High Ion Exchange Capacity Research Articles

Bio-amine crosslinking reforming sulfonated polymer shaped like deoxyribonucleic acid for use in proton exchange membrane fuel cells

This article reports on a study that investigated the use of blended sulfonated polymer membranes for fuel cell applications. The researchers blended a sulfonated poly(arylene ether) polymer material with an amine-based crosslinking agent in 1%–5% varying weight percentages. By replacing the sulfonates' hydrogen bonds with the amine groups in the crosslinking agent, the researchers were able to enhance the structure of the polymer material. This, in turn, can help resolve the issue of inadequate dimensional stability of SA8, thereby prolonging the lifespan of fuel cells. The resulting membranes showed improved dimensional stability, oxidative stability, and cell component efficiency, with the 5% crosslinking agent blend ratio demonstrating decrease 30.8 times in swelling ratio and a 4.9% increase in oxidative stability. Additionally, the fuel cell efficiency of the 1% crosslinking agent blend ratio membrane was 20.4% higher than that of the commercial membrane, with a power density of 1.21 W/cm2. The SA8+1P blend ratio had the highest ion exchange capacity and water uptake, resulting in increased proton conductivity and power density. Furthermore, the dimensional stability of the membranes improved with the blend ratio, with the SA8+5P membrane outperforming the commercial Nafion 211 membrane. The SA8+1P and SA8+5P membranes have been proven to demonstrate exceptional performance in terms of ion exchange capacity, conductivity, and dimensional stability. Furthermore, these membranes also show high efficiency in fuel cell efficiency. Overall, the results suggest that blending sulfonated polymer membranes with an amine-based crosslinking agent has the potential to improve the performance of fuel cell components.

Composite membranes for fuel cells

The current ecological situation attracts particular attention to alternative energy sources with no detrimental impact on the ecosystem. In comparison with conventional energy sources, fuel cells exhibit the following advantages: small and compact size, light weight, lack of noise when working, and cost-effectiveness in terms of fuel consumption. Most importantly, fuel cells are environmentally friendly, since no harmful substances are released into the atmosphere during their operation. Their goal is to convert chemical energy from various sources into environmentally friendly electric power. At present, chemical sources of energy are used everywhere, including batteries for mobile phones, laptops, as well as cars and uninterruptible power supplies, to name a few. The main components of solid polymer fuel cells are proton-exchange membranes, the main function of which is to ensure the transfer of protons from the anode to the cathode. The proton conductivity of such materials is determined by the presence of hydrophilic channels that transport mobile protons. The proton-exchange membrane must meet the following requirements: electrochemical and chemical stability in aggressive chemical environments, mechanical and thermal strength, low permeability to reagent gases (fuel and oxidizer), high ion exchange capacity and electrical conductivity, as well as a relatively low cost. This paper considers perfluorinated sulfonic acid membranes, organic–inorganic and acid–base composite membranes, as well as hybrid membranes obtained by sol-gel process, which can contribute to the development of technologies related to fuel cells in the future.

3D printed heterogeneous cation exchange membrane processed using stereolithography

AbstractMembrane chemistry belongs to the field in which 3D printing can advantageously also be used because of enabling the production of prototypes with precisely defined dimensions. The presented work aimed to develop new polymeric compositions for heterogeneous cation exchange membranes manufactured using stereolithography (SLA) from commercially available materials. Three types of photo‐curable thermoset resins (acrylic resin and two types of epoxy resins) were used as polymer matrixes in combination with strong acid cation exchange resin (CER) powder. The membrane production consisted of several stages, namely mixing the photo‐curable resin with finely ground CER powder, processing using SLA, and appropriate post‐curing using UV light and elevated temperature. The work aimed to monitor the influence of the photo‐curable resin type and post‐curing on the microstructural, electrochemical, and mechanical properties of resulting membrane objects. The results revealed that heterogeneous cation exchange membranes could be processed using SLA from the mixture of the acrylic photo‐curable resin and CER powder (weight ratio of 60/40) without the need for post‐curing. These products exhibited high permselectivity (93%), high ion exchange capacity (2.23 meq⋅g−1), and sufficiently low electrical resistance (2200 Ω⋅cm), which predetermines them for efficient electrophoretic separation.

