Catalysts For Direct Methanol Fuel Cells Research Articles

Gold nanoparticles: novel catalyst for the preparation of direct methanol fuel cell.

The authors report the biosynthesis of gold nanoparticles (Au-NPs) using plant pathogenic Phoma glomerata (MTCC 2210). The synthesis of nanoparticles was characterised by visual observation followed UV-visible spectrophotometric analysis, Fourier transform infrared spectroscopy and nanoparticle tracking analysis. Later, direct methanol fuel cell (DMFC) was constructed using two chambers (anodic chamber and cathodic chamber). These Au-NPs as catalysts have various advantages over the other catalysts that are used in the DMFC. Most importantly, it is cheaper as compared with other catalysts like platinum, and showed higher catalytic activity because of its effective surface structure. Being nano in size, it provides more surface area for the attachment of reactant molecules (methanol molecules). The DMFC catalysed by Au-NPs are found to be suitable to replace lithium ion battery technology in consumer electronics like cell phones, laptops and so on due to the fact that they can produce a high amount of energy in a small space. As long as fuel and air are supplied to the DMFC, it will continue to produce power, so it does not need to be recharged. The use of Au-NPs as catalyst in DMFC has not been reported in the past; it is reported here the first time.

Pt–Ru/Al2O3–C nanocomposites as direct methanol fuel cell catalysts for electrooxidation of methanol in acidic medium

We have employed different ratios of Al2O3 and Vulcan carbon as supporting matrices for a Pt–Ru catalyst for direct methanol fuel cell catalysts.

Novel cathode catalyst for DMFC: Study of the density of states of oxygen adsorption using density functional theory

Platinum (Pt) is the most common cathode catalyst in Direct Methanol Fuel Cells (DMFC). However, Pt involved both in the oxidation reaction of methanol and the reduction of oxygen on the cathode side, which limits the performance of DMFCs. Therefore, this study investigates cobalt phthalocyanine (CoPc) as a potential DMFC cathode catalyst capable of inhibiting the reactivity of methanol oxidation. This study investigates the reaction mechanism and adsorption energy of oxygen molecules on Cobalt Phthalocyanine (CoPc) using the Density Functional Theory (DFT). The basis sets of semi-core pseudopotential (DSPP) and effective core potential are used to compare the geometric optimization of the Cobalt Phthalocyanine structure. The adsorption strength of molecular oxygen on the Cobalt metal center of Phthalocyanine is investigated using Partial Density of States and compared with that of Iron Phthalocyanine (FePc). Finally, the results show that the adsorption energy of carbon monoxide and methanol on the Cobalt and Iron metal centers of the Phthalocyanine complex yield low energy adsorption on CoPc. It was observed that the adsorption energy when two metal sites of CoPc and supported CoPc on tungsten atom are involved yields high energy adsorption and bond length of molecular oxygen that would lead to oxygen bond dissociation. Therefore, this study concludes that CoPc has the potential to replace Pt due to its high tolerance to methanol and carbon monoxide oxidation.

Modulating Effect of Core Composition in AuxCuy@Pt/C Core-Shell Nanoparticles for the Methanol Oxidation Reaction

In the past decades, direct methanol fuel cell (DMFC) has attracted much interest for their significant advantages in portable and automobile applications, for this technology the anode electrocatalyst is the most important part. The Pt catalyst is widely recognized as the best catalyst for DMFC and one of the key objectives in fuel cell technology is to improve the electrochemical activity and reduce Pt loading of the electrocatalyst. One way to reduce the Pt content in the electrocatlyst is by synthetizing core–shell structural catalysts, in which only surface atoms are active in the catalytic reaction (i.e. Pt as shell). In this work, the modulating effect given by the composition of the core in AuxCuy@Pt/C for the methanol oxidation reaction (MOR) is analyzed. For this purpose, AuxCuy@Pt/C catalysts were prepared varying the Au:Cu percentage (i.e. 100:0%, 75:25%, 50:50%, 25:75%, 0:100%), the catalysts were prepared by a two-step method.

