Search Results (34)

This study systematically investigated the physicochemical properties and proton exchange membrane fuel cell (PEMFC) performance of perfluorosulfonic acid (PFSA) membranes with different thicknesses, which were prepared based on the resins produced by Dongyue (China) in comparison with commercial Nafion membranes. It was found that the water uptake of Dongyue membranes is significantly higher than that of Nafion, showing a significant upward trend with the thickness increase. The ion exchange capacity (IEC) of these membranes is ca. 1 mmol·g⁻¹. Moreover, the tensile strength of the Dongyue membrane was positively correlated with the thickness and was significantly higher than that of recast Nafion. Under 80 °C, all Dongyue membranes with various thicknesses (15~45 μm) exhibited PEMFC single-cell performance superior to that of Nafion. The maximum power density is observed with a thickness of 25 μm, reaching 851.76 mW·cm⁻², which is higher than that of Nafion (635.99 mW·cm⁻²). However, the oxidative stability of the prepared Dongyue PFSA series membranes exhibits a slight deficit compared to commercial Nafion membranes. Subsequently, the modification and optimization of preparation processes can be employed to improve the mechanical and chemical stability of Dongyue PFSA membranes. Full article

This study presents the integration and evaluation of commercially available gas diffusion electrodes (GDEs), specifically designed for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) within membrane electrode assemblies (MEA) for electrochemical hydrogen pump/compressor applications (EHP/C). Using Nafion 117 as a solid polymer electrolyte, the MEAs were analyzed for cell efficiency, hydrogen evolution, and hydrogen oxidation reactions (HER and HOR) under differential pressure up to 16 bar and a temperature ranging from 20 °C to 60 °C. Key properties of the GDEs, such as electrode thickness and conductivity, were investigated. The catalytic layer was characterized via XRD and EDX analyses to assess its surface and bulk composition. Additionally, the effects of increasing MEA’s geometric size (from 1 cm² to 5 cm²) and hydrogen crossover phenomena on the efficiency were examined in a single-cell setup. Electrochemical performance tests conducted in a single electrochemical hydrogen pump/compressor cell under hydrogen flow rates from 36.6 Ml·min⁻¹·cm⁻² to 51.3 mL·min⁻¹ cm⁻² at atmospheric pressure provided insights into the optimal operational parameters. For a double-stage application, the MEAs demonstrated enhanced current densities, achieving up to 0.6 A·cm⁻² at room temperature with further increases to 1 A·cm⁻² at elevated temperatures. These results corroborated the single-cell data, highlighting potential improvements in system efficiency and a reduction in adverse effects. The work underscores the potential of HT-PEMFC-based GDEs for the integration of MEAs applicable to advanced hydrogen compression technologies. Full article

The conversion of chemical energy to electricity in proton exchange membrane fuel cells (PEMFCs) is essential for replacing fossil fuel engines and achieving net-zero CO₂ emissions. In the pursuit of more efficient PEMFCs, certain often-overlooked parameters significantly influence cell performance by either weakening the interaction between the catalytic layer (CL) and the membrane or restricting gas access to the CL. This study examines the effects of cell tightening and hot-pressing conditions on three similar-thickness perfluorosulfonic acid (PFSA) membranes: Aquivion^®, Fumapem, and Nafion^®. The results reveal that the hot-pressing method employing higher pressure and a lower temperature (125C method) yields lower fuel cell performance compared to the method utilizing a higher temperature and lower pressure (145C method). Furthermore, incorporating cellulose paper as a pressure homogenizer in the MEA preparation setup significantly improved current density by approximately 2.5 times compared to the traditional assembly method. Cyclic voltammetry with Ar-feed in the cathode showed that all prepared MEAs exhibited a similar platinum surface area; however, MEAs pressed at higher temperatures displayed slightly lower hydrogen desorption charge values. The torque applied to the bolts does not show a consistent trend in fuel cell performance, but optimal torque values can enhance PEMFC performance under certain conditions. Full article

In this study, mono- and bimetallic platinum (Pt), palladium (Pd) and Pt-Pd nanoparticles were synthesized using the wet sol–gel method, employing a carbon-based XC72R as catalytic carrier. The overall metal content was set at 40 wt.% at varying Pt:Pd ratios. Characterization of the morphology and surface structure was conducted through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD) analyses. The electrochemical performance and catalytic activity against the hydrogen evolution reaction (HER) were assessed in a three-electrode cell for screening purposes, as well as in a prototype cell of an electrochemical hydrogen pump/compressor (EHP/C) where the catalysts served as cathodes, while the anode was Pt/XC72 40% wt. with 0.38 mg_Pt·cm⁻² within a membrane electrode assembly (MEA) with a 180 µm thick Nafion 117 proton-conductive membrane. The results obtained indicated superior catalytic activity of the bimetallic catalysts in comparison to the pure metal samples. Further electrochemical tests in an EHP/C cell at varying differential pressures in the range of 0–3 bar revealed stable behavior and high current density, reaching approximately 0.7 A cm⁻² at 60 °C. The accelerated durability tests performed demonstrated excellent stability of the synthesized composite catalysts. These findings underscore the potential of Pt-Pd nanoparticles as efficient catalysts with sustainable performance for electrochemical hydrogen pumping/compressing applications. Full article

