Preparation of 2D Carbon Materials by Chemical Carbonization of Cellulosic Materials to Avoid Thermal Decomposition.

Cellulosic materials, including regenerated cellulose, are promising precursors for a variety of carbon materials. However, thermal decomposition, typically accompanying carbonization at high temperatures, hinders cellulosic materials from being efficiently carbonized (i.e., very low carbon yields). Herein, this study presents a new and efficient method for the preparation of porous 2D carbon materials from sheet-like cellulosic materials, such as papers and fabrics, involving a catalyzed chemical reaction at high temperatures without thermal decomposition. Thus, cellulosic materials are treated with sulfonic acid solutions and significantly dehydrated at high temperatures via evaporation of water. As a result, black materials are obtained at a weight near the theoretical carbon content of cellulose and remain in the carbonized materials. The as-obtained porous 2D carbon materials are flexible and suitable for a wide range of applications such as in electrodes and gas absorbents.

Formic acid electrooxidation on Pd in acidic solutions studied by surface-enhanced infrared absorption spectroscopy.

A mechanistic study of electrocatalytic oxidation of formic acid on Pd in sulfuric and perchloric acids is reported. Surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode (ATR-SEIRAS) shows the adsorption of CO, bridge-bonded formate, bicarbonate, and supporting anions on the electrode surface. Poisoning of the Pd surface by CO, formed by dehydration of formic acid, is very slow and scarcely affects formic acid oxidation. The anions are adsorbed more strongly in the order of (bi)sulfate > bicarbonate > perchlorate, among which the most strongly adsorbed (bi)sulfate considerably suppresses formic acid oxidation in the double layer region. The oxidation is suppressed also at higher potentials in both acids by the oxidation of the Pd surface. Adsorbed formate is detected only when formic acid oxidation is suppressed. The results show that formate is a short-lived reactive intermediate in formic acid oxidation and is hence detected when its decomposition yielding CO(2) is suppressed. The high electrocatalytic activity of Pd can be ascribed to the high tolerance to CO contamination and also high catalytic activity toward formate decomposition.

Quantized hydration energies of ions and structure of hydration shell from the experimental gas-phase data.

With previous data on alkali metal and halide ions included [Rais, J.; Okada, T. Anal. Sci. 2006, 22, 533], we analyzed rather broad data on ionic hydration from the point of view of gaseous cluster energetics. We have now added alkaline earth cations, Zn(2+), H(+), OH(-), Cu(+), Ag(+), Bi(+), Pb(+), and alkylammonium cations. The present analysis revealed the octa-coordinated nature of alkaline earth cations, which is not fully pronounced for Be(2+) and Zn(2+), existence of Eigen protonium complex, which is trigonally hydrated, and particular property of the first OH-, H(2)O cluster. Whereas these findings are generally in accordance with theoretical model calculation studies, we have foreseen in addition tetrahedral hydration for halide anions and Rb(+) and Cs(+), as well as for alkylammonium ions. The obtained picture of the quantized solvation of ions is mirrored in the ionization potentials of outer electrons of pertinent atoms. This is a second independent phenomenon, and together, they invoked a common pattern formation ("Aufbau") obeying tetra- and octa-coordinated principles.

Alcohol and proton transport in perfluorinated ionomer membranes for fuel cells.

To clarify the transport mechanisms of alcohols and proton in perfluorosulfonated ionomer (PFSI) membranes for fuel cells, four membranes having different equivalent weight (EW) values were examined. Membranes were immersed in methanol, ethanol, and 2-propanol to prepare a total of 12 samples, and membrane swelling, mass (alcohol and proton) transports, and interactions between alcohols and proton were investigated systematically in the fully penetrated state. The membrane expansion fraction theta and alcohol content lambda increased with decreasing the EW value for all the samples. The self-diffusion coefficients (D's) of the alkyl group and of OH (including protons) were measured separately by the pulsed-gradient spin-echo (PGSE)-NMR method and the D's also increased with decreasing the EW value. These results implied that the alcohols penetrate into the hydrophilic regions of the PFSI membranes and diffuse through the space expanded by the alcohols. The ionic cluster regions formed by the alcohols resemble those induced by water in the water swollen membrane, where protons dissociated from sulfonic acid groups transport through the regions together with water molecules. The D values decreased with increasing the molecular weight of alcohols. This trend was supported by activation energies Ea estimated from the Arrhenius plots of D in the temperature range from 30 to -40 degrees C. The PGSE-NMR measurements also revealed that protons move faster than the alkyl groups in the membranes. The proton transport by the Grotthuss (hopping) mechanism was facilitated by the increase of the alcohol content and the decrease of the molecular weight. This result was also supported by the experimental results of proton conductivity kappa and mobility u(H(+)). Density functional theory (DFT) calculations of the interaction energy DeltaE(int) between proton and alcohol (including OH) showed that the /DeltaE(int)/ increases with increasing the molecular weight of alcohols, which is in a inverse relationship with the kappa and u(H(+)) values. The proton transport depends strongly on the DeltaE(int) in the membranes.

