Nafion Composite Membranes Research Articles

Potential of kaolin as filler in Nafion composite membranes for PEM fuel cells

Nafion is one of the polymer materials used as a polymer exchange membrane (PEM) in fuel cells due to its high proton conductivity, chemical stability, and fuel cell performance. However, Nafion membranes still have notable disadvantages, such as decreased proton conductivity at high temperatures and low humidity. One of the methods applied to overcome these limitations is to add inorganic compounds to the Nafion matrix. In this study, kaolin, a hygroscopic clay, was incorporated into Nafion for the first time to enhance proton conductivity of the membrane. Kaolin-doped composite membranes (5 %, 10 %, and 15 % kaolin by weight) were produced through the solution casting method and analyzed using various characterization techniques. The synthesized membranes exhibited significantly higher water uptake, lower swelling, higher proton conductivity, and better mechanical properties compared to recast Nafion. Among all composite membranes, Nafion-Kaolin-15 demonstrated a proton conductivity of 0.330 S/cm, which is a remarkable enhancement of 1.43 times compared to recast Nafion. These findings revealed the potential of kaolin-doped Nafion membranes for future applications in PEMFCs.

Renewable and hydrophilic carbon quantum dots derived from human hair as the filler in Nafion composite membrane for vanadium redox flow battery application

Renewable and environmentally benign hydrophilic carbon quantum dots (CQDs) were synthesized using a hydrothermal method. Subsequently, composite membranes of Nafion/CQDs, demonstrating outstanding performance metrics for vanadium redox flow batteries (VRFBs), were developed. Employing a straightforward solution-casting technique, these membranes exhibited superior proton conductivity and reduced vanadium ion permeability. Tested at an elevated current density of 120 mA/cm2, the single cell VRFB integrated with the optimized Nafion/CQDs composite membrane outperformed its commercial counterparts, achieving a high coulombic efficiency of approximately 96.13 % and an energy efficiency of nearly 85.46 %. Moreover, it demonstrated significant cycle life, retaining about 17.1 % of its capacity after 100 cycles, compared to 27.2 % capacity retention for the N-recast membrane over the same period. These results position the Nafion/CQDs composite membrane as a formidable contender in the VRFB domain, emphasizing its potential for broader commercial applications.

UiO‐66‐NH2 anchored sulfonated polyphenylene sulfide proton exchange membrane with high proton conductivity and low methanol permeability

AbstractThis study loaded different amounts of UiO‐66‐NH2 onto sulfonated polyphenylene sulfide fibers (SPPS), successfully loading UiO‐66‐NH2 on SPPS fibers confirmed by energy dispersive x‐ray spectroscopy, x‐ray diffraction, and Fourier transform infrared spectroscopy. The UiO‐66‐NH2‐X@SFM were then impregnated in Nafion solution to obtain UiO‐66‐NH2‐X@SFM/Nafion composite membranes. The thermal stability, dimensional stability, mechanical properties, proton conductivity, methanol resistance, and other properties of the UiO‐66‐NH2‐X@SFM/Nafion composite membranes were subsequently comprehensively characterized. The proton conductivity of the UiO‐66‐NH2‐8@SFM/Nafion composite membrane at 80°C and 100% RH was measured to be 0.286 S cm−1, which exhibited a significant enhancement of 1.75 times compared with the original membrane. Simultaneously, the composite membrane demonstrated a remarkable reduction in methanol permeation rate. At 40°C and 100% RH, the UiO‐66‐NH2‐8@SFM/Nafion composite membrane has a selectivity of up to 20.7 × 104 S s cm−3 and a single cell density of 88.3 m W cm−2 at 60°C and 100% RH.

The Incorporation of Sulfonated PAF Enhances the Proton Conductivity of Nafion Membranes at High Temperatures.

