Anodic Oxidation Of Methanol Research Articles

Role of surfactant-mediated electrodeposited titanium oxide substrate in improving electrocatalytic features of supported platinum particles

A new hybrid system with improved photocatalytic and electrocatalytic performances was obtained by two-step potentiostatic deposition on highly boron-doped diamond (BDD) substrate. First, hydrated TiO2 was anodically deposited from a TiCl3 aqueous solution, both in the presence and in the absence of sodium dodecyl sulfate (SDS). The study of the UV irradiation effect evidenced that titanium oxide coatings obtained by surfactant-assisted electrodeposition (TiO2:SDS) exhibit enhanced photocurrent, due to its very rough texture and presumably to better efficiency of charge carrier separation. Electrochemical deposition of platinum on the oxide-coated BDD was carried out in a second step and AFM, SEM and XPS measurements have shown that, on the TiO2:SDS substrate, Pt particles are smaller, more uniformly distributed, and tend to form clusters, leading to a specific surface area of the electrocatalyst of ca. 6.55m2g−1. Carbon monoxide stripping experiments demonstrated that, when deposited on TiO2:SDS, Pt particles are also less sensitive to CO-poisoning during methanol anodic oxidation.

Platinum catalysts supported on Nafion functionalized carbon black for fuel cell application

We report a high performance supported Pt catalyst, in which a perfluorosulfonic acid (Nafion) functionalized carbon black is used as support. The catalyst is characterized by infrared spectroscopy (IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM image shows that the active Pt component is in nanoparticles and highly dispersed on the carbon black with an average particle size of 1.9 nm. The catalyst shows improved activity towards the methanol anodic oxidation and oxygen reduction reaction (ORR), resulting from the high dispersion of active Pt component. It leads to increases in electrochemically accessible surface areas and ion channels, as well as easier charge-transfer at polymer/electrolyte interfaces. The high platinum utilization and high performance of Pt/Nafion-C catalyst make it a promising electrocatalyst for fuel cell application.

Size-controlled synthesis and characterization of polyvinyl alcohol-coated platinum nanoparticles: role of particle size and capping polymer on the electrocatalytic activity

Electrocatalytically active polymer–platinum nanocomposites have been synthesized in one pot by refluxing an aqueous solution consisting of chloroplatinic acid, PVA and formic acid. The as-synthesized platinum nanoparticles have large variations in their average size from 2.9 to 60.0 nm. The size of the nanoparticles is tuned by changing the concentration of the stabilizer as well as that of the reducing agent. In addition, the particle size is also controlled by varying the reflux time for a particular precursor solution. In this study, the nanoparticles have been characterized by UV-visible spectroscopy, XRD, TEM, FE-SEM and cyclic voltammetry. The study also shows that nanoparticles have size-dependent electrocatalytic behavior for anodic oxidation of alkaline methanol when the particle surface bears almost the same concentration of PVA. But the expected catalytic activity based on the particle size is found to alter when the nanoparticles possess a different surface concentration of PVA.

The Effect of Appending of I<sup>-</sup>，Fe<sup>2+</sup> and MnO<sub>4</sub><sup>-</sup> to the Electro-Oxidation of Methanol on Platinum Electrode

Three kinds of ions (I-、Fe2+and MnO4-) were appended into the methanol aqueous solution respectively as an additive and the Cyclic voltammograms of the aqueous solutions were studied. The results showed that Fe2+had obvious promotion effect for electro-oxidation of methanol and could improve the methanol anodic oxidation current by 85 percent. The promotion effect of the thulium Ions were related with the electronic distribution of these elements and their adsorption on the Pt electrode surface. I-and MnO4-could facilitate the electro-oxidation of methanol at different extent.

Electrocatalytic and photocatalytic activity of Pt–TiO2 films on boron-doped diamond substrate

In the present work boron-doped diamond (BDD) polycrystalline films were used as support for direct anodic deposition of hydrous titanium oxide, and continuous TiO2 coatings were obtained by appropriately adjusting the deposition charge. The photoelectrochemical activity of the TiO2/BDD electrodes was investigated and it was found that, in terms of charge carriers separation efficiency, conductive diamond is a much better support for TiO2, compared to traditional carbonaceous materials such as glassy carbon. Further electrochemical deposition of platinum particles on the oxide-coated conductive diamond enabled the formation of a composite with enhanced electrochemically active surface area. The electrocatalytic and photocatalytic properties of the Pt/TiO2/BDD electrodes thus obtained were also scrutinized and it appeared that these hybrid systems also exhibit promising features for methanol anodic oxidation.

