DMFC Applications Research Articles

Optimizing Sodium Alginate/PVA Polymer Electrolyte Membrane with Montmorillonite for Enhanced Architectural Features and Performance in DMFC Application

Optimizing Sodium Alginate/PVA Polymer Electrolyte Membrane with Montmorillonite for Enhanced Architectural Features and Performance in DMFC Application

Synergistic effect of Ag-doped Mn3O4 and AgCl composite as a regenerable and high-performance catalyst for the oxygen reduction reaction

This work demonstrated the excellent ORR activity of Ag–Mn3O4 and AgCl–Ag:Mn3O4, highlighting the significant role of AgCl in enhancing the catalytic activity of Ag-doped Mn3O4 for DMFC application.

Layer-by-Layer Assembly of CTAB-rGO-Modified MXene Hybrid Films as Multifunctional Electrodes for Hydrogen Evolution and Oxygen Evolution Reactions, Supercapacitors, and DMFC Applications.

Exceptional electrical conductivity and abundance of surface terminations like-F- and OH- leading to hydrophilicity make the family of 2D transition metal carbides/nitrides and carbonitrides (MXene) excellent candidates for energy storage and conversion applications. MXenes, however, undergo restacking of nanosheets via van der Waals interaction, hindering the active sites, leading to slow electronic and ionic kinetics, and ultimately affecting their electrochemical performance. Herein, we report binder-free cetyltrimethylammonium bromide-reduced graphene oxide (CTAB-rGO)-modified MXene hybrid films on nickel foam as a promising noble metal-free multifunctional electrode synthesized via layer-by-layer assembly and dip coating techniques, which effectively reduce restacking while improving the kinetics. The properties of the as-prepared electrocatalysts are investigated using various physiochemical characterizations and electrochemical measurements to accomplish the objective of "creating one kind of electrocatalyst for multiapplication" with a thorough understanding of the relationship between the material structure, morphology, and electrocatalytic performance. In energy conversion, the synergetic effect of MXene and the CTAB-rGO support helped increase the catalytic activity of the composite for electrochemical water splitting, demonstrating a current density of 10 mA/cm2 at an overpotential (η) of 360 V and a Tafel slope value of 56.6 mV/dec for hydrogen evolution reaction and a current density of 10 mA/cm2 at an overpotential (η) of 179 mV and a Tafel slope value of 47.03 mV/dec for oxygen evolution reaction in an alkaline medium. The electrode material also exhibited a higher oxidation current density (373.60 mA/cm2) compared to that of synthesized MXene toward methanol oxidation reaction in direct methanol fuel cell application. Additionally, the energy storage potential of CTAB-rGO modified MXene as electrode materials for supercapacitors with a high specific capacitance (544.50 F g-1 at 0.5 A g-1) and a good capacity retention of 87% after 5000 cycles was studied. These findings of this work showcase the potential of the electrocatalyst in both conversion and storage of electrochemical energy.

Silane cross-linked network and concentrated flexible sulfoalkyl groups for forming a novel C-SPAEK membrane with enhanced methanol resistance and proton conductivity for DMFC applications

In the present work, a novel poly(arylene ether ketone) with a unique molecular design that included concentrated flexible sulfoalkyl groups and a silane cross-linked network (C-SPAEK) was prepared and used as a PEM for DMFCs. The chemical structures, sulfonation degree and phase-separated morphology were characterized and identified by 1H NMR, FT-IR and SAXS. The resulting copolymers exhibited excellent thermal stability (T5%>263.8 °C) and mechanical properties (tensile strength>52.88 MPa). Additionally, the high IEC values and obvious hydrophilic/hydrophobic phase-separated structure (d > 2.71 nm) ensured that the C-SPAEK membranes possessed high proton conductivities. The C-SPAEK PEMs also displayed enhanced methanol resistance and dimensional stability, which were much better than those of a recast Nafion membrane under the same conditions. The C-SPAEK-0.4 membrane maintained a low methanol absorption of less than 48.7%, even in 4 M methanol solution. In particular, the C-SPAEK-0.6 membrane exhibited the best comprehensive performance, with a high proton conductivity (0.164 S cm−1), low methanol uptake (52.1%) and permeability (3.63 × 10−7 cm2 s−1), and maximum power density (83.2 mW cm−2), when immersed in 2 M methanol at 80 °C in a DMFC single-cell. These results suggested that the C-SPAEK membranes were sufficiently tough and had the potential to overcome the problems caused by the high methanol permeability of PEMs. The unique molecular design of C-SPAEK guaranteed a rare combination of high proton conductivity and enhanced methanol resistance, which are the key determining factors for DMFC applications.