Proton-exchange membrane (PEM) fuel cells are increasingly used in the automotive sector. A crucial point for estimating the performance of such systems is open-circuit voltage (OCV) losses, among which the most influential are mixed potential, hydrogen crossover, and internal short circuits. These losses are often overlooked in the modeling of such electrochemical cells, leading to an inaccurate estimation of the real voltage that is calculated starting from the Nernst Equation. An innovative method is presented to estimate the losses based on the division of the membrane into two domains: solid and aqueous. The influence of the macro-parameters (temperature, pressure, and RH) was analyzed for each phenomenon and was linked to the membrane water content. For low levels of PEM hydration, internal short circuits were of the same order of magnitude as hydrogen crossover. The OCV model accuracy was assessed on a commercial stack, used on a vehicle prototype competing in the Shell Eco-Marathon challenge. The data of interest were obtained through laboratory tests and subsequent disassembly of the stack. A PEM thickness of 127 μm was measured corresponding to Nafion 115. For further validation, the model results were compared with data in the literature. Full article

In this work, homogeneous, thin-film proton exchange membranes (PEMs) with superior proton conductivities and high methanol rejection were fabricated via a facile synthesis procedure. Sulfonated polyether ether ketone (sPEEK) was crosslinked via a Friedel–Crafts reaction by α,α′-dichloro-p-xylene, a non-hazardous and hydrophobic compound. PEMs with varying crosslinking and sulfonation degrees were fabricated to overcome the traditional trade-off between methanol rejection and proton conductivity. The sulfonation of PEEK at 60 °C for 24 h resulted in a sulfonation degree of 56%. Those highly sulfonated backbones, in combination with a low membrane thickness (ca. 20 µm), resulted in proton conductivities superior to Nafion 117. Furthermore, X-ray photoelectron spectroscopy proved it was possible to control the crosslinking degree via the crosslinking time and temperature. The PEMs with the highest crosslinking degree showed better methanol rejection compared to the commercial benchmark. The introduction of the crosslinker created hydrophobic membrane sections, which reduced the water and methanol uptake. Subsequently, the membrane became denser due to the crosslinking, hindering the solute permeation. Those two effects led to lower methanol crossovers. This study proved the successful fabrication of PEMs overcoming the trade-off between proton conductivity and methanol rejection, following a facile procedure using low-cost and non-hazardous materials. Full article

For an iron-chromium redox flow battery (ICRFB), sulfonated poly(ether ether ketone) (SPEEK) membranes with five various degrees of sulfonation (DSs) are studied. To select the SPEEK membrane with the ideal DS for ICRFB applications, the physicochemical characteristics and single-cell performance are taken into consideration. Following all the investigations, it has been determined that the SPEEK membrane, which has a DS of 57% and a thin thickness of 25 μm, is the best option for replacing commercial Nafion 212 in ICRFB. Firstly, it exhibits a better cell performance according to energy efficiency (EE) and coulombic efficiency (CE) at the current density range between 40 mA cm⁻² and 80 mA cm⁻². Additionally, it has a more stable EE (79.25–81.64%) and lower discharge capacity decay rate (50%) than the Nafion 212 (EE: 76.74–81.45%, discharge capacity decay: 76%) after 50 charge–discharge cycles, which proves its better oxidation stability as well. In addition, the longer self-discharge time during the open-circuit voltage test further demonstrates that this SPEEK membrane could be employed for large-scale ICRFB applications. Full article

