Search Results (41)

Anion exchange membrane fuel cells (AEMFCs) have garnered significant attention for their potential to advance fuel cell technology. In this study, we developed and characterized anion exchange membranes (AEMs) composed of quaternized poly(vinyl alcohol) (QPVA) electrospun nanofiber mats with poly(acrylamide-co-diallyldimethylammonium chloride) (PAADDA) as a matrix filler for interfiber voids. The objective was to investigate the effect of varying PAADDA concentrations as a matrix filler for interfiber voids on the structural, mechanical, and electrochemical properties of QPVA-based electrospun AEMs. Membranes with various concentrations of PAADDA were fabricated and extensively characterized using FTIR, SEM, tensile strength, water uptake, swelling degree, ion exchange capacity (IEC), and hydroxide ion conductivity (σ). FTIR confirmed the successful incorporation of PAADDA into the membrane structure, while SEM images showed that PAADDA effectively filled the voids between the QPVA fibers, resulting in denser membranes. The results indicated that the eQPAD5.0 membrane, with the highest PAADDA content, exhibited the best overall performance. The incorporation of PAADDA into QPVA-based electrospun AEMs significantly enhanced their mechanical strength, achieving a tensile strength of 23.9 MPa, an IEC of 1.25 mmol g⁻¹, and hydroxide conductivity of 19.49 mS cm⁻¹ at 30 °C and 29.29 mS cm⁻¹ at 80 °C, making them promising candidates for fuel cell applications. Full article

This work reports the synthesis of PdNi bimetallic particles and Pd on Carbon black (Vulcan XC-72) by reverse microemulsion and the chemical reduction of metallic complexes. The physicochemical characterization techniques used for the bimetallic and metallic materials were TGA, STEM, ICP-OES, and XRD. Also, the electrocatalysts were studied by electrochemical techniques such as anodic CO stripping and β-NiOOH reduction to elucidate the Pd and Ni surface sites participation in the reactions. The electrocatalysts were evaluated in the anodic reaction in anion-exchange membrane fuel cells (AEMFC) and the hydrogen oxidation reaction (HOR) in alkaline media. The results indicate that PdNi/C electrocatalysts exhibited higher electrocatalytic activity than Pd/C electrocatalysts in both the half-cell test and in the AEMFC, even with the same Pd loading, which is attributed to the bifunctional mechanism that provides OH^- groups in oxophilic sites associated to Ni, that can facilitate the desorption of Hads in the Pd sites for the bimetallic material. Full article

The proton exchange membrane (PEM) is a critical component of fuel cells, responsible for controlling the flow of protons while minimizing fuel crossover through its channels. The commercial membrane commonly used in fuel cells is made of Nafion, which is expensive and prone to swelling when in contact with water. To address these limitations, various polymers have been explored as alternatives to replace the costly Nafion membrane. Styrene, a versatile and cost-effective material, has emerged as a promising candidate. It can be modified into different forms to meet the requirements of a fuel cell membrane. The aromatic rings in styrene can copolymerize with hydrophilic functional groups, enhancing water (H₂O) uptake, proton conductivity, and ion exchange capacity (IEC) of the membrane. Additionally, the hydrophobic nature of styrene helps maintain the structural integrity of the membrane’s channels, reducing excessive swelling and minimizing fuel crossover. The flexible aromatic chains in styrene facilitate the attachment of hydrophilic functional groups, such as sulfonic groups, further improving the membrane’s ion conductivity, IEC, thermal stability, mechanical strength, and oxidative stability. This review article explores the application of styrene and its derivatives in fuel cell membranes, with a focus on proton exchange membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), and anion exchange membrane fuel cells (AEMFCs). Full article