Nafion membranes are widely used as proton exchange membranes, but their proton conductivity deteriorates in high-temperature environments due to the loss of water molecules. To address this challenge, we propose the utilization of porous aromatic frameworks (PAFs) as a potential solution. PAFs exhibit remarkable characteristics, such as a high specific surface area and porosity, and their porous channels can be post-synthesized. Here, a novel approach was employed to synthesize a PAF material, designated as PAF-45D, which exhibits a specific surface area of 1571.9 m2·g-1 and possesses the added benefits of facile synthesis and a low cost. Subsequently, sulfonation treatment was applied to PAF-45D in order to introduce sulfonic acid groups into its pores, resulting in the formation of PAF-45DS. The successful incorporation of sulfonic groups was confirmed through TG, IR, and EDS analyses. Furthermore, a novel Nafion composite membrane was prepared by incorporating PAF-45DS. The Nyquist plot of the composite membranes demonstrates that the sulfonated PAF-45DS material can enhance the proton conductivity of Nafion membranes at high temperatures. Specifically, under identical film formation conditions, doping with a 4% mass fraction of PAF-45DS, the conductivity of the Nafion composite membrane increased remarkably from 2.25 × 10-3 S·cm-1 to 5.67 × 10-3 S·cm-1, nearly 2.5 times higher. Such promising and cost-effective materials could be envisioned for application in the field of Nafion composite membranes.

Comparative Study on the Proton Conduction Behaviors of Two Acidic Amphiphilic and Hydrophilic Coordination Compounds in Nafion Composite Membranes.

The acidic amphiphilic compound H[Co(H2L1)(HL1)(phen)]·3H2O (H4(Co-L1), H3L1 = 5-(3', 5'-dicarboxylphenyl)-pyridine-2-carboxylic, phen = phenanthroline) and the hydrophilic compound [Ni(HL2)(H2O)5]·H2O (H(Ni-L2), H3L2 = 5-(3',5'-dicarboxylphenyl)-pyridine-3-carboxylic) were synthesized via hydrothermal reactions at acidic conditions. The acidity of H4(Co-L1) is stronger than of H(Ni-L2); while the hydrogen bond continuity in H4(Co-L1) extended monodirectionally, which is smaller compared to the three-directional extension observed in H(Ni-L2). The proton conduction behaviors of these two compounds as fillers of Nafion composite membranes have been investigated. The results indicate that the optimal doping amounts of H4(Co-L1) and H(Ni-L2) are 2 and 1%, respectively; the proton conductivities of H4(Co-L1)/Nafion-2 and H(Ni-L2)/Nafion-1 composite membranes are 0.243 and 0.212 S·cm-1, respectively, which are approximately 50.2 and 30.6% higher than that of pure Nafion membrane, respectively. A higher doping amount of H4(Co-L1) can be attributed to its hydrophobic phen ligand, which promotes compatibility with Nafion membrane and reduces aggregation. Hydrogen bond continuity has a more significant effect on proton conductivity than acidity at relatively low doping amounts; conversely, this relationship reverses at relatively high doping amounts.

Impact of SiO2 Modification on the Performance of Nafion Composite Membrane

Using Nafion212 membrane and TEOS solution as raw materials, Nafion212/SiO2 composite membranes were prepared. In the in situ sol-gel reaction process, a series of Nafion/SiO2 composite membranes were prepared by varying the reaction temperature and reaction time. The effects of different modification schemes on Nafion/SiO2 composite membranes were studied using SEM, EDS, TEM, TGA, XRD, and mechanical tensile experiments, among other methods. The results show that Nafion/SiO2 composite membranes prepared at 3°C exhibit a well-separated phase structure and excellent water retention properties, with a water uptake of 29.23% and a swelling ratio of 24.25%. These membranes also demonstrate outstanding physical and chemical performance, with a maximum tensile stress of 13.6 MPa and an elongation at a break of 270%. At 110°C, the proton conductivity of the Nafion/SiO2 composite membrane reaches 0.172 S/cm, meeting the requirements for high-temperature proton exchange membrane fuel cells.

