The Experts below are selected from a list of 10860 Experts worldwide ranked by ideXlab platform
Jarl B. Rosenholm - One of the best experts on this subject based on the ideXlab platform.
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surface induced electrolytic dissociation of oxalic and phosphoric acid in mixed alcohol water solvents
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011Co-Authors: Per Dahlsten, Marek Kosmulski, Jarl B. RosenholmAbstract:Abstract The Electric Conductance of solutions of oxalic, phosphoric and sulfuric acid (up to 0.025 M) in ethanol, methanol, and mixed alcohol–water solvents has been studied in the presence and absence of TiO2 (1–10% by mass). TiO2 enhanced the Conductance of solutions of oxalic and phosphoric acid in anhydrous alcohol and in alcohol-rich mixed solvents. In water-rich mixed solvents “normal” behavior was observed, that is, TiO2 depressed the Conductance of electrolyte solutions. The enhanced Conductance is interpreted in terms of surface-induced electrolytic dissociation. In nonaqueous solvents, oxalic and phosphoric acid occur chiefly in molecular form, even in very dilute solutions. TiO2 binds the hydrogen oxalate or dihydrogen phosphate anions (which originate from neutral acid molecules) and the protons remain in solution in form of solvated cations. The lyonium cations have a substantially higher molar Conductance than other ions due to the Grotthuss mechanism. This is why the enhancement of Conductance is more substantial in solutions of weak acids than in solutions of other electrolytes.
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surface induced electrolytic dissociation of weak acids in ethanol
Journal of Physical Chemistry C, 2010Co-Authors: Marek Kosmulski, Piotr Prochniak, Edward Maczka, Jarl B. RosenholmAbstract:Positively charged particles of metal oxides (alumina, hematite, and titania) enhance the electrolytic dissociation of phosphoric, oxalic, citric, and succinic acids in 94% ethanol (by mass). This results in enhanced Electric Conductance of dispersions of these oxides, which is higher than the Conductance of dispersion containing only solvent and metal oxide and of an alcoholic solution of a weak acid. This phenomenon is accompanied by a shift of the ζ potential of the oxide particles to more negative values. The changes in the ζ potential indicate strong positive adsorption of anions from solution.
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surface induced electrolytic dissociation of oxalic acid in polar organic solvents
Langmuir, 2010Co-Authors: Marek Kosmulski, Piotr Prochniak, Jarl B. RosenholmAbstract:The presence of titania powder (chiefly anatase) enhanced electrolytic dissociation of oxalic acid in lower aliphatic alcohols (but not in water). The surface-induced dissociation was manifested in enhanced Electric Conductance of a dispersion containing solvent, oxalic acid, and titania, which was substantially higher than the Conductance of dispersion containing only solvent and titania and of solution of oxalic acid in that solvent. This phenomenon can be applied to control the electrokinetic potential of particles in polar organic solvents.
Liqiang Mai - One of the best experts on this subject based on the ideXlab platform.
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unveiling the role of surface p o group in p doped co3o4 for electrocatalytic oxygen evolution by on chip micro device
Nano Energy, 2021Co-Authors: Xunbiao Zhou, Xiaobin Liao, Xuelei Pan, Mengyu Yan, Yan Zhao, Wen Luo, Liqiang MaiAbstract:Abstract Transition metal phosphides or partially phosphatized oxides usually suffer from surface reconstruction during oxygen evolution reaction (OER), but still possess enhanced catalytic activity than directly synthesized oxides, which has aroused great interest in exploring the causes of such high catalytic activity. To monitor electronic property of catalyst during the OER can provide crucial insights into catalytic ability. Here we design a planar electrochemical microdevice based on individual thin-film catalyst, and for the first time explore the continuous Electric Conductance evolution of lattice P-doped oxides during the electrochemical activation process. Moreover, combining on-chip electrochemical impedance spectra measurements, in situ I-V measurements, and theoretical simulations of reconstructed lattice P-doped oxides, the effect of P–O groups on new-formed oxides is clarified. The induced electronic coupling between new-formed oxides and P-O groups has been studied and demonstrated. The coupled P–O groups effectively promote the metal–oxygen covalency of new-formed oxides, which accelerates electron transfer between active metallic center and oxygen adsorbates, thus leading to the enhanced electrocatalytic activity. Our study highlights the role of surface P–O groups in Co3O4 during the OER, and such unique on-chip electrochemical microdevice platform can also be applied in other related fields to understand the dynamic behavior of energy materials at nanoscale.