Anion exchange membrane fuel cells (AEMFCs) are versatile power generation devices that can be fed by both gaseous (H₂) and liquid fuels. The development of sustainable, efficient, and stable catalysts for the oxidation of hydrogen (HOR) and oxygen reduction (ORR) under alkaline conditions remains a challenge currently facing AEMFC technology. Reducing the loading of PGMs is essential for reducing the overall cost of AEMFCs. One strategy involves exploiting the synergistic effects of two metals in bimetallic nanoparticles (NPs). Here, we report that the activity for the HOR and the ORR can be finely tuned through surface engineering of carbon-supported PdAu-PVA NPs. The activity for both ORR and HOR can be adjusted by subjecting the material to heat treatment. Specifically, heat treatment at 500 °C under an inert atmosphere increases the crystallinity and oxophilicity of the nanoparticles, thereby enhancing anodic HOR performance. On the contrary, heat treatment significantly lowers ORR activity, highlighting how reduced surface oxophilicity plays a major role in increasing active sites for ORR. The tailored activity in these catalysts translates into high power densities when employed in AEMFCs (up to 1.1 W cm⁻²). Full article

This study investigated the modification of nanosilver (Ag) by Co-Pc (phthal–cyanine) and the synergistic effect of Ag-Co/CNT (carbon nanotube) for the long-term stability of AEMFCs (anion exchange membrane fuel cells). This study also aimed to use non-precious metal catalysts on both the cathode and anode to reduce the catalyst costs. Through a simple and efficient chemical synthesis method, a composite catalyst consisting of Co-Pc-modified Ag/CNT was successfully prepared and characterized for its structure and composition. Co-Pc and Ag were chosen for their high durability and catalytic activity in fuel cells, combined with a multi-wall carbon nanotube (MWCNT) as a carrier for the cathode catalyst, and the anode catalyst used Pd-CeO₂/C. The performance of the cell module was tested based on a commercial anion exchange membrane (X37-50RT). The experiment focused on different synthesis times and ratios of catalyst and ionomer, observing the enhancement in Co on the active sites of Ag/CNT. Finally, the cell performance was tested for the optimal loading amount. It was observed that when the loading of the nanosilver–cobalt/carbon nanotube (Ag-Co/CNT) is 1 mg/cm², the highest power density is 434.1 mW/cm². Through 100 cycles of testing, only an 18% decrease was observed, while the decrease in open circuit voltage was approximately 4.6%. Compared to nanosilver (Ag/CNT), the Co-Pc-modified nano-Ag with the degradation rate has significantly slowed down, and its catalytic activity has also improved significantly. The enhanced stability of this synergistic effect is mainly attributed to the introduction of cobalt metal, which prevents excessive fusion of nano-Ag particles and surface oxidation, effectively maintaining durability in catalytic activity. Full article

This work aims at the effects of anion-exchange membranes (AEMs) and ionomer binders on the catalyst electrodes for anion-exchange membrane fuel cells (AEMFCs). In the experiments, four metal catalysts (nano-grade Pt, PtRu, PdNi and Ag), four AEMs (aQAPS-S8, AT-1, X37-50T and X37-50RT) and two alkaline ionomers (aQAPS-S14 and XB-7) were used. They were verified through several technical parameters examination and cell performance comparison for the optimal selection of AMEs. The bimetallic PdNi nanoparticles (PdNi/C) loaded with Vulcan XC-72R carbon black were used as anode electrodes by using the wet impregnation method, and Ag nanoparticles (Ag/C) were used as the catalyst cathode. It was found that the power density and current density of the X37-50RT are higher than the other three membranes. Also, alkaline ionomers of XB-7 had better performance than aQAPS-S14. The efficiency was improved by 32%, 155% and 27%, respectively, when compared to other membranes by using the same catalyst of PdNi/C, Ag/C and Pt/C. The results are consistent with the membrane ion conductivity measurements, which showed that the conductivity of the X37-50RT membrane is the highest among them. The conductivity values for hydroxide ions (OH⁻) and bromide ions (Br⁻) are 131 mS/cm and 91 mS/cm, respectively. These findings suggest that the properties (water uptake, swelling rate and mechanical) of the anion-exchange membrane (AEM) can serve as a key reference for AEM fuel cell applications. Full article

