DMFC Applications Research Articles

Mesopore‐controllable Carbon Aerogel and their Highly Loaded PtRu Anode Electrocatalyst for DMFC Applications

AbstractCatalyst loading and layer thickness are crucial factors to enhance the cell performance and to reduce cost of membrane electrode assemblies (MEAs). Outstanding properties, such as large surface area to disperse metal nanoparticles and sufficient pore volume and size, is needed in utilization of fuel cell. Carbon aerogels are one of the good candidates that meets the above conditions. Those are synthesized by polycondensation reaction of resorcinol and formaldehyde (RF) polymer, supercritical drying to keep pore skeleton structure caused by capillary force and calcination of RF polymer in nitrogen atmosphere to be controllable meso pore (2∼43 nm) as role of support for electric conductor and dispersion of metal nanoparticles. In order to utilization of anode catalyst in direct methanol fuel cell, highly loaded (80 weight percent) platinum and ruthenium onto carbon aerogel are synthesized by Bönnemann colloid method. The single cell test of carbon aerogel supported PtRu anode catalyst is performed and over 40 nm pore sized‐catalysts are the best performance due to sufficient surface area to anchor uniform and small metal nanoparticles and good pathway to drive fuel and outgas even though PtRu nanoparticles are anchored on the outer surface of carbons.

Highly branched poly (arylene ether)/surface‐functionalized fullerene‐based composite membrane electrolyte for DMFC applications

In the article by Neelakandan et al,1 the second affiliation was missing. The corrected affiliations for all authors are shown above.

Electro-spun of novel PVDF-Pt-Pd/RGO-CeO2 composite nanofibers as the high potential of robust anode catalyst in direct methanol fuel cell: Fabrication and characterization

For the first time, the novel of PVDF-Pt-Pd/RGO-CeO2 composite nanofibers were successfully fabricated by a facile and effective approach of electrospinning method. The as-synthesized PVDF-Pt-Pd/RGO-CeO2 composite nanofibers were characterized in term of surface morphology, crystallinity and structural properties. Morphological and structural characterizations indicated that the Pt-Pd/RGO-CeO catalysts were successfully decorated homogenously on the surface of PVDF nanofiber. The as-prepared PVDF-Pt-Pd/RGO-CeO2 composite nanofibers with the large specific surface area could possibly open up as the new catalyst material for DMFC application.

A Highly Efficient and Stable Copper BTC Metal Organic Framework Derived Electrocatalyst for Oxidation of Methanol in DMFC Application

In present work the development of copper benzenetricarboxylic acid metal organic framework (Cu-BTC MOF) based electrocatalyst and the effect of graphene oxide on catalytic activity of metal organic framework were studied for methanol oxidation reaction. Cu-MOF was prepared by a facile hydrothermal method and graphene oxide flakes were synthesized via improved Hummer’s method. Surface morphological studies of catalyst were analyzed through scanning electron microscopy technique, which revealed cubic structure of crystals, while the crystallinity and functional groups present were characterized through X-ray Diffraction and FTIR spectroscopy respectively. Electrochemical studies were conducted by using cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry techniques. Among all series of catalyst, 5 wt% GO/Cu-MOF exhibit highest current density of 120 mA/cm2 at a scan rate value of 50 mV/s at a voltage of 0.9 V.

Highly branched poly(arylene ether)/surface functionalized fullerene‐based composite membrane electrolyte for DMFC applications

Highly branched poly(arylene ether)/surface functionalized fullerene‐based composite membrane electrolyte for DMFC applications

Fabrication and characterization of PVA/NNSA/GLA/nano-silica proton conducting composite membranes for DMFC applications

ABSTRACTBlends of PVA and 2-nitroso-1-naphtol-4-sulfonic acid (NNSA) ranging from 10 to 40 wt% were crosslinked in the presence of glutaraldehyde (GLA) to produce hybrid membranes. The structure and morphology of the hybrid membranes were studied by XRD, FE-SEM, EDX, and elemental mapping experiments. The mechanical performance and thermal stability of the membranes were also examined by dynamic mechanical analysis (DMA) and thermogravimetry analysis (TGA), respectively. Increasing the concentration of NNSA resulted in the improvement of mechanical and thermal performances of the membrane. The addition of NNSA and SiO2 to the solution of PVA makes the resultant hybrid membrane more hydrophilic, and therefore, the proton conductivity, water uptake and ion exchange capacity (IEC) improved. The highest proton conductivity value (0.18 S cm−1 at 30 °C) was found for the PVA/GLA/NNSA (40 wt%)/SiO2 (5 wt%) composite membrane. It was also demonstrated that the methanol permeability values decreased with increasing NNSA content.