Ion exchange membranes, especially cation exchange membranes (CEMs), are an important component in membrane-based energy generation and storage because of their ability to transport cations via the electrochemical potential gradient while preventing electron transport. However, developing a CEM with low areal resistance, high permselectivity, and stability remains difficult. In this study, electrospun graphene oxide/polyethersulfone (GO/PES) composite nanofibers were prepared with varying concentrations of GO. To fabricate a CEM, the pores of the electrospun GO/PES nanofiber substrates were filled with a Nafion ionomer. The pore-filled PES nanofiber loaded with 1% GO revealed a noticeable improvement in hydrophilicity, structural morphology, and mechanical properties. The 1% GO/PES pore-filled CEM was compared to a Nafion membrane of a varying thickness and without a nanofiber substrate. The CEM with a nanofiber substrate showed permselectivity of 85.75%, toughness of 111 J/m³, and areal resistance of 3.7 Ω cm², which were 12.8%, 4.3 times, and 4.0 times better, respectively, than those of the Nafion membrane at the same thickness. The development of a reinforced concrete-like GO/PES nanofiber structure containing stretchable ionomer-enhanced membrane surfaces exhibited suitable areal resistance and reduced the thickness of the composite membrane without compromising the mechanical strength, suggesting its potential application as a cation exchange membrane in electrochemical membrane-based systems. Full article

Hydrogen production using polymer membrane electrolyzers is an effective and valuable way of generating an environmentally friendly energy source. Hydrogen and oxygen generated by electrolyzers can power drone fuel cells. The thermodynamic analysis of polymer membrane electrolyzers to identify key losses and optimize their performance is fundamental and necessary. In this article, the process of the electrolysis of water by a polymer membrane electrolyzer in combination with a concentrated solar system in order to generate power and hydrogen was studied, and the effect of radiation intensity, current density, and other functional variables on the hydrogen production was investigated. It was shown that with an increasing current density, the voltage generation of the electrolyzer increased, and the energy efficiency and exergy of the electrolyzer decreased. Additionally, as the temperature rose, the pressure dropped, the thickness of the Nafion membrane increased, the voltage decreased, and the electrolyzer performed better. By increasing the intensity of the incoming radiation from 125 $\mathrm{W}/{\mathrm{m}}^2$ to 320 $\mathrm{W}/{\mathrm{m}}^2$, the hydrogen production increased by 111%, and the energy efficiency and exergy of the electrolyzer both decreased by 14% due to the higher ratio of input electric current to output hydrogen. Finally, machine-learning-based predictions were conducted to forecast the energy efficiency, exergy efficiency, voltage, and hydrogen production rate in different scenarios. The results proved to be very accurate compared to the analytical results. Hyperparameter tuning was utilized to adjust the model parameters, and the models’ results showed an MAE lower than 1.98% and an $R^2$ higher than 0.98. Full article

Single crystalline ZSM-5 ZNs with thicknesses around 6 nm were obtained by secondary growth of silicalite nanoparticles using diquaternary bis-1,5(tripropyl ammonium) pentamethylene diiodide (dC₅) as a structure-directing agent (SDA). The dC₅ could be effectively removed from the ZN pores by either high-temperature calcination or UV irradiation in air at room temperature but not by the piranha solution treatment. Ultrathin ZN-laminated membranes (ZNLMs) were fabricated by sandwiching a UV-activated multilayered ZN film between two recast Nafion^® layers (ZNLM-Nafion) and by filtration coating from a suspension of thermally activated ZNs on a nonionic porous PVDF (ZNLM-PVDF). The ZNLMs on both supports demonstrated the ability of highly proton-selective ion conduction with low resistances in aqueous electrolyte solutions. The ZNLM-PVDF with PVDF binder was structurally stable, and it achieved a comparably low ASR but much higher proton selectivity compared with a Nafion membrane of same overall thickness. However, detachment between the ZNLM and Nafion layers occurred when the ZNLM-Nafion operated in aqueous electrolyte solutions. Results of this study show the potential for developing ZNLMs as efficient proton-conducting membranes without using expensive ionic polymer matrices. However, the development of polymer-supported ZNLMs is hindered by the current inefficiency in preparing well-dispersed suspensions of open-pore ZNs. Future development of efficient methods for synthesizing open-pore ZNs in dispersed states is key to realizing high-performance ZNLMs on polymers. Full article

Membrane technologies and materials development appear crucial for the hydrogen/natural gas separation in the impending transition to the hydrogen economy. Transporting hydrogen through the existing natural gas network could result less expensive than a brand-new pipe system. Currently, many studies are focused on the development of novel structured materials for gas separation applications, including the combination of various kind of additives in polymeric matrix. Numerous gas pairs have been investigated and the gas transport mechanism in those membranes has been elucidated. However, the selective separation of high purity hydrogen from hydrogen/methane mixtures is still a big challenge and nowadays needs a great improvement to promote the transition towards more sustainable energy source. In this context, because of their remarkable properties, fluoro-based polymers, such as PVDF-HFP and Nafion^TM, are among the most popular membrane materials, even if a further optimization is needed. In this study, hybrid polymer-based membranes were deposited as thin films on large graphite surfaces. Different weight ratios of PVDF-HFP and Nafion^TM polymers supported over 200 μm thick graphite foils were tested toward hydrogen/methane gas mixture separation. Small punch tests were carried out to study the membrane mechanical behaviour, reproducing the testing conditions. Finally, the permeability and the gas separation activity of hydrogen/methane over membranes were investigated at room temperature (25 °C) and near atmospheric pressure (using a pressure difference of 1.5 bar). The best performance of the developed membranes was registered when the 4:1 polymer PVDF-HFP/Nafion^TM weight ratio was used. In particular, starting from the 1:1 hydrogen/methane gas mixture, a 32.6% (v%) H₂ enrichment was measured. Furthermore, there was a good agreement between the experimental and theoretical selectivity values. Full article

