Search

The behavior of a Pt electrode/solution of lithium perchlorate and lithium hexafluorophosphate in a γ-butyrolactone (GBL) interface has been investigated by using in situ FTIR spectroscopy and single reflection ATR-FTIR spectroscopy. The bands due to free GBL and GBL solvated to lithium ions in the solution were confirmed by the single reflection ATR-FTIR spectra. The dependence of potential on the concentration of GBL and solvated GBL in the vicinity of a Pt electrode was investigated. In the FTIR spectra, the reversible changes in the concentration of free GBL and solvated GBL in the diffuse double layer were observed with change in potentials. As the potential decreased, the free GBL concentration increased, while the concentration of the GBL solvated to lithium ions decreased. The reverse phenomenon was observed as the potential increased. Thus, it can be concluded that the equilibrium shifts from Li + (GBL) 4 to Li + (GBL) 3 and GBL as the potential decreases. It became clear for low potentials that the product material contained lithium ions in irreversible reactions.

The relationship between the interface structure and the macroscopic properties of composites composed of isotactic polypropylene (iPP) and magnesium hydroxide (MH) was investigated with a focus on mechanical properties, thermal stability, and flame retardancy. Surface treatment of MH was carried out using dodecanoic acid (DA) and dodecylphosphate (DP), both of which interacted with MH to form submonolayer coverages. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that both organic reagents adhere to the MH surface via ionic interactions. Even low amounts of organic reagents on the MH surface were sufficient to improve the mechanical, thermal, and flame retardant properties of the composites. The incorporation of 1.8 wt% of DP in (70/30) iPP/MH-DP composite decreased the peak heat release rate (PkHRR) to 39% compared with that of neat iPP. Since the effects of DA with the same dodecyl chains were not significant, it is concluded that the phosphate groups ...

3-Fluorobenzoic acid adsorbed on Au(1 1 1), Au(1 0 0) and Au(1 1 0) electrodes has been investigated using in situ IR reflection spectroscopy, UV–visible reflectivity measurements, and differential capacity measurements. As determined by IR reflection spectroscopy, the vertically adsorbed 3-fluorobenzoate is the predominant species at positive potentials, and the flat-lying type is adsorbed at negative potentials. In the UV–visible reflectivity measurements, the reflectivity changes for the vertically adsorbed and flat-lying 3-fluorobenzoates on the Au(1 0 0) electrode were observed at different frequency regions. No UV–visible reflectivity signal was observed for the Au(1 1 0) electrode, and it was proved that the UV–visible reflectivity change has a strong single crystal surface dependence. For the vertical configuration, a large contribution between the 5d orbital of Au and the 2p orbital of oxygen in 3-fluorobenzoate was found for the cluster model by DFT calculation.

The mechanism of hydrogen evolution by a core/shell noble-metal/Cr2O3 particulate as a highly efficient cocatalyst for overall water splitting under visible light using the photocatalyst (Ga1−xZnx)(N1−xOx) is investigated by electrochemical and in situ spectroscopic measurements of model electrodes. The electrodes are prepared by electrochemical deposition of 1.8−3.5 nm thick Cr2O3 films on Rh and Pt plates and are evaluated as model systems of Rh/Cr2O3 and Pt/Cr2O3 core/shell particulates, which have previously been applied effectively as cocatalysts for hydrogen evolution in this system. Proton adsorption/desorption and H2 evolution currents are observed for both the Cr2O3-coated and the bare electrodes, and the infrared absorption band due to Pt−H stretching (2039 cm−1) is apparent for both the coated and the bare electrodes. These observations indicate that the Cr2O3 layer does not interfere with proton reduction or hydrogen evolution and that proton reduction takes place at the Cr2O3/Pt interface. Ho...

3-Pyridinecarboxylic acid (3-PC) adsorbed on low index face electrodes in NaF solution were investigated using in situ Fourier transform-infrared (FTIR) spectroscopy and differential capacity measurements. Two types of vertically adsorbed 3-PC were confirmed on the electrodes, while flat-lying adsorbed species were not observed at the potentials measured. At negative potentials, 3-PC molecules adsorb vertically on the electrode via the lone pair electrons of the pyridine ring nitrogen atom, and at positive potentials, 3-PC adsorbs vertically via the two oxygen atoms of the carboxyl group.

