Carbonate formation on a carbon electrode for rechargeable zinc-air batteries can lead to degraded battery performance and limited lifetime for practical use. In this study, the carbonate formation is observed at an unexpected early working state through in-situ Raman measurements. The origin of carbonate formation from carbon corrosion in the alkaline electrolyte is revealed by its distribution near the potassium hydroxide solution via our self-developed multi-point Raman mapping apparatus. More importantly, it is found that during charging, the carbonate formation affects the formation of the zinc oxide byproduct and impedes the oxygen evolution reaction due to its consumption of hydroxyl ions. In comparison, insoluble carbonate precipitation is generated within the porous carbon electrode during discharging, which could block the oxygen throughput and consequently deteriorate the air electrode performance. This in-situ study clarifies the initial state of carbon electrode corrosion in the alkaline electrolyte, providing an insight into the future optimizations towards the air electrode design.

In this work, a novel electroless deposition process on the anion exchange membrane (AEM) is proposed. AEM surface has a positively charged functional group, which in general does not allow the catalyst particle, such as Pd, to be formed on the surface. Hence, a different strategy from the conventional catalyzation process was required. We found that the sensitization process using Sn-containing solution, which is widely applied in the electroless plating on nonconductive substrates, hindered the Pd particle modification, which hence inhibited the following deposition reaction. Our several experiments and density functional theory analyses suggest that for Pd particle modification, anion in the bath turned out to play a key role. In particular, Cl provides the sufficiently strong connection between the precursor Pd and positive functional group of the substrate. This leads to favorable deposition of Pd catalyst particles and metal layer formation on the AEM. Therefore, we conclude that just a single pre-treatment to immerse the AEM films into PdCl /HCl solution is capable to perform electroless plating on it. We applied the novel process to the electrode formation, such as Pt and Ni-P, on the AEM for hydrogen evolution reaction (HER) as a case study. Both Pt and Ni-P was successfully formed on the AEM. The electrochemical measurements show that those electrodes are able to serve as the catalytic electrode for HER. The electroless process proposed here opens possibility of the direct metal fabrication on ion exchange membrane surface. − 2+ 2

The behavior of bubbles generated by the hydrogen evolution reaction (HER) and the effect of these bubbles on HER performance were investigated using Ni micro-patterned electrodes. This study focused on the correlation between bubble behaviors affecting potential increase of HER and the surface microstructures of micro-patterned Ni cathode. Ni microdot array structures with diameters of approximately 5–10 μm, pitch of approximately 5–10 μm, and various dot heights were fabricated for alkaline water electrolysis measurements. The Ni micro-patterned structures controlled the surface wettability of the electrode. The change in the wettability influenced the HER efficiency during galvanostatic electrolysis at –20 mA cm . Moreover, in situ observation of the evolved bubbles on the electrode surface revealed that bubbles with larger diameters evolved on the electrode surface with lower wettability, and bubbles tended to detach from the electrode surface by decreasing the contact area between the bubbles and the electrode. It was also observed that bubbles evolved more easily on the sidewall of Ni microdots and that generated bubbles moved onto the surface of the microdots in high-aspect Ni micro-patterned electrodes, indicating that an increase in the overpotential can be suppressed by different bubble nucleation behaviors. Therefore, the micro-patterned surface texture affected the bubble nucleation and growth behaviors, which would suppress the decrease in HER efficiency. These results can provide insights for fabricating highly efficient surfaces for HER catalytic electrodes. –2

The internal structure of self -assembled monolayers (SAMs) such as 3-aminopropyltriethoxysilane (APTES) fabricated on a glass substrate is difficult to characterize and analyze at nanometer level. In this study, we employed surface -enhanced Raman spectroscopy (SERS) to study the internal molecular structure of APTES SAMs. The sample APTES SAMs were deposited with Ag nanoparticles to enhance the Raman signal and to obtain subtler structure information, which were supported by density functional theory calculations. In addition, in order to carry out high -resolution analysis, especially for vertical direction, a fine piezo electric positioner was used to control the depth scanning with a step of 0.1 nm. We measured and distinguished the vertical Raman intensity variations of specific groups in APTES, such as Ag/NH2, CH2, and Si-O, with high resolution. The interfacial bond at the two interfaces of Ag-APTES and APTES-SiO2 was identified. Moreover, APTES molecule orientation was demonstrated to be inhomogeneous from frequency shift. (C) 2017 Elsevier B.V. All rights reserved.