High-performance Pd@PtRu/C catalyst for the anodic oxidation of methanol prepared by decorating Pd/C with a PtRu shell

A high-performance, low platinum loading catalyst for the anodic oxidation of methanol, Pd@PtRu/C, is prepared by a two-step colloidal approach. The activity of the Pd@PtRu/C catalyst is 1.67 times and 1.81 times that of PtRu/C and PtRuPd/C catalysts, respectively. The catalysts are characterized by TEM, XPS, and XRD. The active components are dispersed on the surface of the carbon support very well, yielding a particle size of ca. 4.7 nm and a shell thickness of ca. 0.25 nm. The catalyst's high activity may be attributed to the high exposure and dispersion of PtRu, as well as the interaction of PtRu in the shell layer with Pd in the core, resulting from the catalyst's core–shell structure.

Electrochemical preparation and characterization of a cobalt oxide–platinum composite with promising capacitive and electrocatalytic features

In the present work, boron-doped diamond polycrystalline films were used as support for direct anodic deposition of the cobalt oxide, and continuous Co3O4 coatings with reasonably good conductivity were obtained by appropriately adjusting the deposition charge. Further electrochemical deposition of platinum particles on the oxide substrate enabled the formation of a stable composite with a specific capacitance of ca. 431 F cm−3 that compares well with that available with similar materials obtained by non-electrochemical methods. Additional advantages of electrochemically obtained composites are the lower content of noble metal, the uniform distribution of the charge over an extended potential range, and, importantly, the simplicity of the preparation method. It was also found that when deposited on a Co3O4 substrate, Pt particles show, besides an enhanced active surface area, an improved catalytic activity for methanol anodic oxidation. This behavior was tentatively ascribed to the presence of a high amount of platinum-oxidized species.

Functional Effects of the Deposition Substrate on the Electrochemical Behavior of Platinum Particles

In the present work, polytyramine (PTy) and cobalt oxide (Co3O4) were used as substrates for platinum electrodeposition, in order to obtain electrode systems with electrocatalytic properties. PTy and Co3O4 were previously electrochemically deposited on graphite and boron-doped diamond (BDD) supports, respectively. Anodic oxidation of methanol was used as a test-reaction for assessing possible functional effects of the substrate on the electrochemical behavior of the Pt particles. It was found that, when deposited on PTy or cobalt oxide, the electrocatalyst exhibits higher activity and is less susceptible to fouling, via strong adsorption of reaction intermediates. X-ray photoelectron spectroscopy (XPS) measurements suggested that these features can be ascribed to the presence of –OH functional groups at the surface of the Pt particles. It was also found that electrodeposition of platinum on BDD resulted only in metallic Pt and Pt(OH)2, whereas when graphite was used as substrate the presence of platinum oxides was also evident. During prolonged anodic oxidation of methanol, a higher stability of the –OH groups from the platinum surface was observed for graphite-supported Pt particles, compared to the case when bare BDD was used as support.

Volume production of high loading Pt/C catalyst with high performance via a microwave-assisted organic colloid route

A scale-up preparation of high-loading Pt/C (40wt%) to 3g per pot has been achieved with a microwave-assisted organic colloid method, followed by appropriate heat treatment in alternating atmospheres (nitrogen, oxygen, and hydrogen). The catalysts prepared in this work were characterized by thermogravimetric analysis, X-ray diffraction analysis, and transmission electron microscopy etc., and were found to be competitive with state-of-the-art HiSPEC 4100 Pt/C catalyst in terms of their activities towards the anodic oxidation of methanol and the cathodic reduction of oxygen. They also displayed better cathodic activity and stability in a hydrogen/air single-cell test. The particle size was as small as 2.3nm, which is smaller than HiSPEC 4100 Pt/C catalyst. The scale-up work reported in this paper provides a practicable method to achieve the volume production of a high-loading Pt/C catalyst for fuel cell applications.

Spontaneous deposition of Pd onto Fe–Cr–Al alloys

The spontaneous deposition of Pd onto Fecralloy sheets and foams was studied. Pd deposits were obtained by immersion of Fecralloy samples in mildly acid, deaerated PdCl2 solutions, at open circuit. Pd displaced all alloy elements and deposited onto the alloy which was initially coated by an oxides film and underwent transpassive dissolution. The Pd loading and the Pd surface area were determined as a function of experimental conditions, like the nature of the Fecralloy sample (sheets or foams of variable grade), the concentration of the PdCl2 solution and the duration of the deposition. The results were compared to those obtained by depositing Pd onto Ni foams, with the same procedure. The Pd deposition rates were not much different on Fecralloy and Ni, but the Pd surface area per unit Pd mass was significantly higher for Ni than for Fecralloy. The Pd deposit morphology was influenced by the presence of passive oxides on the Fecralloy surface. The catalytic activity in methanol anodic oxidation depended only on the Pd surface area, irrespective of the nature of the support (Ni or Fecralloy).