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unveiling the role of surface p o group in p doped co3o4 for electrocatalytic oxygen evolution by on chip micro device
Nano Energy, 2021Co-Authors: Xunbiao Zhou, Xiaobin Liao, Xuelei Pan, Mengyu Yan, Yan Zhao, Wen Luo, Liqiang MaiAbstract:Abstract Transition metal phosphides or partially phosphatized oxides usually suffer from surface reconstruction during the oxygen evolution reaction (OER), but still possess enhanced catalytic activity than directly synthesized oxides, which has aroused great interest in exploring the causes of such high catalytic activity. To monitor electronic property of catalyst during the OER can provide crucial insights into catalytic ability. Here we design a planar electrochemical microdevice based on individual thin-film catalyst, and for the first time explore the continuous Electric Conductance evolution of lattice P-doped oxides during the electrochemical activation process. Moreover, combining on-chip electrochemical impedance spectra measurements, in situ I-V measurements, and theoretical simulations of reconstructed phosphide, the effect of P-O groups on new-formed oxides is clarified. We demonstrate that the induced electronic coupling between new-formed oxides and P-O groups. The coupled P-O groups effectively promote the metal–oxygen covalency of new-formed oxides, which accelerates electron transfer between active metallic center and oxygen adsorbates, thus leading to the enhanced electrocatalytic activity. Our study highlights the role of surface P-O groups in Co3O4 during the OER, and such unique on-chip electrochemical microdevice platform can also be applied in the other related fields to understand the dynamic behavior of energy materials at nanoscale.
Manabu Kiguchi - One of the best experts on this subject based on the ideXlab platform.
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effect of mechanical strain on Electric Conductance of molecular junctions
Journal of Physical Chemistry C, 2015Co-Authors: Junichi Inatomi, Shintaro Fujii, Santiago Marquesgonzalez, Hiroshi Masai, Yasushi Tsuji, Jun Terao, Manabu KiguchiAbstract:Electromechanical properties of single molecular junctions are investigated using scanning tunneling microscopy based break junction method. Two types of molecular junctions consisting of π-conjugated backbones with and without coordinative bonding (i.e., Co((4-aniline)-terpyridine)2 complex and oligo(phenylene-ethynylene) derivative) are prepared between two Au electrodes. Electronic transport measurements revealed molecular Conductance of ca. 10–4 G0 (G0 = 2e2/h) for both of the molecular junctions. Then we assessed the electronic transport properties of the two types of molecular junctions under mechanical strain in their compression–elongation cycle. We found significant asymmetric electromechanical response for all covalent systems of the oligo(phenylene-ethynylene) derivative, while the Co complex with the coordinative bonding exhibits symmetric modulation of the electronic transport property in the compression–elongation cycle of the molecular junctions. The asymmetric and symmetric electromechanic...
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Electric Conductance of single ethylene and acetylene molecules bridging between pt electrodes
Journal of Physical Chemistry C, 2012Co-Authors: Tomoka Nakazumi, Satoshi Kaneko, Ryuuji Matsushita, Manabu KiguchiAbstract:We have investigated the Conductance and atomic structure of single ethylene and acetylene molecule junctions on the basis of the Conductance measurement and vibration spectroscopy of the single molecule junction. Single molecule junctions have a Conductance comparable to that of metal atomic junctions (around 0.9G0: G0 = 2e2/h) due to effective hybridization between metal and the π molecular orbital. The ethylene molecules are bound to Pt electrodes via a di-σ bond, while the acetylene molecules are bound to Pt electrodes via di-σ and π bonds. By using the highly conductive single molecule junctions, we investigated the characteristics of vibration spectroscopy of the single molecule junction in an intermediate regime between tunneling and contact. The vibration modes that could modify the conduction orbital were excited for the ethylene and acetylene molecule junctions. The crossover between Conductance enhancement and suppression was observed for the single ethylene molecule junction, whereas clear cro...
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single molecule Conductance of π conjugated rotaxane new method for measuring stipulated Electric Conductance of π conjugated molecular wire using stm break junction
Small, 2012Co-Authors: Manabu Kiguchi, Yasushi Tsuji, Shigeto Nakashima, Tomofumi Tada, Satoshi Watanabe, Susumu Tsuda, Jun TeraoAbstract:An electronic Conductance with small fluctuations, which is stipulated in single-molecule junctions, is necessary for the precise control of single-molecule devices. However, the suppression of Conductance fluctuations in conventional molecular junctions is intrinsically difficult because the fluctuations are related to the contact fluctuations and molecular motion. In the present study involving experimental and theoretical investigations, it is found that covering a single π-conjugated wire with an α-cyclodextrin molecule is a promising technique for suppressing Conductance fluctuations. The Conductance histogram of the covered molecular junction measured with the scanning tunneling microscope break-junction technique shows that the Conductance peak for the covered junction is sharper than that of the uncovered junction. The covering technique thus has two prominent effects: the suppression of intramolecular motion, and the elimination of intermolecular interactions. Theoretical calculations of electronic Conductance clearly support these experimental observations.