Improved performance of lanthanide-doped UIO-66/Nafion hybrid proton exchange membrane for water electrolyzer

Incorporating metal-organic frameworks (MOFs) especially the ones with protic functional groups into proton exchange membrane (PEM) can effectively improve its proton conductivity. Lanthanide MOFs (Ln-MOFs) have been recognized as more potential candidates exhibiting proton dissociation capability. However, the performance of PEM upon integrating Ln-MOFs in water electrolyzer has yet to be investigated. In this study, Nafion composites with different loadings of lanthanide Ce-UiO-66 were prepared, characterized and tested by comparing with the non-lanthanide Zr-UiO-66. It was revealed that the proton conductivity of Ce-UiO-66/Nafion composite membrane was higher than pristine Nafion and Zr-UiO-66/Nafion membrane, which was attributed to the fact that the Ce-UiO-66 doping contributed to the construction of the hydrogen-bonded network to enhance the proton conductivity. At 3 wt% Ce-UiO-66 doping, the proton conductivity of the composite membrane can reach 124.45 mS/cm, which is significantly improved by 17 % compared with Zr-UiO-66/Nafion. Such a trend is mainly contributed by the lower proton affinity and proton transfer capability of Ce atoms in Ce-UiO-66, and the higher number of water molecules around Ce atoms favors the reduced tortuosity of the proton conduction pathway in membranes. Single electrolytic cell tests demonstrated the enhancement of electrolysis efficiency upon Ce-UiO-66 doping was improved from 58.77 % to 65.37 % at a current density of 2 A cm−2.

Two water-rich amphiphilic and hydrophilic coordination polymers: syntheses, structures and proton conduction behaviors in Nafion composite membranes

Two amphiphilic and hydrophilic coordination compounds were obtained, which can be doped into Nafion membranes with different optimal amounts and improve the proton conductivity of Nafion composite membranes to different degrees.

Interconnected hollow metal–organic framework network towards excellent proton transfer for proton exchange membrane

Interconnected hollow metal–organic framework (MOF) network (GO@HZIF-8) was designed as an efficient proton transfer accelerator in Nafion membrane. GO@HZIF-8 was constructed by in situ synthesis of ZIF-8 onto graphene oxide (GO) and succedent etching with tannic acid (TA). The hollow construction and surface TA functionalization of hollow ZIF-8 (HZIF-8) bestowed composite membrane with superior water retention. This was highly beneficial to the rapid proton transfer. Besides, the hollow construction could effectively reduce the proton transfer resistance onto GO@HZIF-8. More importantly, the interconnective architecture between HZIF-8 by the tethering function of GO and the interfacial hydrogen bond interaction between GO@HZIF-8 and Nafion resulted in connective proton transfer routes at GO@HZIF-8 surfaces and GO@HZIF-8/Nafion interfaces. These dramatically accelerated the proton transfer of GO@HZIF-8/Nafion composite membrane, enabling a considerable proton conductivity (PC) of 0.301 S cm−1 under 90 °C, 95 % RH, ∼1.33-fold greater than that of the pure Nafion membrane (RN). Moreover, the composite membrane exhibited a peak power density of 45.8 mW cm−2, ∼1.22-fold higher than that of RN. These results menifest that constructing hollow MOF network possesses grand prospect in the construction of high performance proton exchange membranes (PEMs).

Non-destructively incorporating ceria in Nafion membrane as hydroxyl radical scavenging agent for long-term PEMFC application

Aiming at enhancing the long-term operation of proton exchange membrane fuel cell (PEMFC), Nafion as a typical example of perfluorosulfonic acid proton exchange membrane is non-destructively modified by sulfonated ceria (CeO2-DS) nanoparticles via a swelling-filling strategy. CeO2-DS nanoparticles in Nafion matrix can not only act as radical scavenging agent to improve the durability of Nafion, but also assist the re-construction of the efficient proton conduction channel in the composite Nafion membrane. Both oxidative stability and proton conductivity of the Nafion membrane are therefore remarkably improved with the great mechanical and thermal stability of Nafion maintained. PEMFC equipped with the modified Nafion membrane therefore outperforms that with the pristine Nafion membrane in terms of both power output and durability. Specifically, the maximum power density of the PEMFC equipped with modified Nafion after Fenton accelerated degradation test was significantly improved by ca. 25 % compared with that of the pristine Nafion membrane. This work hence provides a facile way to improve the durability of the PEMFC for practical applications.