Porous Proton Exchange Membrane Based Zeolitic Imidazolate Framework-8 (ZIF-8)

Metal-organic frameworks (MOFs) are emerging material class for the past few years due to its tailorability characteristics for various applications. However, the research and development (RD in conjunction with the properties, the synthesis and fabrication of ZIF-8 membrane as alternative proton conductor and methanol barrier for DMFC application have also been highlighted.

Sulfonated poly(phenylene ether ether sulfone) membrane tailored with layer‐by‐layer self‐assembly of poly(diallyldimethylammonium chloride) and phosphotungstic acid for DMFC applications

ABSTRACTPoly(diallyldimethylammonium chloride) (PDDA) and phosphotungstic acid (PTA) were used as cationic and anionic polyelectrolyte layers, respectively, in an alternating fashion to enhance the methanol barrier property and oxidative stability of sulfonated poly (phenylene ether ether sulfone) (SPEES) proton exchange membranes (PEMs). The multilayer PEMs were characterized by AFM, FTIR, and AC impedance spectroscopy. Methanol permeability of the multilayered membranes was found to be much lower than the bare SPEES membrane. The multilayered membranes displayed significantly improved oxidative stability and dimensional stability compared to pristine SPEES membrane. Conversely, the water uptake (%) and proton conductivity (S cm−1) of the prepared membranes decrease to some extent with increasing the PDDA/PTA bilayers in comparison to the pristine SPEES membrane. The maximum relative selectivity (2.23 × 104 S cm−3 s) and retained weight (88.9%) were observed for SPEES‐[PDDA/PTA]5 multilayered membrane. The obtained results exposed the possibility of SPEES‐[PDDA/PTA]5 multilayered membrane to serve as high‐performance PEMs in direct methanol fuel cells. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47344.

Performance of crosslinked sodium alginate/sulfonated graphene oxide as polymer electrolyte membrane in DMFC application: RSM optimization approach

DMFC received great consideration since it was developed due to its efficiency in electricity production and easy start-up and process. The selectivity of sodium alginate-based membrane as a function of sulfonated graphene oxide and glycerol content is analysed using response surface methodology. It is observed that the properties of the membrane are strongly influenced by the glycerol and sulfonated graphene oxide loading in order to produce the optimum morphology and conducting properties, thus affecting the selectivity of the membrane and consequently the overall performance of the direct methanol fuel cell. The objective of this study is to determine the parameters that significantly affecting the performance of the membrane. Two parameters were taken into consideration that is the weight percentage of sulfonated graphene oxide and glycerol loadings. Both are determined approximately 0.5 wt% to 5 wt% and 0.5 ml–6.0 ml, respectively. The best selectivity result is achieved by using SA/SGO biomembrane with loadings of 2.78 wt% SGO and 3.11 ml of glycerol, respectively. The selectivity is determined as 12.956 × 104 S scm−3. This study proves that the sulfonated graphene oxide and glycerol improved the final membrane structures and performances of the membrane based on numerical analysis, the observation from field emission scanning electron microscopy, atomic force microscope structural analysis as well as the performance of direct methanol fuel cell.

Molecular dynamics simulations of sodium alginate/sulfonated graphene oxide membranes properties

The influence of methanol as a solvent on the properties of sodium alginate/sulfonated graphene oxide (SA/SGO) membranes was explored in water-methanol mixed conditions with various methanol concentrations and temperatures through molecular dynamics simulations. The methanol uptake of the membrane showed an isolation phase determined from the simulation results. The distance between the sulfonic acid groups increased in higher methanol concentrations, as observed from S-S RDFs. Furthermore, the distance between the SA-chain RDFs and the solvent molecules was analysed to determine a) the affinity of water towards the sulfonic acid groups and b) the affinity of the aromatic backbone of the SA towards methanol molecules. A decrease in water molecule diffusion led to an increase in methanol diffusion and uptake. SA/SGO membranes exhibited a smaller diffusion coefficient than that for the Nafion membranes, as calculated from simulation results and compared to the experimental work. Additionally, the diffusion ability increased at higher temperatures for all permeants. The interaction information obtained is useful for DMFC applications.