Synthesis of α-germyl and α-silylcarboxylic acids and selected electrochemical oxidations

New α-germylcarboxylic acids, α-silyl-α-halocarboxylic and α-silyl-α-alkylcarboxylic acids including some known α-silyl(cycloalkyl)carboxylic acids have been prepared by different synthetic methods. The anodic oxidation in basic methanol of selected examples of these acids has been investigated under various experimental conditions to afford mainly oxidative degermylation/desilylation and decarboxylation products. Based on the emerged products, various mechanisms are suggested and discussed.

CeO2/rGO/Pt sandwich nanostructure: rGO-enhanced electron transmission between metal oxide and metal nanoparticles for anodic methanol oxidation of direct methanol fuel cells

Pt-based nanocomposites have been of great research interest. In this paper, we design an efficient MO/rGO/Pt sandwich nanostructure as an anodic electrocatalyst for DMFCs with combination of the merits of rigid structure of metallic oxides (MOs) and excellent electronic conductivity of reduced oxidized graphene (rGO) as well as overcoming their shortcomings. In this case, the CeO(2)/rGO/Pt sandwich nanostructure is successfully fabricated through a facile hydrothermal approach in the presence of graphene oxide and CeO(2) nanoparticles. This structure has a unique building architecture where rGO wraps up the CeO(2) nanoparticles and Pt nanoparticles are homogeneously dispersed on the surface of rGO. This novel structure endows this material with great electrocatalytic performance in methanol oxidation: it reduces the overpotential of methanol oxidation significantly and its electrocatalytic activity and stability are much enhanced compared with Pt/rGO, CeO(2)/Pt and Pt/C catalysts. This work supplies a unique MO/rGO/Pt sandwich nanostructure as an efficient way to improve the electrocatalytic performance, which will surely shed some light on the exploration of some novel structures of electrocatalyst for DMFCs.

Synthesis of NaA zeolite using PTMAOH(phenyltrimethylammoniumhydroxide): hydrothermal and microwave heating methods and comparison of their XRD patterns

Ion exchanging is one of the characteristics of the zeolites. Zeolites have octahedral and tetrahedral holes to trap ions and molecules. They also can exchange many ions in solution because of the size of the attendant ions. As a matter of fact, the property of the ion-exchanged zeolites depends on the ligands involved in the ion exchanging solutions. Ion exchanged zeolites are used as catalyst for studying the anodic oxidation of methanol in an acidic medium to investigate their suitability for use in direct methanol fuel cells (DMFCs). Some of the zeolites that have exchanged ions are shown to have redox and catalytic properties [1-3]. As an example A. Itadani et al., have reported the preparation of copper ion exchanged ZSM-5 for calorimetric study of N2 adsorption on Cu-ZSM-5 zeolite [4]. In another study, A. Ribera et al. have reported the characterization of redox properties and application of Fe-ZSM-5 catalysts [5]. In this research we prepared silicate solutions by dissolving silica in sodium hydroxide. Aluminosilicate solutions with different Al/Si ratios were prepared by mixing appropriate quantities of sodium silicate solutions with freshly prepared sodium aluminate solutions and the NaA zeolites were made by hydrothermal method. Then, their XRD patterns and IR spectra were also considered. Obviously, those zeolites which have Al-OH and Si-OH groups can lose their protons in basic solutions. In this way zeolites can adsorb many ions with positive charge. We investigated ion exchange property of Fe3+, Cu2+, Ni2+ and Hg2+ in systems with pH equals to 2, 4, 6 and 8. We found that the aluminosilicate with Si/Al = 1, has greatest exchange capacity for all of the ions studied in this work.

The Role of Nanostructured Active Support Materials in Electrocatalysis of Direct Methanol Fuel Cell Reactions

The necessity for developing oxidation–resistant noncarbon catalyst support materials for use in the electrode/electrolyte interface of proton exchange membrane (PEM) based direct methanol fuel cells (DMFCs) is emphasized. A great deal of attention is currently being paid to nanostructured catalytic and support materials for electrocatalysing both anodic methanol oxidation reaction (MOR) and cathodic oxygen reduction reaction (ORR). The performances of various nanostructured transition metal oxides have been reviewed. Mn3O4 nanorods have been synthesized by us and their performances for electrocatalysing the MOR with Pd catalyst are discussed. A model explaining how nanostructured active support materials can extract active oxygen atoms required for complete oxidation of methanol from the electrolyte and supply to the adjacent catalytic sites has been proposed.

