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As a promising alternative to petroleum fossil energy, polymer electrolyte membrane fuel cell has drawn considerable attention due to its low pollution emission, high energy density, portability, and long operation times. Proton exchange membrane (PEM) like Nafion plays an essential role as the core of fuel cell. A good PEM must have satisfactory performance such as high proton conductivity, excellent mechanical strength, electrochemical stability, and suitable for making membrane electrode assemblies (MEA). However, performance degradation and high permeability remain the main shortcomings of Nafion. Therefore, the development of a new PEM with better performance in some special conditions is greatly desired. In this review, we aim to summarize the latest achievements in improving the Nafion performance that works well under elevated temperature or methanol-fueled systems. The methods described in this article can be divided into some categories, utilizing hydrophilic inorganic material, metal-organic frameworks, nanocomposites, and ionic liquids. In addition, the mechanism of proton conduction in Nafion membranes is discussed. These composite membranes exhibit some desirable characteristics, but the development is still at an early stage. In the future, revolutionary approaches are needed to accelerate the application of fuel cells and promote the renewal of energy structure.

Metal-organic frameworks (MOFs) are considered emerging materials as they further improve the various properties of polymer membranes used in energy applications, ranging from electrochemical storage and purification of hydrogen to proton exchange membrane fuel cells. Herein, we fabricate composite membranes consisting of polybenzimidazole (PBI) polymer as a matrix and MOFs as filler. Synthesis of ZIF-8 and UiO-66 MOFs are conducted through a typical solvothermal method, and composite membranes are fabricated with different MOF compositions (e.g., 2.5, 5.0, 7.5, and 10.0 wt %). We report a significant improvement in proton conductivity compared with the pristine PBI; for example, more than a three-fold increase in conductivity is observed when the PBI-UiO66 (10.0 wt %) and PBI-ZIF8 (10.0 wt %) membranes are tested at 160 °C. Proton conductivities of the composite membranes vary between 0.225 and 0.316 S cm−1 at 140 and 160 °C. For the comparison, pure PBI exhibits 0.060 S cm−1 at 140 °C and 0.083 S cm−1 at 160 °C. However, we also report a decrease in permeability and mechanical stability with the composite membranes.

Silica nanosheets (SN) derived from natural vermiculite (Verm) were successfully incorporated into polyethersulfone–polyvinylpyrrolidone (PES–PVP) polymer to fabricate high–temperature proton exchange membranes (HT–PEMs). The content of SN filler was varied (0.1–0.75 wt%) to study its influence on proton conductivity, power density and durability. Benefiting from the hydroxyl groups of SN that enable the formation of additional proton–transferring pathways, the inorganic–organic membrane displayed enhanced proton conductivity of 48.2 mS/cm and power density of 495 mW/cm2 at 150 °C without humidification when the content of SN is 0.25 wt%. Furthermore, exfoliated SN (E–SN) and sulfonated SN (S–SN), which were fabricated by a liquid–phase exfoliation method and silane condensation, respectively, were embedded in PES–PVP polymer matrix by a simple blending method. Due to the significant contribution from sulfonic groups in S–SN, the membrane with 0.25 wt% S–SN reached the highest proton conductivity of 51.5 mS/cm and peak power density of 546 mW/cm2 at 150 °C, 48% higher than the pristine PES–PVP membranes. Compared to unaltered PES–PVP membrane, SN added hybrid composite membrane demonstrated excellent durability for the fuel cell at 150 °C. Using a facile method to prepare 2D SN from natural clay minerals, the strategy of exfoliation and functionalization of SN can be potentially used in the production of HT–PEMs.

Mechanical durability of hydrocarbon-based proton exchange membranes in long-term fuel cell operation is vital for their successful commercialization. Herein, a complex finite element model is developed that couples electrochemical performance of sulfonated poly(ether ether ketone) (SPEEK) membrane with its mechanical response at different operating conditions to predict the susceptible sites to mechanical failure. To this end, the impacts of cell voltage (0.1–0.9 V), operating temperature (30–80 °C) and backpressure (0.3–1.5 bar), inlet reactants relative humidity (30–100%), and clamping pressure (1–5 MPa) on hydration and consequently, stress and strain formation in the SPEEK membrane are investigated. Results suggest that SPEEK membrane, particularly at the channel outlet, undergoes the greatest swelling-induced degradation when the cell is running at low voltages, high temperature and backpressure values. Clamping pressure, however, imposes compressive stress and thinning upon the land region and is the dominant factor compared to hygrothermal swelling, albeit high hydration level shifts the maximum stress to the channel region. Despite superior resistance to different hygrothermal conditions and lower chance of thinning under the clamping pressure, Nafion membrane exhibits a relatively higher risk of wrinkle deformation under compression. This study provides insights into the mechanical response of hydrocarbon-based membranes under various fuel cell conditions.