In-situ precise electrocatalytic behaviors of Pt/C and PtRu/C for methanol oxidation of DMFCs via the designed micro-MEA

Modified micro-MEA is developed and employed to evaluate the electrocatalytic performance of Pt/C and PtRu/C. Firstly, micro-MEA displays better electrocatalytic performance including lower onset potential and higher peak current in comparison with traditional glass carbon electrode (GCE), because that micro-MEA effectively avoids interferences from specific adsorption of bisulfate ions on platinum and improve mass transfer of the fuel. Then, evaluation of the effect of Nafion content and methanol concentration on the MOR performance of Pt/C and PtRu/C is carried out. The results reveal that Pt/C shows optimized performance with 30 wt% Nafion in low concentration methanol (0.5–1 M), while PtRu/C displays best performance when Nafion content was adjusted to 10 wt% because of easier formation of complete proton pathway and triple-phase boundary (TPB) compared to Pt/C, indicating that the optimized in-situ work condition is significantly different for different electrocatalysts. Our work in this paper indicates that micro-MEA as a kind of in-situ characterization method can give more precise electrocatalytic performance of electrocatalysts close to work condition and facilitate their sieving and further application in DMFC.

Effect of Co‐Ni Ratio in Graphene Based Bimetallic Electro‐catalyst for Methanol Oxidation

AbstractIn this paper the electro‐catalytic oxidation of methanol is studied on the non‐noble catalysts Ni–Co/graphene. The bimetallic electro‐catalyst was prepared with different Co–Ni ratios by using simple solution synthesis method. The synthesized materials were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM) for their structure and morphological changes. The electro‐catalytic activity of Ni–Co/graphene for methanol oxidation was investigated by cyclic voltammetry (CV) on glass carbon electrode (GCE) in alkaline medium with 1M methanol solution. The results of various electro‐catalysts have shown significant electro‐oxidation towards methanol. Increasing the Ni concentration in catalyst has promoted the oxidation reaction at the Co–Ni/graphene catalyst. This study reveals that the low‐cost electro‐catalyst Ni–Co/graphene has great potential for DMFC applications.

Cross-linked fully aromatic sulfonated polyamide as a highly efficiency polymeric filler in SPEEK membrane for high methanol concentration direct methanol fuel cells

The current direct methanol fuel cells are still largely limited to the neat methanol operation due to the high methanol permeation of the currently used Nafion membranes. To achieve high methanol concentration DMFC application of the sulfonated poly(ether ether ketone) (SPEEK)-based proton exchange membrane, the neat SPEEK membrane is here modified by blending with the designed cross-linked fully aromatic sulfonated polyamide (Cr-fa-SPA). As the similar fully aromatic features of the SPEEK and the Cr-fa-SPA and the formed hydrogen bonding interactions between the SPEEK and the Cr-fa-SPA, the SPEEK/Cr-fa-SPA membranes show good compatibility, which is beneficial for the construction of the uniform and contact morphology of the membrane. In addition, the cross-linking network and the hydrogen bonding interactions in the SPEEK/Cr-fa-SPA membranes are favorable for enhancing the dimensional stability and reducing the methanol permeation. In particular, the lowest methanol permeability of 0.46 × 10−7 cm2/s is successfully obtained by blending 40 wt% Cr-fa-SPA in the SPEEK/Cr-fa-SPA membrane, which is almost two magnitudes lower than that of the Nafion 117 membrane. Finally, the SPEEK/Cr-fa-SPA DMFC devices were successfully demonstrated with the highly concentrated 20 M methanol fuels with remarkable performance.

