Showing papers on "Direct methanol fuel cell published in 2014"

Carbonized nanoscale metal-organic frameworks as high performance electrocatalyst for oxygen reduction reaction.

Abstract: The oxygen reduction reaction (ORR) is one of the key steps in clean and efficient energy conversion techniques such as in fuel cells and metal-air batteries; however, several disadvantages of current ORRs including the kinetically sluggish process and expensive catalysts hinder mass production of these devices Herein, we develop carbonized nanoparticles, which are derived from monodisperse nanoscale metal organic frameworks (MIL-88B-NH3), as the high performance ORR catalysts The onset potential and the half-wave potential for the ORR at these carbonized nanoparticles is up to 103 and 092 V (vs RHE) in 01 M KOH solution, respectively, which represents the best ORR activity of all the non-noble metal catalysts reported so far Furthermore, when used as the cathode of the alkaline direct fuel cell, the power density obtained with the carbonized nanoparticles reaches 227 mW/cm2, 17 times higher than the commercial Pt/C catalysts

Ni2P enhances the activity and durability of the Pt anode catalyst in direct methanol fuel cells

Abstract: Pt is the state-of-the-art anode catalyst in direct methanol fuel cells. Here we report that Ni2P promotes the activity and stability of Pt in electrochemical methanol oxidation. Nanoparticles of Ni2P and Pt were co-deposited on a carbon support and their activity in electrochemical methanol oxidation was measured by cyclic voltammetry. Among all Pt–Ni2P/C catalysts, the sample with a 30 wt% loading of Ni2P exhibits the highest electrochemical surface area and activity. The activity of the Pt–Ni2P/C-30% catalyst is significantly higher than that of Pt/C, Ni-promoted Pt/C, and P-promoted Pt/C catalysts, revealed by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Accordingly to X-ray photoelectron spectroscopy, there is a partial electron transfer from Ni2P to Pt, which might be an origin of the enhanced catalytic activity of the Pt/Ni2P bimetallic catalyst. The Pt–Ni2P/C-30% was integrated into a direct methanol fuel cell; this fuel cell exhibits a maximum power density of 65 mW cm−2, more than twice of that of an analogous fuel cell using Pt/C as the anode catalyst. The Pt–Ni2P/C-30%-integrated direct methanol fuel cell has also the highest discharge stability among a series of fuel cells with different Pt-based anode catalysts.

SGO/SPES-based highly conducting polymer electrolyte membranes for fuel cell application.

Abstract: Proton-exchange membranes (PEMs) consisting of sulfonated poly(ether sulfone) (SPES) with enhanced electrochemical properties have been successfully prepared by incorporating different amount of sulfonated graphene oxide (SGO). Composite membranes are tested for proton conductivity (30–90 °C) and methanol crossover resistance to expose their potential for direct methanol fuel cell (DMFC) application. Incorporation of SGO considerably increases the ion-exchange capacity (IEC), water retention and proton conductivity and reduces the methanol permeability. Membranes have been characterized by FTIR, XRD, DSC, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in composite membranes are established by FTIR. The distribution of SGO throughout the membrane matrix has been examined using SEM and TEM and found to be uniform. The maximum proton conductivity has been found in 5% SGO composite with higher methanol crossover resistance.

Rapid Microwave-Assisted Polyol Reduction for the Preparation of Highly Active PtNi/CNT Electrocatalysts for Methanol Oxidation

Abstract: PtNi nanoparticle catalysts supported on oxygen functionalized carbon nanotubes were prepared by microwave-assisted polyol reduction using two different modes of irradiation, namely, continuous or pulsed irradiation. The influence of irradiation time or pulse number on catalyst structure and activity in methanol electrooxidation has been studied. Characterization was done with ICP-OES, XRD, TEM, XPS, and XAS to determine composition, morphology, crystal structural and chemical state. The electrocatalytic activity has been evaluated by cyclic voltammetry (CV) and chronoamperometry (CA). PtNi nanoparticles are present in alloy form and are well dispersed on the carbon nanotubes. Pt is in its metallic state, whereas Ni is present in metallic and oxidized form depending on the preparation conditions. The electrocatalytic activity both in terms of surface and mass specific activity is higher than that of the state-of-the-art-catalyst Pt/C (E-TEK). The enhancement of the electrocatalytic activity is discussed w...

