Showing papers on "Direct methanol fuel cell published in 2015"

Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphene.

Abstract: Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum-nickel hydroxide-graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts.

Dramatic Improvement in Water Retention and Proton Conductivity in Electrically Aligned Functionalized CNT/SPEEK Nanohybrid PEM

Abstract: Nanohybrid membranes of electrically aligned functionalized carbon nanotube f CNT with sulfonated poly ether ether ketone (SPEEK) have been successfully prepared by solution casting. Functionalization of CNTs was done through a carboxylation and sulfonation route. Further, a constant electric field (500 V·cm–2) has been applied to align CNTs in the same direction during the membrane drying process. All the membranes are characterized chemically, thermally, and mechanically by the means of FTIR, DSC, DMA, UTM, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in hybrid membranes are established by FTIR. Physicochemical measurements were done to analyze membrane stability. Membranes are evaluated for proton conductivity (30–90 °C) and methanol crossover resistance to reveal their potential for direct methanol fuel cell application. Incorporation of f CNT reasonably increases the ion-exchange capacity, water retention, and proton conductivity while it reduces the methanol perme...

A review on direct methanol fuel cells–In the perspective of energy and sustainability

Abstract: The direct methanol fuel cell (DMFC) enables the direct conversion of the chemical energy stored in liquid methanol fuel to electrical energy, with water and carbon dioxide as by-products. Compared to the more well-known hydrogen fueled polymer electrolyte membrane fuel cells (H 2 -PEMFCs), DMFCs present several intriguing advantages as well as a number of challenges. This review examines the technological, environmental, and policy aspects of direct methanol fuel cells (DMFCs). The DMFC enables the direct conversion of the chemical energy stored in liquid methanol fuel to electrical energy, with water and carbon dioxide as byproducts. Compared to the more well-known hydrogen fueled PEMFCs, DMFCs present several intriguing advantages as well as a number of challenges. Factors impeding DMFC commercialization include the typically lower efficiency and power density, as well as the higher cost of DMFCs compared to H 2 -based fuel cells. Because of these issues, it is likely that DMFC technology will first be commercialized for small portable power applications (e.g., the displacement of batteries in consumer electronic applications), where the shorter product lifetimes (∼ 1–2 yrs for a battery versus 8–15 yrs for a car) and the much higher price points (∼ $10/W for a laptop battery vs. ∼ $0.05/W for a vehicle engine) provide a more attractive entry point. While such applications are not likely to significantly impact the global energy sustainability picture, they provide an important initial market for fuel cell technology. As such, in this review, we provide an overview of recent research and the challenges to the development of DMFCs for both the portable (shorter-term) and transport (longer-term) sectors.

Functionalization of polymeric materials as a high performance membrane for direct methanol fuel cell: A review

Abstract: A coherent review on the advanced proton exchange membranes (PEMs) for direct methanol fuel cell (DMFC) application and the future direction in the development of a high performance polymeric membrane for DMFC were discussed in this paper. PEMs have a profound influence on performance of DMFC. The PEMs are categorized into five groups which are partially fluorinated, perfluorinated ionomers, acid–base complexes, non-fluorinated ionomers, hydro carbon and aromatic polymers. Many researchers have investigated the functionalization methods on the PEMs to solve methanol crossover problem while obtaining low electronic conductivity, high proton conductivity, low electro osmotic drag coefficient, high mechanical properties and good chemical and thermal stability. Including in this review, fabrication of PEM using electrospinning process coupled with the promising functionalized polymeric materials which were known to be the most important initiatives at present in order to further expand the full potential of DMFC performance.