Ni nanoparticles supported on graphene-based materials were tested as catalysts for the oxygen reduction reaction (ORR) to be used in anion exchange membrane fuel cells (AEMFCs). The introduction of N into the graphene structure produced an enhancement of electrocatalytic activity by improving electron transfer and creating additional active sites for the ORR. Materials containing both N and S demonstrated the highest stability, showing only a 3% performance loss after a 10 h stability test and therefore achieving the best overall performance. This long-term durability is attributed to the synergetic effect of Ni nanoparticles and bi-doped (S/N)-reduced graphene oxide. The findings suggest that the strategic incorporation of both nitrogen and sulphur into the graphene structure plays a crucial role in optimising the electrocatalytic properties of Ni-based catalysts. Full article

As a central component for anion exchange membrane fuel cells (AEMFCs), the anion exchange membrane is now facing the challenge of further improving its conductivity and alkali stability. Herein, a twisted all-carbon backbone is designed by introducing stereo-contorted units with piperidinium groups dangled at the twisted sites. The rigid and twisted backbone improves the conduction of hydroxide and brings down the squeezing effect of the backbone on piperidine rings. Accordingly, an anion exchange membrane prepared through this method exhibits adapted OH⁻ conductivity, low swelling ratio and excellent alkali stability, even in high alkali concentrations. Further, a fuel cell assembled with a such-prepared membrane can reach a power density of 904.2 mW/cm² and be capable of continuous operation for over 50 h. These results demonstrate that the designed membrane has good potential for applications in AEMFCs. Full article

In this paper, a cobalt (Co)-chelated polynaphthalene imine (Co-PNIM) was calcined to become an oxygen reduction reaction (ORR) electrocatalyst (Co-N-C) as the cathode catalyst (CC) of an anion exchange membrane fuel cell (AEMFC). The X-ray diffraction pattern of CoNC-1000A900 illustrated that the carbon matrix develops clear C(002) and Co(111) planes after calcination, which was confirmed using high-resolution TEM pictures. Co-N-Cs also demonstrated a significant ORR peak at 0.8 V in a C–V (current vs. voltage) curve and produced an extremely limited reduction current density (5.46 mA cm⁻²) comparable to commercial Pt/C catalysts (5.26 mA cm⁻²). The measured halfway potential of Co-N-C (0.82 V) was even higher than that of Pt/C (0.81 V). The maximum power density (P_max) of the AEM single cell upon applying Co-N-C as the CC was 243 mW cm⁻², only slightly lower than that of Pt/C (280 mW cm⁻²). The Tafel slope of CoNC-1000A900 (33.3 mV dec⁻¹) was lower than that of Pt/C (43.3 mV dec⁻¹). The limited reduction current density only decayed by 7.9% for CoNC-1000A900, compared to 22.7% for Pt/C, after 10,000 redox cycles. Full article

The utilization of anion exchange membranes (AEMs) has revolutionized the field of electrochemical applications, particularly in water electrolysis and fuel cells. This review paper provides a comprehensive analysis of recent studies conducted on various commercial AEMs, including FAA3-50, Sustainion, Aemion™, XION Composite, and PiperION™ membranes, with a focus on their performance and durability in AEM water electrolysis (AEMWE) and AEM fuel cells (AEMFCs). The discussed studies highlight the exceptional potential of these membranes in achieving high current densities, stable operation, and extended durability. Furthermore, the integration of innovative catalysts, such as nitrogen-doped graphene and Raney nickel, has demonstrated significant improvements in performance. Additionally, the exploration of PGM-free catalysts, such as Ag/C, for AEMFC cathodes has unveiled promising prospects for cost-effective and sustainable fuel cell systems. Future research directions are identified, encompassing the optimization of membrane properties, investigation of alternative catalyst materials, and assessment of performance under diverse operating conditions. The findings underscore the versatility and suitability of these commercial AEMs in water electrolysis and fuel cell applications, paving the way for the advancement of efficient and environmentally benign energy technologies. This review paper serves as a valuable resource for researchers, engineers, and industry professionals seeking to enhance the performance and durability of AEMs in various electrochemical applications. Full article

