Showing papers on "Direct methanol fuel cell published in 2016"

Palladium Nanoparticles Supported on Nitrogen and Sulfur Dual-Doped Graphene as Highly Active Electrocatalysts for Formic Acid and Methanol Oxidation

Abstract: Optimized designing of highly active electrocatalysts has been regarded as a critical point to the development of portable fuel cell systems with high power density. Here we report a facile and cost-effective strategy to synthesis of ultrafine Pd nanoparticles (NPs) supported on N and S dual-doped graphene (NS-G) nanosheets as multifunctional electrocatalysts for both direct formic acid fuel cell and direct methanol fuel cell. The incorporation of N and S atoms into graphene frameworks is achieved by a thermal treatment process, followed by the controlled growth of Pd NPs via a solvothermal approach. Owning to the unique structural features as well as the strong synergistic effects, the resulting Pd/NS-G hybrid exhibits outstanding electrocatalytic performance toward both formic acid and methanol electro-oxidation, such as higher anodic peak current densities and more exceptional catalytic stability than those of Pd/Vulcan XC-72R and Pd/undoped graphene catalysts. These findings open up new possibility in the construction of advanced Pd-based catalysts, which is conducive to solving the current bottlenecks of fuel cell technologies.

Proton-conducting electrolytes for direct methanol and direct urea fuel cells – A state-of-the-art review

Abstract: This review focuses on the protonicisuperprotonic electrolytes used for application in direct methanol and direct urea/urine fuel cells. Since, methanol has. high energy density, which is essential for portable direct methanol fuel cells, and is simpler to store and transport than conventional hydrogen as fuel. However, methanol is not readily available, which makes waste an attractive option as a fuel source, resulting in the development of direct urea fuel cells. Fuel cells that use waste that contains hydrogen, like waste water or urine, are attractive because of their potential to generate energy from low-cost, abundant sources.

PdAg/CNT catalyzed alcohol oxidation reaction for high-performance anion exchange membrane direct alcohol fuel cell (alcohol=methanol, ethanol, ethylene glycol and glycerol)

Abstract: s PdAg supported on carbon nanotubes (PdAg/CNT) with an average particle size of 2.7 nm is prepared by an aqueous phase reduction method for alcohol oxidation reaction in direct alcohol fuel cells. In a half-cell system with three electrodes, the peak mass activity of PdAg/CNT reaches 0.105 mA μgPd−1, 0.305 mA μgPd−1, 2.105 mA μgPd−1, and 8.53 mA μgPd−1 for methanol oxidation reaction, ethanol oxidation reaction, ethylene glycol oxidation reaction, and glycerol oxidation reaction, respectively, in 1 M KOH 0.1 M alcohol electrolyte. These values are higher than the mass activity of Pd/CNT at the same applied potential. With PdAg/CNT (0.5 mgPdperMEA−1) as an anode catalyst, a direct methanol fuel cell, a direct ethanol fuel cell, a direct ethylene glycol fuel cell and a direct glycerol fuel cell achieve peak power densities of 135.1 mW cm−2, 202.3 mW cm−2, 245.2 mW cm−2, and 276.2 mW cm−2, with corresponding peak mass activities of 270.2 mW mgPdperMEA−1, 404.6 mW mgPdperMEA−1, 490.4 mW mgPdperMEA−1, and 552.4 mW mgPdperMEA−1, respectively, at 80 °C and ambient pressure. Ag has shown excellent activity towards aldehyde (formaldehyde, acetaldehyde, and glyoxylate) oxidation, thus, the enhancement in alcohol oxidation on PdAg/CNT is proposed due to Ag’s promotion of intermediate aldehyde oxidation. PdAg/CNT also improves the fuel efficiency of glycerol oxidation by contributing to the C C bond cleavage of C3 glycerol to C2 oxalate.

Direct‐methanol Fuel Cell Based on Functionalized Graphene Oxide with Mono‐metallic and Bi‐metallic Nanoparticles: Electrochemical Performances of Nanomaterials for Methanol Oxidation

Abstract: The catalysts based on 2-aminoethanethiol functionalized graphene oxide (AETGO) with several mono-metallic and bi-metallic nanoparticles such as rod gold (rAuNPs), rod silver (rAgNPs), rod gold-platinum (rAu-Pt NPs) and rod silver-platinum (rAg-Pt NPs) were synthesized. The successful synthesis of nanomaterials was confirmed by various methods. The effective surface area (ESA) of the rAu-Pt NPs/AETGO is 1.44, 1.64 and 2.40 times higher than those of rAg-Pt NPs/AETGO, rAuNPs/AETGO and rAgNPs/AETGO, respectively, under the same amount of Pt. The rAu-Pt NPs/AETGO exhibited a higher peak current for methanol oxidation than those of comparable rAg-Pt NPs/AETGO under the same amount of Pt loading.

