Alkaline methanol–air system

Methanol is a promising fuel for power devices such as fuel cells because it has a high theoretical capacity per volume and weight, is relatively easy to handle and is easy to store. Many studies on the alkaline methanol fuel cell system were made in the 1960s and 1970s. The article gives a brief summary of these studies and shows some results of the new work started recently at the TU Graz, AustriaDedicated to Prof. Wolf Vielstich on the occasion of his 80th birthday in recogniton of his numerous contributions to interfacial electrochemistry.     

Phase diagram studies of methanol–CHF3 and methanol–H2O–CHF3 mixtures

Comprehensive phase diagrams of methanol/CHF₃ and methanol/H₂O/CHF₃ mixtures over the temperature range of 25–100°C and pressure range of atmospheric to 340 atm are reported. Fluoroform is expected to be useful as an alternative to CO₂ for enhancing the fluidity of liquid mixtures due to its high polarity and low viscosity. Therefore, these mixtures will be studied as mobile phases for enhanced-fluidity liquid chromatography and extraction. The phase behavior of methanol/CHF₃ and methanol/H₂O/CHF₃ was compared to that of methanol/CO₂ and methanol/H₂O/CHF₃. Fluoroform is markedly more miscible with methanol or methanol/H₂O than is CO₂. Data for methanol/CHF₃ binary mixtures were also modeled by the Peng–Robinson equation of state. The correlation results showed that the PR equation of state with two temperature-independent binary parameters was capable of representing the experimental data over the entire temperature range with an average relative deviation within 6%.     

Pd/Pt core–shell nanowire arrays as highly effective electrocatalysts for methanol electrooxidation in direct methanol fuel cells

Highly ordered Pd/Pt–core–shell nanowire arrays (Pd/Pt NWAs) have been prepared by anodized aluminum oxide (AAO) template-electrodeposition and magnetron sputtering methods. Pd/Pt NWA electrode shows a very high electrochemical active surface area and high electrocatalytic activity for the methanol electrooxidation in acid medium for direct methanol fuel cells (DMFCs). The mass specific anodic peak current density is 756.7 mA mg⁻¹ Pt for the methanol oxidation on the Pd/Pt NWA electrode, an increase by a factor of four as compared to conventional E-TEK PtRu/C electrocatalysts. The mechanism of the significant enhancement of the Pd/Pt core/shell NWA nanostructure in the efficiency and electrocatalytic activity of Pt for the methanol electrooxidation in acid medium is discussed.     

Liquid—liquid equilibrium in methanol + gasoline blends

An investigation has been carried out to study the limited miscibility of methanol and gasoline blends over the temperature range −20 to 20°C. Two liquid phases in equilibrium were analysed by mass spectrometric methods and their composition reported, in addition to the methanol content, in terms of six principal classes of hydrocarbons. Liquid—liquid equilibrium was predicted using the UNIFAC group contribution model. In liquidliquid equilibrium calculations, gasoline was represented by a set of model compounds. The number of the different groups that comprise each model molecule was determined using the result of a distillation analysis and the paraffin—naphthene—aromatic composition. Estimation of conjugate phase composition using the UNIFAC model is reasonable at temperatures above 0°C. To describe correctly the limited miscibility of methanol+gasoline blends over the whole temperature range studied, we found that ‘specific’ UNIFAC interaction parameters were necessary.     

Thermodynamic characteristics of the adsorption of 1,3,4-oxadiazoles and 1,2,4,5-tetrazines from methanol and water–methanol solutions onto hypercrosslinked polystyrene

Russian Journal of Physical Chemistry A - The thermodynamic characteristics of the adsorption of several 1,3,4-oxadiazoles and 1,2,4,5- tetrazines from methanol and water-methanol solutions onto...     

Liquid—liquid equilibria for the methanol—toluene—n-octane and methanol—toluene—n-hexane systems at 25°C

Ternary liquid—liquid equilibrium data have been measured for the methanol—toluene—n-octane and the methanol—toluene—n-hexane systems at 25°C. The results have been correlated using a modified Wilson equation.     

Inclusion complexes ofγ-cyclodextrin with coronene in aqueous methanol

Coronene has been found to form an inclusion complex with -cyclodextrin (-CD) in methanol-H₂O (6:4 v/v). The inclusion complex, which has a 2 : 1 stoichiometry of -CD to coronene, tends to bind methanol. Upon addition of 1-adamantanol or adamantane to a solution of -CD and coronene, the absorption spectrum of coronene underwent changes in a manner similar to that observed when the -CD concentration was increased in a coronene solution, indicating the formation of a ternary complex composed of -CD, coronene, and 1-adamantanol or adamantane. The complex-forming equilibrium was investigated on the basis of fluorescence measurements.     