A review on the fabrication of electrospun polymer electrolyte membrane for direct methanol fuel cell

Abstract: Proton exchange membrane (PEM) is an electrolyte which behaves as important indicator for fuel cell's performance. Research and development (R&;D) on fabrication of desirable PEM have burgeoned year by year, especially for direct methanol fuel cell (DMFC). However, most of the R&;Ds only focus on the parent polymer electrolyte rather than polymer inorganic composites. This might be due to the difficulties faced in producing good dispersion of inorganic filler within the polymer matrix, which would consequently reduce the DMFC's performance. Electrospinning is a promising technique to cater for this arising problem owing to its more widespread dispersion of inorganic filler within the polymer matrix, which can reduce the size of the filler up to nanoscale. There has been a huge development on fabricating electrolyte nanocomposite membrane, regardless of the effect of electrospun nanocomposite membrane on the fuel cell's performance. In this present paper, issues regarding the R&;D on electrospun sulfonated poly (ether ether ketone) (SPEEK)/inorganic nanocomposite fiber are addressed.

Fe–N supported on graphitic carbon nano-networks grown from cobalt as oxygen reduction catalysts for low-temperature fuel cells

Abstract: a b s t r a c t Three iron-nitrogen-containing non-noble metal electrocatalysts supported on networked graphitic structures, carbon nano-networks (CNNs), were synthesized using a wet-impregnation method. The CNN supports were produced in-house by chemical vapor deposition of ethene over cobalt nanoparticles that were previously synthesized in bicontinuous microemulsions. The three CNN supports differed in cobalt content, ranging from 0.1 to 1.7% in weight. These CNN supports were used to prepare Fe-N/CNN electrocatalysts. The oxygen reduction reaction (ORR) activity was evaluated by rotating disk electrode measurements. Interestingly, the highest ORR activity belonged to the catalyst with the highest iron and cobalt content. The most promising catalyst was investigated as the cathode material in a polymer electrolyte membrane fuel cell (PEMFC) and a direct methanol fuel cell (DMFC). The maximum recorded power densities were 121 mW cm −2 for PEMFC and 15 mW cm −2 for DMFC, respectively. These values are superior or comparable to the best state of the art for similar materials. The durability to potential cycling was tested in half-cell studies and an activity loss around 10% was found after 1000 cycles, which is not significantly different from what is reported in the literature. The relatively simple synthesis approach and the cheap precursor materials make this electrocatalyst promising for low-temperature fuel cell applications.

Aligned Nanocomposite Membranes Containing Sulfonated Graphene Oxide with Superior Ionic Conductivity for Direct Methanol Fuel Cell Application

Abstract: In this work, iron oxide (Fe3O4) nanoparticles are deposited onto sulfonated graphene oxide (SGO) nanosheets using a solvothermal method. By applying a magnetic field on the solution during casting, the SGO/Fe3O4 nanosheets are drawn to the through-plane direction of the membrane. The structures of the nanosheets and membranes are characterized. The aligned poly(vinyl alcohol) (PVA)/SGO/Fe3O4 membrane shows higher proton conductivity, water uptake, thermal stability, methanol permeability, and selectivity compared to a nonaligned membrane. By orientation of nanosheets, 5.7% improvement in the tensile stress of the membranes is observed. The aligned PVA/SGO/Fe3O4 nanocomposite membrane generates the highest power density of 25.57 mW cm–1 at 30 °C. As a result, the aligned PVA/SGO/Fe3O4 nanocomposite membrane appears to be a good candidate for direct methanol fuel cell application.

Selectivity of Direct Methanol Fuel Cell Membranes

Abstract: Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion® were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate–PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion® 115-based MEA (77 mW·cm−2 vs. 64 mW·cm−2). This result was due to a lower methanol crossover (47 mA·cm−2 equivalent current density for s-PEEK vs. 120 mA·cm−2 for Nafion® 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm2 for s-PEEK vs. 0.22 Ohm cm2 for Nafion® 115).