Novel anode catalyst for direct methanol fuel cells.

PtRu catalyst is a promising anodic catalyst for direct methanol fuel cells (DMFCs) but the slow reaction kinetics reduce the performance of DMFCs. Therefore, this study attempts to improve the performance of PtRu catalysts by adding nickel (Ni) and iron (Fe). Multiwalled carbon nanotubes (MWCNTs) are used to increase the active area of the catalyst and to improve the catalyst performance. Electrochemical analysis techniques, such as energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS), are used to characterize the kinetic parameters of the hybrid catalyst. Cyclic voltammetry (CV) is used to investigate the effects of adding Fe and Ni to the catalyst on the reaction kinetics. Additionally, chronoamperometry (CA) tests were conducted to study the long-term performance of the catalyst for catalyzing the methanol oxidation reaction (MOR). The binding energies of the reactants and products are compared to determine the kinetics and potential surface energy for methanol oxidation. The FESEM analysis results indicate that well-dispersed nanoscale (2–5 nm) PtRu particles are formed on the MWCNTs. Finally, PtRuFeNi/MWCNT improves the reaction kinetics of anode catalysts for DMFCs and obtains a mass current of 31 A g−1 catalyst.

Phosphotungstic acid-assisted preparation of carbon nanotubes-supported uniform Pt and Pt bimetallic nanoparticles, and their enhanced catalytic activity on methanol electro-oxidation

A 3–4 nm thickness of phosphotungstic acid (H3PW12O40, PW) layer is deposited on to the surface of multiwalled carbon nanotubes (MWCNTs) via sorption by ultrasonic method. These PW/MWCNT hybrids can be used as the promising supports for anode catalysts of the direct methanol fuel cell (DMFC). A facile polyol thermo-reduction method has been put forward to prepare PtIr (PtRu or Pt)/PW/MWCNT hybrids. In the presence of PW, PtIr (PtRu or Pt) nanoparticles can be uniformly dispersed on the surface of the MWCNTs in high density with a small size and a narrow distribution, and these Pt and Pt bimetallic catalysts exhibit a significantly improved electrochemically active surface area and a remarkably enhanced activity toward methanol oxidation. Besides, these Pt and Pt bimetallic catalysts on PW/MWCNT hybrids also show longer operation stability and higher CO tolerance as well as better cell performance compared with those on MWCNTs without PW. The evaluation of anode catalysts in DMFC indicates that the observed power density depends on the intrinsic property of the size, dispersion and composition of Pt and Pt bimetallic catalysts.

Tungsten Carbide Nanofiber Prepared by Electrospinning for Methanol Oxidation Reaction

Tungsten carbide nanofibers for the anode catalyst of direct methanol fuel cells (DMFCs) were prepared from the precursor nanofibers with the diameter around 250 nm using an electrospinning technique. The electrospun nanofibers from the mixture of ammonium metatungstate and polyvinylpyrrolidone were dried and calcined in air at 700 °C to form tungsten oxide nanofibers, and reduced in 20 vol.% CH4/H2 atmosphere at 700 °C for 2 h. Surface morphology and crystalline structure of the prepared nanofibers were investigated using FE-SEM and XRD. The methanol oxidation reaction (MOR) activity of the prepared samples was evaluated by cyclic voltammetry (CV). The FE-SEM and XRD analyses showed that beaded nanofibers of tungsten carbide were successfully obtained. The WC nanofiber electrocatalyst exhibited a MOR activity suggesting it can be a candidate of the catalyst for DMFC. The presence of impurities, carbon and tungsten oxide, which may affect the activity, were detected at the surface.