FT-IR studies of molecular interactions in formamide–methanol mixtures

FT-IR spectra of formamide (FA)–methanol (MeOH) mixtures have been measured by ATR technique. Factor analysis applied to the spectra has shown two kinds of intermolecular complexes differing in a manner of polarization of component molecules. The composition of the complexes changes monotonically with the composition of the mixtures. The spectra in the CO stretching region have been analyzed separately using both: the factor analysis and the difference spectra method. Four different environments of carbonyl group of formamide has been revealed over the whole range of the mixture composition. The mean number of formamide molecules disturbed by one methanol molecule via carbonyl group in the formamide-rich region has been found as equal to 1.5. Presumable structures for the molecular complexes have been proposed to explain the results of the analyses.     

Methane oxidation by green oxidant to methanol over zeolite-based catalysts

To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals（rather） than to flare it.Conversion of methane to liquid oxygenates（mainly methanol） has attracted extensive attention and countless efforts have been made;however,running this reaction in a green,efficient,and practical way has remained elusive.The novel catalyst and oxidants play a critical role in activating methane and converting it to oxygenates（methanol）.In this revie...     

Platinum–polytyramine composite material with improved performances for methanol oxidation

Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward method exhibited, for platinum loadings as low as ca. 0.12 mg cm⁻², a specific electrochemically active surface area of the electrocatalyst of ca. 54 m² g⁻¹, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH₃OH oxidation.     

Solubilities of isobutane in methanol + benzene,methanol + cyclohexane and benzene + cyclohexane mixed solvent solutions at 298 K and 40–102 kPa

The solubilities of isobutane at pressures from 40 to 102 kPa and a temperature of 298.15 K are presented for three mixed solvent solutions: methanol + benzene, methanol + cyclohexane, and benzene + cyclohexane.     

Photochemical addition of methanol to V60:Formation of 1,4-dimethoxyfullerene

The addition of methanol to C60 in the presence of acetylglycine (AG) was carried out under irradiation.The novel compound,1,4-dimethoxyl-l,4-dihydrofullerene (1),was isolated and characterized by FTIR,UV-vis,1H and 13C NMR,and FDMS.     

Reduction of the quinizarin molecule in methanol as studied by γ-radiolysis

The disproportionation of quinizarin semiquinones in methanol solutions of different pH has been investigated using the -radiolysis method. After⁶⁰Co-irradiation of deaerated solutions the corresponding changes in the optical absorption spectra were recorded. In solutions of different pH the semiquinones disproportionate to give appropriate forms of quinizarin hydroquione which can react with oxygen to regenerate the parent compound. In neutral and acidic methanol the corresponding form of hydroquinone (1,4,9,10-tetrahydroxyanthracene) undergoes a transformation leading to formation of 9,10-dihydroxy-2,3-dihydro-1,4-anthraquinone which is unreactive towards oxygen.     

PPO-based acid–base polymer blend membranes for direct methanol fuel cells

New acid–base polymer blend membranes for direct methanol fuel cells (DMFC) have been designed using a very accessible commercial polymer, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). The preparation begins with the sulfonation and bromination of PPO to sulfonated PPO (SPPO) and bromomethylated PPO (BrPPO), respectively. Blend membranes are formed by mixing n-propylamine(PrNH₂)-neutralized SPPO and PrNH₂-aminated BrPPO solutions in N-methyl-2-pyrrolidone (NMP), and casting the mixed solution on glass petri dishes followed by acidification with aqueous hydrochloric acid. The compatibility between the acid and base components of the blend is assured by using acidic and basic polymers deriving from the same parent polymer (PPO). Ionic crosslinking is established between the sulfonic groups of SPPO and the amine groups of aminated BrPPO. The ionic crosslinking strengthens the membrane dimensional stability by reducing water uptake and membrane swelling up to temperatures as high as 80 °C. The membranes fabricated as such display good resistance to methanol crossover amidst some, but acceptable loss of proton conductivity. The characteristic factor (i.e. the ratio of proton conductivity to methanol permeability) increases noticeably with the BrPPO content, with the sample containing 30 wt.% BrPPO showing a 16-fold improvement over Nafion 117. The mechanical properties and oxidative stability of the blend membranes also satisfy the requirements for fuel cell assembly and operation.     