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effect of anchoring group position on formation and Conductance of a single disubstituted benzene molecule bridging au electrodes change of conductive molecular orbital and electron pathway
Journal of Physical Chemistry C, 2010Co-Authors: Manabu Kiguchi, Hisao Nakamura, Yuuta Takahashi, Takuya Takahashi, Tatsuhiko OhtoAbstract:We investigated the effect of anchoring group position on the formation and Electric Conductance of single molecule junctions for benzenedithiol and benzenediamine by the scanning tunneling microscope break junction technique. The Conductances of the single 1,4-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenediamine, and 1,3-benzenediamine molecules were 0.005 (±0.001) G0 (G0 = 2e2/h), 0.004 (±0.001) G0, 0.01 (±0.003) G0, and 0.005 (±0.002) G0, respectively. No 1,2-disubstituted benzene molecules formed junctions. While the 1,4-position provided larger Conductance than the 1,3-position for both anchoring groups, the effect of the anchoring position on Conductance was clearer for benzenediamine than benzenedithiol. The resulting anchoring position and its stability are discussed in consideration of the formation of the single molecular junction. The relationship between Conductance and anchoring group (position) was analyzed based on ab initio transport calculations. The deformation and change of the energy...
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Electric Conductance of metal nanowires at mechanically controllable break junctions under electrochemical potential control
Surface Science, 2007Co-Authors: Manabu Kiguchi, Nobuo Sekiguchi, Kei MurakoshiAbstract:Abstract We have developed the mechanically controllable break junction setup with an electrochemical cell (EC–MCBJ) to measure the Electric Conductance of metal nanowires under electrochemical potential control. The Electric Conductance of Au nanowires was investigated in 0.1 M Na 2 SO 4 solution using EC–MCBJ. The Conductance of the Au nanowires was quantized in units of G 0 (=2 e 2 / h ), showing clear features in the Conductance histogram. The atomic contact with a specific Conductance value was kept for >5 s, indicating the relatively high stability of the present EC–MCBJ system.
Marek Kosmulski - One of the best experts on this subject based on the ideXlab platform.
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surface induced electrolytic dissociation of oxalic and phosphoric acid in mixed alcohol water solvents
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011Co-Authors: Per Dahlsten, Marek Kosmulski, Jarl B. RosenholmAbstract:Abstract The Electric Conductance of solutions of oxalic, phosphoric and sulfuric acid (up to 0.025 M) in ethanol, methanol, and mixed alcohol–water solvents has been studied in the presence and absence of TiO2 (1–10% by mass). TiO2 enhanced the Conductance of solutions of oxalic and phosphoric acid in anhydrous alcohol and in alcohol-rich mixed solvents. In water-rich mixed solvents “normal” behavior was observed, that is, TiO2 depressed the Conductance of electrolyte solutions. The enhanced Conductance is interpreted in terms of surface-induced electrolytic dissociation. In nonaqueous solvents, oxalic and phosphoric acid occur chiefly in molecular form, even in very dilute solutions. TiO2 binds the hydrogen oxalate or dihydrogen phosphate anions (which originate from neutral acid molecules) and the protons remain in solution in form of solvated cations. The lyonium cations have a substantially higher molar Conductance than other ions due to the Grotthuss mechanism. This is why the enhancement of Conductance is more substantial in solutions of weak acids than in solutions of other electrolytes.
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surface induced electrolytic dissociation of weak acids in ethanol
Journal of Physical Chemistry C, 2010Co-Authors: Marek Kosmulski, Piotr Prochniak, Edward Maczka, Jarl B. RosenholmAbstract:Positively charged particles of metal oxides (alumina, hematite, and titania) enhance the electrolytic dissociation of phosphoric, oxalic, citric, and succinic acids in 94% ethanol (by mass). This results in enhanced Electric Conductance of dispersions of these oxides, which is higher than the Conductance of dispersion containing only solvent and metal oxide and of an alcoholic solution of a weak acid. This phenomenon is accompanied by a shift of the ζ potential of the oxide particles to more negative values. The changes in the ζ potential indicate strong positive adsorption of anions from solution.
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surface induced electrolytic dissociation of oxalic acid in polar organic solvents
Langmuir, 2010Co-Authors: Marek Kosmulski, Piotr Prochniak, Jarl B. RosenholmAbstract:The presence of titania powder (chiefly anatase) enhanced electrolytic dissociation of oxalic acid in lower aliphatic alcohols (but not in water). The surface-induced dissociation was manifested in enhanced Electric Conductance of a dispersion containing solvent, oxalic acid, and titania, which was substantially higher than the Conductance of dispersion containing only solvent and titania and of solution of oxalic acid in that solvent. This phenomenon can be applied to control the electrokinetic potential of particles in polar organic solvents.