Applicability of Phosponated Poly(pentafluorostyrene) Fiber Reinforced Nafion Composite Membranes in Low-Temperature Fuel Cells

Reducing the fuel crossover of proton exchange membranes (PEMs) is an important measure to improve the fuel efficiency and performance of fuel cells and electrolyzers 1, 2. Additionally, the long-term stability and safety of PEM-based systems increase with a reduction in the gas crossover 1, 3, 4. A possible approach for reducing the gas crossover of a PEM is the implementation of fiber meshes to form a composite membrane 5. Furthermore, fiber-reinforced composite membranes can also increase the mechanical properties of PEMs and therefore enable the utilization of thinner membranes without sacrificing the mechanical integrity of the membrane or causing safety risks 6.In this work, we demonstrate the successful fabrication of electrospun fibers of a partially phosophonated, conductive polymer (phosponated poly(pentafluorostyrene); PWN70) and its non-phosphonated and, therefore, non-conductive equivalent (poly(pentafluorostyrene); PPFSt). Two different loadings of both fiber meshes were successfully infiltrated with Nafion, analyzed mechanically and electrochemically, and compared to a non-reinforced Nafion reference. We show that the mechanical properties of both fiber-reinforced composite membranes are superior to the reference membrane. The electrochemical analysis of the membrane electrode assemblies (MEAs) shows a reduction in performance with the incorporation of the non-conductive PPFSt fibers. An increase in the high-frequency resistance (HFR) of the MEAs containing the non-conductive PPFSt fibers explains the reduced performance and scales with fiber loading. In contrast, the MEAs with the proton conductive PWN70 fiber reinforcement maintained the same HFR and performance as the reference, independently of the fiber loading. Additionally, hydrogen crossover measurements revealed a significantly reduced hydrogen crossover of the MEAs composed of the conductive PWN70 fiber-reinforced membranes (between 30 and 40 % less than the reference). We hypothesize that PWN70 shows a decreased diffusivity for hydrogen compared to Nafion, and therefore, the fibers in the Nafion matrix increase the tortuosity of the membrane for fuel crossover.In summary, we developed a fiber-reinforced Nafion membrane with improved mechanical and gas barrier properties while maintaining the membrane's proton conductivity compared to the same membrane without reinforcement.References Q. Tang, B. Li, D. Yang, P. Ming, C. Zhang and Y. Wang, Int. J. Hydrog. Energy, 46(42), 22040–22061 (2021).M. Schalenbach, M. Carmo, D. L. Fritz, J. Mergel and D. Stolten, Int. J. Hydrog. Energy, 38(35), 14921–14933 (2013).B. Wu, M. Zhao, W. Shi, W. Liu, J. Liu, D. Xing, Y. Yao, Z. Hou, P. Ming, J. Gu and Z. Zou, Int. J. Hydrog. Energy, 39(26), 14381–14390 (2014).C. Klose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach and S. Thiele, J. Electrochem. Soc., 165(16), F1271-F1277 (2018).J. Choi, K. M. Lee, R. Wycisk, P. N. Pintauro and P. T. Mather, Macromolecules, 41(13), 4569–4572 (2008).J. B. Ballengee and P. N. Pintauro, Macromolecules, 44(18), 7307–7314 (2011).