Multi-functional reactively-sputtered copper oxide electrodes for supercapacitor and electro-catalyst in direct methanol fuel cell applications

Abstract: This work reports on the concurrent electrochemical energy storage and conversion characteristics of granular copper oxide electrode films prepared using reactive radio-frequency magnetron sputtering at room temperature under different oxygen environments. The obtained films are characterized in terms of their structural, morphological, and compositional properties. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscope studies reveal that granular, single-phase Cu2O and CuO can be obtained by controlling the oxygen flow rate. The electrochemical energy storage properties of the films are investigated by carrying out cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy tests. The electrochemical analysis reveals that the Cu2O and CuO electrodes have high specific capacitances of 215 and 272 F/g in 6 M KOH solution with a capacity retention of about 80% and 85% after 3000 cycles, respectively. Cyclic voltammetry and chronoamperometry are used to study the electrochemical energy conversion properties of the films via methanol electro-oxidation. The results show that the Cu2O and CuO electrodes are electro-catalytically active and highly stable.

The Importance of the Electrochemical Environment in the Electro-Oxidation of Methanol on Pt(111)

Abstract: The electro-oxidation of methanol on Pt(111) is studied based on periodic density functional theory calculations. The aqueous electrolyte is taken into account using an implicit solvent model, and the dependence of the reaction energetics on the electrode potential is derived using the concept of the computational hydrogen electrode. The total oxidation of methanol becomes thermodynamically preferred at electrode potentials above U = 0.6 V relative to the standard hydrogen electrode. We propose a most favorable reaction path involving surface carboxyl as the last reaction intermediate before CO2 formation, which can either be formed in a indirect mechanism from adsorbed CO or in a direct mechanism from formic acid. The presence of the aqueous electrolyte significantly stabilizes reaction intermediates that contain hydrophilic groups. This also leads to a selectivity for the initial C–H bond breaking process with respect to the initial O–H bond breaking of methanol that is increased by 3 orders of magnitud...

Performance analysis of a non-platinum group metal catalyst based on iron-aminoantipyrine for direct methanol fuel cells

Abstract: A highly active non-platinum group metals (non-PGMs) catalyst for oxygen reduction reaction (ORR) was synthesized by the sacrificial support method (SSM) developed at the University of New Mexico (UNM). SSM was modified in order to control hydrophobicity and morphology of transition metal–nitrogen–carbon material (M–N–C). As prepared catalyst was evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) methods. Electrochemical activity towards ORR and tolerance to methanol poisoning of Fe–N–C catalyst were studied by rotating disk electrode (RDE). A performance analysis was carried out at the cathode of a direct methanol fuel cell (DMFC) comprising the variation of fuel concentration and temperature. A peak power density of about 50 W g−1 was recorded at 90 °C in a wide range of methanol concentration (1–10 M). It was found that the non-PGM catalyst possesses an extraordinarily high tolerance to methanol crossover, with no significant decay of performance up to 10 M of alcohol concentration, making this material state-of-the-art in DMFC application. Chronoamperometric tests in DMFC at 90 °C and 5 M methanol concentration (100 h) showed also a suitable stability.

High Performance and Cost-Effective Direct Methanol Fuel Cells: Fe-N-C Methanol-Tolerant Oxygen Reduction Reaction Catalysts.

Abstract: Direct methanol fuel cells (DMFCs) offer great advantages for the supply of power with high efficiency and large energy density. The search for a cost-effective, active, stable and methanol-tolerant catalyst for the oxygen reduction reaction (ORR) is still a great challenge. In this work, platinum group metal-free (PGM-free) catalysts based on Fe-N-C are investigated in acidic medium. Post-treatment of the catalyst improves the ORR activity compared with previously published PGM-free formulations and shows an excellent tolerance to the presence of methanol. The feasibility for application in DMFC under a wide range of operating conditions is demonstrated, with a maximum power density of approximately 50 mW cm−2 and a negligible methanol crossover effect on the performance. A review of the most recent PGM-free cathode formulations for DMFC indicates that this formulation leads to the highest performance at a low membrane–electrode assembly (MEA) cost. Moreover, a 100 h durability test in DMFC shows suitable applicability, with a similar performance–time behavior compared to common MEAs based on Pt cathodes.

Facile Synthesis of Core/Shell-like NiCo2O4-Decorated MWCNTs and its Excellent Electrocatalytic Activity for Methanol Oxidation.