New generation radiation-grafted PVDF-g-VBC based dual-fiber electrospun anion exchange membranes

Anion Exchange Membranes (AEM) have the potential to solve the cost issues of fuel cell technologies due to their basic environment that can allow the use of cheaper components. However, there is still a need to develop an ideal inexpensive, mechanically robust AEM with high ionic conductivity and ion exchange capacity (IEC). In this work, we present various dual-fiber electrospun membranes based on a novel radiation-grafted copolymer. First, the synthesis route of radiation-induced grafting of vinyl benzyl chloride (VBC) onto poly (vinylidene fluoride) (PVDF) to prepare PVDF-g-VBC was optimized. Then, PVDF-g-VBC powders were used to fabricate dual-fiber electrospun mats with inert PVDF and commercial Fumion-FAA-3 ionomer. Dual-fiber electrospun mats were hot-pressed and then quaternized with trimethylamine. Finally, mechanical properties, ion exchange capacity, ionic conductivity, and morphology of these prepared dual-fiber electrospun membranes were investigated. The dual-fiber membrane prepared with PVDF-g-VBC (88% of the total weight of the membrane) and PVDF: Fumion-FAA-3 (1:2) mix (12 wt%) realized ionic conductivity of 4.67 mS/cm at 25 °C, high ion exchange capacity of 1.35 mmol/g with Young's Modulus of 761 MPa. The membrane based on the combination of radiation grafting and dual-fiber electrospinning was prepared for the first time in literature and offers the prospect of tuning and fine-control of mechanical and physicochemical properties of AEMs.

Durability and Performance of Poly(norbornene) Membranes and Ionomers in Alkaline Electrolyzers

The anion conductive ionomer in the oxygen-producing anode is a critical part of the three-dimensional electrode in the anion exchange membrane alkaline electrolysis. In this study, self-adhesive anode ionomers were designed to chemical bond the anode catalyst particles to the porous transport layer and to the ionomer. It was found that high ion exchange capacity ionomers were not needed for effective electrode polarization because the anode was fed with alkaline electrolyte through the flow channel. The hydrophobic nature of anode ionomer and intimate contact with the catalyst by chemical bonding to the catalyst was key to improving anodic polarization and cell durability. The catalyst and self-adhesive ionomer contents of anode were optimized for the mechanically durable and energy-efficient alkaline water electrolysis.

Preparation of amine-modified amphiphilic resins for the extraction of trace pharmaceuticals and personal care products in environmental waters

Herein, four amine-modified amphiphilic resins were synthesized and utilized as solid-phase extraction (SPE) materials to enrich pharmaceuticals and personal care products (PPCPs) from environmental water. The obtained materials (Strong anion-exchange amphiphilic materials, SAAMs; Weak anion-exchange amphiphilic materials, WAAMs) possessed large specific surface area (473–626 m2/g), high ion exchange capacity (0.89–1.97 mmol/g), and small contact angle (74.41–79.74°), indicating good hydrophilicity. The main factors affecting the efficiency of the extraction process were studied, including column volume, column flow rate, sample salinity and sample pH. Notably, the trend observed in absolute recovery was significantly correlated with the Zeta potential of the employed adsorbents. Furthermore, based on the obtained materials, a method of SPE coupled with ultra-performance liquid chromatography and tandem mass spectrometry (SPE/LC-MS/MS) was developed, and then utilized to determine PPCPs in the samples collected from the Yangtze River Delta. The Method detection limit (MDL) and Method quantification limit (MQL) ranged from 0.05 to 0.60 ng/L and 0.17 to 2.00 ng/L, respectively, with a relative standard deviation (RSD) below 6.3%, demonstrating good accuracy and sensitivity. As evidenced by comparison with previous literature, the developed method exhibited satisfactory performance, showing great potential for further commercial application in the extraction of trace PPCPs from environmental water samples.