Outstanding proton conductivity over wide temperature and humidity ranges and enhanced mechanical, thermal stabilities for surface-modified MIL-101-Cr-NH2/Nafion composite membranes

High-performance proton exchange membranes are of great importance for fuel cells. Here, we have synthesized polycarboxylate plasticizer modified MIL-101-Cr-NH2 (PCP-MCN), a kind of hybrid metal−organic framework, which exhibits a superior proton conductivity. PCP-MCN nanoparticles are used as additives to fabricate PCP-MCN/Nafion composite membranes. Microstructures and characteristics of PCP-MCN and these membranes have been extensively investigated. Significant enhancement in proton conduction for PCP-MCN around 55 °C is interestingly found due to the thermal motion of the PCP molecular chains. Robust mechanical properties and higher thermal decomposition temperature of the composite membranes are directly ascribed to strong intermolecular interactions between PCP-MCN and Nafion side chains, i.e. the formation of substantial acid–base pairs (-SO3-⋅⋅⋅+H–NH-), which further improves compatibility between additive and Nafion matrix. At the same humidity and temperature condition, the water uptake of composite membranes significantly increases due to the incorporation of porous additives with abundant functional groups and thus less crystallinity degree in comparison to pristine Nafion. Proton conductivity (σ) over wide ranges of humidities (30 − 100 % RH at 25 °C) and temperatures (30 − 98 °C at 100 % RH) for prepared membranes is measured. The σ in PCP-MCN/Nafion composite membranes is remarkably enhanced, i.e. 0.245 S/cm for PCP-MCN-3wt.%/Nafion is twice that of Nafion membrane at 98 °C and 100 % RH, because of the establishment of well-interconnected proton transport ionic water channels and perhaps faster protonation–deprotonation processes. The composite membranes possess weak humidity-dependence of proton transport and higher water uptake due to excellent water retention ability of PCP-MCN. In particular, when 3 wt.% PCP-MCN was added to Nafion, the power density of a single-cell fabricated with this composite membrane reaches impressively 0.480, 1.098 W/cm2 under 40 % RH, 100 % RH at 60 °C, respectively, guaranteeing it to be a promising proton exchange membrane.

Metal-organic framework-decorated PTFE reinforced membranes with immobilized caffeic acid radical scavenger towards improved performance and durability of PEMFC

During the continuous operation of fuel cell, the generated free radicals have an irreversible effect on the proton exchange membrane (PEM), and the introduction of free radical scavengers is an effective strategy for improving its durability. In this study, we proposed to prepare thin and highly durable reinforced membranes by immobilizing organic radical scavenger caffeic acid on the fibrous PTFE supporting layer decorated with amino-functionalized metal-organic framework. The electrostatic force between the amino and sulphonic acid groups can induce an orderly aggregation of hydrophilic cationic groups within the Nafion, endowing the reinforced composite PEMs with superior proton conductivity. The mechanical properties and dimensional stability of the reinforced membranes were effectively enhanced by the reinforcement of the PTFE layer decorated with the MOF network, and the hydrogen crossover was mitigated. The thickness of Nafion reinforced membranes was reduced to 25 µm with the PTFE reinforcement. After assembling in a single cell, the Nafion composite membrane (PPUC-Nafion-3) with a 3 wt% doping of caffeic acid achieved a maximum power density (PDmax) of 812.64 mW cm−2 and the open circuit voltage (OCV) decay rate of only 1.11 mV h−1 over 100 h. For comparison under the same conditions, recast Nafion possessed a much lower PDmax of only 486.30 mW cm−2 and a higher OCV decay rate of 1.91 mV h−1. This study demonstrates an effective approach to developing highly durable and thin PEMs for the realization of PEMFC with improved output performance and durability simultaneously.

Proton-exchange polymer composite membrane of Nafion and microcrystalline cellulose for performance improvement of direct glycerol fuel cell

