Incorporation Of Layered Double Hydroxides Research Articles

Evaluation of surface organic layered double hydroxides on the anti-ageing performance of asphalt

To promote the anti-ageing performance of asphalt, layered double hydroxides (LDHs) modified by propyl trimethoxylsilane (MPMS) was prepared and applied to modify asphalt. Fourier transform infrared spectroscopy (FTIR) showed that MPMS was chemically-grafted on the surface of LDHs. The interaction between LDHs and asphalt was significantly enhanced after MPMS organic modification, and MPMS organic LDHs (OMLDHs) exhibited better compatibility in asphalt. OMLDHs and LDHs could enhance the high-temperature properties of asphalt, particularly OMLDHs. After ageing, the properties and structure of asphalt were dramatically degenerated. The incorporation of LDHs could inhibit the oxygenic groups increase in asphalt molecules during ageing, and retard the gelatinization of colloidal structures. LDHs could alleviate the negative effect of ageing on asphalt, and improve the anti-ageing performance of asphalt. The improvement effectiveness of LDHs on the anti-ageing performance of asphalt was remarkably improved after MPMS modification.

Multi-scale evaluation of sodium dodecyl sulfate intercalated LDHs on the ageing resistance of SBS modified bitumen

Sodium dodecyl sulfate (SDS) intercalated layered double hydroxides (LDHs) were prepared to enhance the ageing resistance of SBS modified bitumen (SMB). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that SDS has been intercalated into the interlayers of LDHs. Compared to LDHs, the interaction between SDS intercalated LDHs (OLDHs) and SMB was obviously stronger, and OLDHs exhibited better dispersity and stability in SMB. After ageing, the viscoelastic properties of SMB were deteriorated. LDHs and OLDHs could obviously alleviate the deterioration of ageing on the properties of SMB, which could improve the ageing resistance of SMB, especially OLDHs. Additionally, the enhancement mechanisms of OLDHs and LDHs for the ageing resistance of SMB at the microscopic scale were investigated by molecular dynamics. The incorporation of LDHs could obstruct the invasion of oxygen into the interior of SMB and inhibit the diffusion rate of oxygen in SMB, which reduced the oxidation reaction probability of SMB during ageing, and eventually achieved the improvement on ageing resistance of SMB. The effectiveness of LDHs was further improved after SDS intercalated modification, that was, SDS intercalated modification was beneficial to enhance the ageing resistance of LDHs for SMB.

PH‐Triggered Release and Degradation Mechanism of Layered Double Hydroxides with High Loading Capacity

AbstractThe loading capacity and strategy of layered double hydroxides (LDHs) determine their suitability for drug delivery applications. In this study, two sizes of MgAl‐CO3 LDHs are converted into MgAl‐NO3 LDHs and MgAl‐Cl LDHs by an acid‐salt method. The influence of the size and type of interlayer anions of LDHs on their loading capacity are studied and compared. Here, Methylene Orange (MO) served as the anionic structure to determine the loading capacity. Due to the strongest anion‐exchange capacity of NO3− and larger interlayer distance of MgAl‐NO3 LDHs, they have impressive high loading capacities, which make these useful as absorbents or drug carriers. Additionally, the pH‐dependent release behaviors of MO‐loaded MgAl‐NO3 LDHs are investigated, which dictates both the release profile and maximum release. Above all, based on the study, it is found that the release of LDHs with agents loaded under mildly acidic environments is not based on its partial dissolution, which is commonly indicated. This study provides a better understanding of the loading and release process of LDHs, which allows for better incorporation of LDHs in biomedical‐related applications.

Effect of different organic layered double hydroxides on the anti-aging property of bitumen

Two organic layered double hydroxides (LDHs) were synthesized and utilized to enhance the anti-aging property of bitumen. Fourier infrared spectroscopy and X-ray diffraction showed that sodium dodecyl sulfate was intercalated into the interlayers of LDHs (I-LDHs), and γ-(2,3-Epoxypropoxy)propyltrimethoxy silane was chemically grafted onto the surface of LDHs (S-LDHs). Compared with LDHs, organic LDHs possessed better compatibility and organic LDHs modified bitumen exhibited better performance in high-temperature regions, especially S-LDHs. After aging, the rheological properties dramatically deteriorated. The content of aromatic in bitumen evidently decreased, and the asphaltene noteworthy increased, the colloid structure verged on the gel system. The incorporation of LDHs could relieve the damage of aging on the rheological properties and colloid structure, and strengthen the anti-aging property of bitumen. Moreover, the consequence of LDHs had been further enhanced obviously after organic modification, and S-LDHs exhibited more excellent performance compared with I-LDHs.