Sulfonated polyimide/acid-functionalized graphene oxide composite polymer electrolyte membranes with improved proton conductivity and water-retention properties.

Abstract: Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized (-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic–hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm–2 maximum power density (in comparison with ...

Nafion-functionalized electrospun poly(vinylidene fluoride) (PVDF) nanofibers for high performance proton exchange membranes in fuel cells

Abstract: Nafion-functionalized poly(vinylidene fluoride) electrospun nanofibers (PVDFNF-Nafion) have been prepared through a 3-step reaction route. The chemical structure of PVDFNF-Nafion is characterized with Fourier transform infrared and X-ray photoelectron spectroscopy. Functionalization with Nafion chains improves the interfacial compatibility between the PVDF-based nanofibers and Nafion matrix in formation of PVDFNF-Nafion reinforced Nafion composite membrane (Nafion-CM1). Aggregation of Nafion chains on the nanofiber surfaces induces the formation of proton-conducting channels so as to increase the proton conductivity of the Nafion-CM1 membrane. In the H2/O2 single cell test, Nafion-CM1 shows a maximum power density of 700 mW cm−2 which is higher than the value of 500 mW cm−2 recorded with commercial Nafion 212 membrane. The presence of PVDFNF-Nafion also depresses the methanol permeability of the Nafion-CM1 membrane with alteration of the crystalline domains of Nafion. In direct methanol fuel cell tests, the low methanol permeability of Nafion-CM1 means it could be operated with 5 M methanol as the fuel and exhibits a maximum power density of 122 mW cm−2, which is larger than the value (60 mW cm−2) recorded with commercial Nafion 117 membrane and 2 M methanol fuel.

An overview of unsolved deficiencies of direct methanol fuel cell technology: factors and parameters affecting its widespread use

Abstract: SUMMARY Direct methanol fuel cells (DMFCs) have evolved over the years as a potential candidate for application as a power source in portable electronic devices and in transportation sectors They have certain associated advantages, including high energy and power densities, ease of fuel storage and handling, ability to be fabricated with small size, minimum emission of pollutants, low cost, ready availability of fuel and solubility of fuel in aqueous electrolytes However, in spite of several years of active research involved in the development of DMFC technology, their chemical-to-electrical energy conversion efficiencies are still lower compared with other alternative power sources traditionally used This review paper will focus on the existing issues associated with DMFC technology and will also suggest on the possible developmental necessities required for this technology to realize its practical potentials Copyright © 2014 John Wiley & Sons, Ltd

High performance of a free-standing sulfonic acid functionalized holey graphene oxide paper as a proton conducting polymer electrolyte for air-breathing direct methanol fuel cells

Abstract: The membranes constructed from sodium dodecylbenzenesulfonate adsorbed holey graphene oxides (SDBS-HGO)s have been used as proton exchange membranes for air-breathing direct methanol fuel cell applications. Due to the specific holey structure of graphene oxide which provides additional transport pathways for protons across the graphene oxide nanosheet and the presence of strong proton exchange groups which provide them with high proton conductivity, the SDBS-HGO membranes exhibit comparable proton conductivity and lower methanol permeability in comparison to the commercial Nafion® 112. The electrochemical results show that the air-breathing direct methanol fuel cell with the SDBS-HGO membranes as the PEMs exhibit much higher performance and better stability than that with Nafion® 112, which clearly demonstrates the possibility of using such SDBS-HGO based papers for air-breathing direct methanol fuel cell applications.