A Comparative Study of Carbon-Supported Pt-Mo and Pt-Ru Catalysts for the Anodic Oxidation of Methanol

Different carbon-supported Pt-Mo and Pt-Ru materials were synthesized and a systematic study was carried out in order to evaluate their catalytic activity towards methanol oxidation. Direct current methods were applied in sulfuric acid and methanol - containing electrolytes, in order to evaluate the electrochemical response of the studied electrodes. Pt-Mo catalysts reveal similar performances and, in some cases, higher than Pt-Ru materials. For both catalysts series, it was found that low loadings of the promoting metal (Ru or Mo) improve the methanol oxidation activity. Characterizations by means of transmission electron microscopy and X-Ray Diffraction allowed to measure mean particle sizes below 10 nm for all phases. The Pt-Ru catalysts consist of metallic Pt and metallic ruthenium, while in the The Pt-Mo materials platinum is present in its metallic state and MoO3 is the predominant molybdenum species.

Synthesis of NiCr Nano Oxides as Anode Electrocatalysts for Direct Methanol Fuel Cell

NiCr nano oxides have been synthesized by impregnation method and were used as the anode electrocatalysts for direct methanol fuel cell(DMFC). The catalysts were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The activity of catalysts with different metal molar ratios and calcination temperatures on the methanol oxidation reaction were investigated by cyclic voltammetry(CV) and bulk electrolysis with coulometry. The results show that the NiCr nano oxides calcined at 500°C for 6h gave an excellent electrocatalytic performance in the anodic oxidation of methanol.

Preparation of High Performance Core-Shell PdRu@Pt/CNT Electrocatalyst

We prepared a low Pt loading core-shell structured catalyst PdRu@Pt/CNT (carbon nanotube) with a PdRu alloy as the core and platinum as the shell in addition to carbon nanotubes as supports in a two-stage precipitation-reduction approach. For the anodic oxidation of methanol the activity in terms of Pt loading increased by 70% compared with the lab-made Pt/CNT catalyst and the ratio of the forward current density (I(subscript f)) to the backward current density (I(subscript b)) was as high as 2, which is two times of that of Pt/CNT, indicating that the dispersion and use of platinum effectively improves by covering the surface of the PdRu cores with platinum. Excellent tolerance towards the intermediates of the anodic oxidation of methanol may result from the interaction between the Pt shell and the PdRu core. The core-shell structure of the catalysts was revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM image showed that the active components are highly dispersed on the CNT with a particle size of 4.0 nm. The high platinum utilization and high performance as well as good tolerance toward poisons make the PdRu@Pt/CNT catalyst a promising low-Pt catalyst for low temperature fuel cell applications.

Shortened Carbon Nanotubes as Enhanced Support for High‐performance Platinum Catalysts

AbstractCarbon nanotubes (CNTs) were shortened from 5 to 15 μm to ca. 200 nm using ball milling with ethanol as the milling aid agent, and a platinum catalyst with these shortened carbon nanotubes (SCNTs) as the support was prepared by a high‐pressure colloidal method. It was found that this catalyst with SCNTs showed much higher activity than a platinum catalyst with normal CNTs as support; for methanol anodic oxidation, the activity of the Pt/SCNTs was 50% higher than that of the Pt/CNTs, and the Pt/SCNTs also showed higher activity for the cathodic reduction of oxygen. The Pt/SCNTs were characterised by X‐ray diffraction scanning and transmission electron microscropy. It is suggested that the significant performance enhancement when SCNTs are used as support might result from the generation of new surfaces and defects, the opening of closed nanotubes in the process of milling, higher platinum dispersion on the shortened nanotubes and the interaction of platinum nanoparticles with the SCNTs.

Investigating the addition of silicon oxide to carbon: Effects of amount and heat treatment on anti-aggregation and electrochemical performance of Pt catalysts

Small nanoparticles offer high surface areas and are certainly desirable for electrocatalytic reactions and fuel cells. However, the drawback of using small nanoparticles is their tendency towards particle aggregation. This paper aims to inhibit platinum agglomeration by adding silicon oxide to a carbon support for enhanced catalytic activity in low-temperature fuel cells. The catalysts are characterized by X-ray diffraction and transmission electron microscopy. Physical characterization and cyclic voltammetry techniques at room temperature are used to assess the effects of silicon oxide amount, post-heating temperature, and holding time on particle size and dispersion of active components, and the catalysts’ activity towards the methanol oxidation and oxygen reduction reactions. It is found that using a support of carbon powder with 3 wt.% silicon oxide can enhance the electrochemically active surface area of Pt catalysts and their activity towards the anodic oxidation of methanol and reduction of oxygen. The active components are also more resistant than Pt/C to agglomeration upon heating.

ChemInform Abstract: Preparation of Platinum Cluster-Derived Electrodes from Metal Carbonyl Complexes and Their Electrocatalytic Properties for Anodic Oxidation of Methanol.

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