Nafion, a perfluoro-sulfonic acid (PFSA)-based polymer, is a promising material that will help realize the commercialization of proton exchange membrane-based fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs). However, Nafion also exhibits reduced mechanical and dimensional stability and increased hydrogen crossover under cell operating conditions in real operational settings, that is, in a hydrated state or in water at 60–80 °C. These factors may negatively affect cell efficiency and durability and thus must be addressed. To overcome these limitations, polyamide-coated Nafion composite membranes were developed for the first time via interfacial polymerization. 3,5-Diaminobenzoic acid (DABA), which contains carboxyl functional groups, was used as a monomer to add hydrophilicity to the membrane, and the coating layer thickness was controlled by adjusting the DABA content. A nanoscale polyamide (PA) layer was coated on the surface of Nafion-212 to fabricate a membrane, PA-c3-Nafion. PA-c3-Nafion was found to show ion conductivity 13.6% higher than that of a pristine Nafion-212 membrane at 80 °C, while providing improved mechanical performance and dimensional stability. In particular, at 95% RH, the hydrogen permeability of PA-c3-Nafion was 16.4% lower than that of Nafion-212 while, in a fully hydrated state, the hydrogen permeability of PA-c3-Nafion was 21.2% lower than that of Nafion-212. The LSV test results also showed that the degree of hydrogen crossover was significantly lower in PA-c3-Nafion than in Nafion-212.

The storage problem at low temperatures is one of the technical barriers to commercialization in the future for the polymer electrolyte membrane fuel cell (PEMFC). In this study, the resistance relaxation characteristic under different pretreatment methods before low-temperature storage of PEMFC is analyzed. The effect of residual water in different PEMFC locations on its storage performance after thermal cycles are investigated. The evolution curves of resistance after the purging process are different under equilibrium, cold, and hot purge and the percentage drop of cell resistance at relaxation stage under three methods are 14.5%, 66.3%, and 73.1%. It is found that the most likely reason for relaxation is membrane water structure reorganization. The voltage of the cell with no purge and purged to the end of the first stage becomes smaller at low current density after 20 freeze/thaw cycles. The charge transfer resistances of the cell with no purge, purged to the end of the first stage, and purged to the end of the second stage increase by 8.2%, 15.6%, and 7.4%, respectively. And the cell purged to the end of the first stage has the largest decay rate of electrochemical surface area. The result implies that the performance degradation after freeze/thaw cycles is associated with the water in the ionomer of catalyst layers, which freezes between ionomers and Pt particles at low temperatures.

Radiation-induced graft polymerization is introduced to effectively fabricate proton exchange membrane based on 12.5 μm fluorinated ethylene propylene (FEP) film. The graft side chains penetrate FEP film and distribute inside the bulk matrix evenly. The membranes exhibit hydrophilic/hydrophobic microphase-separated morphology as well as good thermal stability. The influences of irradiation parameters on the membrane property are investigated and the resulting membranes (named FEP-g-PSSA) exhibit excellent physicochemical properties. Membrane with 27.48% degree of graft and 130.1 mS cm−1 proton conductivity is employed for fuel cell performance measurement. Under optimized operate conditions (80 °C, 75% relative humidity), the power density could reach up to 0.896 W cm−2, inspiring for fuel cell application. The mass-transport-controlled polarization of membrane electrode assembly (MEA) based on FEP-g-PSSA membrane is higher than Nafion® 211 within the whole current density range and the gap is widening with increasing current density. At 2.0 A cm−2, the mass transfer polarization of FEP-g-PSSA reaches up to 0.204 V, far higher than Nafion® 211 (0.084 V). By promoting the compatibility between the ionomer in the catalyst layer and FEP-g-PSSA membrane and optimizing the membrane/catalyst layer/gas diffusion layer interfaces, the fuel cell performance could be significantly enhanced, making the FEP-g-PSSA membranes promising in fuel cell application.

High–temperature proton exchange membrane fuel cells (HT–PEMFCs) are pursued worldwide as efficient energy conversion devices. Great efforts have been made in the area of designing and developing phosphoric acid (PA)–based proton exchange membrane (PEM) of HT–PEMFCs. This review focuses on recent advances in the limitations of acid–based PEM (acid leaching, oxidative degradation, and mechanical degradation) and the approaches mitigating the membrane degradation. Preparing multilayer or polymers with continuous network, adding hygroscopic inorganic materials, and introducing PA doping sites or covalent interactions with PA can effectively reduce acid leaching. Membrane oxidative degradation can be alleviated by synthesizing crosslinked or branched polymers, and introducing antioxidative groups or highly oxidative stable materials. Crosslinking to get a compact structure, blending with stable polymers and inorganic materials, preparing polymer with high molecular weight, and fabricating the polymer with PA doping sites away from backbones, are recommended to improve the membrane mechanical strength. Also, by comparing the running hours and decay rate, three current approaches, 1. crosslinking via thermally curing or polymeric crosslinker, 2. incorporating hygroscopic inorganic materials, 3. increasing membrane layers or introducing strong basic groups and electron–withdrawing groups, have been concluded to be promising approaches to improve the durability of HT–PEMFCs. The overall aim of this review is to explore the existing degradation challenges and opportunities to serve as a solid basis for the deployment in the fuel cell market.