Proton exchange membrane (PEM) technology may regulate the electrical grid connected to intermittent power sources. The growing pace of R&D in alternative components is widening manufacturing methods and testing procedures across the literature. This turns the comparison between performances into a more laborious task, especially for those starting research in this area, increasing the importance of testing components accessible to all. In this study, an electrochemical characterization is performed on a commercial single-cell PEM water electrolyzer with commercial catalyst-coated membranes (CCMs) and one prepared in-house. Two membrane thicknesses and the effect of different catalysts are assessed. The thicker membrane, Nafion 117, operates with 5% greater ohmic overvoltage than the thinner Nafion 115, resulting in up to 1.5% higher voltage for the former membrane. Equivalent Ir black CCMs provided by different suppliers and one prepared in-house perform similarly. Regarding the influence of the anode catalyst, Ir black, IrRuOx and IrRuOx/Pt have similar performance, whereas IrOx has worse performance. Compared with Ir black, the mix of IrRuOx/Pt operated with 1.5% lower voltage at 2.6 A cm⁻², whereas IrRuOx performed with 2% lower voltage at 0.3 A cm⁻². A temporary increase in performance is observed when the anode is purged with hydrogen gas. Full article

In this work, we reported a novel preparation method for a proton exchange membrane (PEM) named, the direct electrostatic deposition method. In theory, any required thickness and size of PEM can be precisely controlled via this method. By direct electrostatic spraying of Nafion solution containing amino modified SiO₂ nanoparticles onto a metal collector, a hybrid membrane of 30 μm thickness was fabricated. The DMFC assembled with a prepared ultrathin membrane showed a maximum power density of 124.01 mW/cm² at 40 °C and 100% RH, which was 95.29% higher than that of Nafion. This membrane formation method provides potential benefits for the preparation of ultrathin PEMs. Full article

Proton-exchange membranes based on gamma-irradiated films of PVDF and radiation-grafted sulfonated polystyrene with an ion-exchange capacity of 1.8 meq/g and crosslinking degrees of 0 and 3% were synthesized. A solvent-free, environmentally friendly method of styrene grafting from its aqueous emulsion, with a styrene content of only 5 vol.% was used. Energy dispersive X-ray mapping analysis showed that the grafted sulfonated polystyrene is uniformly distributed throughout the membrane thickness. The obtained materials had a proton conductivity up to 132 mS/cm at 80 °C and a hydrogen permeability of up to 5.2 cm²/s at 30 °C, which significantly exceeded similar values for Nafion^®-212 membranes. The resulting membranes exhibited a H₂/O₂ fuel cell peak power density of up to 0.4 W/cm² at 65 °C. Accelerated stability tests showed that adding a crosslinking agent could significantly increase the stability of the membranes in the fuel cells. The thermal properties and crystallinity of the membranes were investigated through differential scanning calorimetry and X-ray powder diffraction methods. The conductivity, water uptake, and mechanical properties of the membranes (stress–strain curves) were also characterized. Full article

The aim of this study is to clarify the impact of the thickness of a gas diffusion layer (GDL) and a micro porous layer (MPL) on the distributions of gas, H₂O, and current density in a polymer electrolyte fuel cell (PEFC) which is operated at 363 K and 373 K and with various thicknesses of polymer electrolyte membrane (PEM) as well as a relative humidity (RH) of supply gas. These investigations are carried out by numerical simulation using the 3D model with COMSOL Multiphysics. In the case of Nafion 115, which is the thicker PEM, the change in the molar concentration of H₂O from the inlet to the outlet with MPL is larger than that without MPL irrespective of the thickness of GDL, T_ini and RH condition. In the case of Nafion NRE-212, which is the thinner PEM, the change in the molar concentration of H₂O from the inlet to the outlet is larger with MPL than that without MPL in the case of TGP-H-060 (the thicker commercial GDL), while that is smaller with MPL than that without MPL in the case of TGP-H-030 (the thinner commercial GDL). These results exhibit the same tendency as the results of the numerical simulation on the current density. Full article