A plasmonic sensor is used for emulation of near field transducer (NFT). Some overcoat films (thickness of 1nm) were coated on Au nanoparticles (NPs) on a convex quartz glass substrate (plasmonic sensor). Heating behavior of the films was examined by laser heating using novel Raman spectroscopic tools, i.e. surface-enhanced Raman scattering (SERS) with the plasmonic sensor, a continuous laser heating tool, in-situ observation of spectra and temperature with a high speed time resolved measurement. The heating temperature of tetrahedral carbon (ta-C) film in He gas is lower than that in air. This is because the thermal conductivity of He is larger than air. Few spectral change of ta-C film (thickness of 1nm) on Au NP's is observed except initial change in around 100 s at the temperature around 500 degrees C, which corresponds to the temperature of the carbon overcoat (COC) for the media temperature of 327 degrees C (600K, Currie temperature for CoPt alloy). Some carbide films, i.e. SiC, TiC, and WC, showed high heat resistance, that is, few spectral change was observed. It is found that lubricant is evaporated from the COC on magnetic media and transferred to the plasmonic sensor.

As one of the most cost-effective methods to produce solar-grade silicon (SOG-Si), purification of silica solution by extracting its impurities through wet chemical processes has been proposed. This paper reports on the design of channel type reactor for liquid-liquid extraction to purify silica solution, focusing particularly on the extraction of B (boric acid) in aqueous phase with 2,2,4-trimethyl-1,3-pentanediol (TMPD) in organic phase. The reactor fabricated by 3D printing technology was designed to have two characteristic structures: (i) a throat structure that shows gradually diverging part after converging near Y shaped inlets and (ii) obstacles structure on downstream. Two solutions were made to contact with each other by turbulent mixing around the throat structure, causing small droplets formation that was dispersed and retained efficiently even on downstream by obstacles structure. This droplet dispersion shortens diffusion distance of boric acid to meet TMPD at the liquid-liquid interface, providing efficient mass transfer. At higher flow rate i.e., 380 ml/min, the extraction efficiency was 97.43% after the multi stage process. The results suggest that the channel type reactor designed here is profitable for elimination of impurities, such as B or P, in silica solution to produce SOG-Si.

Elementary steps in the electrochemical reduction process of SiCl4 in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) was investigated, focusing on molecular level behavior of the reactants at solid-liquid interface. Electrochemical measurements using an electrochemical quartz crystal microbalance (EQCM) identified a reduction peak corresponding to Si electrodeposition and several elementary steps with stable intermediates forming prior to the deposition. For detailed analysis, X-ray reflectivity (XRR) measurements with synchrotron radiation were applied in situ. The change in reflectivity of the electrode surface during the deposition was found to be due to the formation of a polymer-like Si such as Si2Cl6, which is an intermediate layer during the deposition process. These results were theoretically supported by density functional theory (DFT) calculations: after an electron transfers from the electrode, the Si in SiCl4 forms the bond with another SiCl4, rather than the Si of the substrate, resulting in the formation of the intermediate structure. These data suggest an elementary step in the SiCl4 reduction process which can be described as follows
when SiCl4 is reduced, a polymer-like Si form such as Si2Cl6 is generated. This intermediate species further reacts with other Si reactants after receiving additional electrons, which then finally deposits as Si on the substrate.