Porous palladium copper nanoparticles for the electrocatalytic oxidation of methanol in direct methanol fuel cells

A facile method has been demonstrated for the preparation of PdCu nanoparticles (NPs) with various morphologies from Pd2+ and Cu2+ reduced by ascorbate in the presence of dodecyltrimethylammonium chloride (DTAC) at 95 °C. We have found that DTAC is important to assist the growth of PdCu with high-energy surfaces through the etching and capping of certain surfaces of Pd and PdCu seeds. By varying the Pd2+/Cu2+ molar ratio, different morphologies of PdCu NPs have been prepared. Cubic PdCu NPs have a dominant Pd3Cu composition when prepared at a high Pd2+/Cu2+ molar ratio (20/1), while porous PdCu NPs have a dominant PdCu3 composition when prepared at a low Pd2+/Cu2+ molar ratio (1/10). The copper content not only controls the morphology, but also affects the catalytic activity toward the methanol oxidation reaction (MOR) in alkaline media. Upon increasing the copper content, the catalytic activity toward the MOR increases, mainly due to the advantages of the electroactive surface area, more direct cathodic oxide reduction (lower onset potential for the formation of Pd–OH), and synergistic effects. Porous PdCu NP-modified electrodes provide a higher catalytic activity (363 A g−1) toward the MOR at a more negative onset potential (−0.62 V vs. Ag/AgCl) on the porous PdCu electrodes than commercial Pd/C-modified ones do (180 A g−1) at −0.52 V. To the best of our knowledge, this is the first example using porous PdCu NP-modified electrodes as anodes under alkaline conditions in direct methanol fuel cells (DMFCs). With the advantages of high electrochemical activity, stability, and cost effectiveness, the porous PdCu NPs have great potential as anode catalysts for DMFCs.

Effect of N-doping on Performance and Durability of Supported PtRu Direct Methanol Fuel Cell Catalyst

not Available.

Tetrahexahedral Pt Nanocrystal Catalysts Decorated with Ru Adatoms and Their Enhanced Activity in Methanol Electrooxidation

Tetrahexahedral Pt nanocrystals (THH Pt NCs) bound by well-defined high index crystal planes offer exceptional electrocatalytic activity, owing to a high density of low-coordination surface Pt sites. We report, herein, on methanol electrooxidation at THH Pt NC electrodes studied by a combination of electrochemical techniques and in situ FTIR spectroscopy. Pure THH Pt NC surfaces readily facilitate the dissociative chemisorption of methanol leading to poisoning by strongly adsorbed CO. Decoration of the stepped surfaces by Ru adatoms increases the tolerance to poisoning and thereby reduces the onset potential for methanol oxidation by over 100 mV. The Ru modified THH Pt NCs exhibit greatly superior catalytic currents and CO2 yields in the low potential range, when compared with a commercial PtRu alloy nanoparticle catalyst. These results are of fundamental importance in terms of model nanoparticle electrocatalytic systems of stepped surfaces and also have practical significance in the development of surface tailored, direct methanol fuel cell catalysts.

N-Modified Carbon Supported Pt-Ru Direct Methanol Fuel Cell Catalyst Performance and Durability

not Available.

Hollow graphitic carbon spheres for Pt electrocatalyst support in direct methanol fuel cell

Hollow graphitic carbon spheres (HGCSs) with a high surface area are produced by the carbonization of hollow polymer spheres obtained by the polymerization of core/shell-structured pyrrole micelles. HGCSs are employed as a carbon support material in a direct methanol fuel cell catalyst, and their effect on the electrocatalytic activity toward methanol oxidation is investigated. Pt catalyst supported on HGCSs shows a better electrocatalytic activity compared to that on Vulcan XC-72, which has been commonly used in fuel cell catalysts. The observed enhancement in the electrocatalytic activity is attributed to the improved electronic conductivity and high surface area of HGCSs.