Positively-charged nanofiltration membrane constructed by polyethyleneimine/layered double hydroxide for Mg2+/Li+ separation

As an important resource, lithium is abundant in Salt Lake. The high Mg2+/Li+ ratio is the main obstacle to lithium extraction. Positively-charged nanofiltration membrane has shown great potential in the separation of Mg2+/Li+. Herein, we report a facile method to construct positively-charged nanofiltration membrane by polyethyleneimine (PEI) and layered double hydroxide (LDH) nanosheets on hydrolyzed polyacrylonitrile ultrafiltration membrane. Subsequently, the PEI-LDH composite membrane was crosslinked with glutaraldehyde (GA) to improve its stability. The incorporation of LDH could improve the positive charge of the membrane. Then, the obtained PEI-LDH/GA membrane showed an enhanced separation performance for separating Mg2+/Li+ in an aqueous solution. When the Mg2+/Li+ ratio was 10, the membrane showed a separation factor (SMg2+/Li+) of 18.7. Moreover, the membrane could maintain the separation performance for 100 h, which exhibited a potential application in Mg2+/Li+ separation.

Comparative Study of M(Ⅱ)Al (M=Co, Ni) Layered Double Hydroxides for Silicone Foam: Characterization, Flame Retardancy, and Smoke Suppression.

To compare the different actions of the two representative transition metal cations of Co2+ and Ni2+ in layered double hydroxides (LDHs), CoAl-LDH and NiAl-LDH intercalated with CO32− were synthesized, and the chemical structures, microstructures, and surface areas thereof were successfully characterized. Then, the two LDHs were utilized as flame retardants and smoke suppressants for silicone foam (SiF). The densities, flame retardancy, smoke suppression, thermal stabilities, and compressive strengths of the two SiF/LDHs nanocomposites were investigated. The introduction of LDHs slightly decreased the density of SiF due to the catalytic actions of Co and Ni during the foaming process of SiF. With respect to the flame retardancy, the addition of only 1 phr of either CoAl-LDH or NiAl-LDH could effectively improve the limiting oxygen index of SiF from 28.7 to 29.6%. Based on the results of vertical flame testing and a cone calorimeter test, the flame retardancy and fire safety of the SiF were effectively enhanced by the incorporation of LDHs. In addition, owing to the good catalytic action and large specific surface area (NiAl-LDH: 174.57 m2 g−1; CoAl-LDH: 51.47 m2 g−1), NiAl-LDH revealed higher efficiencies of flame retardancy and smoke suppression than those of CoAl-LDH. According to the results of energy-dispersive X-ray spectroscopy, Co and Ni participated in the formation of protective char layers, which inhibited the release of SiO2 into the gas phase. Finally, the influences on the thermal decomposition and compressive strength for SiF resulting from the addition of LDHs are discussed.

The Curing Kinetics of Multiscale [Ni(EDTA)]-2 Intercalated Zn-Al Layered Double Hydroxides: Glass Fiber–Epoxy Composite Prepreg

In the present research, the effect of Zn2Al layered double hydroxides (LDH) and nickel (II)-EDTA complex intercalated LDH (LDH-[Ni(EDTA)]-2) on the cure kinetics of glass fiber/epoxy prepreg (GEP) was explored using nonisothermal differential scanning calorimetry (DSC). The results showed that LDH caused a shift in the cure temperature toward lower temperatures while accelerating the curing of epoxy prepregs. The use of LDH-[Ni(EDTA)]-2 more profoundly influenced the acceleration of the curing process. The curing kinetics of prepregs was assessed through the differential isoconversional Friedman (FR) technique and the integration method of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). A decrease was detected in the E α value of glass fiber/LDH-[Ni(EDTA)]-2/epoxy (GELP) and glass fiber/LDH-[Ni(EDTA)]-2/epoxy (GELNiP) prepregs at small cure degrees relative to GEP, suggesting the catalytic effect of LDH or LDH-[Ni(EDTA)]-2 on the initial epoxy/amine reaction. Furthermore, LDH-[Ni(EDTA)]-2 performed better due to the catalyst role of nickel (II). Moreover, the activation energy exhibited lower reliance on the degree of conversion in the cases of GELP and GELNiP rather than pure epoxy prepregs. An autocatalytic model was used to evaluate the curing behavior of the system. Based on the results, the curing reaction of the epoxy prepreg can be described by the autocatalytic Šesták-Berggren model even after the incorporation of LDH or LDH-[Ni(EDTA)]-2. The kinetic parameters of the autocatalytic model (such as E α , A , m , n ) and the equations explaining the curing behavior of prepregs were introduced as well whose predictions were in line with the experimental findings.