Adsorption of terephthalic acid on Au(1 0 0), Au(1 1 1) and Au(1 1 0) electrodes in neutral solution has been investigated using in situ Fourier transform infrared (FT-IR) spectroscopy, differential capacity measurements and scanning tunneling microscopy (STM). At negative potentials, the terephthalate anions in solution adsorb in a flat orientation onto the electrode via the π electrons of the aromatic ring. At positive potentials, the terephthalate anions adsorb in a vertical orientation via the oxygen atoms of one of the carboxyl groups as a form of dianion. At more positive potentials, the anions adsorb in a vertical orientation as a form of hydrogen terephthalate. For the three electrodes examined, the overtone and/or combination bands, due to vertically oriented hydrogen terephthalate, were observed at 2642 and 2517 cm −1 , respectively. For the Au(1 1 1) electrode, STM observations indicated a flat orientation in the form of terephthalic acid.

The interfacial phenomena between Cu electrode and solution of lithium perchlorate in ethylene carbonate (EC)–dimethyl carbonate (DMC) have been investigated using in situ reflection absorption Fourier transform infrared (FTIR) spectroscopy and single reflection ATR–FTIR spectroscopy. The ATR spectra confirmed the bands due to free EC and DMC and the molecules solvated to lithium ions in the solution. The bands due to the result of the interaction between ClO 4 − and DMC in the mixture solution also appeared in the ATR spectra. In the FTIR spectra, the potential dependence on the concentration of EC and DMC in the vicinity of the Cu electrode was observed. It was understood that the reversible changes in the concentration of free EC and DMC and solvated EC and DMC in the diffuse double layer take place with changing in potential. As the potential decreased, the free EC and DMC concentrations increased, while the concentration of the EC and DMC solvated to lithium ions decreased. Thus, it can be concluded that the equilibrium shifts from Li + (EC) 2 (DMC) 2 to Li + (EC) 2 (DMC) + DMC or Li + (EC)(DMC) 2 + EC as the potential decreases. The bands due to (CH 2 OCO 2 Li) 2 and CH 3 OCO 2 Li were observed for an irreversible reaction.

In situ Fourier transform infrared spectroscopy (FTIR) spectra measurements were obtained for a Cu electrode/solution of lithium perchlorate in propylene carbonate (PC). The dependence of potential on the concentration of PC in the vicinity of the electrode was investigated. The bands due to free PC and PC solvated to lithium ions in the solution were distinguished by the single reflection attenuated total reflection (ATR) spectra. In the FTIR spectra, the reversible change in the concentration of free PC and solvated PC in the diffuse double layer was observed to be accompanied by a change in potential. As the potential decreased, the free PC concentration increased, while the concentration of the PC solvated to lithium ions decreased. Thus, it can be concluded that the equilibrium shifts from Li + (PC) 4 to Li + (PC) 3 + PC as the potential decreases. Furthermore, Li + (PC) 3 orientates itself so that it is parallel to the electrode surface.

Adsorption behaviors of 2-fluoro-, 2-chloro-, and 2-bromobenzoic acids on Au(1 0 0) electrode in 0.1 M HClO4 have been investigated by using in situ reflection adsorption IR spectroscopy and differential capacity measurements. It is found for the 2-substitued benzoic acids that the flat lying adsorbed species is present at negative potentials, and the vertically adsorbed benzoate with both oxygen atoms oriented toward the metal surface is present at positive potentials. A new adsorbed state due to the vertical orientation was observed around 0.75 V only in 2-fluorobenzoic acid solution, as well as the case of benzoic acid. This indicates that the new band is due to the formation of an ordered adsorption layer of the vertical 2-fluorobenzoate, and the formation of the arrangement adsorption is dependent on the size of the adsorbed molecule.

The effect of halide anions on pyridine- d 5 adsorbed on Au(111) electrode has been studied in neutral solutions containing F − , Cl − , and Br − by IRAS and differential capacity measurement. In the NaF solution, N-bonded pyridine increases up to 0.1 V, and a new adsorbed state due to the N-bonded type grows at positive potentials. In the NaCl solution, the N-bonded type grows at all of adsorbed potential except for the appearance of the new adsorbed state at 0.2 V. In the NaBr containing solution, the new adsorbed state is not observed. In the NaCl and NaBr solutions, the total amount of the N-bonded pyridine is suppressed at positive potentials. We propose that the new band is attributed to an ordered layer of the N-bonded pyridine on the Au(111) electrode, and that the formation of the ordered layer is inhibited by the adsorption of Cl − and Br − .