A DMFC with Methanol-Tolerant-Carbon-Supported-Pt-Pd-Alloy Cathode

Methanol-tolerant Pt-Pd alloy catalysts supported on to carbon with varying Pt:Pd atomic ratios of 1:1, 2:1 and 3:1 are prepared by a novel wet-chemical method and characterized using powder XRD, XPS, FESEM, EDAX and TEM techniques. The optimum atomic weight ratio for Pt to Pd in the carbon-supported alloy catalyst as established by linear-sweep voltammetry (LSV) and cell polarization studies is found to be 2:1. A direct methanol fuel cell (DMFC) employing carbon-supported Pt-Pd (2:1) alloy (Pt-Pd/C) catalyst as the cathode catalyst delivers a peak-power density of 115 mW/cm2 at 70°C as compared to peak-power density of 60 mW/cm2 obtained with the DMFC employing carbon-supported Pt (Pt/C) catalyst operating under similar conditions. In the literature, DMFCs operating with Pt-TiO2 (2:1)/C and Pt-Au (2:1)/C methanol-tolerant cathodes are reported to exhibit maximum ORR activity among the group of these methanol-tolerant cathodes with varying catalysts compositions. Accordingly, the present study also provides an effective route to design methanol-tolerant-oxygen-reduction catalysts for DMFCs.

Facile Preparation of an Excellent Pt/RuO2‐MnO2/CNTs Nanocatalyst for Anodes of Direct Methanol Fuel Cells

AbstractRuO2‐MnO2 complex supported by multi‐wall carbon nanotubes (CNTs) was firstly synthesised by the oxidation–reduction precipitation of RuCl3 and KMnO4 in one step. Then Pt was loaded onto the obtained RuO2‐MnO2/CNTs to fabricate a novel anodic catalyst Pt/RuO2‐MnO2/CNTs for direct methanol fuel cells (DMFCs). The catalyst was characterised by transmission electron microscopy (TEM), X‐ray diffraction (XRD), temperature programmed reduction (TPR), X‐ray photoelectron spectroscopy (XPS) and BET specific surface areas (BET). Pt nanoparticles were found uniformly dispersed on the surface of CNTs, with the average diameter of about 2.0 nm. The activities of methanol and CO electrocatalytic oxidation were analysed, and the reaction mechanism of methanol electro‐oxidation on Pt/RuO2‐MnO2/CNTs catalyst was discussed. The MnO2 in the catalysts improves the proton conductivity and electrochemical active surface area (EAS) for the catalysts. RuO2 improves the CO oxidation activity and Pt dispersion. CNTs provide effectively electron channels. Thus, the Pt/RuO2‐MnO2/CNTs catalyst has high utilisation of the noble metal Pt, high CO oxidation ability and excellent methanol electro‐oxidation activity, being an outstanding anode catalyst for DMFC.

The problem of Ru dissolution from Pt–Ru catalysts during fuel cell operation: analysis and solutions

Platinum–ruthenium catalysts are widely used as anode materials in polymer electrolyte fuel cells (PEMFCs) operating with reformate gas and in direct methanol fuel cells (DMFCs). Ruthenium dissolution from the Pt–Ru anode catalyst at potentials higher than 0.5 V vs. DHE, followed by migration and deposition to the Pt cathode can give rise to a decrease of the activity of both anode and cathode catalysts and to a worsening of cell performance. A major challenge for a suitable application of Pt–Ru catalysts in PEMFC and DMFC is to improve their stability against Ru dissolution. The purpose of this paper is to provide a better knowledge of the problem of Ru dissolution from Pt–Ru catalysts and its effect on fuel cell performance. The different ways to resolve this problem are discussed.

Rapid optical screening technology for direct methanol fuel cell (DMFC) anode and related electrocatalysts

We describe here the development of an optical high-throughput screening method for direct methanol fuel cell catalysts based on the fluorescence of protonated quinine generated during electro-oxidation of methanol. The design of the working electrode allows the parallel quantification of the fluorescence development for up to 60 materials. For the preparation of the working electrode a coating routine has been developed, which allows the use of sol–gel derived materials. Due to the required stability of the electrode catalysts towards the acidic polymer membrane, a fast optical pre-screening method for acid stable materials has been developed. The electrochemical high-throughput system has been validated with Pt-Ru catalysts. Automation of data acquisition and data processing led to a fast and reliable high-throughput screening setup.