Incorporating inorganic fillers, such as SiO2, TiO2, and CeO2, into the electrolyte membrane via the conventional casting and evaporation process is proved to intensify the water retention, thus improve the proton conductivity of the polymer electrolyte membrane (PEM) under high temperature. However, this approach does not dramatically enhance the performance of the composite membrane due to the issue of proton pathway reduction and fillers agglomeration. Herein, uniformly patterned mesoporous TiO2 microplates (PTMPs) are successfully embedded on the anode side surface of the Nafion® membrane by using micro-hole stencil for spatially localizing the PTMPs and well-controlled ionomer spray technique. Interestingly, the membrane comprised of PTMPs with a diameter of ∼50 μm and a height of ∼5.2 μm exhibits the maximum power density by more than 35.2% compared to the reference Nafion® membrane with the same thickness (∼25 μm) under 120 °C and relative humidity of 35% condition. The result indicates that suitably designed PTMPs-embedded Nafion® membrane is effective for improving the PEMFC performance under elevated temperature and low humidity conditions.

Exploiting advanced electrocatalysts for the sluggish oxygen reduction reaction (ORR) of the cathode is greatly crucial for proton-exchange membrane fuel cell (PEMFC) commercial application but sti...

As the high-power density and environmentally friendly energy resources, proton exchange membrane fuel cells (PEMFCs) have a promising future in portable power generation. Herein, the hybrid Nafion membranes of ionic hydrogen-bonded organic frameworks (iHOFs) for PEMFC applications are demonstrated. By adjusting the position of sulfonic groups on naphthalene disulfonic acid compounds, four iHOFs with different types of hydrogen bonds were synthesized successfully based on 1,1'-diamino-4,4'-bipyridylium and naphthalene disulfonic acid. The formation of hydrogen bond interactions between amino and sulfonate groups provides a rich hydrogen bond network, which makes such iHOFs have high conductivity, and the maximum value is 2.76 × 10-3 S·cm-1 at 100 °C and 98% RH. Besides, composite membrane materials were obtained by mixing Nafion and iHOFs, and the maximum proton conductivity values can achieve 1.13 × 10-2 S·cm-1 for 6%-iHOF-3/Nafion and 2.87 × 10-3 S·cm-1 for 6%-iHOF-4/Nafion membranes at 100 °C under 98% RH. Through the H2/O2 fuel cell performance test by using iHOF/Nafion as the solid electrolyte, the maximum power and current density values of hybrid membranes are 0.36 W·cm-2 and 1.10 A·cm-2 for 6%-iHOF-3/Nafion and 0.42 W·cm-2 and 1.20 A·cm-2 for 6%-iHOF-4/Nafion at 80 °C and 100% RH. This work provides a practicable approach for establishing high-performance proton exchange hybrid membranes by doping high proton-conducting iHOFs into the Nafion matrix.

The catalyst layer's high durability is essential in commercializing polymer electrolyte membrane fuel cells (PEMFCs), particularly for vehicle applications, because their frequent on/off operation can induce carbon corrosion, which affects surface properties and morphological characteristics of the carbon and results in aggregation and detachment of Pt nanoparticles on the carbon surface. Herein, to address the carbon corrosion problem while delivering a high-performance PEMFC, polydimethylsiloxane (PDMS) with high gas permeability, chemical stability, and hydrophobicity was employed to protect the catalyst layer from carbon corrosion and improve the mass transport. Because the catalyst slurry using alcohol-based solvents showed low compatibility with nonpolar solvents of the PDMS solution, a parallel two-nozzle system with separated solution reservoirs was developed by modifying a conventional three-dimensional printing machine. To determine the optimal PDMS amount in the cathode catalyst layer, PDMS solution concentration was varied by quantitatively controlling the PDMS amount coated on the electrode layer. Finally, the PEMFC with the PDMS-modified cathode of 0.1 mg

It is of great significance to explore an approach for developing high-strength and enhanced stability materials for high-temperature proton exchange membranes (HT-PEMs) due to their high temperatu...

Humidifiers are used to control humidity of the air flowing into the cathode of a proton exchange membrane fuel cell to handle flooding and dehydration phenomena. In this study, a membrane module was tested in a humidifier designed with isothermal condition. While the effect of shell side convection was neglected, diffusive vapor transport was investigated via the impact of operating parameters including temperature, wet side relative humidity, air flow rate, pressure, and flow arrangement. The results show that the temperature and wet side relative humidity have more profound effects than the air flow rate and pressure on the vapor transport rate. The counter-current flow continually showed better performance than the co-current flow when operating at the same conditions. New diffusivity correlations for the membrane module were proposed as functions of temperature, relative humidity, and pressure, with R-square values of about 0.9.

In fuel cell technologies, low-temperature proton exchange membrane fuel cells (LT-PEMFC), high-temperature proton exchange membrane fuel cells (HT- PEMFC), and direct methanol fuel cells (DMFC) are gained significant attention as a promising energy system for practical applications. The developments of cost-effective membrane materials with excellent physicochemical properties are indispensable for replacing the high cost of commercial membranes and achieving the higher performance of fuel cell systems. This review focuses on the developments and modifications of cost-effective poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as a cation exchange membrane for LT-PEMFC, HT- PEMFC and DMFC. Notably, this review bridges the understanding of PPO based membranes, current advancements, structure, physicochemical properties and fuel cell performances. Progressive developments and a systematic overview of PPO-based membrane developments are explained in detail in terms of functionalization, blend, composite, acid-base, cross-linking, copolymerization, coated and reinforcement. Moreover, the changes in physicochemical properties and fuel cell performances in the membrane are deeply reviewed. Additionally, the utilization of PPO based membranes in different kinds of redox flow battery systems are reviewed. Overall, this review provides an exclusive vision and perspectives to develop the PPO based advanced, cost-effective, and high-performance membranes for fuel cell technologies and redox flow battery systems.