Theoretical analyses of L-alanine (L-Ala)- and L-homocysteine (L-Hcy)-Cu(II) complexes in basic, neutral, and acidic solutions were carried out using density functional theory to investigate the pH dependence of the formation mechanism of amino acid-Cu(II) complexes. The calculated complex formation energies indicate that the amino acid-Cu(II) complexes were expected to form in basic and neutral solutions but not in acidic solutions. The factors that determine the stability of these complexes are the coordination ability of each amino acid and the significance of intramolecular interactions among ligands within the complexes. As predicted from the molecular structure, in neutral solutions, the coordination ability of amino acid becomes lower than that in basic solutions because of the inert structure of the protonated amino group, -NH3+; however, the coordination ability originating from the -COO- group is estimated to be sufficient for stabilizing the entire complex system. Moreover, two H2O molecules coordinate with the central Cu2+ ion from the equatorial direction and interact with the coordinating amino acids, providing additional stability within the complex. In contrast, in acidic solutions, the complex does not have either sufficient coordination ability of amino acids or effective intramolecular interactions within the complex.

A structure's temperature can be determined from the Raman spectrum using the frequency and the ratio of the intensities of the anti-Stokes and Stokes signals (the I-as/I-s ratio). In this study, we apply this approach and an equation relating the temperature, Raman frequency, and I-as/I-s ratio to in-situ estimation of the phase change point of a (3-aminopropyl)triethoxysilane self-assembled monolayer (APTES SAM). Ag nanoparticles were deposited on APTES to enhance the Raman signals. A time-resolved measurement mode was used to monitor the variation in the Raman spectra in situ. Moreover, the structural change in APTES SAM (from ordered to disordered structure) under heating was discussed in detail, and the phase change point (around 118 degrees C) was calculated. (C) 2015 Elsevier B.V. All rights reserved.

A chemical depth profile in lubricant films, carbon films, and their interfaces is an informative parameter for hard disk media because molecular features of lubricants bonded to a surface of carbon overcoats (COCs), which usually consist of a nitrogen doped layer, are important to achieve high tribological performance. However, it was difficult to analyze their interfaces with high depth resolution because thickness of lubricant films and COC films are so thin, i.e. 1.5nm and 2nm, respectively. We have developed new method using plasmonic sensors, which has measurement capability for chemical structures with depth resolution of 0.1nm by surface-enhanced Raman spectroscopy (SERS). We examined the lubricant film composed of perfluorinated polyether (PEPE) with phosphazene derivative (A2OH) on a diamond-like carbon (DLC) film. The result shows that the functional group is adsorbed on the DLC surface, where lower shift in the wave number of phenyl group is observed. The depth profile of the intensity ratio of D-peak to G-peak shows the maximum at around the surface of the DLC film. A variety of organic components in the DLC films, fabricated by a chemical vapor deposition (CVD), were observed in it. Besides, the depth profiles shows that organic materials, involving methyl, ethyl, or ethylene groups, Co(OH)x exist in the film

A heat-assisted magnetic recording (HAMR) is expected for a future high density recording of a hard disk drive. However, a. carbon overcoat (COC) composed of diamond-like carbon (DLC) or a lubricant film is possibly damaged when a magnetic medium, i.e. CoPt alloy, is heated at around Curie temperature (Tc) of 600K by a near-field HAMR head. We carried out HAMR. simulation experiments by using newly developed Raman spectroscopic systems, composed of plasmonic sensors for surface-enhanced Raman scattering (SERS), a pulsed laser heating, and an in-situ temperature measurement with an intensity ratio of anti-Stokes/Stokes lines. It was found that the heated temperature of the COC is higher than that of the magnetic film, i.e., 580 degrees C and 366 degrees C, respectively. Intensity changes of G-band peak in Raman spectra for DLC films were observed during the pulsed laser heating. The Raman intensity was exponentially decreased by oxidation in air, where time constants were calculated as a parameter of a pulse width. Degradation life of the DLC film can be estimated from a critical pulse width, where the time constant is extrapolated to zero. The estimated pulse width for no degradation was 250 mu s at the heating temperature of 580 degrees C. The result shows no damage can be estimated in DLC films for HAMR. because the effective irradiation time is 5ns and the accumulated irradiation time is 0.5ms in HAMR operations.