2-chloropyridine (2Clpy) adsorbed on Au(111) and Au(110) electrodes in 0.1 M KClO4 containing 2 mM 2Clpy has been investigated using in-situ infrared spectroscopy and differential capacity measurements. For both the electrodes, an in-plane ring vibration due to N-bonded 2Clpy was observed, which was accompanied by a loss in the in-plane ring vibrations due to dissolved 2Clpy. However, the integrated band intensity ratios between the adsorbed 2Clpy and the loss of dissolved 2Clpy for both electrodes are quite different in all potentials measured. The relative band intensity of the N-bonded 2Clpy for Au(110) is much stronger than that for the Au(111). This indicates that for the Au(111) the adsorbed 2Clpy is mainly flat type or the tilt angle of the N-bonded 2Clpy is large. It can be explained by the configuration of adsorbed 2Clpy on the electrode surface. For Au(111) terrace, N-bonded configuration is obstructed by the presence of Cl atom. There is no obstruction for the Au(110) step if the N-bonded 2Clpy is adsorbed on the overtop layer.

Pyrazine adsorbed on Au(111), Au(100) and Au(110) electrodes in 0.1 M NaF containing 5 mM pyrazine have been investigated by using in-situ infrared spectroscopy. For each of the three electrodes, an in-plane ring symmetrical vibration due to vertically adsorbed pyrazine was observed around 1045 cm−1, which was accompanied by a loss in the in-plane ring asymmetrical vibration at 1419 cm−1 due to dissolved pyrazine. For the Au(111), the behavior of the 1419 cm−1 band intensities corresponding to the total amount of adsorbed pyrazine was coincident with previous results of the Gibbs surface excess investigated by using of chronocoulometry. The behavior of 1045 cm−1 band intensity as a function of the applied potential was similar to that of the 1419 cm−1 band for the Au(111) and Au(100). We propose that the tilt orientation is present at negative potentials and the vertical orientation increases as the potential becomes more positive. For all the electrodes, a new band appeared around 1035 cm−1 for positive potentials, which was assigned to an in-plane ring symmetrical vibration, as for the 1045 cm−1 case. We propose that the new band is associated with some adsorption behavior such as a change in the vertically adsorbed pyrazine orientation.

Adsorption of 2-, 3- and 4-fluorobenzoic acids on an Au(100) electrode in 0.1 M HC1O 4 have been studied using in situ reflection adsorption IR spectroscopy and cyclic voltammetry. It is found that for the fluorobenzoic acids the vertically adsorbed benzoate with both oxygen atoms oriented toward the metal surface is present at positive potentials, and a new adsorbed state due to this vertical orientation appears around 0.75 V. The OCO symmetrical stretch band corresponding to the new adsorbed state is observed at a higher frequency than that of the original band. However, the bands due to ring stretches display no change at that potential. In the voltammetry, broad and sharp reversible peaks corresponding to both the adsorbed states are observed. This indicates that the new band should be associated with some interaction of the COO − group and the hydrated water.

Adsorption of benzoic acid onto Au(111) and Au(110) electrodes in 0.1 M HClO4 has been investigated by IRAS, voltammetry and differential capacity measurements. For both electrodes, the presence of the vertically adsorbed benzoate anion was confirmed by IRAS. A reversible current peak corresponding to the appearance of the COO− band for Au(111) was observed around 0.4 V. For the Au(111) electrode, the capacity curve at negative potentials and the IRA spectrum observed at 0.3 V suggest the presence of adsorbed species in other than the vertical orientation. This suggests that the flat-lying benzoic acid is present at negative potentials, and the vertically adsorbed benzoate increases at positive potentials. The amount of the vertical type for Au(111) reached saturation at 0.8 V, while that for Au(110) increases for all the potentials observed.

Adsorption of benzoic acid on an Au (100) electrode in 0.1 M HClO 4 has been investigated by IRAS and voltammetry. In the IRAS, the vibrational band of COO − symmetrical stretch corresponding to the vertically adsorbed benzoate anion species were observed. At slightly higher frequency a new band also due to the symmetrical stretch of the benzoate anion, and overlapping with the original band, appeared at 0.8 V (RHE). In the voltammogram, three reversible couple were observed; a peak at 0.5 V corresponds to the appearance of the COO − band and a peak observed at 0.8 V corresponds to the appearance of the new band. This indicates that the new band should be associated with some adsorption behavior of the vertical type such as a change of the packing arrangement at that potential.