Studies have been carried out to optimize the composition, formation technique and test conditions of membrane electrode assemblies (MEA) of hydrogen–oxygen anion-exchange membranes fuel cells (AEMFC), based on Fumatech anion-exchange membranes. A non-platinum catalytic system based on nitrogen-doped CNT (CNT_N) was used in the cathode. PtMo/CNT_N catalysts with a reduced content of platinum (10–12 wt.% Pt) were compared with 10 and 60 wt.% Pt/CNT_N at the anode. According to the results of studies under model conditions, it was found that the PtMo/CNT_N catalyst is significantly superior to the 10 and 60 wt.% Pt/CNT_N catalyst in terms of activity in the hydrogen oxidation reaction based on the mass of platinum. The addition of the Fumion ionomer results in minor changes in the electrochemically active surface area and activity in the hydrogen oxidation reaction for each of the catalysts. In this case, the introduction of ionomer–Fumion leads to a partial blocking of the outer surface and the micropore surface, which is most pronounced in the case of the 60Pt/CNT_N catalyst. This effect can cause a decrease in the characteristics of MEA AEMFC upon passing from 10PtMo/CNT_N to 60Pt/CNT_N in the anode active layer. The maximum power density of the optimized MEA based on 10PtMo/CNT_N was 62 mW cm⁻², which exceeds the literature data obtained under similar test conditions for MEA based on platinum cathode and anode catalysts and Fumatech membranes (41 mW cm⁻²). A new result of this work is the study of the effect of the ionomer (Fumion) on the characteristics of catalysts. It is shown that the synthesized 10PtMo/CNT_N catalyst retains high activity in the presence of an ionomer under model conditions and in the MEA based on it. Full article

In this work, the synthesis of bimetallic Ag and Cu particles on carbon vulcan (AgCu/C) is reported, synthesized by a simple galvanic displacement method using citrate tribasic hydrate as a co-reducing agent and a commercial material based on Cu/C as a template. The materials were characterized by several physicochemical techniques, including TGA, ICP-OES, XRD, SEM, and BET. The catalysts were evaluated as cathodic catalysts for the oxygen reduction reaction (ORR) and were used for the preparation of membrane electrode assemblies for evaluation in an Anion Exchange Membrane Fuel Cell (AEMFC). The results were compared with the commercial Ag/C and Cu/C catalysts; the bimetallic catalyst obtained a higher power density, which was attributed to a synergistic effect between Ag and Cu particles. Full article

Platinum group metal (PGM)-free oxygen reduction reaction (ORR) catalysts are of utmost importance for the rapid development of anion-exchange membrane fuel cell (AEMFC) technology. In this work, we demonstrate the improved ORR performance and stability of Co and Fe oxide-decorated/N-doped reduced graphene oxide (CoO_x-Fe₃O₄/N-rGO) prepared via a hydrothermal method at the low temperature of 150 °C. The catalysts were characterized thoroughly using transmission electron microscopy, high-angle annular dark field-scanning electron microscopy, X-ray diffraction, N₂ physisorption, Raman spectroscopy, and X-ray photoelectron spectroscopy to obtain information about morphology, elemental distribution, phases, porosity, defects, and surface elemental compositions. Significant ORR activity improvement (130 mV@-1.5 mA cm⁻²) was achieved with this catalyst compared to the pristine graphene oxide, and the ORR limiting current was even 12%@0.5 V higher than the commercial Pt/C. The enhanced ORR activity of CoO_x-Fe₃O₄/N-rGO was attributed to the uniform dispersion of Co, Fe, and N on reduced graphene oxide (rGO) sheets. Furthermore, ORR accelerated stress tests revealed excellent durability, suggesting that this material could be a promising and durable catalyst. With a cathode layer of the CoO_x-Fe₃O₄/N-rGO catalyst, we achieved a peak power density of 676 mW cm⁻² in an operando H₂-O₂ AEMFC. To the best of our knowledge, this is the highest reported power density per cathode catalyst mass in a reported PGM-free cathode catalyst. Finally, we quantified the various cell polarization losses as a function of cathode catalyst loadings to obtain insights for future work with AEMFCs based on this catalyst. The improvement in the AEMFC performance using CoO_x-Fe₃O₄/N-rGO as a cathode catalyst can be attributed to the synergistic effects of (i) the high turnover frequency of the transition metals (Co and Fe) for ORR and (ii) the enhancement provided by N doping to the metal distribution and stability. Full article