Three empirical correlations connecting gaseous cluster energies and solvation energies of alkali metal and halide ions.

This paper gives two empirical correlations of formation Gibbs energies of gaseous clusters DeltaG(f)n as function of number of solvent molecules attached to the ion, n, and one correlation connecting the DeltaG(f)n for each individual cluster with the total DeltaG(o)hydr value. The experimental ratios of DeltaG(f)2/DeltaG(f)1 and DeltaG(f)3/DeltaG(f)1 for both alkali metal and halide ions are on average equal to 0.75 and 0.5, respectively. DeltaG(f)n values for n > or = 4 are correlated with n as DeltaG(f)n = [a/(n - 1)] DeltaG(f)1 + b DeltaG(f)1. For all available data on cluster energies and each individual cluster, the DeltaG(f)n's are straight-line functions of DeltaG(o)hydr. This well corresponds to another empirical rule stating that the Gibbs energies of transfer of ions between two solvents are often as well straight-line functions of DeltaG(o)(hydr) [J. Rais and T. Okada, J. Phys. Chem. A, 2000, 104, 7314]. Tentative models of the found behavior are proposed. A full data set of the gaseous cluster energies of formation based on inclusion of new, usually not used entries from the literature is provided.

Gibbs energies of transfer of alkali metal cations between mutually saturated water-solvent systems determined from extraction experiments with radiotracer 137Cs.

Thermodynamic standard Gibbs energies of transfer of alkali metal cations related to Cs+ cation [DeltatG degrees*,(Cs+)-[DeltatG degrees*,(M+)] between several mutually saturated solvents of the type water-solvent were calculated from determined extraction exchange constants Kexch degrees,*(Cs+/M+). The used liquid-liquid extraction method with radioactive tracing by 137Cs permits attaining higher precision of the values as compared to the methods used up to now. The data for o-nitrophenyloctyl ether, 1,2-dichloroethane, and 1-octanol were compared with literature sources and recommended absolute values of DeltatG degrees,*M+) are reported. For dissociating solvents, the dependences of [DeltatG degrees,*(Cs+) - [DeltatG degrees,*(M+)] on Gibbs energy of hydration of an ion, DeltaGhydr degrees are straight lines either for four cations Cs+, Rb+, K+, and Na+ (nitrosolvents) or for three cations Cs+, Rb+, and K+ (1,2-dichloroethane and 1-octanol). The hydration of Na+ and still more of Li+ in the water-saturated organic phase is apparent from the results. This manifests for high-water-content equilibrium 1-octanol even in a reversal of the values [i.e., DeltatG degrees*,(Li+) being more negative than DeltatG degrees,*(Na+)], although for Cs+, Rb+, and K+, the general trend is conserved. Water-saturated 1-octanol is thus slightly less basic than water, but the overall selectivity is very low. For one studied nondissociating solvent, dioctyl sebacate, the trend of the dependences of log Kexch degrees,*(CsB/M+) on DeltaGhydr degrees is similar to that of Kexch degrees,*(Cs+/M+) for polar solvents, but different for different anions B, thus reflecting ion association in the organic phase.

Mechanism of selective oxygen reduction on platinum by 2,2'-bipyridine in the presence of methanol.

Mechanism of selective oxygen reduction on platinum by 2,2'-bipyridine in the presence of methanol has been investigated by in situ surface-enhanced infrared absorption spectroscopy. The addition of 2,2'-bipyridine caused the decrease of adsorbed water molecules and those existing near the surface of platinum. The formation of both CO and formate, the latter being the intermediate in the non-CO path for methanol oxidation, depressed in the presence of 2,2'-bipyridine, suggests that 2,2'-bipyridine hinders methanol oxidation via both non-CO and CO paths on platinum. The geometrical effect of 2,2'-bipyridine adsorbed onto platinum was also investigated by multisite Monte Carlo simulation. It is indicated that selective oxygen reduction is caused by the difference in the number of required adsorption sites between methanol and dioxygen molecules. The suppression of Pt oxide species by 2,2'-bipyridine is found to be another factor that enhances the oxygen reduction.