Effect of zinc oxide on the mechanical, thermal and physiochemical properties of chitosan-based hybrid membrane for DMFC application

This work uses zinc oxide (ZnO) as a filler to prepare a chitosan-based hybrid membrane. The mechanical, thermal and physiochemical properties of the membranes were studied using different experimental techniques. The water uptake capacity and swelling degree of the composite membranes were increased whereas ion exchange capacity (IEC) decreases with the increase of ZnO content. The ZnO filler reduces the crystalline phase of the hybrid membranes. The hybrid membrane's proton conductivity was measured by EIS experiment and fitted into a comparable circuit model. The ZnO filler improves the membrane's proton conductivity, and the proton transport is controlled by the Grotthus mechanism.

Preparation and characterization of poly (vinyl alcohol)/Carboxymethyl Cellulose/ Acrylamide - based membranes for DMFC applications

Preparation and characterization of poly (vinyl alcohol)/Carboxymethyl Cellulose/ Acrylamide - based membranes for DMFC applications

Characterization of Sodium Alginate Membrane Plasticized by Polyols and Polyamine for DMFC Applications

This study reports the effect of plasticizers namely isopropanol, polyethylene glycol, maltitol and spermidine on the properties of the sodium alginate composite membrane. The concentration of each potential plasticizer was set at minimum to execute performance. Properties of sodium alginate were studied through characterization studies - Field Emission Scanning Electron Microscope (FESEM) to observe on the morphology structure. The membrane performance is also seen through water uptake and swelling ratio tests. Isopropanol produced better plasticizer with the lowest water uptake of 575.53% and less hydrophilic compared to spermidine (1268.46%), polyethylene glycol (1014.30%) and maltitol (595.82%). Further study may require copolymerization to support polyol for ensuring structure firmness. This study proven the plasticizers could enhance membrane’s flexibility in DMFC and becoming a promising choice of additives for better alginate-based membrane establishment.

In-situ preparation of PSSA functionalized ZWP/sulfonated PVDF composite electrolyte as proton exchange membrane for DMFC applications

A series of proton exchange electrolytes were synthesized by blending polystyrene sulfonic acid (PSSA) functionalized ZWP ion exchanger and sulfonated poly(vinylidene fluoride) (SPVDF) as base by using solution casting method. The poly(vinylidene fluoride) was sulfonated by employing a direct sulfonation technique demonstrated in the literature. Surface modification of the ZWP was done to obtain the PSSA-ZWP ion exchanger. The membranes were synthesized by using ZWP and PSSA-ZWP as ion exchangers in the SPVDF polymer matrix. The physicochemical characterization of the membranes was performed by using FT-IR and XRD. The scanning electron microscope (SEM) was used to investigate the surface morphology of the fabricated membranes for any possible defects. Important membrane parameters, such as water uptake (up to 26%), methanol uptake (up to 22%), chemical stability (7.4%) and mechanical stability (tensile strength of up to 44 MPa), were measured and are reported. The ion exchange capacity (max 0.62 meq g−1) and electrochemical characterization of the membranes was conducted and parameters such as transport number (max 0.84) indicating good ion selectivity of the membranes and proton conductivity (max 3.89 mS/cm) were also determined. The single cell DMFC performance of the SPVDF-ZWP-PSSA membrane was evaluated at three different operating temperatures of 30 °C, 60 °C and 90 °C, out of which the synthesized membrane performed best at 60 °C with maximum current density and power density of 49.8 mAcm−2 and 20.1 mWcm−2 respectively.

Functionalization of Reduced Graphene Oxide (Rgo) in Chitosan/Pahae Natural Zeolite-Based Polymer Electrolyte Membranes for Direct Methanol Fuel Cell (Dmfc) Applications

Functionalization of Reduced Graphene Oxide (Rgo) in Chitosan/Pahae Natural Zeolite-Based Polymer Electrolyte Membranes for Direct Methanol Fuel Cell (Dmfc) Applications

Morphology and Topography Studies of Composite Membranes Developed from Chitosan/Phthaloyl Chitosan Consisting Multi-Walled Carbon Nanotube/Montmorillonite as Filler