Facile synthesis of layered double hydroxide/superabsorbent polymer composites for water and wastewater treatment

Layered double hydroxides (LDH) possess high anion adsorptivity and are attractive for water and wastewater treatment, but are available mainly in a powder form that has low hydraulic conductivity and difficulties in solid-liquid separation and handling. Incorporation of LDH into a polymer gel produces composite granules that are suitable for use in water and wastewater treatment. This study demonstrates a simple and new method for synthesizing an LDH-containing hydrogel that exhibits high anion adsorption, using SO42− as a model anion. Chloride-containing LDH particles were obtained by coprecipitation, and were subsequently either treated hydrothermally or left untreated. The superabsorbent polymer poly(acrylic acid) was mixed with aqueous suspensions of LDH particles and was swollen in the suspensions to form LDH-containing hydrogels, followed by rinsing with water and vacuum drying. LDH particles appeared to enter gels via macroscopic features—gaps like cracks, slits, and fractures—that may have widened during gel swelling, and larger, hydrothermally-treated LDH particles got stuck in the gaps within gels to a greater extent than smaller, non-hydrothermally treated particles. When the superabsorbent polymer was added to a 5 mM Na2SO4 solution in the absence of LDH particles, the SO42− concentration outside the resulting gel increased by 18%, likely due to electrostatic repulsion between SO42− ions and carboxylate groups in the polymer. Interference of anionic polymer carboxylates groups with SO42− adsorption was assessed. Despite this negative effect of SO42− adsorption by the polymer, 86% of LDH in gel with hydrothermally-treated LDH particles actively adsorbed SO42−, indicating that the easily-synthesized LDH-containing gel is highly effective anion adsorbents.

Mixed Matrix Membrane Incorporating of MgAl-CO3 Layered-Double-Hydroxide for Enhanced Carbon Dioxide Separation

In this study, mixed matrix membranes were fabricated by incorporating MgAl-CO3 layered double hydroxides (LDH) into polysulfone (PSF) coated with low-cost commercial PEBAX polymer for enhancing CO2/CH4 separation. LDH was synthesized via a simple co-precipitation method and flat sheet membranes were fabricated by dry/wet inversion phase. The gas separation performance on pure PSF and LDH/PSF membranes were investigated. The physical property, chemical structure and membrane morphology were characterized by XRD, FTIR, and SEM. The sample membranes were tested with CO2 and CH4 gas for permeance performance and selectivity of CO2/CH4 was calculated. By incorporation of LDH, the CO2 permeance increased about 54.6%. LDH mixed matrix membranes displayed the 18.2 GPU of CO2 permeance and CO2/CH4 selectivity of 18.0. The LDH based membrane produces innovation in membrane technology by improving its morphology and permeance performance with great potential for large-scale CO2 capture and separation.

Effect of layered double hydroxides addition on the ageing and self-healing properties of asphalt binder

In this paper, the effects of Layered Double Hydroxides (LDHs) incorporation on the ageing resistance and self-healing properties of asphalt binder were studied. Matrix asphalt (MA) and LDHs modified asphalt (LMA) binders were aged by short-term thermal oxidation and ultraviolet ageing and their ageing performance was characterized through the analysis of the SARA fractions and temperature sweep test. Frequency sweep test and capillary flow test were conducted to characterize the fluidity of the asphalts, and fatigue life recovery test was used to characterize the asphalt self-healing properties. The main results indicate that under the same ageing conditions, the light component contents of LDHs modified asphalt are higher than that of matrix asphalt and the complex modulus increment of LMA is lower than that of matrix asphalt. It means that LDHs modified asphalt has better anti-ageing performance. Besides, LDHs modified asphalt has higher fluidity and lower self-healing threshold temperature than matrix asphalt binder under the same ageing conditions, indicating that the incorporation of LDHs can effectively retard the reduction of asphalt flow capacity due to ageing. It was also found that asphalt binder containing LDHs had better self-healing potential due to the improvement of the ageing resistance. It was concluded that the addition of LDHs can effectively improve the ageing resistance and self-healing properties of asphalt binder.

