Structure of the α-phase of solid methanol

The crystal structure of α-methanol at 15K has been determined from neutron powder diffraction measurements. The structure is orthorhombic, space group P2₁2₁2₁. The molecular geometry is found to be very similar to that in the gas phase, but the methyl group no longer has ideal 3-fold symmetry. The crystal is formed by infinite hydrogen-bonded chains of molecules with adjacent chains ‘pointing’ in opposite directions. The O-H … O hydrogen bonds are almost linear. No phase intermediate between the low temperature α-phase and the high temperature β-phase was found, but a new, metastable phase was discovered.     

I–V characteristics of a methanol concentration sensor for direct methanol fuel cell (DMFC) by using catalyst electrode of Pt dots

In this work, the methanol sensors were fabricated by using Pt dot catalyst electrode and the level of electrochemical response was analyzed. This kind of sensors can be applicable to sensing the methanol concentration in real-time. When we measured the methanol sensor with 5 nm of Pt dot, we could get 2.00 × 10⁻⁶, 3.06 × 10⁻⁶ and 6.25 × 10⁻⁶ A of electric current value for the methanol concentration of 1, 2 and 3 mole, respectively. The measured voltage was 1 V. To optimize the sensitivity level of Pt dot catalyst electrode, the electrodes were made in H-grid shape. The distance between electrode branches was designed to be 80, 150 and 300 μm, respectively. When we measured the electric current–voltage characteristics of methanol sensor with 2 M of methanol, it was 3.06 × 10⁻⁶, 2.02 × 10⁻⁶ and 1.50 × 10⁻⁶ A, for 80, 150 and 200 μm, respectively. Thus it is suggested that more efficient response of methanol sensing is possible when the distance between electrodes is reduced.     

On interpretation of EPR spectrum of free radicals in γ-irradiated methanol

Some authors interpret the EPR spectrum in-irradiated methanol at 77K either by the radical H₂OH or by ⁺ H₂. In order to contribute to this question we have calculated the values of the hyperfine splitting constants of this EPR spectrum as a function of the valence angle H-C-H in a CH₂ fragment. The comparison of the experimental and calculated values of the hyperfine splitting constant and a discussion of the possible valence angles leads us to the conclusion that the EPR spectrum in irradiated methanol originates from the radical H₂OH.The author thanks J. Teplý for valuable remarks which helped this work.     

Hydrogen bond lifetimes in supercritical methanol–water mixtures via MD simulation

Dynamical features of hydrogen bonds in methanol–water mixtures have been analysed in terms of lifetime in the wide range of conditions, including supercritical states, using a molecular dynamics simulation with flexible potential models. Hydrogen bond characteristics in methanol–water mixtures were investigated by considering the combination of molecular species and donor–acceptor of hydrogen-bonded molecules. The hydrogen bond lifetimes mainly depend on temperature, and those in supercritical condition were about 1/10th of that at ambient condition. Focusing on the composition dependence of the hydrogen bond lifetime, the unique behaviour of that resulting from hydration structure was observed. Moreover, the molecular combination, which showed the largest hydrogen bond lifetime, was different for ambient and high temperature and high pressure conditions. The relationship between hydrogen bond lifetime and molar volume was also calculated to discuss the hydrogen bond lifetime in terms of the collision frequency of molecules and the intermolecular distance.     

Quantitative analysis of ethanol–methanol–water ternary solutions using Raman spectroscopy

Raman spectroscopy was used for rapid in-situ measurement of alcohols in ethanol-methanol-water ternary systems. Mass fractions of the individual components were determined using calibration curves for binary systems of ethanol-water, methanol-water, and ethanol-methanol. Calibration curves were constructed by calculating the ratio of the Raman peak intensity of a component and that of an external standard (acetonitrile). Assuming additivity of the spectra, simultaneous equations were written, and mass fractions of ethanol, methanol, and water in the ternary solutions were determined by solving the system of equations through calculating an inverse matrix. The relative errors between the mass fractions obtained from the Raman spectra and those obtained from mass measurements were <0.6%.     