Polymer Electrolyte Fuel Cells: Physical Principles of Materials and Operation

Abstract: Contents Preface Introduction Global Energy Challenge Towards an Age of Electrochemistry Energy Conversion in Chemistry, Biology, and Electrochemistry Principles of Electrochemical Energy Conversion Sleeping Beauty: 100 Years Is Not Enough! Polarization Curves and "Moore's Law" of Fuel Cells About This Book Basic Concepts Fuel Cell Principle and Basic Layout Fuel Cell Thermodynamics Mass Transport Processes Potentials Heat Production and Transport Brief Discourse on Fuel Cell Electrocatalysis Key Materials in PEFC: Polymer Electrolyte Membrane Key Materials in PEFC: Porous Composite Electrodes Performance of Type I Electrodes Space Scales in Fuel Cell Modeling Polymer Electrolyte Membranes Introduction State of Understanding Polymer Electrolyte Membranes The Theory and Modeling of Structure Formation in PEMs Water Sorption and Swelling of PEMs Proton Transport Electro-Osmotic Drag Concluding Remarks Catalyst Layer Structure and Operation Powerhouses of PEM Fuel Cells Theory and Modeling of Porous Electrodes How to Evaluate Structure of CCL? State-of-the-Art in Theory and Modeling: Multiple Scales Nanoscale Phenomena in Fuel Cell Electrocatalysis Electrocatalysis of the Oxygen Reduction Reaction at Platinum ORR in Water-Filled Nanopores: Electrostatic Effects Structure Formation in Catalyst Layers and Effective Properties Structural Model and Effective Properties of Conventional CCL Concluding Remarks Modeling of Catalyst Layer Performance Framework of Catalyst Layer Performance Modeling Model of Transport and Reaction in Cathode MHM with Constant Coefficients: Analytical Solutions Ideal Proton Transport Ideal Oxygen Transport Weak Oxygen Transport Limitation Polarization Curves for Small to Medium Oxygen Transport Loss Remarks to Sections 4.4-4.7 Direct Methanol Fuel Cell Electrodes Optimal Catalyst Layer Heat Flux from the Catalyst Layer Applications Introduction PEM in Fuel Cell Modeling Dynamic Water Sorption and Flux in PEMs Membrane in Fuel Cell Modeling Performance Modeling of a Fuel Cell Impedance Model of a Single Water-Filled Nanopore Physical Modeling of Catalyst Layer Impedance Impedance of the Cathode Side of a PEM Fuel Cell Carbon Corrosion due to Feed Maldistribution Dead Spots in the PEM Fuel Cell Anode Tables Bibliography Abbreviations Index Nomenclature

Improved Pd electro-catalysis for oxygen reduction reaction in direct methanol fuel cell by reduced graphene oxide

Abstract: Noble metallic nano-catalysts supported on carbon based substrates are extensively used as electrodes for direct methanol fuel cells (DMFCs). Pd is a promising alternative to the more expensive Pt whether its catalytic properties should be improved. To this aim, reduced graphene oxide (rGO) was employed in this study as an alternative to conventional carbon black (C) substrates to improve the catalytic properties of Pd. Pd nanobars and Pt nanoparticles were synthesized, by the polyol method, and deposited for comparison both on commercial carbon and rGO. The oxygen reduction reactions (ORRs) at the fabricated electrodes were tested by the Rotating Disk Electrode (RDE) technique in acidic media. To correlate the activity to other physico-chemical properties, the nano-catalysts were characterized by Thermo Gravimetric Analysis (TGA), X-Ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The electro-catalytic activity of the electrode is importantly affected by the support chosen. Specifically, the Pd nano-catalyst proved an enhanced performance when on rGO, while the Pt counterpart was found being more active when placed on C. This result can be explained with a strong dependence of the ORR on the interaction between the metal nano-catalyst and the carbon based support.

Utilization of Conducting Polymers in Fabricating Polymer Electrolyte Membranes for Application in Direct Methanol Fuel Cells

Abstract: Search for suitable materials for fabricating polymer electrolyte membranes (PEMs) for application in polymer electrolyte membrane fuel cells, and particularly in direct methanol fuel cells (DMFCs)...

High oxygen reduction activity of few-walled carbon nanotubes with low nitrogen content

Abstract: Nitrogen-containing few-walled carbon nanotubes (N-FWCNTs) with very low nitrogen content (0.56 at.%) were obtained by a process involving the coating of acid functionalized FWCNTs with polyaniline (PANI) followed by pyrolysis at high temperatures. The resulting N-FWCNTs exhibited a remarkable electrocatalytic activity for the oxygen reduction reaction (ORR), despite significantly lower nitrogen content than previously reported in literature. The N-FWCNTs performed on par or better than Pt-C in the cathode of an alkaline direct methanol fuel cell, corroborating the ORR activity observed in the electrochemical cell and exhibiting a higher methanol tolerance. Interestingly, N-FWCNTs showed a high activity for the hydrogen evolution reaction and for the hydrogen peroxide decomposition, suggesting that the active sites involved in ORR can simultaneously catalyze other reactions. This unprecedentedly high activity for such a low N-content can be explained by the exceptional accessibility for the catalytic sites located in open and porous N-doped layer surrounding the FWCNT core, along with the minimization of inactive inner volume and mass compared to larger nitrogen doped multiwalled tubes.