A high-performance proton exchange membrane was successfully prepared by incorporating an interconnected PMIA nanofiber@ZIF-8 network (ZHNFs) into Nafion solution, in which the unique ZHNFs were fabricated via in-situ growth of ZIF-67 on the surface of hierarchical PMIA nanofibers (HNFs) with multiscale nanofibers and high hydrophilicity. The hybrid membrane presents an outstanding performance with a peak proton conductivity of 0.277 S cm−1 at 80 °C, 100RH% and a decreased methanol permeability of 1.415 × 10−7 cm2 s−1, implying a promising application in direct methanol fuel cells. The superior performance of the membranes could be due to the interconnected structure, high specific surface area of 122.637 m2 g−1 and active chemical bond of (−N–H) of ZHNFs. Specifically, the 3D interconnected structure of ZHNFs provides consecutive conduction path for protons, ensuring the improvement of proton conductivity. The effective interfacial acid-base pairs (−N–H … −SO3H) formed via the tight interactions between the –N–H bonds in ZHNFs and –SO3H groups in Nafion matrix could effectively ameliorate the compatibility of the nanofiber fillers and Nafion matrix, further promoting the methanol barrier of the hybrid membranes. Moreover, the generated acid-base pairs are beneficial for the efficient and rapid proton transfer via providing abundant proton conducting sites.

The present study presents a new method for optimal identification of the output voltage of a Proton Exchange Membrane Fuel Cell based on an optimized Deep Belief Network. According to the designed method, the Deep Belief Network structure is optimized based on a modified version of the Water Strider Algorithm. The main idea is to minimize the error value between the observed and the obtained output voltages of the Proton Exchange Membrane Fuel Cell. Simulations specified that the suggested Deep Belief Network-Modified Water Strider Algorithm method provides accurate tracking for the voltage signal prediction of the Proton Exchange Membrane Fuel Cell. Final results are also compared with Deep Belief Network-Water Strider Algorithm, and DBN/TLBO-DE from the literature to show the proposed method dominance.

High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) have shown a broad prospect of applications due to the enhanced reaction kinetics and simplified supporting system. However, the proton conductor, phosphoric acid, tends to poison the active sites of Pt, resulting in high Pt consumption. Herein, Pt nanoparticles anchored on SiO2-modified carbon nanotubes (CNT@SiO2-Pt) are prepared as high-performance cathode catalysts for HT-PEMFCs. The SiO2 in CNT@SiO2-Pt can induce the adsorption of phosphoric acid transferring from Pt active sites in the catalytic layer, avoiding the poisoning of the Pt, and the phosphate fixed by SiO2 provide a high-speed proton conduction highway for oxygen reduction reactions. Accordingly, The CNT@SiO2-Pt cathode achieve superior power density of 765 mW cm−2 (160 °C) and 1,061 mW cm−2 (220 °C) due to the rapid proton-coupled electron process and outstanding stability in HT-PEMFCs. This result provides a new road to resolve the phosphate poisoning for the commercialization of HT-PEMFCs.

The aim of this study is to synthesise SPEEK composite proton exchange membrane with the addition of TiO2 nanofillers for microbial fuel cell application. SPEEK composite membrane with varying weight percentage of TiO2 (2.5, 5, 7.5 and 10%) was prepared to study the effect of TiO2 concentration on membrane performance. Synthesized composite membranes were subjected to various characterization studies such as FT-IR, XRD, Raman spectroscopy, TGA, UTM and SEM. Physico-chemical properties of membrane such as water uptake capacity, ion exchange capacity and thickness were also analyzed. 5% TiO2 – SPEEK composite membrane exhibited the higher water uptake capacity value and Ion exchange capacity value of 31% and 1.71 meq/g respectively. Performance of the MFC system with TiO2 – SPEEK membranes were evaluated and compared with the pristine SPEEK and Nafion membrane. 5% TiO2 – SPEEK membrane produced the higher power density (1.22 W/m2) and voltage (0.635 V) than the other membranes investigated. Efficacy of MFC in wastewater treatment was evaluated based on the chemical oxygen demand (COD), total organic carbon content and turbidity. Biofilm growth over the surface of the electrodes was also analyzed using scanning electron microscopy. HIGHLIGHTS Use of TiO2 – SPEEK composite membrane as alternate for the Nafion 117.; Energy generation from dairy wastewater was investigated using dual chambered MFC.; Low cost membrane.; Green energy.; TiO2 – SPEEK can be used to overcome drawbacks of Nafion 117.