New CO tolerant electro-catalysts exceeding Pt-Ru for the anode of fuel cells.

Novel types of CO tolerant electro-catalysts from Pt and organic metal complexes that are far superior to Pt-Ru and practically usable as anode catalysts in reformate gas fuel cells with 100 ppm CO tolerance have been developed.

Temperature dependence of ion and water transport in perfluorinated ionomer membranes for fuel cells.

To clarify the mechanisms of transport of ions and water molecules in perfluorosulfonated ionomer membranes for fuel cells, the temperature dependence of their transport behaviors was investigated in detail. Two types of Flemion membranes having different equivalent weight values (EW) were utilized along with Nafion 117 as the perfluorinated ionomer membranes, and H-, Li-, and Na-form samples were prepared for each membrane by immersion in 0.03 M HCl, LiCl, and NaCl aqueous solutions, respectively. The ionic conductivity, water self-diffusion coefficient (D(H)(2)(O)), and DSC were measured in the fully hydrated state as a function of temperature. The ionic conductivity of the membranes was reflected by the cation transport through the intermediary of water. Clearly, H(+) transports by the Grotthuss (hopping) mechanism, and Li(+) and Na(+) transport by the vehicle mechanism. The differences of the ion transport mechanisms were observed in the activation energies through the Arrhenius plots. The D(H)(2)(O) in the membranes exhibited a tendency similar to the ionic conductivity for the cation species and the EW value. However, no remarkable difference of D(H)(2)(O) between H- and the other cation-form membranes was observed as compared with the ionic conductivity. It indicates that water in each membrane diffuses almost in a similar way; however, H(+) transports by the Grotthuss mechanism so that conductivity of H(+) is much higher than that of the other cations. Moreover, the D(H)(2)(O) and DSC curves showed that a part of water in the membranes freezes around -20 degrees C, but the nonfreezing water remains and diffuses below that temperature. This fact suggests that completely free water (bulk water) does not exist in the membranes, and water weakly interacting with the cation species and the sulfonic acid groups in secondary and higher hydration shells freezes around -20 degrees C, while strongly binding water in primary hydration shells does not freeze. The ratio of freezing and nonfreezing water was estimated from the DSC curves. The D(H)(2)(O) in the membranes was found to be influenced by the ratio of freezing and nonfreezing water. DFT calculation of the interaction (solvation) energy between the cation species and water molecules suggested that the water content and the ratio of freezing and nonfreezing water depend strongly on the cation species penetrated into the membrane.

Study of adsorption of methylene blue and new methylene blue in liquid-solid interface by slab optical waveguide spectroscopy.

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. Effect of pH on adsorption on MB and NMB was investigated. Binding rate constant analysis showed that both MB and NMB on bare SOWG demonstrates larger association constants than those on ODS-SOWG. Interactions of MB and NMB on bare SOWG and ODS-SOWG were analyzed by molecular mechanics calculation method. The binding energy change was in the following order: E(NMB-bare)>E(MB-bare)>E(NMB-ODS)>E(MB-ODS).

The study on a PVC membrane electrode for gemfibrozil.

In this paper, a poly(vinyl chloride) (PVC) membrane electrode is prepared for gemfibrozil, 2, 2-dimethyl-5-(2,5-xylyloxy) valeric acid, based on its ion pair complexes with hexadecyltrioctyl ammonium iodide (HTOA). The membrane composition of the electrode was optimized by using the sequential level elimination method for orthogonal experimental design. The electrode has a Nernstian response range from 2.5 x 10(-5) to 0.1 mol/l with an average slope of 55.3 mV/decade. The limit of detection is 7.1 x 10(-6) mol/l. The electrode responses were not affected by pH in the range 10.0-12.3. A Na2B4O7-Na2CO3 buffer of pH = 11.0 was selected as the background electrolyte solution for potentiometric measurements. The electrode was used for determining gemfibrozil in pharmaceutical preparations with satisfactory results.