In this research, glycerol was used as fuel for a direct glycerol fuel cell (DGFC). Nafion (NF) was used to fabricate a proton exchange membrane and microcrystalline cellulose (MCC) was used as a filler for fabricating the NF composite membranes with different MCC loadings (0, 5, 10, or 15 wt%). The composite membranes were characterized using X-ray diffraction XRD for study of the crystallinity index (CI), SEM-EDS was applied to observe the atom dispersion of membranes, and FTIR-ATR was used to identify the chemical bonds of samples. The results showed that the 15 % MCC/NF membrane had a greater CI than the 5 % MCC/NF composite membrane, while the atom dispersion of the 5 % MCC/NF membrane was better than the others. The composite membrane properties were tested based on water uptake, solubility, ion exchange capacity, chemical degradation, 1 M and 2 M glycerol permeability, proton conductivity, selectivity, and fuel cell performance. The 5 wt% MCC loading increased the water uptake and proton conductivity and decreased the glycerol crossover compared to the other membranes. However, 15 wt% MCC had more durable chemical membrane degradation than the 5 wt% MCC membrane and the solubility test identified that the 5 %, 10 %, and 15 % MCC/NF composite membranes had 2.97, 3.08, and 4.92 times, respectively, that of the recast NF membrane. The highest selectivity (1.54 × 105 Sscm−1) of the membranes was recorded for the 5 % MCC/NF composite membrane at 50 °C. The DGFC performance with 1 M glycerol at 70 °C of the 5 % MCC/NF composite membrane had a maximum power density 18.07 mW/cm2 and a current density 0.139 mA/cm2.

Polarization Processes in Nafion Composite Membranes Doped with Rare-Earth Metals.

Dielectric spectroscopy (frequency range f = 100…107 Hz and temperatures T = 293…403 K (accuracy 0.5 K), measuring voltage applied to the sample was 1.0 V) was used to study composite materials based on perfluorosulfonic membranes with inclusions of rare-earth elements, in particular, europium (III) and terbium (III) chlorides. The dispersion of the permittivity and the presence of maxima, corresponding to losses, were revealed, which indicates that relaxation processes of various natures were present. The membrane layers under investigation are characterized by relaxation parameters that correspond to a symmetrical distribution of relaxers over relaxation times. The spectrum of relaxers changed when terbium and europium metal impurities were introduced into the polymer matrix. The investigation of these polymer systems demonstrated a power-law dependence of the specific conductivity on frequency. A decrease in the exponent with increasing temperature indicates the existence of a traditional hopping mechanism for charge transfer. The observed changes in the dielectric permittivity and specific conductivity are due to a change in the nature of polarization processes because of the strong interaction of metal (terbium and europium) ions with the polymer matrix of Nafion.

Low-Cost Pore-Filled PVDF–Nafion Composite Membrane for the Vanadium Redox Flow Battery

Low-Cost Pore-Filled PVDF–Nafion Composite Membrane for the Vanadium Redox Flow Battery

Porous lanthanum titanium oxide nanostructure composite membrane to enhance the power output and chemical durability of low-humidifying polymer electrolyte fuel cells: impact of additive morphology

Tuning the morphologies for improving the properties of the additive materials receives immense attention during the fabrication of proton-exchange membranes for fuel cells. This study reports the synthesis of lanthanum titanium oxide (LTO) nanostructures with different morphologies (cube, spherical, and tubular) via the pyrolysis of nanofibers containing metal precursors. A mixed matrix membrane is fabricated by incorporating LTO cubes (LTO-C), LTO spheres (LTO-S), or LTO tubes (LTO-T) into a Nafion matrix, with improved physicochemical, thermomechanical, and electrochemical properties compared to those of the unmodified Nafion and Nafion-212 membranes. We investigate the effect of LTO morphology on the performance of the Nafion membranes in low-humidity polymer electrolyte fuel cells (LH-PEFCs). The water retention and diffusion behavior of LTO-T nanostructures improve the proton conductivity and LH-PEFC performance of the Nafion composite membranes. The coexistence of La3+ and Ti4+ affords efficient radical scavenging during long-term LH-PEFC operation, which realizes higher durability for the composite membranes compared to Nafion. Accordingly, this study proposes a novel strategy to resolve the major challenges associated with the operation of LH-PEFCs with Nafion membranes: dehumidification and oxidative degradation.

Quantitative Study of Charge Distribution Variations on Silica-Nafion Composite Membranes under Hydration Using an Approximation Model.