G Cressey - One of the best experts on this subject based on the ideXlab platform.
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phase transitions in the system mgo co2 h2o during co2 degassing of mg bearing solutions
Geochimica et Cosmochimica Acta, 2012Co-Authors: Laurence Hopkinso, Petra Kristova, G CresseyAbstract:Abstract This study documents the paragenesis of magnesium carbonates formed during degassing of CO 2 from a 0.15 M Mg 2+ aqueous solution. The starting solutions were prepared by CO 2 sparging of a brucite suspension at 25 °C for 19 h, followed by rapid heating to 58 °C. One experiment was performed in an agitated environment, promoted by sonication. In the second, CO 2 degassing was exclusively thermally-driven (static environment). Electric Conductance, pH, and temperature of the experimental solutions were measured, whereas Mg 2+ was determined by atomic absorption spectroscopy. Precipitates were analysed by X-ray diffraction, Fourier transform (FT) mid-infrared, FT-Raman, and scanning electron microscopy. Hydromagnesite [Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O] precipitated at 25 °C was followed by nesquehonite [Mg(HCO 3 ,OH)·2H 2 O] upon heating to 58 °C. The yield of the latter mineral was greater in the agitated solution. After 120 min, accelerated CO 2 degassing resulted in the loss of nesquehonite at the expense of an assemblage consisting of an unnamed mineral phase: [Mg 5 (CO 3 ) 4 (OH) 2 ·8H 2 O] and hydromagnesite. After 240 min, dypingite [Mg 5 (CO 3 ) 4 (OH) 2 ·5H 2 O (or less H 2 O)] appears with hydromagnesite. The unnamed mineral shows greater disorder than dypingite, which in turn shows greater disorder than hydromagnesite. In the static environment, there is no evidence for nesquehonite loss or the generation of [Mg 5 (CO 3 ) 4 (OH) 2 · X H 2 O] phases over the same timeframe. Hence, results indicate that the transformation of nesquehonite to hydromagnesite displays mixed diffusion and reaction-limited control and proceeds through the production of metastable intermediates, and is interpreted according to the Ostwald step rule. Nevertheless, variations in the chemistry of nesquehonite, combined with the established tendency of the mineral to desiccate, implies that its transformation to hydromagnesite is unlikely to follow a single simple sequential reaction pathway.
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phase transitions in the system mgo co2 h2o during co2 degassing of mg bearing solutions
Geochimica et Cosmochimica Acta, 2012Co-Authors: Laurence Hopkinson, Petra Kristova, Ken J Rutt, G CresseyAbstract:Abstract This study documents the paragenesis of magnesium carbonates formed during degassing of CO 2 from a 0.15 M Mg 2+ aqueous solution. The starting solutions were prepared by CO 2 sparging of a brucite suspension at 25 °C for 19 h, followed by rapid heating to 58 °C. One experiment was performed in an agitated environment, promoted by sonication. In the second, CO 2 degassing was exclusively thermally-driven (static environment). Electric Conductance, pH, and temperature of the experimental solutions were measured, whereas Mg 2+ was determined by atomic absorption spectroscopy. Precipitates were analysed by X-ray diffraction, Fourier transform (FT) mid-infrared, FT-Raman, and scanning electron microscopy. Hydromagnesite [Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O] precipitated at 25 °C was followed by nesquehonite [Mg(HCO 3 ,OH)·2H 2 O] upon heating to 58 °C. The yield of the latter mineral was greater in the agitated solution. After 120 min, accelerated CO 2 degassing resulted in the loss of nesquehonite at the expense of an assemblage consisting of an unnamed mineral phase: [Mg 5 (CO 3 ) 4 (OH) 2 ·8H 2 O] and hydromagnesite. After 240 min, dypingite [Mg 5 (CO 3 ) 4 (OH) 2 ·5H 2 O (or less H 2 O)] appears with hydromagnesite. The unnamed mineral shows greater disorder than dypingite, which in turn shows greater disorder than hydromagnesite. In the static environment, there is no evidence for nesquehonite loss or the generation of [Mg 5 (CO 3 ) 4 (OH) 2 · X H 2 O] phases over the same timeframe. Hence, results indicate that the transformation of nesquehonite to hydromagnesite displays mixed diffusion and reaction-limited control and proceeds through the production of metastable intermediates, and is interpreted according to the Ostwald step rule. Nevertheless, variations in the chemistry of nesquehonite, combined with the established tendency of the mineral to desiccate, implies that its transformation to hydromagnesite is unlikely to follow a single simple sequential reaction pathway.