Surface modification of bulk n-InAs (111)A etched in bromine–methanol

X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Raman and photoluminescence spectroscopy were used to evaluate the surface properties of n-type InAs (111)A etched in a 1% Br–methanol solution. Etching completely removes the native oxides from the surface and enhances the photoluminescence response. The adsorption of bromine onto the InAs surface leads to the formation of In–Br_x and As–Br_x bonds (x = 1, 2, 3) as inferred from changes in the In 3d_3/2;5/2 and As 3d core level binding energies. The etch rate is found to decrease due to strong anisotropic effects and the high volatility of the bromine species. A 1 min Br–methanol etch was found to enhance the photoluminescence intensity by a factor of 3, probably due to a reduction in the surface state density upon de-oxidation of the surface. This is thought to be due to reductions in the surface state density. The presence of native oxides enhances both the surface accumulation layer and the surface state density.     

Tuning of size and shape of Au–Pt nanocatalysts for direct methanol fuel cells

In this article, we report the precise control of the size, shape, and surface morphology of Au–Pt nanocatalysts (cubes, blocks, octahedrons, and dogbones) synthesized via a seed-mediated approach. Gold “seeds” of different aspect ratios (1–4.2), grown by a silver-assisted approach, were used as templates for high-yield production of novel Au–Pt nanocatalysts at a low temperature (40 °C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis, UV–Vis spectroscopy, zeta-potential (surface charge), atomic force microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry were used to better understand their physico-chemical properties, preferred reactivities and underlying nanoparticle growth mechanism. A rotating disk electrode was employed to evaluate the Au–Pt nanocatalysts electrochemical performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction of direct methanol fuel cells. The results indicate the Au–Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au–Pt dogbones and Pt-black; however, its performance is affected by the presence of MeOH.     

Ion-molecular interactions in the methylsulfonic acid—methanol system according to the IR spectral data

The methylsulfonic acid (MSA)—methanol (MeOH) liquid binary system was studied over the whole concentration range by the MBTIR IR spectroscopy method at 30°C. Quasi-ion pairs with the 1: 1 composition formed by a strong symmetrical H-bond were only present in solutions with an equimolar acid: base ratio. The addition of methanol caused the solvation of quasi-ion pairs by MeOH molecules, and, in the presence of the base in a substantial excess (C _MeOH⁰: C _MSA⁰ > 2), proton disolvates (Me(H)O⋯H⋯O(H)Me)⁺ with strong symmetrical H-bonds were formed; that is, there was B⋯H⋯A + B ↔ (B⋯H⋯B)⁺ + A⁻ equilibrium, where B is the base molecule and HA is the acid. In the presence of excess acid, methanol was protonated, and negatively charged proton disolvates were formed, B⋯H⋯A + HA ↔ BH⁺ + (AHA)⁻. This equilibrium was fully shifted to the right.     

Does methanol produce a stable methoxy species on Ru(0001) at low temperatures?

Soft X-ray photoelectron spectroscopy (SXPS) and energy-scanned photoelectron diffraction (PhD) have been used to study the surface species produced by exposure of Ru(0001) to methanol at ~ 150 K. SXPS shows a single surface species is formed at sub-monolayer coverages with an O 1s peak binding energy of ~ 532.6 eV, 2.8 eV greater than that of chemisorbed atomic oxygen. O 1s PhD data from this species shows no significant modulations, in contrast to simulated PhD spectra from a methoxy species occupying a three-fold coordinated hollow site, as predicted by earlier density functional theory calculations, or atop or bridging sites. By contrast, PhD data from the O 1s of the atomic oxygen species in the Ru(0001)(2 × 1)–O phase are consistent with the oxygen atoms occupying ‘hcp’ hollow sites (above second-layer Ru atoms) at a RuO bondlength of 2.01 ± 0.02 Å, essentially identical to previous structure determinations of this phase. O 1s PhD recorded at normal emission from adsorbed CO are also consistent with the known CO atop adsorption species. We conclude that the methanol-derived surface molecular species is not methoxy in a well-defined local site on the surface, but is consistent with clusters of intact methanol identified in a recent infrared spectroscopy investigation.     