To reduce cost and energy consumption of fuel cell vehicles, constructing membrane electrode assemblies (MEAs) with low Pt loading and outstanding performance at low relative humidity (RH) conditio...

A new type of metal-organic framework, [Cd2(pdc)(H2O)(DMA)2]n (pdc = 3,5-pyrazoledicarboxylic acid; DMA = dimethylamine), named Cd-MOF, was synthesized and characterized. There are regular rectangular pore channels containing a large number of dimethylamine cations in the crystal structure. AC impedance test results show the proton conductivity of Cd-MOF reaches 1.15 × 10-3 S cm-1 at 363 K and 98% RH. In order for its application in fuel cells, the Cd-MOF was introduced into a sulfonated polyphenylene oxide matrix to prepare a hybrid membrane, and the proton conductivity of the hybrid membrane has a high value of 2.64 × 10-1 S cm-1 at 343 K and 98% RH, which is higher than those of most MOF polymer hybrid membranes. The proton conductivity of the hybrid membrane of the SPPO polymer still maintains a certain degree of stability in a wide temperature range. To the best of our knowledge, it is the first proton exchange membrane that combines pyrazolecarboxylate cadmium MOFs and an SPPO polymer with high proton conductivity and good stability. This research may help to further develop the application of MOFs in the field of proton exchange membrane fuel cells.

A proton exchange membrane (PEM) is one of the most critical and expensive components in a dual‐chamber microbial fuel cell (MFC) that separates the anode and cathode chambers. The novel macroporous kaolin earthenware coated with polybenzimidazole (NKE‐PBI) fabricated in this study could become an alternative to PEM membranes. Briefly, PBI powder was dissolved in dimethylacetamide. Thereafter, NKE was fabricated at different porosities (10%, 20%, and 30%) using different starch powder volumes, which acted as pore‐forming agents. The NKE‐PBI with 30 vol% starch powder content produced the highest power output of 2450 ± 25 mW m−2 (10.50 A m−2) and internal resistance of 71 ± 19 Ω under batch mode operation. The MFC–PEM reactor generated the lowest power output at the highest internal resistance of up to 1300 ± 15 mW m−2 (3.7 A m−2) and 313 ± 16 Ω, respectively. In this study, the nonselective porous NKE coated with PBI membranes improved proton conduction activity and displayed comparable power performance with that of Nafion 117 in a dual‐chambered MFC. Therefore, a porous earthenware membrane coated with a proton conductor could become a potential separator in a scaled‐up MFC system for commercialization.

Due to environmental pollution and global warming, research on new energy sources that can replace fossil fuels is important. A fuel cell is an eco-friendly energy conversion system that discharges water, and uses hydrogen as fuel. Although platinum is a widely used catalyst in PEMFCs, it has commercial limitations because of its low stability and high cost. Pt-based bimetal catalysts are being studied to improve performance and reduce the cost of fuel cell catalysts. Pt-M is excellent in terms of performance, stability, and cost, avoiding the disadvantages of the Pt catalyst. Studies on various bimetallic catalysts have been conducted, and among them, studies on Pt-Ni, Pt-Co, and Pt-Fe have been the most active. This review summarizes reports of fuel cell catalysts using Pt-M from 2014 to 2020. In recent studies, in order to improve the Pt-M performance, there have been attempts to change the pretreatment, the type of support, and the composition of Pt and M. There have also been studies that have applied new synthetic methods, which are different from traditional synthetic methods. Many Pt-M catalysts have shown better performance than commercial Pt/C, and exhibited stable performance in durability tests.

In this study, the lattice Boltzmann method was used to simulate the three-dimensional intrusion process of liquid water in the gas diffusion layer (GDL) of a polymer electrolyte membrane fuel cell (PEMFC). The GDL was reconstructed by the stochastic method and used to investigate fiber orientation's influence on liquid water transport in the GDL of a PEMFC. The fiber orientation can be described by the angle between a single fiber and the in-plane direction; three different samples were simulated for three different fiber orientation ranges. The simulated permeability correlated well with the anisotropic characteristics of reconstructed carbon papers. It was concluded that the fiber orientation had a significant effect on the liquid invasion pattern in the GDL by changing the pore shape and distribution of the GDL. The results indicated that the stochastically reconstructed GDL, taking into account the fiber orientation, better demonstrates the mass transport properties of the GDL.

UVC (ultrathin vapor chamber) simultaneously has a high heat-conducting property, excellent temperature uniformity and simple structure. These advantages are very suitable for thermal management of the open-cathode PEMFC (proton exchange membrane fuel cell) stack. In this work, two-type UVCs with different appearances are integrated into a conventional PEMFC stack respectively. The effect of UVC on the output performance, thermal management and operating stability is investigated by the experiment combined with simulation. The results show that UVC can significantly increase the output voltage under high current density. In 35 A, the output voltage of the stack integrated the vertical UVC increases by 20.25% relative to the conventional stack. Thermal management is also improved by UVC. The highest temperature inside the stack decrease by 9 °C in 35 A, and the membrane temperature is decreased obviously. But it still exceeds the optimal operating temperature of open-cathode PEMFC stack due to the poor cooling type in the condensation side of UVC. UVC improves the operation stability of the stack and slows the deteriorative speed of output performance. This work hopes to attract more attention to the application of UVC on the thermal management of portable power sources used open-cathode PEMFC stack.