Multi-Block Copolymer Membranes Consisting of Sulfonated Poly(p-phenylene) and Naphthalene Containing Poly(arylene Ether Ketone) for Proton Exchange Membrane Water Electrolysis

Glassy hydrocarbon-based membranes are being researched as a replacement for perfluorosulfonic acid (PFSA) membranes in proton exchange membrane water electrolysis (PEMWE). Here, naphthalene containing Poly(arylene Ether Ketone) was introduced into the Poly(p-phenylene)-based multi-block copolymers through Ni(0)-catalyzed coupling reaction to enhance π-π interactions of the naphthalene units. It is discovered that there is an optimum input ratio of the hydrophilic monomer and NBP oligomer for the multi-block copolymers with high ion exchange capacity (IEC) and polymerization yield. With the optimum input ratio, the naphthalene containing copolymer exhibits good hydrogen gas barrier property, chemical stability, and mechanical toughness, even with its high IEC value over 2.4 meq g-1. The membrane shows 3.6 times higher proton selectivity to hydrogen gas than Nafion 212. The PEMWE single cells using the membrane performed better (5.5 A cm-2) than Nafion 212 (4.75 A cm-2) at 1.9 V and 80 °C. These findings suggest that naphthalene containing copolymer membranes are a promising replacement for PFSA membranes in PEMWE.

Solid-state synthesis of intrinsically proton-conducting covalent organic framework membrane

Ionic covalent organic framework (iCOF) membranes are attractive for a myriad of applications. Here, we report a mechanochemistry-based solid-state synthesis method to fabricate iCOF membranes with simplicity, scalability and sustainability. Time-dependent experiments reveal that the iCOF membrane formation process includes the structural transformation from disorder to order and the morphology change to the dense structure formed by the restacking of nanosheet-like crystallites simultaneously. The obtained free-standing iCOF membranes demonstrate high ion exchange capacity, mechanical strength and comparable proton conductivity, benefiting from the rigid crystalline framework structure and one-dimensional channels decorated with abundant proton-conducting sites. This work paves the way for synthesis of iCOF membranes in a simple and environmentally friendly manner.

Acid Resistance and Ion-Exchange Capacity of Natural Mixtures of Heulandite and Chabazite

The recovery and immobilization of metals from wastewater often occurs in an acidic environment that destroys the structure of adsorbents such as zeolites, which are porous crystalline aluminosilicates. The influence of hydrochloric acid solutions on the structure and properties of two natural mixtures of heulandite (HEU) and chabazite (CHA)—tuff from the Georgian Dzegvi-Tedzami deposit (HEU/CHA ≈ 8) and rock from the Kazakhstani deposit Chankanay (HEU/CHA≈1)—was studied by the X-ray energy dispersion spectra and diffraction patterns, as well as by adsorption of water, benzene, and nitrogen methods. It was found that acid-mediated dealumination, decationization, dissolution, and changes in systems of micro- and mesopores depend on the nature and chemical composition of the initial zeolites. It is concluded that, under the influence of acid, (i) zeolite micropores become accessible to relatively large molecules and ions, and the surface area of the adsorbent increases; (ii) the volume of mesopores decreases, and pores with a diameter of less than 4 nm become predominant; (iii) in terms of the degree of dealumination and dissolution rate, Kazakhstani zeolite is more acid-resistant than Georgian heulandite; and (iv) Kazakhstani zeolite retains a high ion-exchange capacity in an acidic environment, while Georgian heulandite, treated with dilute hydrochloric acid solutions, uptakes relatively high amounts of valuable silver, copper, and zinc.

Highly ion-conductive anion exchange membranes with superior mechanical properties based on polymeric ionic liquid filled functionalized bacterial cellulose for alkaline fuel cells

How to simultaneously improve the ionic conductivity and mechanical properties is a key problem facing currently used anion-exchange membranes (AEMs). Here, biomass-based bacterial cellulose (BC) was used as a porous template to make TiO2 localized mineralization around the surface of BC nanofibers, and constructed a TiO2-coated BC porous substrate (TiO2@BC) with hierarchical structure. Then, the coated TiO2 nanoparticles was densely grafted by quaternary ammonium groups to obtain high ionic conduction ability. After filling with a polymeric ionic liquid (PIL) with high ion exchange capacity through in situ polymerization and crosslinking, the obtained novel PIL-filled AEM possessed ultrahigh ionic conductivity of 100.5 mS cm−1 at 80 °C, which was 72.1% higher than that of the PIL-filled pure BC membrane (only 58.4 mS cm−1). Moreover, by the aid of the synergistic reinforcement effect of TiO2@BC, the membrane exhibited extremely high dry strength of 95.3 MPa and satisfactory wet strength and flexibility. When at fully hydrate state, the membrane with the size of 1 × 4 cm (width × length) can hang a bottle containing 1000 g of water. The single cell equipped with this membrane output the peak power density of 40.2 mW cm−2, showing its great potential as a high-performance biomass-based AEM.