To elucidate the catalytic reaction mechanism of BH₄^－ (a reducing agent) on metal surfaces during electroless deposition, its oxidation reaction was investigated theoretically using density functional theory (DFT) calculation. Particularly in this study, dehydrogenation reaction of BH₄^－ was modeled and analyzed because it is the most important elementary step of overall oxidation for the catalytic behavior of metal surfaces. To ascertain the tendencies of catalytic activity of metal surfaces, the reaction on Cu(111) and that on Pd(111) were compared. Actually, Cu shows little catalytic activity toward BH₄^－ oxidation, whereas Pd shows strong catalytic activity. Results of reaction energy calculations show that the BH₄^－ dehydrogenation occurs with difficulty on Cu(111), but it occurs easily on Pd(111), which corresponds to experimental results. Detailed analyses of reaction system electronic structures show that the d-band states of each surface are important to assess the background of the difference. Because the Pd surface has a high-energy d-band, it can interact with high-energy unoccupied orbitals of BH₄^－, leading to electron donation from the surface toward BH₄^－. This electron donation effect from Pd provides dissociation activity of the B-H bond, which promotes dehydrogenation of BH₄^－.

Elimination of boron species via solvent extraction with 2,2,4-trimethyl-1,3-pentandiaol was engaged in a flow-type device into which the aqueous solution dissolving diatomaceous earth, a -candidate of the resource for high-purity silicon material. The flow-type device has a 2-stage channel with 1.0 mm width, 0.10 mm depth, and 25 mm length each, and the specific interfacial area is comparable to a typical microchannel device. Residual boron content in the aqueous solution decreased to less than 0.1 ppm after the solvent extraction under the restriction of short contact duration shorter than 100 ms. In addition, the analysis with density functional theory indicated that the number of neighbor carbon on the central carbon is one of the keys for improvement of reactivity of extractant. Hence, it is suggested that the flow-type microchannel device with solvent extraction with alkyldiol extractant can be utilized as an attractive approach toward the production of high-purity silica as a source for solar-grade silicon.

The technical potential of a new plasmonic sensor, which can acquire surface-enhanced Raman spectra with high sensitivity by controlling surface plasmons is demonstrated for the chemical analysis of diamond-like carbon (DLC) films, lubricant films, and the DLC/lubricant interface on magnetic disks of sub-nanometer scale. The Raman spectra of thin DLC films and lubricated DLC carbon can be acquired with a high S/N ratio. Raman spectra of lubricated DLC carbon can also be acquired with the high S/N ratio. The wavenumber shift and intensity change of the Raman peaks of the phenyl and hydroxyl groups in the mixed lubricants (ADOH and Z-tetraol) show that the chemical interaction with the DLC surfaces of the phenyl group in the lubricant molecule decreases with increasing nitrogen content, whereas that of the hydroxyl group with the nitrogenated carbon increases. Raman spectra of nitrogenated DLC films are also acquired, the peaks show good agreement with density functional theory calculations. The calculated bonding energy indicates that the hydroxyl groups interact with the nitrogenated carbon.

We attempted to theoretically investigate cathodic reaction of Au thiosulfate complex at Au (111) surface. Theoretical model of the solid-liquid interface was built using density functional theory calculation and Monte-Carlo method. As a comparison, the cathodic reaction of Au cyanide complex is also analyzed. Calculated results from this model successfully reproduced behavior of the reactions of two complexes. Furthermore, detailed analyses on the results indicated that total charge, dipole moment, and end atom of coordinates play key roles to determine the reactivity of complexes.

Oxidation of the reductants is a dominant factor in the electroless deposition process. In order to obtain fundamental knowledge about the reaction mechanism of reductant oxidation for more precise control of the solid-liquid interface in this process, we have attempted to characterize the behavior of reductants adsorbed on Cu surface by using plasmon antenna enhanced Raman scattering. The concentric-patterned antenna coated with Cu, which consisted of a dimple array with single hole or a single hole with coaxial dimples, was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmons. By using this antenna and comparing the spectra to the results of Density Functional Theory (DFT) calculations, Raman peaks of adsorbed reductants on Cu were identified. Furthermore, we examined the conformation of adsorbed reductants by DFT calculation of the adsorption model of reductants on fcc-Cu(111) surface. As a result, the nature of reductant adsorption on Cu surface has been investigated from a computational point of view and an experimental point of view, and such in-situ characterization will be useful for analysis of a variety of systems at solid-liquid interface. (c) The Electrochemical Society of Japan, All rights reserved.