Silica/montmorillonite nanoarchitectures and layered double hydroxide-SPEEK based composite membranes for fuel cells applications

Anionic and cationic clays were here evaluated as nanofillers of low sulfonated polyetheretherketone (SPEEK, DS = 56%) for preparation of nanocomposite electrolyte membranes for PEMFC (Proton Exchange Membrane Fuel Cells) applications. A synthetic MgAl layered double hydroxide (LDH) exchanged with sulfate anions and a porous SiO2-montmorillonite heterostructured material containing delaminated clay particles, were added to SPEEK polymer for preparation of composite membranes with different nanofiller content (3, 6 and 9%). The resulting membranes were characterized concerning their structure, morphology and electrical conductivity performance. The incorporation of the MgAl LDH and the SiO2-motmorillonite fillers into the SPEEK seems to enhance water retention and the thermal stability of the resulting composite electrolyte membranes. Moreover, the composite electrolyte membranes show higher proton conductivity than the neat SPEEK membrane (0.023 S cm−1) after incorporation of the LDH and the SiO2-motmorillonite fillers (0.070 and 0.158 S cm−1 respectively) at 120 °C and 100% relative humidity, which can be relevant for increasing the performance at high temperature of this type of membranes in fuel cell applications.

Incorporation of layered double hydroxide nanofillers in polyamide nanofiltration membrane for high performance of salts rejections

Abstract In this work, thin film composite (TFC) membrane embedded with self-synthesized layered double hydroxide (LDH) nanofillers was prepared via interfacial polymerization technique for nanofiltration (NF) process. Prior to filtration experiments, the morphologies and physicochemical properties of the prepared LDH nanofillers and TFC membranes were characterized using TEM, XRD, FESEM, FTIR, AFM, zeta potential analyzer and contact angle goniometer. The results revealed that the self-synthesized LDH nanofillers possessed layered structured materials with typical hexagonal plate-like shape. Meanwhile, it was found that the membrane contact angle decreased remarkably from 53° to 33.96° upon addition of 0.1 wt% LDH nanofillers in the active polyamide layer. TFN membrane of 0.1 wt% LDH loading possessed the highest water flux of 54.62 Lm−2 h−1 at 7 bar. The highest rejections of Na2SO4 (97.3%), MgSO4 (95.5%), MgCl2 (95.2%) and NaCl (63.7%) were also achieved by the TFN embedded with 0.1 wt% LDH in polyamide layer. In addition to the excellent water flux and rejection, incorporation of LDH also enhanced the fouling resistance, proven by the improvement of pure water flux recovery by 52% after BSA filtration. The findings indicated the potential of the newly developed TFN membrane incorporated with LDH nanofillers for efficient NF membrane in water softening and pre-desalination process.

Temperature and frequency‐dependent creep and recovery studies on PVDF‐HFP/organo‐modified layered double hydroxides nanocomposites

ABSTRACTA series of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) loaded with various contents of layered double hydroxides (LDHs) nanoparticles were prepared via a melt mixing method. Detailed investigations on LDH dispersion state in the polymeric matrix conducted by TEM revealed intercalated/exfoliated, and agglomerated structures at low (1 wt %) and high (>3 wt %) loadings of LDH contents, respectively. Wide angle X‐ray scattering and DSC results showed that incorporation of LDH into PVDF‐HFP matrix reduced its overall crystallinity and helped to form polar crystallites, while the crystal size at 020 crystallographic directions was found to be most affected by presence and dispersion state of LDH in the matrix. TGA results showed LDH improved thermal stability of matrix however, unlike many other nanomaterials it significantly reduced the residual mass which highlights catalytic role of LDH in degradation of residual carbon char. Detailed analysis on creep and recovery data over wide range of selected temperatures revealed that the creep compliance of nanocomposites are basically controlled by crystallinity and presence of LDH at low and high temperatures, respectively. Based on obtained storage modulus and creep compliance master curves it was also found that the influence of LDH on decreasing the creep compliance and improving viscoelastic properties of PVDF‐HFP over long time period and over high frequency ranges becomes more pronounced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46352.