Biomass-Based Anion Exchange Membranes Using Poly (Ionic Liquid) Filled Bacterial Cellulose with Superior Ionic Conductivity and Significantly Improved Strength

ABSTRACT How to simultaneously improve the ionic conductivity and mechanical properties is a key problem facing currently used anion-exchange membranes (AEMs). Here, novel AEMs were prepared using quaternized bacterial cellulose (QBC) as a dual-functional substrate and then filled with a polymeric ionic liquid (poly(vinylbenzyl) trimethylammonium chloride, PVD) with high ion-exchange capacity through in situ polymerization and crosslinking. The dense quaternary ammonium groups grafted on the surface of BC nanofibers greatly increased the ionic conductivity, while the special three-dimensional network structure of BC significantly enhanced the tensile strength and chemical stability of the obtained PVD filled quaternized BC (QBC/PVD) membranes. The ionic conductivity of QBC/PVD membrane reached as high as 111 mS cm−1 at 80°C, which was 109% higher than that of the pure BC/PVD membrane (only 53 mS cm−1). Moreover, the QBC/PVD membrane exhibited extremely high dry strength of 72.3 MPa and satisfactory wet strength and flexibility, this membrane can hang a container containing 500 g of water when at fully hydrated state. The alkaline direct methanol fuel cell equipped with QBC/PVD output a peak power density of 64 mW cm−2, showing its great application potential as an AEM.

The use of organopalygorskite as rheological additive in non-aqueous drilling fluids: Colloidal stability, contact angle, and cutting's transport ratio

Studies involving clays are becoming increasingly more in demand due to their use as rheological additives. Clay have properties such as swelling capacity, high ion exchange capacity, strong adsorption capacity, and is used as rheological additive in drilling fluids. The present work used a Brazilian organopalygorskite to verify its performance as viscosity agent in non-aqueous drilling fluids. Its affinity for oil was also verified through colloidal stability and contact angle tests. The cutting carrying capacity of non-aqueous fluids was also obtained through the application of Moore and Chien empirical correlations. Results confirmed the hydrophobic characteristic of organopalygorskite. The viscous fluid with organopalygorskite showed higher cutting carrying capacity when compared to the viscous fluid with the original palygorskite.

Tuning side group structures of series-connected di-cations to achieve improved electrodialysis acid recovery performances

The electrodialysis (ED) technology for waste acids recovery has become a hotspot due to the advantages of low cost, high efficiency and no-pollution. The ED acid recovery efficiency is strongly controlled by the ionomer aggregation structure of the applied anion exchange membrane (AEM). To investigate the effects of different side group structures on the ED acid recovery performance of AEMs, a series of series-connected di-cation ionomers based AEMs named QPPO-DABCO-R with high ion exchange capacities were tailor-made from the commercial polyphenylene oxide with series-connected 1,4-diazabicyclo[2.2.2]octane di-cation groups as the transport cores, and hydroxyethyl, methyl and hexyl groups of various hydrophilic-hydrophobic balances as the auxiliary side groups. The aggregation structure, water uptake, mechanical properties, thermal stability, ion selectivity and ED acid recovery performance of the AEMs were systematically investigated. The results confirm that the modified microphase separation structures with the strong hydrophobic side groups show the enhanced abilities to increase the fixed charge density, to block proton leakage and promote the transport of counterions through the membrane. Interestingly, QPPO-DABCO-C6 with the most hydrophobic side group exhibits the acid recovery performances much better than those of the commercial acid block ACM. The results demonstrate convincingly that the strategy of combining appropriately sized hydrophobic weak polar alkyl groups with high-density series-connected di-ions is an effective method to develop electrodialysis AEM with excellent acid recovery performance.