This paper described characterization of hydrazine adsorption on Cu surface with high-selectivity of component at right angle down to single molecular level using a plasmonic antenna enhancing Raman scattering. The antenna deposited by Cu with concentric pattern was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmon. By using this antenna, Raman peaks of adsorbed hydrazine on Cu was provided at 385 cm(-1). Furthermore, these peaks were only observed at 1-2 nm from the antenna surface which meant that this approach had a potential to define the structure of adsorbed hydrazine just only on the plasmon antenna. The structure of adsorbed hydrazine was gauche-conformation. This data corresponded to the Density Functional Theory (DFT) of adsorption model of hydrazine on fcc-Cu (1 1 1) surface. These results suggest that this method creates a wide range of spin-off effects to the characterization of solid-liquid interface. (c) 2012 Elsevier Ltd. All rights reserved.

Thiourea is well known and widely used additive for controlling the rate of electroless Ni deposition, and it is known to show complicated behavior in acidic/alkaline electroless deposition baths. To understand this, several experiments and theoretical calculations were performed. In the experiments, the adsorption of thiourea and the reducing agent (i.e., hypophosphite ions) on a Ni surface was characterized with a high-selectivity component at a right angle down to the sub-monolayer level using surface-enhanced Raman spectroscopy. By comparing the results with those obtained from the theoretical calculation, co-adsorption of thiourea and hypophosphite ions on the Ni surface was confirmed. Moreover, the acceleration or suppression effects of thiourea on the oxidation of hypophosphite ions on a Ni surface in acidic/alkaline bath were analyzed from the experimental and computational perspectives. Accordingly, an explanation that unifies both the acceleration and suppression mechanisms of thiourea in terms of its own fundamental characteristics is proposed; this will be one of the most important processes for industrial applications of electroless Ni deposition. (C) 2013 The Electrochemical Society. All rights reserved.

The influence of water molecules on the reaction behavior of hypophosphite ion, which acts as a reducing agent for electroless deposition, on metal surfaces was elucidated by calculating the adsorption structure of hydrated hypophosphite ion on a Pd surface using Monte-Carlo simulation and density functional theory calculations. Through geometrical optimization, the most favorable structure of the hydrated hypophosphite ion was obtained, in which six water molecules interact with the oxygen of hypophosphite ion and no water interacts with the hydrogen of hypophosphite ion. Further calculations indicated that the hydrated hypophosphite ion adsorbed on the Pd surface via hydrogen.

The elementary steps of the reactions of hypophosphite ions with Cu, Ni, and Pd were calculated theoretically using Density Functional Theory (DFT) to demonstrate the reaction mechanism and gain insight at the molecular level. The elementary steps of these reactions are adsorption, dehydrogenation, and oxidation (hydroxyl base attack). In the adsorption step, hypophosphite ions adsorb onto each surface spontaneously with stabilities in the order of Ni (111) > Pd (111) > Cu (111). In the dehydrogenation step, hypophosphite ions dehydrogenate on Ni (111) and Pd (111) with small reaction barriers, whereas they react on Cu (111) with a large reaction barrier. The large reaction barrier on Cu (111) is not compensated for by the adsorption energy on the surface. In the oxidation step, dehydrogenated anions on each metal surface react spontaneously with the hydroxyl base. The reaction barriers on each metal surface in this step are not so significant compared to the adsorption energies on each surface, suggesting that a reaction barrier of hypophosphite ion oxidation should exist in the dehydrogenation step and only be observed for Cu (111). This proposition elucidates the experimental catalytic behaviors of metal surfaces in the electroless deposition process using hypophosphite ions. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3609000] All rights reserved.