The present study aims to assess the proton conductivities of the most investigated proton exchange membranes (PEMs) used in PEM fuel cells (PEMFCs). Specifically, PEMs are analyzed for their use in anhydrous fuel cells and proton conductivity upper bounds were provided for them. Considering the direct relationship between proton conductivity and temperature, an upper bound is presented. Based on the obtained upper bounds, suitable membranes for high-temperature performance are determined, and the average range of proton conductivity for each polymer group is discussed. By comparing the available proton conductivity data with upper bound, it was demonstrated that some of poly (ionic liquid)s have provided the highest proton conductivities, however aromatic polymers such as polybenzimidazole (PBI) are found more suitable choices for application at anhydrous conditions and high temperatures. The proton conductivity upper bound for anhydrous PEMs demonstrates the availability of promising polymer options for the deployment of anhydrous fuel cells.

This mini-review presents a short account of materials with exceptional activity towards oxygen reduction reaction. Two main classes of catalytic materials are described, namely platinum group metal (PGM) catalyst and Non-precious metal catalyst. The classes are discussed in terms of possible application in low-temperature hydrogen fuel cells with proton exchange membrane and further commercialization of these devices. A short description of perspective approaches is provided and challenging issues associated with developed catalytic materials are discussed.

Proton exchange membrane fuel cells (PEMFCs) are operated in a range of different environments including near-dry operating conditions. When a PEMFC operates under low relative humidity (RH) conditions, performance degradation rapidly occurs because of the decreased ionic conductivity of dehydrated membrane electrode assemblies (MEAs). As such, securing additional water inside the MEA is important for achieving a high-performance PEMFC under low RH operating conditions. Herein, amorphous carbon-encapsulated carbon nano-onions (AC-CNOs) were prepared by laser pyrolysis method. The hydrophilicity of AC-CNOs varied on the basis of particle size, which affected the amount of oxygen functional groups attached to the amorphous carbon. To confirm the water retention effect of the AC-CNOs, three different catalysts were incorporated into the MEA of the anode electrode, and a Pt@AC–CNO–3 with an average AC-CNO size of ∼164 nm exhibited a significantly improved performance under low RH condition. Moreover, to achieve a synergetic effect from both the anode and cathode, an additional AC-CNO layer was introduced on the cathode catalyst layer. The dual-side MEA with the hydrophilic catalyst layer at the anode and an additional carbon covering layer at the cathode showed significantly increased performance relative to the reference MEA, i.e., >80.2% under RH44%@90 °C conditions.

Copoly (arylene ether sulfone)s was employed for proton exchange membrane preparation via atom transfer radical polymerization followed by mild sulfonation, enhanced phase-separated morphology and favorable proton conductivity were achieved. The comprehensive ex-situ properties of a range of membranes with different ion exchange capacities were characterized alongside the fuel cell performances investigation. The membranes exhibit higher water uptake, which is beneficial to the proton conduction, compared to Nafion® 211 while maintaining similar swelling ratio. The prepared membranes exhibit reasonably high proton conductivity (0.16 S/cm at 85 °C) benefitting from the well-defined microstructure and high connectivity of the hydrophilic domains. Considering the comprehensive property, membrane with moderate ion exchange capacity (1.39 mmol/g) was employed to fabricate the membrane electrode assembly and peak power density of 0.65 W/cm2 at 80 °C, 60% relative humidity was achieved for a H2/O2 fuel cell, these hydrocarbon membranes can therefore be implemented in PEMFCs.

Water electrolysis (WE) is a key technology for a decarbonized society and is essential for hydrogen isotope separation for a future fusion reactor. In this study, deuterium (D) separation was performed by anion exchange membrane WE (AEMWE) and compared with our previous results from proton exchange membrane WE (PEMWE). WE allows D to become concentrated in solution and diluted in hydrogen gas compared with the D concentration in feed water. The separation effect increases with decreasing water stoichiometric ratio, λ, of the water feed to electrolysis volume. Owing to little water drainage from the cathode, AEMWE can be performed at λ ≈ 1.05, while λ ≈ 4.0 is the lowest for PEMWE. When the feed rate is reduced (λ

The metallic bipolar plates (BPs) in the Proton-Exchange Membrane Fuel Cells (PEMFCs) are usually made of a coating of TiN on Stainless Steel 316 L (SS316L) by the sputtering method. However, the a...

The high cost of platinum (Pt)-group metal (PGM)-based catalysts used in proton-exchange membrane fuel cells (PEMFCs) poses a critical roadblock to their widespread adoption. Although using low PGM loading PEMFCs can largely address this challenge, high current density performance will be severely compromised consequently. To overcome this dilemma, we report the development of ultra-thin platinum-cobalt nanowires (PtCoNWs) as the cathode catalysts for ultralow Pt loading and high-performance membrane electrode assembly (MEA). The PtCoNWs delivered a record-high mass activity (MA) of 1.06 ± 0.14 AmgPt−1 of Pt-alloy catalysts towards oxygen reduction reaction (ORR) in MEA, yielding an impressive total Pt utilization of 5.14 WratedmgPt−1. The PtCoNWs retained a respectable end-of-life MA of 0.45 A mgPt−1 after the 30,000 cycles square-wave accelerated stability test, which is still above the Department of Energy 2020 beginning-of-life target for catalysts. In-situ X-ray absorption spectroscopy studies suggest that the high degree of alloying in the PtCoNWs stabilizes the ultrathin structure and may contribute to the high ORR activity and power density performance in PEMFC.