Abstract: The design and development of an economic and highly active non-precious electrocatalyst for methanol electrooxidation is challenging due to expensiveness of the precursors as well as processes and non-ecofriendliness. In this study, a facile preparation of core-shell-like NiCo2O4 decorated MWCNTs based on a dry synthesis technique was proposed. The synthesized NiCo2O4/MWCNTs were characterized by infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and selected area energy dispersive spectrum. The bimetal oxide nanoparticles with an average size of 6 ± 2 nm were homogeneously distributed onto the surface of the MWCNTs to form a core-shell-like nanostructure. The NiCo2O4/MWCNTs exhibited excellent electrocatalytic activity for the oxidation of methanol in an alkaline solution. The NiCo2O4/MWCNTs exhibited remarkably higher current density of 327 mA/cm(2) and a lower onset potential of 0.128 V in 1.0 M KOH with as high as 5.0 M methanol. The impressive electrocatalytic activity of the NiCo2O4/MWCNTs is promising for development of direct methanol fuel cell based on non-Pt catalysts.

Proton Conducting Nafion-Sulfonated Graphene Hybrid Membranes for Direct Methanol Fuel Cells with Reduced Methanol Crossover

Abstract: Sulfonic acid functionalized graphene (S-graphene) is explored as a potential inorganic filler as well as a solid acid proton conducting medium to realize a hybrid membrane with Nafion for a direct methanol fuel cell (DMFC). The simple, but effective, functionalization of graphene is performed by sulfonic acid containing aryl radicals to increase the number of sulfonate groups per unit volume of graphene domain. Nafion–S-graphene hybrid membranes increase compactness of ionic domains and enhanced proton conductivity while restricting the methanol crossover across the membrane. DMFCs with a Nafion–S-graphene (1 wt %) hybrid membrane deliver a peak power density of 118 mW cm–2 at a load current density of 450 mA cm–2 while operating at 70 °C under an ambient pressure. By contrast, operating under identical conditions, a peak power density of 54 mW cm–2 at a load current density of 241 mA cm–2 is obtained with the pristine recast Nafion membrane. The Nafion–S-graphene hybrid membranes are extremely beneficia...

Vapor feed direct methanol fuel cells (DMFCs): A review

Abstract: Direct methanol fuel cells (DMFCs) are attractive portable energy source for several applications like mobile phone and notebook PCs charging, however the various critical challenges, limit the widespread commercial application of these DMFCs. A review of the experimental and numerical studies on the vapor feed DMFCs is conducted. The critical challenges of a vapor feed DMFC are methanol crossover (MCO), water management layer (WML), carbon dioxide release and operation at high temperature have been discussed and analyzed in detail. It is shown that the critical challenge regarding to the MCO is how to feed vapor methanol with minimum MCO through the membrane so that the cell performance can be maximized. The several methods related to the WML deals with transport of the water produced on the cathode to the anode through the membrane and helps to operate the anode with vapor methanol and the cathode with minimum water flooding. The critical challenge related to the high temperature vapor feed DMFC is the selection of the membrane electrode assembly (MEA) materials so that it can be operated at high temperature which critically affects the cell performance. The various vaporization methods of the liquid methanol supplying to DMFC have been discussed in detail. The recent developments in the stacking of vapor feed DMFC to increase the power density have also been discussed. Based on the literature surveys, a statistical flow chart is proposed to optimize a passive vapor feed DMFC with concentrated methanol.

Biopolymer-based electrolyte membranes from chitosan incorporated with montmorillonite-crosslinked GPTMS for direct methanol fuel cells

Abstract: A composite membrane was fabricated from biopolymer chitosan and montmorillonite (MMT) filler as an alternative membrane electrolyte for direct methanol fuel cell (DMFC) application. To first improve the organic–inorganic interfacial morphology, the pristine MMT was pre-treated using 3-glicidoxy propyltrimethoxysilane (GPTMS) surface modifier to produce organophilic MMT (O-MMT). The GPTMS modified MMT was mixed with chitosan in acetic acid solution and cast into membranes. SEM images and FTIR analysis showed that the O-MMT was successfully incorporated into the chitosan polymer matrix. Water and methanol uptake of the Ch/O-MMT composite membranes decreased with increasing O-MMT loadings, but the ion exchange capacity (IEC) value increased. The Ch/O-MMT with 5 wt% O-MMT loading exhibited the best methanol permeability and proton conductivity characteristics among the other Ch/O-MMT membranes, which were 3.03 × 10−7 cm2 s−1 and 4.66 mS cm−1, respectively. All the results obtained from this study can be used to conclude that the chitosan membrane with O-MMT filler is a promising high performance PEM candidate for DMFC application.