Effect of reduced graphene oxide (rGO) in chitosan/Pahae natural zeolite-based polymer electrolyte membranes for direct methanol fuel cell (DMFC) applications

The use of electrolyte membranes for fuel cell applications has grown rapidly, and one of the materials often developed is chitosan. In this study, polymer electrolyte membranes were successfully produced using chitosan and Pahae natural zeolite with the addition of various reduced Graphene Oxide (rGO) concentrations. Furthermore, water and methanol uptake values, methanol permeability, ion exchange capacity, and proton conductivity were the basic characteristics of Direct Methanol Fuel Cells (DMFC) applications. The optimum water uptake value was observed in the CS/PNZ/rGO 2.0 % membrane at 294.5 %. This value increased with the addition of rGO concentration and is in line with the increasing ion exchange capacity. The CS/PNZ/rGO 2.0 % membrane has the optimum ion exchange capacity with a value of 0.8121 mmol/g. Meanwhile, the membrane permeability value tends to decrease with increasing rGO composition at each variation of methanol concentration. The proton conductivity value also increased along with rGO concentration, and the highest value was found in CS/PNZ/rGO 2.0 % at 6.777×10−6 S/cm. Based on the results, high ion exchange capacity, low permeability, and high proton conductivity indicate that CS/PNZ/rGO-based polymer electrolyte membranes can be used in Direct Methanol Fuel Cells (DMFC) applications.

Efficacy of orally administered montmorillonite in myoglobinuric acute renal failure model in male rats.

Acute kidney injury can be associated with serious consequences and therefore early treatment is critical to decreasing mortality and morbidity rate. We evaluated the effect of montmorillonite, the clay with strong cation exchange capacity, on the AKI model in rats. Glycerol (50% solution, 10 ml/kg) was injected in the rat hind limbs to induce AKI. 24 hr after induction of acute kidney injury, the rats received oral doses of montmorillonite (0.5 g/kg or 1 g/kg), or sodium polystyrene sulfonate (1 g/kg) for three consecutive days. Glycine induced acute kidney injury in rats with high levels of urea (336.60± 28.19 mg/dl), creatinine (4.10± 0.21 mg/dl), potassium (6.15 ± 0.28 mEq/L), and calcium (11.52 ± 0.19 mg/dl). Both doses of montmorillonite (0.5 and 1 g/kg) improved the serum urea (222.66± 10.02 and 170.20±8.06, P<0.05), creatinine (1.86±0.1, 2.05± 0.11, P<0.05), potassium (4.68 ± 0.4, 4.73 ± 0.34, P<0.001) and calcium (11.15 ± 0.17, 10.75 ± 0.25, P<0.01) levels. Treatment with montmorillonite especially at a high dose reduced the kidney pathological findings including, tubular necrosis, amorphous protein aggregation, and cell shedding into the distal and proximal tubule lumen. However, administration of SPS could not significantly decrease the severity of damages. According to the results of this study, as well as the physicochemical properties of montmorillonite, such as high ion exchange capacity and low side effects, montmorillonite can be a low-cost and effective treatment option to reduce and improve the complications of acute kidney injury. However, the efficacy of this compound in human and clinical studies needs to be investigated.

Preparation of NaA and NaY zeolites from kaolin and their use as adsorbent for the removal of Ni2+ and Co2+ in aqueous solution

Heavy metal ions can cause environmental problems and affect human health if they are not properly removed before waste water released into the environment. Adsorption is one of the most widely used method for removal of heavy metal ions due to its simplicity and efficiency. Among many adsorbents, NaA and NaY zeolites showed good ability to remove metal ions in aqueous solution due to their high ion exchange capacity. However, the cost of zeolites NaA and NaY, synthesized from pure chemical sources, is still quite high. Therefore, this paper presented the synthesis of NaA and NaY from kaolin, a commercial available and cheap material. Experimental results showed that kaolin calcined at 500°C was appropriate to be used as and source for synthesis of zeolite. NaA and NaY zeolites were synthesized by reaction at 100°C in 24 hours. NaA zeolite was synthesized in a gel with the molar ratio in term of 1.0 Al2O3/2.0 SiO2/1.6 Na2O/76 H2O and NaY zeolite was synthesized with the molar ratio of 1.0 Al2O3/3.7 SiO2/2.7 Na2O/76 H2O with the addition of from industrial fly ash. XRD results of both synthesized NaA and NaY zeolites showed that the diffraction peaks of these zeolites matched with simulated XRD pattern of NaA and NaY zeolite. Synthesized NaA and NaY zeolites were used as adsorbents to remove Ni2+ and Co2+ in aqueous solution. NaY zeolite showed the highest adsorption capacity of 56.5 mg/g and 58.2 mg/g for Ni2+ and Co2+, respectively. NaA zeolite showed higher metal removal efficiency than that of NaY zeolite, with the highest adsorption capacity for Ni2+ and Co2+ at 80 mg/g and 123.2 mg/g, respectively. Experimental data fit the pseudo-second-order model and Langmuir isotherm adsorption model well. The results showed that the removal of Ni2+ and Co2+ ions by NaA and NaY zeolites was of the .