Understanding the ionic structure and charge transport on proton exchange membranes (PEMs) is crucial for their characterization and development. Electrostatic force microscopy (EFM) is one of the best tools for studying the ionic structure and charge transport on PEMs. In using EFM to study PEMs, an analytical approximation model is required for the interoperation of the EFM signal. In this study, we quantitatively analyzed recast Nafion and silica-Nafion composite membranes using the derived mathematical approximation model. The study was conducted in several steps. In the first step, the mathematical approximation model was derived using the principles of electromagnetism and EFM and the chemical structure of PEM. In the second step, the phase map and charge distribution map on the PEM were simultaneously derived using atomic force microscopy. In the final step, the charge distribution maps of the membranes were characterized using the model. There are several remarkable results in this study. First, the model was accurately derived as two independent terms. Each term shows the electrostatic force due to the induced charge of the dielectric surface and the free charge on the surface. Second, the local dielectric property and surface charge are numerically calculated on the membranes, and the calculation results are approximately valid compared with those in other studies.

Calcium carbonate from chicken eggshells as filler in composite Nafion membrane for direct ethanol fuel cell: a molecular dynamics study

AbstractBACKGROUNDDirect ethanol fuel cells (DEFC) need fillers to mitigate the issue of ethanol crossing over from the anode to the cathode, which lowers performance. Therefore, this study developed calcium carbonate (CaCO3) from chicken eggshells as a filler in a Nafion composite membrane for DEFC. Three cluster models of CaCO3 filler were developed, namely (CaCO3)2, (CaCO3)3, and (CaCO3)4, to form the Nafion composite membranes. The properties of composite membranes, such as proton conductivity, ethanol permeability, and selectivity, were studied using the molecular dynamics method. In addition, the three main factors influencing the composite membranes’ properties were analyzed in this study; these were cluster size of CaCO3, mass loading of the filler, and ethanol concentration.RESULTSThe results show that filler has reduced proton conductivity and ethanol permeability in the DEFC application compared to the Nafion membrane. However, the selectivity is used as a trade‐off between ion conductivity and ethanol permeability in the composite membrane, thus requiring a suitable size structure and mass loading to balance the high ion conductivity rate and reduce the ethanol permeability rate. The composite membrane C‐(CaCO3)4, which has a large cluster size in this study, shows that it is necessary to restrict ethanol permeability at a high ethanol concentration of 5 mol L−1. However, the structure size in cluster B – (CaCO3)3 – can reduce ethanol permeability but requires high mass loading by 5 wt%. Analysis of variance showed significant values for ion conductivity, ethanol permeability, and selectivity responses.CONCLUSIONCaCO3 successfully reduced ethanol crossover in DEFC, with all three composite membranes being suitable for use at low ethanol concentrations. However, specific size structure and mass loading are required to overcome ethanol crossover at high ethanol concentration. © 2023 Society of Chemical Industry (SCI).

Glucose Biosensor Based on Glucose Oxidase Immobilized on BSA Cross-Linked Nanocomposite Modified Glassy Carbon Electrode

Glucose sensors based blood glucose detection are of great significance for the diagnosis and treatment of diabetes because diabetes has aroused wide concern in the world. In this study, bovine serum albumin (BSA) was used to cross-link glucose oxidase (GOD) on a glassy carbon electrode (GCE) modified by a composite of hydroxy fullerene (HFs) and multi-walled carbon nanotubes (MWCNTs) and protected with a glutaraldehyde (GLA)/Nafion (NF) composite membrane to prepare a novel glucose biosensor. The modified materials were analyzed by UV-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), and cyclic voltammetry (CV). The prepared MWCNTs-HFs composite has excellent conductivity, the addition of BSA regulates MWCNTs-HFs hydrophobicity and biocompatibility, and better immobilizes GOD on MWCNTs-HFs. MWCNTs-BSA-HFs plays a synergistic role in the electrochemical response to glucose. The biosensor shows high sensitivity (167 μA·mM-1·cm-2), wide calibration range (0.01-3.5 mM), and low detection limit (17 μM). The apparent Michaelis-Menten constant Kmapp is 119 μM. Additionally, the proposed biosensor has good selectivity and excellent storage stability (120 days). The practicability of the biosensor was evaluated in real plasma samples, and the recovery rate was satisfactory.