Sulfonated poly(etheretherketone) and sulfonated polyvinylidene fluoride-co-hexafluoropropylene based blend proton exchange membranes for direct methanol fuel cell applications

Abstract: In this work, blend membranes based on sulfonated poly(etheretherketone) (SPEEK) and sulfonated polyvinylidene fluoride-co-hexafluoropropylene (SPVDF-co-HFP) with a 10 wt% concentration of a polymer blend in solution were prepared by a solution casting method. The PEEK and PVDF-co-HFP were sulfonated with a direct sulfonation method to reach sulfonation degrees of 68% and 31%, respectively. The different weight ratios of the blend polymers were synthesized and a weight ratio of 20 wt% PVDF-co-HFP and SPVDF-co-HFP exhibited the best properties in terms of a few essential membrane properties such as membrane swelling, liquid uptake, thermal and mechanical stability, methanol permeability, proton conductivity and DMFC performance. The prepared blend membranes presented excellent swelling and methanol barrier properties while the proton conductivities were acceptable. Also, the effect of the casting solvent on the morphology and properties of the prepared membranes was investigated. The membranes cast on N-methyl-2-pyrrolidone (NMP) showed the best results compared to the others. The SPEEK/SPVDF-co-HFP blend membrane cast in NMP had good interaction and showed the highest proton conductivity of 35.7 S cm−1 for 10 wt% SPVDF-co-HFP and the highest power density of 43.02 mW cm−2 for 20 wt% SPVDF-co-HFP, among all of the prepared membranes, at room temperature.

Liquid feed passive direct methanol fuel cell: challenges and recent advances

Abstract: This paper provides an overview of technological challenges and recent advances in the liquid feed passive direct methanol fuel cells (DMFC). Important issues viz. species management, thermal management, methanol crossover, sluggish anode kinetics, durability and stability, and cost are discussed in detail. Methanol management, water management, oxygen management, and carbon dioxide management are covered under species management. The present technological status is given and future research directions are suggested.

Methanol Oxidation on Pt3Sn(111) for Direct Methanol Fuel Cells: Methanol Decomposition

Abstract: PtSn alloy, which is a potential material for use in direct methanol fuel cells, can efficiently promote methanol oxidation and alleviate the CO poisoning problem. Herein, methanol decomposition on Pt3Sn(111) was systematically investigated using periodic density functional theory and microkinetic modeling. The geometries and energies of all of the involved species were analyzed, and the decomposition network was mapped out to elaborate the reaction mechanisms. Our results indicated that methanol and formaldehyde were weakly adsorbed, and the other derivatives (CHxOHy, x = 1–3, y = 0–1) were strongly adsorbed and preferred decomposition rather than desorption on Pt3Sn(111). The competitive methanol decomposition started with the initial O–H bond scission followed by successive C–H bond scissions, (i.e., CH3OH → CH3O → CH2O → CHO → CO). The Bronsted–Evans–Polanyi relations and energy barrier decomposition analyses identified the C–H and O–H bond scissions as being more competitive than the C–O bond scissio...

Carbon-supported Pt-free catalysts with high specificity and activity toward the oxygen reduction reaction in acidic medium

Abstract: Specific carbon-supported Pt-free catalysts (Pd, PdFe, PdIr and PdFeIr) toward the oxygen reduction reaction (ORR) were developed. With this end, materials with high and low activity toward the ORR and the methanol oxidation reaction (MOR) were synthesized by the borohydride method (BM). Physicochemical characterization was carried out by several x-ray techniques, such as x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD) and x-ray dispersive energy (EDX). The ORR was studied at these materials in absence and presence of methanol in acidic medium in a half-cell configuration by the rotating disk electrode (RDE) technique. Additionally, the performance of the catalysts was evaluated as cathode material in a direct methanol fuel cell (DMFC) station. Main results indicate enhanced catalysis toward the ORR and improved tolerance toward the methanol by Fe and Ir insertion into the material, respectively. Membrane electrode assembly (MEA) with a cathode containing PdFeIr/C catalyst yields elevated performance in DMFC, while the electrode cost is dramatically reduced.

Cost Analysis of Direct Methanol Fuel Cell Stacks for Mass Production

Abstract: Fuel cells are very promising technologies for efficient electrical energy generation. The development of enhanced system components and new engineering solutions is fundamental for the large-scale deployment of these devices. Besides automotive and stationary applications, fuel cells can be widely used as auxiliary power units (APUs). The concept of a direct methanol fuel cell (DMFC) is based on the direct feed of a methanol solution to the fuel cell anode, thus simplifying safety, delivery, and fuel distribution issues typical of conventional hydrogen-fed polymer electrolyte fuel cells (PEMFCs). In order to evaluate the feasibility of concrete application of DMFC devices, a cost analysis study was carried out in the present work. A 200 W-prototype developed in the framework of a European Project (DURAMET) was selected as the model system. The DMFC stack had a modular structure allowing for a detailed evaluation of cost characteristics related to the specific components. A scale-down approach, focusing on the model device and projected to a mass production, was used. The data used in this analysis were obtained both from research laboratories and industry suppliers specialising in the manufacturing/production of specific stack components. This study demonstrates that mass production can give a concrete perspective for the large-scale diffusion of DMFCs as APUs. The results show that the cost derived for the DMFC stack is relatively close to that of competing technologies and that the introduction of innovative approaches can result in further cost savings.