Air and hydrogen supply systems are key subsystems of polymer electrolyte membrane (PEM) fuel cell systems. This paper reviews the research on the gas (air and hydrogen) supply systems and equipmen...

Sulfonated poly(ether ether ketone) − MO2 (M = Zr, Si) − carbon nanotube nanofiller-enhanced composite membrane in the proton exchange membrane fuel cell is fabricated to enhance the proton mobility and water maintenance at elevated temperature (100 °C). It is observed that the synergic effect of SiO2@CNT and ZrO2@CNT as nanofiller dramatically enhanced the proton conductivity, thermal stability, chemical reliability, and mechanical strength of the proton exchange membranes. This study shows that between 40 and 60 °C, vehicular mechanism plays key a role, and between 80 and 100 °C, Grotthuss mechanism plays vital role in proton migration. Moreover, the combined proton transfer effect is observed in case of SPEEK/SiO2@CNT/ZrO2@CNT membrane, which exhibits 2 times better conductivity at 40 and 60 °C, 5 times better at 80 °C, and 8 times better at 100 °C in comparison with the commercial Nafion 212 membrane, under the same setup and conditions.

Since agglomerates in catalyst inks affect the catalyst layers (CL) and membrane electrode assemblies (MEA) of proton exchange membrane fuel cell (PEMFC), it is important to study the connection among catalyst agglomerates, CL structure, and MEA performance. This study investigates the effect of Pt/GC catalyst agglomerates on the morphology and permeability of the CL by modulating the properties of the catalyst ink in two different ways. Additionally, MEA was further electrochemically tested to understand the relationship between the catalyst agglomerates and MEA performance. The result shows that High-pressure homogenization is more effective than mechanical shear mixing in dispersing the agglomerates in catalyst inks. However, the excessive homogenization pressure produced larger agglomerated particles, probably because more effective dispersion caused by higher homogenization pressure supplies new chain carriers for polymerization and higher temperature caused by higher homogenization pressure. Moreover, the surface of the CL fabricated in inks prepared by a homogenizer is more uniform, neat, and hydrophilic. But the number of secondary pores in the catalyst layer decreases at excessive homogeneous pressure, and the water permeability becomes poor, which in turn result in lower performance and higher mass transfer resistance. The electrochemical performance test results showed that the MEA with a relatively hydrophobic CL had a performance of 0.707 V at 1000 mA cm−2, which was 30 mV higher than that with a relatively hydrophilic CL. This study provides insights for better tuning the properties of catalyst ink, CL morphology, and permeability to obtain better performance of MEA.

During the past decade proton exchange membrane fuel cells (PEMFCs) as one kind of the potential clean energy sources for electric vehicles and portable electronic devices are attracting more and more attentions. Although Nafion® membranes are considered as the benchmark of proton exchange membranes (PEMs), the drawbacks of Nafion® membranes restrict the commercialization in the practical application of PEMFCs. As of today, the attention is to focus on developing both high-performance and low-cost PEMs to replace Nafion® membranes. In all of these PEMs, sulfonated poly(arylene ether ketone)s (SPAEKs) and sulfonated poly(arylene ether sulfone)s (SPAESs) are the most promising candidates due to their excellent performance and low price. In this review, the efforts of SPAEK and SPAES membranes are classified and introduced according to the chemical compositions, the microstructures and configurations, as well as the composites with polymers and/or inorganic fillers. Specifically, several perspectives related to the modification and composition of SPAESs and SPAEKs are proposed, aiming to provide the development progress and the promising research directions in this field.

Sulfonated poly(ether ether ketone) (SPEEK) membrane with high sulfonation degree (SD) is a promising substitute of Nafion as proton exchange membrane (PEM), due to the excellent proton conductivity and low cost. However, its widespread application is limited by the inferior structural stability. Here, we report the fabrication of high SD SPEEK membrane with outstanding structural stability through an in-situ molecular-level hybridization method. Concretely, the ionic nanophase of SPEEK membrane is filled with precursors, which are then in-situ converted into polymer quantum dots (PQDs) by a microwave-assisted polycondensation process. In this manner, the micro-phase separation structure of SPEEK membrane is well maintained. PQDs with abundant hydrophilic functional groups together with the inherent –SO3H groups impart hybrid membrane highly enhanced proton conductivity of 138.2 mS cm−1 at 80 °C, which is comparable to Nafion. This then offers a 116.3% enhancement in device output power. Meanwhile, PQDs act as cross-linkers via generated electrostatic interactions with SPEEK, affording hybrid membrane with SD of 94.1% an ultralow swelling ratio of 1.35% at 25 °C, about 35 times lower than control membrane. More importantly, the in-situ molecular-level hybridization method is versatile, which can also boost the performances of chitosan (CS)-based membranes.