Effect of O2Plasma Treatments of Carbon Supports on Pt-Ru Electrocatalysts

In the present study, carbon supports mixed with purified multi-walled carbon nanotubes (MWNTs) and carbon blacks (CBs) were used to improve the cell performance of direct methanol fuel cells (DMFCs). Additionally, the effect of <TEX>$O_2$</TEX> plasma treatment on CBs/MWNTs supports was investigated for different plasma RF powers of 100, 200, and 300 W. The surface and structural properties of the CBs/MWNTs supports were characterized by FT-IR, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and inductive coupled plasma-mass spectrometer (ICP-MS). The electrocatalytic activity of PtRu/CBs/MWNTs catalysts was investigated by cyclic voltammetry measurement. In the experimental results, the oxygen functional groups of the supports were increased with increasing plasma RF power, while the average Pt particle size was decreased owing to the improvement of dispersibility of the catalysts. The electrochemical activity of the catalysts for methanol oxidation was gradually improved by the larger available active surface area, itself due to the introduction of oxygen functional groups. Consequently, it was found that <TEX>$O_2$</TEX> plasma treatments could influence the surface properties of the carbon supports, resulting in enhanced electrocatalytic activity of the catalysts for DMFCs.

Graphene Oxide as a Carbon Support for Direct Methanol Fuel Cell Catalysts

not Available.

Effect of operating conditions on the performance of a direct methanol fuel cell with PtRuMo/CNTs as anode catalyst

PtRu/CNTs and PtRuMo/CNTs catalysts have been synthesized by microwave-assisted polyol process and used as the anode catalysts for a direct methanol fuel cell (DMFC). The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS). The effect of different anode catalysts, membrane electrode assembly (MEA) activation, methanol concentration, methanol flow rate, oxygen flow rate and cell temperature on the DMFC performance has been investigated. The results show that the PtRu or PtRuMo particles with face-centered cubic structure are uniformly distributed on CNTs, and the addition of Mo to PtRu/CNTs makes the binding energies of each Pt species shift to lower values. PtRuMo/CNTs is a promising anode catalyst for DMFCs, and the appropriate operating conditions of the DMFC with PtRuMo/CNTs as the anode catalyst are MEA activation for 10 h, 2.0–2.5 M methanol at the flow rate of 1.0–2.0 mL/min, and oxygen at the flow rate of 100–150 mL/min. The DMFC performance increases significantly with an increase in cell temperature.

Carbon-Supported Pt – TiO2 as a Methanol-Tolerant Oxygen-Reduction Catalyst for DMFCs

Carbon-supported catalysts with varying at. wt ratios of Pt to Ti, namely, 1:1, 2:1, and 3:1, are prepared by the sol–gel method. The electrocatalytic activity of the catalysts toward oxygen reduction reaction (ORR), both in the presence and absence of methanol, is evaluated for application in direct methanol fuel cells (DMFCs). The optimum at. wt ratio of Pt to Ti in is established by fuel cell polarization, linear sweep voltammetry, and cyclic voltammetry studies. heat-treated at with Pt and Ti in an at. wt ratio of 2:1 shows enhanced methanol tolerance, while maintaining high catalytic activity toward ORR. The DMFC with a cathode catalyst exhibits an enhanced peak power density of in contrast to the achieved from the DMFC with carbon-supported Pt catalyst while operating under identical conditions. Complementary data on the influence of on the crystallinity of Pt, surface morphology, and particle size, surface oxidation states of individual constituents, and bulk and surface compositions are also obtained by powder X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive analysis by X-ray, and inductively coupled plasma optical emission spectrometry.