover through Nafion® membranes in PEMFC. However, the low activity of the state-of-the-art catalyst (Pt50Ru50) for DME oxidation is the main hurdle in the development of efficient fuel cell devices. In this work, fine layers of SnO2 on high surface-area carbon (PtxPdy/SnO2/C) catalysts were synthesized by ethylene glycol-assisted reduction and characterized by X-ray diffraction, TEM, EDX, XPS, and ICP-OES. The electro-oxidation of DME was systematically studied in a conventional three-electrode cell and a laboratory prototype direct DME fuel cell (DDMEFC) operating at 70 °C. Compared to other catalysts reported for DME oxidation, the Pt0.75Pd0.25/SnO2/C shows higher specific power density in both the conventional three-electrode cell and the fuel cell configurations. The peak power density delivered by direct gas feed DDMEFCs is 110 mW cm-2 at 0.4 V with only 1.2 mg cm−2 of platinum group metal (PGM) loading.

Dielectric relaxations and conductivity of cross-linked PVA/SSA/GO composite membranes for fuel cells

Composite membranes obtained from Poly(vinyl Alcohol) (PVA) with sulfosuccinic acid (SSA) as crosslinking agent, and two different proportions of graphene oxide (GO), were prepared to be used in Proton Exchange Membrane Fuel Cells (PEMFCs). The superficial micrographs from transmission electron microscopy (TEM) confirmed a good dispersion of GO. Fourier Transform Infrared spectroscopy (FTIR) was used to evaluate the final chemical structure. Differential Scanning Calorimetry (DSC) showed that glass transition and crystalline phase were not present in the cross-linked PVA/SSA/GO composites membranes. Thermogravimetric analysis (TGA) demonstrated that the addition of GO reduced the moisture content and increased the thermal stability of the membranes. The electrical properties of PVA/SSA and PVA/SSA/GO composite membranes and the effect of GO concentration were evaluated by means of dielectric spectra in a broad range of temperatures and frequencies. The dielectric permittivity of these membranes was significantly promoted at low filler concentration due to an interfacial polarization effect. From the analysis of the dielectric relaxation spectrum, it can be deduced that the origin of the associated molecular movements is intramolecular and occurs in the working range of the PMEFC. In addition, the direct current conductivity, the protonic conductivity, and the polarization currents were correlated to the power produced in a hydrogen monocell. It was observed that low and no high GO concentrations of filler in PVA/SSA composite membranes enhanced their performance. The systematic characterization procedure based on the study of dielectric spectra and conductivity allowed to establish a potential approach to control the addition of GO in the design of other composite membranes for PEMFC with improved properties.

Improving the Performance of Nafion®-Based Fuel Cell Membranes by Introducing Histidine Functionalized Carbon Nanotubes

ABSTRACTA new polymer nanocomposite membrane based on Nafion and functionalized carbon nanotubes (CNTs) was developed for proton exchange membrane fuel cell (PEMFC) applications. Histidine, an imidazole-based amino acid, was used for modifying the surface of CNTs. The modification of CNTs was characterized by means of Fourier transform infrared spectroscopy (FTIR) and their Zeta potential. The imidazole groups, due to forming and breaking of hydrogen bonding, can facilitate proton transport across the polymer matrix by the Grotthuss mechanism. The final structure of the Nafion/CNT nanocomposites was investigated by small angle X-ray scattering (SAXS). The results confirm that the transport properties of the fabricated new membranes were significantly improved in comparison with unmodified and conventional Nafion® membranes. The power density of the imidazole-CNT (Im-CNT) Nafion® composite membranes was about three times more than Nafion® membranes. Also, the experimental results showed that the proton conductivity for the conventional Nafion® membranes decreased over 100°C but the conductivity for the Nafion®/Im-CNT remained at a nearly constant value above 100°C up to 120°C. Thus, the nanocomposite based on Nafion/imidazole functionalized CNT can be considered as an anhydrous PEMFC membrane for high-temperature applications.