In this work, fully polysaccharide based membranes were presented as self-standing, solid polyelectrolytes for application in anion exchange membrane fuel cells (AEMFCs). For this purpose, cellulose nanofibrils (CNFs) were modified successfully with an organosilane reagent, resulting in quaternized CNFs (CNF (D)), as shown by Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 (C13) nuclear magnetic resonance (¹³C NMR), Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC), and ζ-potential measurements. Both the neat (CNF) and CNF(D) particles were incorporated in situ into the chitosan (CS) membrane during the solvent casting process, resulting in composite membranes that were studied extensively for morphology, potassium hydroxide (KOH) uptake and swelling ratio, ethanol (EtOH) permeability, mechanical properties, ionic conductivity, and cell performance. The results showed higher Young’s modulus (119%), tensile strength (91%), ion exchange capacity (177%), and ionic conductivity (33%) of the CS-based membranes compared to the commercial Fumatech membrane. The addition of CNF filler improved the thermal stability of the CS membranes and reduced the overall mass loss. The CNF (D) filler provided the lowest (4.23 × 10⁻⁵ cm² s⁻¹) EtOH permeability of the respective membrane, which is in the same range as that of the commercial membrane (3.47 × 10⁻⁵ cm²s⁻¹). The most significant improvement (~78%) in power density at 80 °C was observed for the CS membrane with neat CNF compared to the commercial Fumatech membrane (62.4 mW cm⁻² vs. 35.1 mW cm⁻²). Fuel cell tests showed that all CS-based anion exchange membranes (AEMs) exhibited higher maximum power densities than the commercial AEMs at 25 °C and 60 °C with humidified or non-humidified oxygen, demonstrating their potential for low-temperature direct ethanol fuel cell (DEFC) applications. Full article

In order to yield more Co(II), 2,6-diaminopyridine (DAP) was polymerized with 4,4-methylene diphenyl diisocyanates (MDI) in the presence of Co(II) to obtain a Co-complexed polyurea (Co-PUr). The obtained Co-PUr was calcined to become Co, N-doped carbon (Co–N–C) as the cathode catalyst of an anion exchange membrane fuel cell (AEMFC). High-resolution transmission electron microscopy (HR-TEM) of Co–N–C indicated many Co-Nx (Co covalent bonding with several nitrogen) units in the Co–N–C matrix. X-ray diffraction patterns showed that carbon and cobalt crystallized in the Co–N–C catalysts. The Raman spectra showed that the carbon matrix of Co–N–C became ordered with increased calcination temperature. The surface area (dominated by micropores) of Co–N–Cs also increased with the calcination temperature. The non-precious Co–N–C demonstrated comparable electrochemical properties (oxygen reduction reaction: ORR) to commercial precious Pt/C, such as high on-set and half-wave voltages, high limited reduction current density, and lower Tafel slope. The number of electrons transferred in the cathode was close to four, indicating complete ORR. The max. power density (P_max) of the single cell with the Co–N–C cathode catalyst demonstrated a high value of 227.7 mWcm⁻². Full article