Adsorption of water—methanol mixtures in carbon and aluminosilicate pores: a molecular simulation study

A theoretical study is reported of the adsorption behaviour of water—methanol mixtures in slit carbon and in uncharged alumino-silicate micropores. The adsorption isotherms are obtained for a pore of width of 2 nm and at a temperature of 298 K from grand canonical ensemble Monte Carlo simulations. The results show that the graphite and uncharged silicate surfaces are covered by a dense layer of flatly adsorbed water and methanol molecules having weaker hydrogen bonding. In the interior of the pore, the fluid exhibits bulk-like behaviour with a stronger hydrogen bonded structure. Solvation forces are also calculated as a function of pore size. The positive values found for the solvation force for all pore sizes reflect the hydrophobic interactions of the mixture with the carbon and uncharged alumino-silicate walls.     

Preparation of Pt–CeO2/MWNT nano-composites by reverse micellar method for methanol oxidation

We report the preparation of Pt–CeO₂ nanoparticles on the multi-walled carbon nanotubes (MWNTs) by a reverse micellar method. Transmission electron microscopy (TEM) analysis indicated that well-dispersed small Pt–CeO₂ nanoparticles were formed on the MWCNTs. X-ray diffraction (XRD) analysis confirmed the formation of the Pt–CeO₂ nanoparticles on the MWNTs. Cyclic voltammetry (CV) results demonstrated that the Pt–CeO₂/MWNT exhibited a higher methanol oxidation than did the Pt/MWNT catalyst. The CO stripping test showed that CeO₂ can make CO stripped at a lower potential, which is helpful for CO and methanol electro-oxidation.     

Effects of potassium on the adsorption of methanol on β-Mo2C(001) surface

We have studied the effect of K on the adsorption of methanol on the β-Mo₂C(001) surface and compared our experimental data with theoretical calculations. We have also performed high resolution electron energy loss spectroscopy (HREELS) (LK, ELS3000). For calculations we used the density functional theory under the VASP implementation. The most favorable sites for methanol adsorption are on top of a Mo atom in the clean surface and on top of a K atom in the pre-dosed surface. The changes in the work function fit our model as the surface withdraws charge from the adsorbate. The changes in the computed vibrational frequencies also agree with the HREELS results at very low coverage. The C–O bond distance increases while the O–H bond decreases making a C–O bond breakage a possibility on K covered surfaces.     

Tuning Pt–Cu nanostructures by bromide ions and their superior electrocatalytic activities for methanol oxidation reaction

Dendritic Pt–Cu nanoparticles were synthesized by a facile one-step method with the help of surfactant Brij58 at room temperature, and we also studied the effects of different Pt–Cu ratios on the morphology and size of nanoparticles. In addition, we further tuned the morphology of the Pt–Cu nanostructures by introducing bromide ions, eventually leading to the appearance of some tripod-like structures. Compared with dendritic Pt–Cu and commercial Pt black, these tripod-like Pt–Cu nanostructures exhibited higher electrocatalytic activity and CO tolerance for catalyzing methanol oxidation.

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Reaction intermediates of methanol synthesis and the water–gas-shift reaction on the ZnO(0001) surface

The polar Zn-ZnO(0001) surface is involved in the catalysis of methanol synthesis and the water–gas-shift reaction. We use density functional theory calculations to explore the favorable binding geometries and energies of adsorption of several molecular species relevant to these reactions, namely carbon monoxide (CO), carbon dioxide (CO₂), water (H₂O) and methanol (CH₃OH). We also consider several proposed reaction intermediates, including hydroxymethyl (CH₂OH), methoxyl (CH₃), formaldehyde (CH₂O), methyl (CH₃), methylene (CH₂), formic acid (HCOOH), formate (HCOO), formyl (HCO), hydroxyl (OH), oxygen (O) and hydrogen (H). For each, we identify the preferred binding geometry at a coverage of 1/4 monolayers (ML), and report calculated vibrational frequencies that could aid in the identification of these species in experiment. We further explore the effects on the binding energy when the adsorbate coverage is lowered to 1/9 and 1/16 ML.     