This work discusses the synthesis and characterizations of the newly developed composite membranes based on chitosan/phthaloyl chitosan (Cs/PhCs) as a matrix with various compositions of multi-walled carbon nanotube/montmorillonite (MWCNT/MMT) filler. The Cs/PhCs/MWCNT/MMT composite membranes are synthesized via the solvent evaporation method and were investigated by Fourier Transform Infrared (FTIR), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and DMFC single cell test. The FTIR characterization result showed that all membranes have origin peaks at 3433, 2943, and 1525 cm-1 contributed to vibrations of O-H, C-H, and N-H group, respectively. Meanwhile, the composite membranes with 7.5 and 8 wt.% filler have characteristic peaks of vibration Si-O-Si, Si-OH, and Si-O at 1209, 886, and 591 cm-1 respectively. Cross-sectional micrographs of SEM and AFM revealed that the composite membrane with 7.5 wt.% filler had moderate surface roughness than the other as-fabricated membranes. As a result, this nanocomposite membrane can be an alternative polyelectrolyte membrane for DMFC applications. The resulting Cs/PhCs/MWCNT/MMT-1 composite membrane has the selectivity up to 5.13×105 S.s.cm-3 with the DMFC performance at 23.60 mW cm-2.

Fabrication and Characterization of Chitosan/N-Phthaloyl Composite Membrane for DMFC Application

Modified chitosan membrane is one of the promising membranes for polymer electrolyte membrane. Chitosan/N-phthaloyl chitosan composite membranes were fabricated to obtain high proton conductivity and low methanol permeability. Membranes were fabricated by casting method and solvent evaporation. Surface morphology, mechanical analysis, methanol permeability, and proton conductivity were used to characterize the overall properties. FT-IR spectra exhibited the presence of interaction of chitosan and n-phthaloyl/chitosan. SEM analysis showed that the surface roughness of composite membrane increases as the n-phthaloyl loading increases. The highest proton conductivity of synthesized membrane is at 2.4 mS.cm-1 and is higher than pristine chitosan membrane at 1.6 mS.cm-1. Moreover, with n-phthaloyl/chitosan addition, the methanol permeability was also improved. The correlation between proton conductivity and methanol permeability in composite membranes suggests that the blend has its potential in DMFC application.

Improvement in properties of nanocrystalline cellulose/poly (vinylidene fluoride) nanocomposite membrane for direct methanol fuel cell application

Improving methanol resistance and dimensional stability are the main challenges in polymer electrolyte membranes for direct methanol fuel cell application. In this study, nanocrystalline cellulose (NCC) was initially synthesized and then blended together with poly (vinylidene fluoride) (NCC/PVDF) and the resultant dope solution was used for the fabrication of membranes via solution casting method. The physical characteristics of the membranes were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Crystallinity differences between all the membranes were confirmed by x-ray diffraction (XRD). Results revealed that the swelling ratio at 80° C and methanol permeability of NCC-3/PVDF were as low as 15.19% and 2.69 × 10−9 cm2/s, respectively compared to Nafion 117 (18.25% and 2.74 ×10−6 cm2/s). It was found that blending hydrophilic NCC with hydrophobic PVDF could profoundly influence the physical properties of the membrane. High crystallinity structure of NCC/PVDF membrane significantly improved the dimensional stability and reduce methanol permeation rate. Although the proton conductivity of NCC-3/PVDF (7.57 ×10−2 mS cm−1) is low, its selectivity (28.141 ×103 Scm−3s) was higher than that of Nafion 117 (0.074 ×103 Scm−3s) due to improvements in methanol barrier. The alternative membrane prepared from NCC and PVDF successfully overcame the weaknesses of Nafion 117, hence exhibiting its potential for DMFC application.

Highly selective SPEEK/ENR blended polymer electrolyte membranes for direct methanol fuel cell

Sulfonated poly (ether ether ketone) (SPEEK) at higher degrees of sulfonation (DS) produced high proton conductivity, but it is impractical for DMFC application due to excessive swelling and severe methanol crossover. In this study, a novel blended membrane based on SPEEK at higher degrees of sulfonation (DS) of 80% and epoxidized natural rubber (ENR-50) are prepared at different mass ratio of SPEEK to ENR-50 (9.5:0.5, 9.0:1.0, 8.5:1.5, 8.0:2.0, and 7.5:2.5) via solution intercalation method. The influence of ENR-50 loading on the physical properties of SPEEK blends membranes was investigated and compared with the pristine SPEEK and Nafion117 membranes. The blended membranes were characterized by FTIR, which showed a successful chemical interaction between ENR-50 and SPEEK matrix. SEM images revealed a uniform dispersion of ENR-50 droplets in the polymer structure. The water uptake and methanol permeability of SPE50 membrane were found to be decreased with increasing of ENR-50 content. The highest proton conductivity of SPE50 membrane obtained was 47% higher than pure SPEEK, whereas the lowest permeability value obtained was 21 times lower than Nafion117 membrane. Consequently, incorporation of ENR-50 into SPEEK matrix has substantially enhanced the selectivity of the membrane by five folds. Apparently, this newly developed SPE blend membrane can be listed as one of the potential proton electrolyte membranes for the usage in DMFCs.