Synthesis of carboxymethyl cellulose-g-poly(acrylic acid)/LDH hydrogel for in vitro controlled release of vitamin B 12

Abstract pH-sensitive nanocomposite hydrogels were synthesized from carboxymethyl cellulose-g-poly(acrylic acid) and LDH (Layered Double Hydroxide). Polymeric hydrogels were characterized using FTIR, XRD, SEM, EDX, TEM, DLS, TGA and DSC. The grafting of partially neutralized acrylic acid (AAc) on carboxymethyl cellulose (CMC) backbone was confirmed by FTIR. XRD has confirmed the presence of LDH fillers inside the nanocomposite hydrogels. Scanning Electron Microscopy (SEM) showed rough surface morphology resulting from incorporation of LDH in the composite hydrogels. Transmission Electron microscopy (TEM) and Dynamic Light Scattering (DLS) confirmed the formation of the nanosized composite. Thermal property of the hydrogels was improved with the incorporation of LDH. Higher swelling was observed in basic pH medium. Controlled release of vitamin B12 in artificial gastric fluid (AGF) and in artificial intestinal fluid (AIF) was evaluated during different time periods using an UV–visible spectrophotometer. In vitro release profile of the drugs in various pH conditions, resulted in different controlled release curves.

Incorporation of layered double nanomaterials in thin film nanocomposite nanofiltration membrane for magnesium sulphate removal

Thin film nanocomposite (TFN) membrane with copper-aluminium layered double hydroxides (LDH) incorporated into polyamide (PA) selective layer has been prepared for magnesium sulphate salt removal. 0, 0.05, 0.1, 0.15, 0.2 wt% of LDH were dispersed in the trimesoyl chloride (TMC) in n-hexane as organic solution and embedded into PA layer during interfacial polymerization with piperazine. The fabricated membranes were further characterized to evaluate its morphological structure and membrane surface hydrophilicity. The TFN membranes performance were evaluated with divalent salt magnesium sulphate (MgSO4) removal and compared with thin film composite (TFC). The morphological structures of TFN membranes were altered and the surface hydrophilicity were enhanced with addition of LDH. Incorporation of LDH has improved the permeate water flux by 82.5% compared to that of TFC membrane with satisfactory rejection of MgSO4. This study has experimentally validated the potential of LDH to improve the divalent salt separation performance for TFN membranes.

Active Polymer Nanocomposites: Application in Thermoplastic Polymers and in Polymer Foams

Layered double hydroxides (LDH) are very used as fillers in polymer nanocomposites research. They cannot be used in their pristine form (magnesium and aluminum hydroxycarbonates) because they exhibit strong interlayer electrostatic interactions and tight basal spacings so that they require the intercalation of organic anions into clay galleries. The organic modification of LDH increases the filler-polymer compatibility, enlarges the basal spacing of the lamellae (making easier the insertion of the polymeric chains into the gallery), and promotes the exfoliation of the filler into the polymeric matrix. Organically modified LDH/polymer nanocomposites exhibit improved mechanical, thermal, and chemical properties when they are compared with pristine polymers or conventional composites. Moreover, the incorporation of LDH allows us to obtain materials with specific functionalities. For example, the intercalation of antimicrobial molecules into LDH (such as benzoate or stearate) and the use of the modified nanoparticles as fillers results in nanocomposites with antimicrobial activity. In this paper, several benzoate and/or stearate LDH/polypropylene (PP) nanocomposites have been produced for food packaging applications. The O2 permeability coefficient of the nanocomposite named 1.5% o-benzoate/1.5% o-stearate LDH/PP/3% PP-g-MAH reduces by 20% compared to unfilled PP and 30% compared to unfilled PP/3%PP-g-MAH. It is accepted that in such a nanocomposite, the lamellar structure of LDH creates a more tortuous path for the progress of oxygen molecules reducing the gas diffusion. For the novel nanocomposite material, the physical, morphological, mechanical, and gas barrier properties have been measured and the antimicrobial effect has been evaluated. In this paper, some benzoate LDH/polyurethane foam (PU) nanocomposites have been also produced. The filler dispersion into the PU has been investigated by scanning electronic microscopy. It was observed that organic LDH particles were uniformly dispersed into the walls of cells, forming small aggregates. The morphological properties of the foam have been analyzed by nanotomography. LDH/PU nanocomposite showed antibacterial and improved mechanical properties.