193Ir and 57Fe Mössbauer characterisation of iridium/iron bimetallic catalysts for methanol synthesis

Fe-Ir/MgO catalysts derived from the [Et₄N]₂[Fe₂Ir₂(CO)₁₂] cluster precursor, which exhibit a high activity in the synthesis of methanol from CO and H₂, were studied by ¹⁹³Ir and ⁵⁷Fe Mössbauer spectroscopy. The study extends from the precursors via the fresh to the aged catalysts. The presence of iridium in the metallic state as well as the presence of trivalent, divalent and alloyed iron is detected. The different structural features of catalysts prepared from mixed-metal cluster compounds and from inorganic salt precursors are discussed.     

The potential of CO2 laser photoacoustic spectrometry for?detection of methanol in alcoholic beverage

The first use of CO₂ laser photoacoustic measurements for detecting the methanol contents in alcohol-like solutions is presented. With an intracavity cell configuration, the minimum detectable concentration was ∼200 ppm for methanol and the linear range of the calibration curve for methanol was from 200 to 70000 ppm. For demonstrating the reliability of analysis in alcoholic beverages, a series of different concentrations of two-component samples was prepared and measured by the same procedures. The results showed the feasibility on determining methanol and ethanol contents accurately within a specific tolerance, limited mainly by background signal and laser stability. This potential method with no pre-treatment of samples takes only ∼10 min to finish one single measurement. It suggests that the PA detection is suitable for routine diagnosis of adulterated wines in commercial products.     

Comparison of O–H and C–H activation of methanol on Ni-based cluster: a DFT investigation

Using the density functional theory, the initial dehydrogenation of methanol on Ni_xM_y (M?=?Ni, Co, Fe, Mn, Cr, x?+?y?=?4, y?=?1, 2) clusters is investigated. Two adsorption and dehydrogenation mechanisms of methanol are studied: one proceeds along the C–H scission and another begins with the breaking of the O-H bond. The adsorption sites of methanol on the Ni or M sites of the Ni_xM_y clusters are considered. The adsorption of methanol on Ni₄ cluster is stronger than those on bimetallic clusters, while the initial dehydrogenation barriers on Ni_xM_y clusters are lower than that on Ni₄ cluster. The comparable energy barriers of two pathways (O–H or C–H dissociation) on Ni-based clusters indicate that these two paths are quite competitive. In addition, the Ni₂M₂ clusters show superior activation performance compared with the Ni₃M clusters, especially for Ni₂Mn₂ and Ni₂Cr₂ clusters. The effects of alloyed metal on the catalytic activity of Ni for methanol initial dehydrogenation, including the adsorption energy, O–H or C–H bond scission barrier and frontier molecular orbital levels, are discussed. It can be concluded that the addition of Co, Fe, Mn and Cr to Ni catalyst is able to enhance the activity of the methanol dehydrogenation reaction.     

Solubility of caffeine in the supercritical CO<Subscript>2</Subscript>–methanol binary solvent

The caffeine–methanol association constant at 313 K has been determined by ¹H NMR spectroscopy. The caffeine solubility in the supercritical carbon dioxide (SC-CO₂)–methanol mixed solvent has been calculated using the association constant experimentally measured by NMR in the framework of the associated solution + lattice (ASL) model, which is based on the theory of molecular association and a simple lattice model. Individual contributions to the solubility have been determined, and the relative role of various factors determining the solubility of caffeine in the mixed solvent has been analyzed. The caffeine solubility as a function of the methanol content of the SC-CO₂–methanol system is predicted to pass through a maximum.     

Ultrasonic-assisted synthesis of Pd–Pt/carbon nanotubes nanocomposites for enhanced electro-oxidation of ethanol and methanol in alkaline medium

Herein, a facile ultrasonic-assisted strategy was proposed to fabricate the Pd–Pt alloy/multi-walled carbon nanotubes (Pd–Pt/CNTs) nanocomposites. A good number of Pd–Pt alloy nanoparticles with an average of 3.4 ± 0.5 nm were supported on sidewalls of CNTs with uniform distribution. The composition of the Pd–Pt/CNTs nanocomposites could also be easily controlled, which provided a possible approach for the preparation of other architectures with anticipated properties. The Pd–Pt/CNTs nanocomposites were extensively studied by electron microscopy, induced coupled plasma atomic emission spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and applied for the ethanol and methanol electro-oxidation reaction in alkaline medium. The electrochemical results indicated that the nanocomposites had better electrocatalytic activities and stabilities, showing promising applications for fuel cells.