Preparation and characterization of proton exchange polyvinylidene fluoride membranes incorporated with sulfonated mesoporous carbon/SPEEK nanocomposite

Sulfonation of mesoporous carbon CMK-3 (sCMK-3) prepared by nano-casting technique was carried out post synthesis using one-step process. The incorporation of the acid groups was confirmed using XRD, Raman spectroscopy, FTIR, SEM, TEM and BET isotherm. The sCMK-3 was incorporated into sulfonated poly(ether ether ketone) to form a nanocomposite which was introduced into polyvinylidene fluoride matrix to form a proton exchange membrane. The physicochemical characteristics of the nanocomposite incorporated membranes were characterized using FTIR, ionic exchange capacity, water uptake, swelling ratio, mechanical stability and TGA. The nanocomposite incorporated membranes showed greater surface wettability and higher ion-exchange capacity. The presence of the –SO3H acid groups plays a major role in improving the proton conductivity through the Grotthuss-type mechanism. M4 membrane was identified to be a suitable replacement in the DMFC as it had sufficiently high tensile strength (862.2 MPa), high proton conductivity (0.081 S cm−1) at 45 °C and ultra-low methanol permeability (2.17 × 10−8 cm2 s−1). No evident hydrolytic damage could be identified and had sufficiently high thermal stability and hence can be proposed as a suitable alternative for Nafion membranes in high temperature, low humidity DMFC applications.

Barrier properties of sulfonated polysulfone/layered double hydroxides nanocomposite membrane for direct methanol fuel cell operating at high methanol concentrations

High performing and cost effective nanocomposite membranes for DMFC application are synthesized by incorporating hygroscopic layered double hydroxides (LDH) particles into sulfonated polysulfone (sPSU). A significant improvement in the dimensional stability as well as in the water and methanol molecular dynamics of the sPSU_LDH composite membrane is observed in comparison with both pristine sPSU and Nafion 212. The strong electrostatic interaction occurring between positively charged LDH platelets and negatively charged polymer chains of sPSU alters the microstructure of the ionic domains, allowing an effective reduction of the methanol permeability whilst improving the proton conductivity. The methanol crossover measurements confirmed that sPSU_LDH membranes are able to withstand high methanol concentration without significant aftermath on the chemical stability of the electrolyte. The features enable the single DMFC assembled with the sPSU_LDH nanocomposite to achieve the remarkable power density of 150 mW cm−2 at 80 °C in 5 M methanol solution.

Synthesis and Characterization of Chitosan-Polyvinyl Alcohol-Fe2O3 Composite Membrane for DMFC Application

This study investigates the utilization of different compositions of Fe2O3 and polyvinyl alcohol (PVA) to modify chitosan in order to prepare a composite membrane. The membranes were synthesized using the phase inversion method and extensively characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical properties analysis, and water uptake analysis, whereby SEM was used to confirm the morphology of the composite membranes. Different electrochemical properties such as ion exchange capacity, proton conductivity, and methanol permeability of these membranes were also measured. The results showed that increasing the PVA mass improved the water uptake, ion exchange capacity (IEC), and proton conductivity because the PVA addition increased the hydrophilicity of the membrane; thus, the pore surface on the membrane was more open, which also caused higher membrane permeability. However, the methanol permeability values of all composite membranes were lower than that of Nafion. The highest IEC and proton conductivity were obtained for the CS-PVA-H3070 membrane, with values of 4.300 meq/g and 6.71 × 10−2 S·cm−1, respectively. The mechanical strength of these membranes showed that the PVA addition increased the elongation break and decreased the tensile strength of the membrane. The results imply that the chitosan membrane modified with PVA and Fe¬2O3 has a potential for DMFC applications.