Electrocatalyst on Insulating Support?: Hollow Silica Spheres Loaded with Pt Nanoparticles for Methanol Oxidation

Abstract: Electrocatalytic oxidation of methanol on silica hollow spheres, loaded with platinum nanoparticles (Pt-SiO2-HS), is reported. The functionalized hollow silica spheres were prepared by the surfactant (lauryl ester of tyrosine) template-assisted synthesis. These spheres were loaded with platinum nanoparticles by γ-radiolysis. Energy-dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS) analyses confirmed presence of Si and Pt in the composite. High-resolution transmission electron microscopy showed the formation of uniformly deposited Pt nanoparticles over the hollow spheres with a predominant Pt(111) lattice plane on the surface. In spite of the poor conducting nature of the silica support, the oxidation potential and current density per unit mass for methanol oxidation were noted to be ca. 0.72 V vs NHE and 270 mA mg–1, respectively, which are among the best values reported in its class. The composite did not show any sign of a degradation even after repeated use. In fact, the anodi...

A simple preparation of very high methanol tolerant cathode electrocatalyst for direct methanol fuel cell based on polymer-coated carbon nanotube/platinum

Abstract: The development of a durable and methanol tolerant electrocatalyst with a high oxygen reduction reaction activity is highly important for the cathode side of direct methanol fuel cells. Here, we describe a simple and novel methodology to fabricate a practically applicable electrocatalyst with a high methanol tolerance based on poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole]-wrapped multi-walled carbon nanotubes, on which Pt nanoparticles have been deposited, then coated with poly(vinylphosphonic acid) (PVPA). The polymer coated electrocatalyst showed an ~3.3 times higher oxygen reduction reaction activity compared to that of the commercial CB/Pt and methanol tolerance in the presence of methanol to the electrolyte due to a 50% decreased methanol adsorption on the Pt after coating with the PVPA. Meanwhile, the peroxide generation of the PVPA coated electrocatalyst was as low as 0.8% with 2 M methanol added to the electrolyte, which was much lower than those of the non-PVPA-coated electrocatalyst (7.5%) and conventional CB/Pt (20.5%). Such a high methanol tolerance is very important for the design of a direct methanol fuel cell cathode electrocatalyst with a high performance.

Emerging methanol-tolerant AlN nanowire oxygen reduction electrocatalyst for alkaline direct methanol fuel cell.

Abstract: Emerging methanol-tolerant AlN nanowire oxygen reduction electrocatalyst for alkaline direct methanol fuel cell

Bimetallic core–shell Ag@Pt nanoparticle-decorated MWNT electrodes for amperometric H2 sensors and direct methanol fuel cells

Abstract: Bimetallic core–shell Ag@Pt nanoparticles (NPs) attached on multiwall carbon nanotube (Ag@Pt-MWNT) were synthesized via the formation of Ag NPs on a MWNT surface through chemical reduction and subsequent galvanic replacement of Ag with PtCl62−. The successful synthesis of Ag@Pt-MWNT was confirmed by probing chemical compositions, absorption, and microstructures using various material analysis methods (UV–vis, SEM, EDS, and TEM). The bimetallic particles were found to have a core–shell structure in the TEM image: an Ag core with an average size of approximately 7 nm was enclosed by a shell composed of small Pt NPs. The electrochemical surface area of the Ag@Pt-MWNT-modified glassy carbon electrode was 896 cm2/mg, which was 1.5 times higher than that of commercial 20 wt% Pt-C (E-Tek). The Ag@Pt-MWNTs electrode also exhibited a higher peak current for methanol oxidation than those of comparable Pt-MWNT and Pt-C under the same amount of Pt loading, thus providing evidence for its higher electrocatalytic activity and CO tolerance. Furthermore, an amperometric gas-sensing electrode was fabricated by filtering an Ag@Pt-MWNT solution on a porous PTFE sheet. The as-fabricated electrode displayed a high sensitivity of 1.1 μA/ppm in H2 detection and an excellent linear response over the wide concentration range of 5–1000 ppm, together with fairly good detection times and long-term stability. This enhanced performance was correlated and discussed to be a result of the unique nanostructural features of the Ag@Pt core–shell structure with a porous Pt layer and the strong anchoring of the bimetallic NPs on the activated MWNT surface, which provides a highly active surface area and effective interactions between Ag and Pt.