Neutron scattering study on the structure-property relationship of radiation-grafted proton exchange membranes

The partial scattering function (PSF) analysis through the contrast variation small-angle neutron scattering technique was used to determine the exact structure of the hydrated radiation-grafted protonexchange membranes, made of poly(styrene sulfonic acid)-grafted poly(ethylene-co-tetrafluoroethylene) (ETFE-g-PSSA) with a high ion exchange capacity of 2.5 mmol/g. The membrane was treated as a threecomponent system composed of ETFE base polymer, PSSA graft polymer, and absorbed water. The analysis on PSF self-terms gave the exact structure of individual components and that on PSF cross-terms explored the correlation between two components to establish their locations. The characterization was performed in multiple length scales, and the mechanistic insights into membrane conductivity and structure correlations were provided.

Giant Water Uptake Enabled Ultrahigh Proton Conductivity of Graphdiyne Oxide

AbstractProton conductors have attracted great attention in various fields, especially in energy production. Here, we find that graphdiyne oxide (GDYO), derived from graphdiyne (GDY), features the highest proton conductivity of 0.54 S cm−1 (100 % RH, 348 K) among the oxidized carbon allotropes reported so far. The sp‐ and sp2‐co‐hybridized carbon skeleton of GDY enables GDYO with the giant water uptake, which is 2.4 times larger than that of graphene oxide (GO), resulting in ultrahigh proton conductivity by increasing the proton concentration and proton conduction pathways. This ultrahigh proton conductivity of GDYO is further proved in a methanol fuel cell by using GDYO membrane as proton exchange membrane. The GDYO membrane enables the cell with higher open circuit voltage, larger power density and lower methanol permeability, compared with commercial Nafion 117. Moreover, the GDYO membrane bears high ion exchange capacity, good acidic stability and low swelling ratio.

Giant Water Uptake Enabled Ultrahigh Proton Conductivity of Graphdiyne Oxide.

Proton conductors have attracted great attention in various fields, especially in energy production. Here, we find that graphdiyne oxide (GDYO), derived from graphdiyne (GDY), features the highest proton conductivity of 0.54 S cm-1 (100 % RH, 348 K) among the oxidized carbon allotropes reported so far. The sp- and sp2 -co-hybridized carbon skeleton of GDY enables GDYO with the giant water uptake, which is 2.4 times larger than that of graphene oxide (GO), resulting in ultrahigh proton conductivity by increasing the proton concentration and proton conduction pathways. This ultrahigh proton conductivity of GDYO is further proved in a methanol fuel cell by using GDYO membrane as proton exchange membrane. The GDYO membrane enables the cell with higher open circuit voltage, larger power density and lower methanol permeability, compared with commercial Nafion 117. Moreover, the GDYO membrane bears high ion exchange capacity, good acidic stability and low swelling ratio.

Experimental Studies of Graphene-Coated Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

Abstract The two main technical limitations of direct methanol fuel cells (DMFCs) are the slow kinetic reactions of the methanol oxidation reaction (MOR) in the anode and the crossing over of unreacted methanol through the proton exchange membrane (PEM). It is a common practice to use Nafion membranes as PEMs, which have high ion exchange capacity. However, Nafion-based membranes also have high fuel permeability, decreasing fuel utilization, and reducing the potential power density. This article focuses on using graphene-coated (Gr-coated) PEMs to reduce fuel crossover. Protons can permeate across graphene, and thus, it can be employed in various devices as a proton conductive membrane. Here, we report the efficiency of Gr-coated Nafions. We tested performance and crossover at three different temperatures with four different fuel concentrations and compared it to a Nafion PEM that underwent the same test conditions. We found that the adhesion of Gr on to PEMs is insufficient for prolonging fuel cell operation, resulting in Gr delamination at high temperatures and higher fuel crossover values compared to lower temperature testing. The results for 7.5M methanol fuel show a reduction of up to 25% in methanol crossover, translating to a peak power density that increases from 3.9 to 9.5 mW/cm2 when using a Gr-coated PEM compared to a Nafion PEM at 30 °C.