English

The immobilization of a whole microbial cell is an important process used in nanotechnology of biosensors and other related fields, especially the development of bio-hybrid materials based on live organisms and inorganic compounds. Here, we described an essay to develop a bio-hybrid material based on Salmonella Typhimurium cells and layered double hydroxides (LDH). The synthetic clays have a good capacity to be a host matrix for immobilization of live entity like bacteria. The incorporation of LDH in the nutritive broth shows the capacity of bacteria to grow under the inorganic conditions. The immobilization of bacteria onto the LDH Layer deposited on gold wafers was successfully done and the verification of the final material consistence was given by Fourier transform infrared spectroscopy (FTIR) analysis that shows the possibility of various covalent links that can be established between the polar functional group of the cell and the interlayer level in the LDH. The roughness of the surface was given by scanning electron microscope (SEM) imaging and shows the homogeneity of cell distribution on the LDH layer. Key words: Layer double hydroxide, Salmonella Typhimurium, Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), X-ray diffraction (XRD), energy dispersive X-ray (EDX); scanning electron microscope (SEM)

Silica-Based Nanocoating Doped by Layered Double Hydroxides to Enhance the Paperboard Barrier Properties

Paperboard is an environment-friendly multi-layer material widely used for packaging applications. However, for food packaging paperboard lacks essential barrier properties towards oxygen and water vapor. Conventional solutions to enhance these barrier properties (e.g. paperboard film coating with synthetic polymers) require special manufacturing facilities and difficult the end-of-life disposal and recycling of the paperboard. Paperboard coating with silica-based formulations is an eco-friendly alternative hereby disclosed. Silica-nanocoatings were prepared by sol-gel synthesis, with or without the addition of Zn(2)-Al-NO3 layered double hydroxides (LDHs), and applied on the surface (ca 2 g/m2) of industrial paperboard samples by a roll-to-roll technique. The physicochemical features of silica-nanocoatings were studied by FTIR-ATR, SEM/EDS, XRD analysis and surface energy measurements. The barrier properties of uncoated and silica-coated paperboard were accessed by water vapor transmission rate (WVTR) and oxygen permeability (Jo2) measurements. The best barrier results were obtained for paperboard coated with a mixture of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES), with and without the incorporation of LDHs.

Synthesis and Characterization of SPEEK/Layered Double Hydroxide Polymer Nanocomposite for Fuel Cell Applications

The development of sulfonated poly (ether ether ketone)-based (SPEEK) membranes by the incorporation of layered double hydroxide (LDH) as inorganic nanofiller has been achieved and its potential application in proton exchange membrane fuel cells (PEMFCs) has been investigated. The physical properties and proton conductivity of SPEEK matrix incorporated layered double hydroxide (LDH) were analyzed and found that the incorporation of LDH to SPEEK improves the thermal stability, water uptake and proton conductivity compared to the virgin SPEEK. The proton conductivity of the SPEEK/LDH composite membrane containing 3 wt% LDH has been found to be 229.9 mS/cm where as the virgin SPEEK shows the proton conductivity value 147.6 ms/cm at 80 °C and 100 %RH.

06/01900 Experimental studies of a direct methanol fuel cell: Ge, J. and Liu, H. Journal of Power Sources, 2005, 142, (1–2), 56–69

In direct methanol fuel cells (DMFCs), the optimum characteristics of ion-exchange membranes are investigated at high concentrations of methanol feed up to 7 M by modifying the diffusion coefficient and the ionic conductivity of the polyelectrolyte material. A Nafion membrane is modified by the incorporation of layered double hydroxide (LDH) nanoplatelets with different Mg2+:Al3+ ratios. When the feed concentration of methanol is lower than 3 M, the DMFC is controlled by the ionic conductivity of the polyelectrolyte membrane because methanol cross-over is not relatively significant. When the feed concentration is high, however, the diffusion coefficient of methanol is the key factor that determines the performance of the fuel cell. This is due to a high concentration gradient of methanol across the polyelectrolyte membrane. The open-circuit voltage is increased by the decreased diffusion coefficient in LDH/Nafion nanocomposite membranes at methanol feed concentrations up to 7 M; apparently because methanol cross-over is suppressed by the incorporation of LDH. The maximum power density of the DMFC is determined by the two competing transport processes of ion conduction and methanol diffusion, especially at a relatively high methanol concentration, that can provide optimum operating conditions in the membrane.