In view of the pressing need for alternative clean energy source to displace the current dependence on fossil fuel, proton exchange membrane fuel cell (PEMFC) technology have received renewed research and development interest in the past decade. The electrolyte, which is the proton exchange membrane, is a critical component of the PEMFC and is specifically targeted for research efforts because of its high commercial cost that effectively hindered the widespread usage and competitiveness of the PEMFC technology. Much effort has been focused over the last five years towards the development of novel, durable, highly effective, commercially viable, and low-cost co-polymers as alternative for the expensive Nafion® proton exchange membrane, which is the current industry standard. Our primary review efforts will be directed upon the reported researches of alternative proton exchange membrane co-polymers which involved Triptycene derivatives. Triptycene derivatives, which contain three benzene rings in a three-dimensional non-compliant paddlewheel configuration, are attractive building blocks for the synthesis of proton exchange membranes because it increases the free volume in the polymer. The co-polymers considered in this review are based on hydrocarbon molecular structure, with Triptycene involved as a performance enhancer. Detailed herein are the development and current state of these co-polymers and their performance as alternative fuel cell electrolyte.

Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area (ECSA) for the oxygen reduction reaction (ORR) in hydrogen-based proton-exchange membrane fuel cells. Accordingly, a facile, low-cost, and hydrogen-assisted two-step method is developed in this work, to massively prepare carbon-supported uniform, small-sized, and surfactant-free Pd nanoparticles (NPs) with ultrathin ∼3-atomic-layer Pt shells (Pd@Pt3L NPs/C). Comprehensive physicochemical characterizations, electrochemical analyses, fuel cell tests, and density functional theory calculations reveal that, benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects, Pd@Pt3L NPs/C exhibits not only significantly enhanced ECSA, electrocatalytic activity, and noble-metal (NM) utilization compared to commercial Pt/C, showing 81.24 m2/gPt, 0.710 mA/cm2, and 352/577 mA/mgNM/Pt in ECSA, area-, and NM-/Pt-mass-specific activity, respectively; but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test. More importantly, the corresponding 25-cm2 H2-air/O2 fuel cell with the low cathodic Pt loading of ∼ 0.152 mgPt/cm2geo achieves the high power density of 0.962/1.261 W/cm2geo at the current density of only 1,600 mA/cm2geo, which is much higher than that for the commercial Pt/C. This work not only develops a high-performance and practical Pt-based ORR electrocatalyst, but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure, which can be further expanded to other metal shells for other energy-conversion applications.

Trifluoromethanesulfonylimide-grafted polybenzimidazole (PBI-TFSI) was synthesized for proton exchange membrane (PEM) applications. Its proton conductivity was (a) less dependent on humidity and (b) higher than that of conventional fluorine-based PEM (Nafion) and propanesulfonic acid-grafted PBI (PBI-PS) at a relative humidity of 40%. The chemical structure of PBI-TFSI was investigated using 1H and 19F nuclear magnetic resonance and Fourier transform infrared spectroscopy. The membranes exhibited good transparency, flexibility, and thermal stability up to 350 °C. Membranes with different side chain grafting ratios were prepared, and the water uptake and hydration number of the PBI-TFSI membranes were lower than those of the PBI-PS membranes, most likely because of the hydrophobicity of the side chain. The higher proton concentration provided by TFSI with stronger acidity than PS might be the reason for the higher proton conductivities of PBI-TFSI. Proton exchange membranes (PEMs) based on trifluoromethanesulfonylimide-grafted polybenzimidazole (PBI-TFSI) were prepared, and their physical and chemical properties were studied. PBI-TFSI showed higher proton conductivity than Nafion and propanesulfonic acid-grafted polybenzimidazole (PBI-PS) at a 40% relative humidity due to its high acidity of side chain. PBI-TFSI membranes are promising materials for next-generation PEM fuel cells.

The approach to constructing proton transport channels via direct adjustments, including hydrophilia and analytical acid concentration in hydrophilic domains, has been proved to be circumscribed when encouraging the flatter hydrophilic-hydrophobic microphase separation structures and reducing conductivity activation energy. Here, we propose a constructive solution by regulating the polarity of hydrophobic domains, which indirectly varies the aggregation and connection of hydrophilic ion clusters during membrane formation, enabling orderly self-assembly and homogeneously distributed microphase structures. Accordingly, a series of comb-shaped polymers were synthesized with diversified optimization, and more uniformly distributed ion cluster lattices were subsequently observed using high-resolution transmission electron microscopy. Simultaneously, combining with density functional theory calculations, we analyzed the mechanism of membrane degradations caused by hydroxyl radical attacks. Experimental results demonstrated that, facilitated by proper molecule polarity, beneficial changes of bond dissociation energy could extend the membrane lifetime more than the protection from side chains near ether bonds, which were deemed to reduce the probability of attacks by the steric effect. With the optimal strategy chosen among various trials, the maximum power density of direct methanol fuel cell and H2/air proton exchange membrane fuel cell was enhanced to 95 and 485 mW cm-2, respectively.