In situ IR spectra of pyridine adsorbed on a polycrystalline gold electrode in 1 M NaF have been measured. An in-plane ring symmetrical vibration due to vertically adsorbed pyridine was observed at around 1605 cm −1 accompanying a decrease of the same mode band at 1596 cm −1 due to dissolved pyridine. The position and shift of the bands due to vertically adsorbed pyridine were independent of the concentration of pyridine, leading us to deduce that it is caused by a weak Stark effect and/or an effect of the electrode potential on the nonbonding orbital of the nitrogen atom. The vertically adsorbed pyridine was observed at 0.7 V (vs Ag/AgCl), at which potential detection of adsorbed pyridine by an electrochemical method has not been reported. A decrease in an asymmetric band at 1446 cm −1 due to dissolved pyridine was also observed at more positive potentials.

In order to improve the anode characteristics of pitch-based carbon fibres for Li secondary batteries, we adopted two kinds of heat treatment procedures, i.e. in vacuo and in a partially oxidizing atmosphere. Heating to 980°C in vacuo was found to remove the surface hydroxyls and adsorbed water effectively. This method improved the high current charge-discharge capacities and cyclability of the carbon fibres.

Crystal structures of the three geometrical isomers (1, 2 and 3) of [RuCl(2eqn)2NO] (H2eqn = 2-ethyl-8-quinolinol) have been determined by X-ray diffraction. The Cl atom is cis to the NO group in 1 and 2, and is trans to the NO group in 3. The N and O atoms of the two quinolinolato ligands for 1, 2 and 3 are in trans(N,N) and cis(O,O), in cis(N,N) and cis(O,O) and in trans(N,N) and trans(O,O) configurations, respectively. Crystallographic data for 1: triclinic, a = 10.140(4), b = 13.498(5), c = 7.902(3) A ; α = 94.08(3), β = 104.19(2), γ = 73.35(3)°, V = 1006.8(6) A 3 , Z = 2 , space group P 1 ; for 2; monoclinic, a = 14.730(2), b = 10.028(2), c = 13.761(4) A , β = 92.65(2)°, V = 2030.5(7) A 3 , Z = 4 , space group P21/a for 3: monoclinic, a = 14.830(4), b = 8.700(2), c = 16.711 (4) A , β = 110.40(3)°, V = 2021,0(9) A 3 , Z = 4 , space group Cc. The structures were solved by the heavy-atom method and were refined by fullmatrix (1 and 2) and block-diagonal (3) least-squares procedures to R = 0.0378 (1), 0.0320 (2) and 0.0397 (3) for 5207 (1), 4032 (2) and 1675 (3) reflections with I≥3 σ(I). The variable-temperature 1H NMR spectra in dimethyl sulfoxide-d6 revealed the steric hindrance due to the ethyl group of the quinolinolato ligands, reflecting the results of the crystal structure analysis. At high temperature (373–413 K), the reversible thermal isomerizaion reaction among the three isomers was observed un degassed dimethyl sulfoxide (DMSO). The mole ratio of 1, 2 and 3 was 19:4:1 at 413 K and did not depend on the starting species. Kinetic analysis revealed that the reaction was reversible between any two isomers and the isomerization between 1 and 3 proceeded by a mechanism distinct from the others.

The adsorption behaviour of CO on a Pt electrode was investigated in 1 M HClO 4 solution by the use of the in situ specular reflectance method. Simultaneous measurement of the reflectivity of the Pt electrode and the suppressed current of hydrogen adsorption enabled us to find the relation between the reflectivity change and the coverage of adsorbed CO. The reflectivity was found to be dependent on the amount of coverage. In the low coverage region, it increased with the increase of the coverage, while in the high coverage region, it decreased rapidly. The reflectivity profile dependence on CO coverage suggests the presence of more than two different types of adsorbed CO. The present results are in accordance with the results obtained with IR measurements, which suggest the presence of reflection absorption spectroscopic inactive CO.

In-situ IR spectra of adsorbed cyanide ion on a platinum electrode have been investigated by PM-IRAS (polarization modulation infrared reflection absorption spectroscopy) in the bulk CN − concentration range of 0.04–10 mM. The absorption band of the C-N stretching vibration of adsorbed CN − was found at around 2070 cm −1 in less dilute solution, the band position being dependent on both the CN − concentration and the electrode potential; it shifted to the higher wavenumber side at more positive potentials and higher CN − concentrations. In the extremely low CN − concentration range of 10 −5 −10 −4 M, however, a new band appeared at around 1980 cm −1 , whose peak position was dependent only on the CN − concentration. The new band was considered to be due to bridged-type CN − adsorbed on a Pt electrode and occupying two sites.