Role of structural modifications of montmorillonite, electrical properties effect, physical behavior of nanocomposite proton conducting membranes for direct methanol fuel cell applications

AbstractProton exchange membranes have been synthesized from polyimide (PI) doped with different contents of montmorillonite (MMT) which was obtained by solution casting technique. The enhancement of conductivity was achieved through modification with the MMT. Prepared membranes were systematically characterized in terms of ion exchange capacity, water uptake, methanol uptake, swelling behavior and proton conductivity. Fourier transform infrared spectroscopy and X-ray diffraction measurements were used to confirm the structures of the PI/MMT composite electrolyte membranes. SEM surface morphological images of the composite membranes showed that the MMT nanoclay particles were dispersed uniformly within the membrane what was also reflected in XRD results which indicated a good compatibility of MMT particles with the polymer complex. The TGA spectra showed that the thermal stability of the membrane was reduced by adding MMT into the polymer network. The prepared membrane with 10 wt.% of modified MMT exhibited the highest proton conductivity value of 7.06 × 10-2S·cm-1at 70 °C. These results imply the potential application of the PI/MMT composite membranes as improved PEMs for DMFC applications.

Enhanced Swelling and Barrier Properties Stability of SPEEKbased Polymer Electrolytes Nanocomposite Membran

The objective of this study is to prepare SPEEK/Cloisite15A®/TAP nanocomposite membranes and to characterize their physicochemical properties as polymeric electrolyte nanocomposites. SPEEK membranes with various degrees of sulfonation (DS) were first prepared. Subsequently, 1 wt. % of Cloisite15A® and 2,4, 6–triaminopyrimidine (TAP), respectively, were introduced into the SPEEK matrices via solution intercalation method. The Cloisite15A® and TAP additives were used as reinforcing material for the SPEEK/Cloisite15A®/TAP (SP/CL/TAP) nanocomposite membranes in terms of the barrier properties, swelling and morphological structure. The effect of DS on the SP/CL/ TAP nanocomposite membranes was studied in terms of their swelling behavior, proton conductivity and methanol permeability. Field emission scanning electron micrographs (FESEM) and X–Ray diffraction (XRD) patterns confirmed that the Cloisite15A® particles were completely distributed to allow the nanosize dispersion in the polymer matrix. The swelling behavior of SPEEK membrane at DS of 88% was improved in the presence of Cloisite15A® and TAP. All SPEEK nanocomposite membranes studied exhibited improved methanol barrier properties compared with the parent SPEEK membranes. Owing to significant conductivity, remarkable barrier properties, high swelling stability and outperformed DMFC performance, SP63/CL/TAP nanocomposite membranes can be considered as a polymer electrolyte membrane for DMFC applications.

Pd nanoparticles-embedded carbon nanotube interface for electrocatalytic oxidation of methanol toward DMFC applications

Pd nanoparticles-embedded multiwalled carbon nanotubes (Pd–MWCNTs) were synthesized via in situ chemical reduction method, which provided promising results for preparing finely divided and uniform sized Pd nanoparticles supported on MWCNTs. The Pd–MWCNT catalysts were synthesized in three different weight (wt) ratios of Pd and MWCNT (1:5, 2:5 and 3:5). Morphology and crystallinity of the catalysts were studied by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Electrocatalytic activity of these catalysts toward methanol oxidation was analyzed with two different dispersing agents, such as chitosan (CS, 0.1% w/v) and Nafion (Nf, 0.05% w/v), for the preparation of catalytic inks. Dramatic increases in the electrocatalytic activity of Pd–MWCNT–CS catalysts compared to Pd–MWCNT–Nf catalysts toward methanol oxidation were revealed from cyclic voltammetric, chronoamperometric and CO stripping analysis studies. The anodic peak current densities of the Pd–MWCNT (2:5 wt ratio) interface prepared with chitosan and Nafion inks in alkaline 1 M CH3OH were 2541 and $$1 0 4 1\,\,{\text{A}}\,\,\mathop {{\text{g}}^{ - 1} }\nolimits_{\text{Pd}}$$ , respectively. High CO tolerance of the Pd–MWCNT catalysts was ascertained from the ratio of peak currents and coulombic charges of forward and reverse scans (I f/I b and Q f/Q b) of CV studies and from the less positive potentials for CO stripping, as low as − 0.2 V versus Ag|AgCl. The steady-state current density for methanol oxidation at Pd–MWCNT–CS electrode is nearly five times higher than that of Pd–MWCNT–Nf electrode.