Investigation of unsupported Pt–Ru catalysts for high temperature methanol electro-oxidation

Two unsupported Pt–Ru catalysts, varying in the nature and content of RuOx species, were investigated for methanol electro-oxidation in a solid polymer electrolyte fuel cell at high temperature. The catalyst containing a lower amount of ruthenium oxide showed higher catalytic activity and lower mass transport limitations. A physicochemical investigation was carried out to support the interpretation of electrochemical results. Pt–Ru alloy appears more active than Pt–RuOx in the chemisorption of labile-bonded oxygenated species, which promote the oxidation of the methanolic residues adsorbed on the catalyst surface.     

Vapor—liquid equilibrium studies for the carbon dioxide—methanol system

Experimental vapor—liquid equilibrium measurements of carbon dioxide and methanol have been conducted from 230 K (−43.15°C) to 330 K (56.85°C) at pressures to the very vicinity of the critical states. The consistency of the data sets are examined and compared to literature values.Unlike the methane—methanol system, which exhibits two liquid phases at low temperatures, the carbon dioxide—methanol system exhibits complete liquid phase miscibility. Accordingly, the effects of critical behavior on the vapor liquid equilibria behavior begin to manifest themselves at much lower pressures.     

Combinatorial screening of ternary Pt–Ni–Cr catalysts for methanol electro-oxidation

Methanol electro-oxidation activity of ternary Pt–Ni–Cr system was studied by using a combinatorial screening method. A Pt–Ni–Cr thin-film library was prepared by sputtering and quickly characterized by a multichannel multielectrode analyzer. Among the 63 different composition thin-film catalysts, Pt₂₈Ni₃₆Cr₃₆ showed the highest methanol electro-oxidation activity and good stability. This new composition was also studied in its powder form by synthesizing and characterizing Pt₂₈Ni₃₆Cr₃₆/C catalyst. In chronoamperometry testing, the Pt₂₈Ni₃₆Cr₃₆/C catalyst exhibited “decay-free” behavior during 600 s operation by keeping its current density up to 97.1% of its peak current density, while the current densities of Pt/C and Pt₅₀Ru₅₀/C catalysts decreased to 14.0% and 60.3% of their peak current densities, respectively. At 600 s operation, current density of the Pt₂₈Ni₃₆Cr₃₆/C catalyst was 23.8 A g_{noble metal}⁻¹, while that of those of the Pt/C and Pt₅₀Ru₅₀/C catalysts were 2.74 and 18.8 A g_{noble metal}⁻¹, respectively.     

Photolysis of [PtBr6]2– complex in frozen methanol matrix

Photochemistry of the [PtBr₆]^2– complex in the low-temperature methanol matrix (77 K) was studied by low-temperature spectrophotometry and ESR spectroscopy. The [PtBr₄]^2– complex is the main photolysis product. The mechanism of two-electron reduction of the platinum(IV) ion is proposed. The primary photochemical process is electron transfer from the solvent molecule to the photoexcited initial complex to form the intermediate radical complex ([PtBr₆]^3–...^·CH₂OH). The transfer of the second electron in the radical complex produces the final reaction products.     

Layer-by-layer electrosynthesis of Pt–Polyaniline nanocomposites for the catalytic oxidation of methanol

A new composite material based on the electrochemical generation of a layer-by-layer structure of polyaniline (PANI) and Pt particles has been prepared. The number of layers and the nature of the external layer (PANI or Pt) determine the electrocatalytic performance of the composite for the oxidation of methanol. We demonstrate that the layer-by-layer approach to form the nanocomposite and modification of the Pt particles with a layer of PANI leads to substantially higher catalytic efficiency.     

Preparation of polyaniline–tin dioxide composites and their application in methanol electro-oxidation

Polyaniline–tin dioxide (PANI-SnO₂) composites were prepared by chemical polymerization method, and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Due to the good stability in diluted acidic solution, PANI-SnO₂ composites were selected as the catalyst support and second catalyst for methanol electro-oxidation. The electrocatalytic properties of the PANI-SnO₂ supported Pt catalyst (Pt/PANI-SnO₂) for methanol oxidation have been investigated by cyclic voltammetry, chronoamperometry, and chronopotentiometry. Under the same loading mass of Pt, the Pt/PANI-SnO₂ catalyst shows higher electrocatalytic activity towards methanol electro-oxidation than Pt/SnO₂ catalyst.