Improving the performance of sulfonated polymer membrane by using sulfonic acid functionalized hetero‐metallic metal‐organic framework for DMFC applications

Proton transport played a crucial part in the fuel cells, sensors, and batteries. The electrolyte used in fuel cells should possess high proton conductivity and good chemical stability. Herein, taking advantage of the high proton conductivity of metal-organic framework (MOF) and the good chemical stability of branched polymers, a new heterometallic mediated MOF (Zr-Cr-SO3H) is synthesized and utilized as a filler in the highly branched sulfonated polymer (BSP). In addition, Zr-SO3H MOF is also prepared for comparison. Transmission electron microscope study shows that the prepared MOF particles are spherical in size and interconnected through nanosheets. The optimized quantity of MOFs inside the polymer matrix improves the water sorption, mechanical property, and proton conductivity. The composite membranes display an improved open-circuit voltage than the pristine BSP membrane. By comparing the Zr-SO3H MOF incorporated composite membrane, Zr-Cr-SO3H MOF incorporated composite membranes display higher proton conductivity and peak power density in a single-cell test. In particular, the single-cell fabricated with Zr-Cr-SO3H MOF incorporated composite membrane is able to reach the peak power density of 64.6 mWcm−2 at 60°C, which is 26% greater than the Nafion 212 membrane. Furthermore, this work offers a new strategy for the utilization of hetero-metal MOF as a filler for proton exchange membrane applications.

Sodium alginate/alumina composite biomembrane preparation and performance in DMFC application

The potential of alumina has been studied as nanofiller in proton exchange membrane (PEM) based sodium alginate biopolymer as the matrix phase. The fabricated membrane improved much better than pure sodium alginate membrane in terms of water uptake, ion exchange capacity, methanol permeability, proton conductivity and oxidative stability results. The well connection between matrix and filler leads in excellent performance by the composite which has good new properties. The best membrane (SAL3) performed highest proton conductivity of 25.6 × 10−3 S cm−1 at 60 °C temperature. The determination on proper amount of nanofiller has result in enhancement of performance such as the conductivity and methanol permeability. Fortunately, the weakness of sodium alginate that so hydrophilic also being covered properly in the presence of alumina which leads in good liquid uptake capacity and swelling ratio. The FESEM, FTIR, XRD, TGA/DSC and mechanical strength analysis has been implemented in order to study the characteristics of the SA/Alumina nanocomposite biomembrane.

Ni/NiO coated on multi-walled carbon nanotubes as a promising electrode for methanol electro-oxidation reaction in direct methanol fuel cell

In the current work, non-precious Nickel/Nickel oxide (Ni/NiO) and Ni/NiO/multi-walled carbon nanotube (Ni/NiO/MWCNT) composites were synthesized by combustion method for methanol oxidation. The fabricated catalysts were characterized by XRD, EDS, SEM, and TEM. From TEM micrographs, Ni/NiO with the particle size in the range of 20–30 nm was synthesized and uniformly embedded on MWCNTs with a diameter of 10–40 nm. It was found from the EIS results that the Ni/NiO/MWCNT has a lower charge transfer resistance than Ni/NiO, indicating a faster electron transfer from the Ni/NiO/MWCNT to methanol and faster reaction kinetics. The Ni/NiO/MWCNT catalyst showed a maximum peak current density of 15.94 mA cm−2 (49.81 mA mg−1) in peak potential of 0.43 mV (at room temperature) and long-term stability, showing good electrocatalytic activity. Also, DMFC single cell test based Ni/NiO/MWCNT anode catalyst showed a maximum power density of 41.8 mW cm−2, indicating its promising application in DMFC.

Nanocomposite membrane electrolyte of polyaminobenzene sulfonic acid grafted single walled carbon nanotubes with sulfonated polyether ether ketone for direct methanol fuel cell

Nanocomposite membranes of sulfonated polyether ether ketone (sPEEK) are prepared with polyaminobenzene sulfonic acid grafted single-walled carbon nanotubes copolymer (PABS-SWCNT) and its zwitterion interactions are studied. The nanocomposite membranes are prepared through solution cast technique using PABS-SWCNT as additive in different weight % (0.1, 0.15, and 0.2) ratio. The additive and nanocomposite membranes are characterized for its surface morphology, composition, thermal and physico-chemical properties. The nanocomposite membrane comprising optimized content of PABS-SWCNT (0.15 wt %) shows improved proton conductivity and reduced methanol crossover resulting in enhanced DMFC peak power density of 150 mW cm−2 in comparison to 110 mW cm−2 for sPEEK and 80 mW cm−2 for Nafion® 117 respectively. The improved durability till 100 h for sPEEK/PABS-SWCNT (0.15 wt %) compared to sPEEK and Nafion-117 confirms its viability in DMFC application.