Novel Slightly Reduced Graphene Oxide Based Proton Exchange Membrane with Constructed Long-Range Ionic Nanochannels via Self-Assembling of Nafion.

A facile method to prepare high-performance Nafion slightly reduced graphene oxide membranes (N-srGOMs) via vacuum filtration is proposed. The long-range connected ionic nanochannels in the membrane are constructed via the concentration-dependent self-assembling of the amphiphilic Nafion and the hydrophilic-hydrophobic interaction between graphene oxide (GO) and Nafion in water. The obtained N-srGOM possesses high proton conductivity, and low methanol permeability benefitted from the constructed unique interior structures. The proton conductivity of N-srGOM reaches as high as 0.58 S cm-1 at 80 °C and 95%RH, which is near 4-fold of the commercialized Nafion 117 membrane under the same condition. The methanol permeability of N-srGOM is 2.0 × 10-9 cm2 s-1, two-magnitude lower than that of Nafion 117. This novel membrane fabrication strategy has proved to be highly efficient in overcoming the "trade-off" effect between proton conductivity and methanol resistance and displays great potential in DMFC application.

Synergistic effect of graphene oxide and carbon nanotubes on sulfonated poly(arylene ether nitrile)-based proton conducting membranes

A strategy to prepare graphene oxide (GO)/carbon nano-tubes (CNTs)/sulfonated poly(arylene ether nitrile) (SPEN) composite membranes aimed for the proton exchange membrane is presented herein. GO and CNTs were incorporated into SPEN to improve the performances of proton exchange membrane. To study the synergistic effect of GO and CNTs, GO/SPEN and CNTs/SPEN membranes were also fabricated. The influences of GO and CNTs upon the microstructures, including thermal and mechanical properties, water uptake, swelling, proton conductivity and methanol permeability of composite membranes were investigated in detail. The membranes combining GO and CNTs could effectively avoid the self-agglomeration of GO or CNTs. In such a way, efficient proton transport channels were constructed by homogeneous dispersion of GO and CNTs within SPEN, leading to enhancement of proton conductivity. The proton conductivity of GO/CNTs/SPEN composite membrane with the ratio of 2:2 achieved the highest value of 0.1197 S/cm at 20 °C. Meanwhile, low methanol permeability (2.015 × 10−7 cm2 s−1) was still maintained. Consequently, the combination of CNTs and GO exhibited a favorable synergistic effect on the selectivity of proton exchange membrane, which is better than pure SPEN, Nafion 117, GO/SPEN, and CNTs/SPEN membranes. This feasibility study could provide an alternative approach to design GO/CNTs-based proton-conducting membranes for DMFC applications.

The Morphology Effect on the Selectivity of SPEEK/ENR Membranes for Direct Methanol Fuel Cell

The objective of this study is to investigate the morphology effect of ENR-50 content on the conductivity and methanol permeability of SPEEK/ENR-50 membranes for DMFC application. Three different ratios (9.5:0.5, 8.5:1.5 and 7.5:2.5) of blended SPEEK/ENR-50 membranes were prepared via solution intercalation method. The cross sectional images of the all SPEEK/ENR-50 membranes studied by SEM shows an existence of ENR-50 droplets in SPEEK matrix which decrease in size with an increasing of ENR-50 content from 1.5 wt% to 2.5 wt%. The study of the performances of the blended membranes shows that the proton conductivity and methanol permeability of the membranes decrease with an increasing of ENR-50 content. However, the proton conductivity of the blended membrane with 0.5 wt% ENR-50 content (9.66x10-3 S cm-1) proven higher than pristine SPEEK but lower than Nafion 117. The barrier performance of all SPEEK/ENR-50 membranes was enhanced compared to the expensive Nafion 117 membrane and pristine SPEEK. Consequently, by incorporating ENR-50 content into SPEEK membrane, the selectivity of the membranes has considerably increased.

The preparation and application of a ROMP-type epoxy-functionalized norbornene copolymer and its hybrid alkaline anion exchange membranes

A ROMP-type epoxy-functionalized norbornene copolymer and its hybrid alkaline anion exchange membranes were prepared and studied for DMFC application.