In the course of in-situ infrared studies on the adsorption of CO at a Rh electrode, we have found that several very strong bands appear in the range 1800-2100 cm-’ after repeated oxidation-reduction cycles of the electrode in the presence of CO in acidic solution. The behaviour of these bands is clearly different from that of the adsorbed CO. In this work, the origin of these new bands will be described in relation to the adsorbed CO.

水素電位領域で白金電極に吸着した一酸化炭素について酸化ボルタモグラムと赤外反射強度の同時測定によりその吸着状態について研究した.1MHClO4及び0.1MNaOH水溶液において共に二つの酸化波とlinear型CO(COL)及びbridge型 CO(COB)に対応する赤外吸収バンドが観測された.HClO4水溶液の場合,高電位の酸化波の一部分がCOLに対応し,COBはCOLより低電位で酸化されたが,低電位側の酸化ピークとも対応しなかった.この高電位側の酸化波の半分以上は,著者らが以前より提案してきた赤外反射法では観測されない吸着一酸化炭素,と結論した.NaOH水溶液の場合,COL及びCOBは両方とも高電位側の酸化波と対応し,低電位側の酸化波とは対応しなかった.

The reflection absorption IR spectra of adsorbed CO on palladium and platinum electrodes were measured to determine the effect of another adsorbate (CS2 or CCl4 at 0.4 V (SHE) in perchloric acid solution). For the palladium electrode, the band intensity and frequency of the C-O stretching mode of the adsorbed bridge-type CO changed with the concentration of the other adsorbate, but those of the linear-type CO were independent of the other adsorbate. For the platinum electrode, the band intensity and frequency of the linear-type CO changed with the concentration of the other adsorbate. The frequency shift in the bridge-type CO caused by the adsorption of another species on the palladium electrode could be explained partially by the change in the dipole-dipole coupling between the adsorbed molecules of the bridge-type CO and partially by the shift in the potential of zero charge.

Carbon monoxide adsorbed on a smooth platinum electrode in the double-layer region was investigated in 1 M HClO4 solution by using in situ polarization modulation IR reflection spectroscopy and an electrochemical oxidation. From the electrochemical oxidation, the adsorbed CO could be distinguished to be comprised of stable and unstable adsorbed CO's. The unstable adsorbed CO constituted about 13 of the adsorbed CO, and corresponded to linearly adsorbed CO, but the band intensity of the linearly adsorbed CO was not proportional to the amount of unstable adsorbed CO. The stable adsorbed CO constituted about 23; it was one-site adsorbed, and was an IR-inactive species. It is presumed that the IR-inactive species is adsorbed on two Pt atoms with the C-O axis parallel to the electrode surface and one of the Pt atoms bound to two CO molecules.

The concentration dependence of the SERS intensity of pyridine adsorbed on a silver electrode is investigated by varying the bulk pyridine concentration. The number of SERS-active depends on the pyridine concentration during the oxidation-reduction cycle. The saturated adsorption is maintained at concentrations higher than 3 mM. The sites are deactivated by diluting the bulk pyridine.

Monolayer and submonolayers of CO adsorbed in the double-layer region on a Pt electrode were investigated in 1M HClO4 by using in situ polarization-modulated IR reflection absorption spectroscopy (IRRAS) and an electrochemical oxidation. As for the monolayer of CO, it was concluded that linear CO accounted tor only 10% of all the adsorbed CO, and the remainder was RAS-inactive CO (reflection absorption spectroscopically inactive CO). As for the submonolayers of CO, the average number of adsorption sites per CO molecule changed from 1.7 to 1.2 with an increase in the total coverage from 0.1 to 0.9. The bridged CO could not be detected for these coverages by the IRRAS method. The band intensity of linear CO was not proportional to the total coverage. Therefore, it was concluded that the RAS-inactive CO were present, and these were one-site occupying and two-site occupying species. The adsorbed species predominating was the two-site occupying RAS-inactive CO for low coverage; and for high coverage the one-site occupying RAS-inactive CO. The RAS-inactive CO are described by a model in which CO is adsorbed on two Pt atoms with the C-O axis parallel to the electrode surface.

The dependency of the SERS intensity on the concentration of pyridine and various monosubstituted stituted pyridines at competitive adsorption on a silver electrode was investigated by varying the concentration of bulk pyridine and monosubstituted pyridines. This co-adsorption behavior was found to be well approximated by Langmuir isotherms for binary systems, and the substituents of 2-substituted-pyridine strongly inhibited the adsorption due to their steric hindrance.