This study investigates the effects of addition of oxygen on the oxidative dehydrogenation （ODH） of methanol when a fluorotetrasilicic mica ion-exchanged with palladium （Pd2^＋-TSM） was used as the catalyst. The r...This study investigates the effects of addition of oxygen on the oxidative dehydrogenation （ODH） of methanol when a fluorotetrasilicic mica ion-exchanged with palladium （Pd2^＋-TSM） was used as the catalyst. The reaction proceeded at a very low temperature in the presence of oxygen, and HCOOCH3 was obtained at high selectivity. By calculating the equilibrium conversion, it has been shown that substantial ODH took place for HCOOCH3 production. Consequently, this reaction would make dehydrogenation the dominant reaction at equilibrium. Not all the H dissociated from CH3OH was converted to H20 by oxidation. It has been shown that the H2O was not produced from oxidative dehydrogenation by the direct reaction of CH3OH and O2 when an attempt was made to carry out oxidative dehydrogenation using an isotope oxygen trace method in the gas phase. Therefore, when CHaOH was converted to CO2 and dehydrogenated to HCOOCH3, the C-O bonds were not dissociated.展开更多
This work examines the ozone electrogeneration （OE） at a binary coating of different nominal compositions （Pt）x-（TaOy）（100-x）, where x （percentage in the precursor solution） varied between 1% and 100%, coate...This work examines the ozone electrogeneration （OE） at a binary coating of different nominal compositions （Pt）x-（TaOy）（100-x）, where x （percentage in the precursor solution） varied between 1% and 100%, coated on titanium substrate prepared by a sol-gel technique, The OE is performed in an artificial tap water at room temperature （25 ℃）. The percentages of Pt and Tatu in the coating significantly affect the electro- catalytic activity towards oxygen evolution. The oxygen evolution was retarded to a different extent based on the electrode composition. The largest retardation was obtained at the （Pt）10-（TaOy）90 electrode （ca. 480 mV positive shift） as compared with the （Pt）100-（TaOy）0 electrode. This was reflected in a high current efficiency （CE） of OE （ca. 19.3%） at the former electrode. This value is considered to be among the highest values reported for OE at 25℃ in neutral media. The composite electrodes were characterized by voltammetric and surface techniques. A plausible explanation for the change of the efficiency of OE with the electrode composition is given based on the electrochemical results.展开更多
It is well known that mineral surfaces play an important role as catalysts for abiotic polymerization of amino acids to form peptides, which are the main components of the first self-replicating system. Understanding ...It is well known that mineral surfaces play an important role as catalysts for abiotic polymerization of amino acids to form peptides, which are the main components of the first self-replicating system. Understanding the mechanism behind the adsorption of simple amino acids on mineral surfaces is a topic of great interest not only in field of prebiotic evolution and but also in many other branches of material sciences. Various clay minerals have been suggested for studying how organic molecules were first synthesized in a prebiotic “inorganic” environment. Among them, pyrite (FeS<sub>2</sub>) is one of the most potential minerals as it possesses a highly reactive surface to drive molecular adsorption in prebiotic chemistry reactions. Recent theoretical experiments suggest that amino acids are adsorbed on the pyrite surface depending on its surface structures. However, these results have not been tested experimentally, and the exact mechanism of the specific interactions on this mineral has not been fully resolved yet at the molecular level. In this work, through quantitative force analysis with atomic force microscope (AFM) in which a single amino acid residue was mounted on the tip apex of AFM probe, we were able to find the reaction sites and study the interaction forces between the amino acid and the pyrite surface. Our results of Raman spectroscopic studies and force measurements with a well-designed AFM probe demonstrated for the first time that pyrite provided higher adsorption probabilities of amino acid residues for the chemical reactions at surfaces.展开更多
Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and trans ? cis isomerization characteristics of azobenzenes...Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and trans ? cis isomerization characteristics of azobenzenes.A blue shift in πDπ* absorption band of ortho-alkylated azobenzenes(1o and 2o) was observed together with a reduction in molar extinction coefficient in comparison with both meta-alkylated azobenzenes(4m and 5m) and 7p lacking the meta and ortho substituents.For ortho-alkylated azobenzene,photochemical trans-to-cis isomerization and thermal back cis-to-trans isomerization in solution occurred slowly when compared with 4m,5m and 7p.The half-life time of the cis form of 2o was found to be 380 h,which is about 8-50 times longer than those of comparable 4m,5m(43-13 h) and 7p(7 h).Furthermore,comparison of the molecular structure and isomerization characteristics of azobenzene thiol(2o and 5m) self-assembled monolayers on flat gold surfaces indicates that the trans-to-cis photoconversion in monolayer systems is influenced by steric hindrance and strong intermolecular interaction between azobenzene units.展开更多
Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and transcis isomerization characteristics of azobenzenes....Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and transcis isomerization characteristics of azobenzenes.A blue shift in π-π* absorption band of ortho-alkylated azobenzenes(1o and 2o) was observed together with a reduction in molar extinction coefficient(ε) in comparison with both meta-alkylated azobenzenes(4m and 5m) and 7p lacking the meta and ortho substituents.For ortho-alkylated azobenzene,photochemical trans-to-cis isomerization and thermal back cis-to-trans isomerization in solution occurred slowly when compared with 4m,5m and 7p.The half-life time of the cis form of 2o was found to be 380 h,which is about 8-50 times longer than those of comparable 4m,5m(43-13 h) and 7p(7 h).Furthermore,comparison of the molecular structure and isomerization characteristics of azobenzene thiol(2o and 5m) self-assembled monolayers on flat gold surfaces indicates that the trans-to-cis photoconversion in monolayer systems is influenced by steric hindrance and strong intermolecular interaction between azobenzene units.展开更多
1 Results As tremendous increase of interest towards the application of LiFePO4 for lithium battery cathode,the mechanism of the intrinsic transport of lithium ions and electrons in LixFePO4 is becoming the intensive ...1 Results As tremendous increase of interest towards the application of LiFePO4 for lithium battery cathode,the mechanism of the intrinsic transport of lithium ions and electrons in LixFePO4 is becoming the intensive and exciting research subject.In the present paper,we will mainly focus on dimension of the transport and the role of solid solution as they seem to be key issues to understand charge movement in the olivine structure.Although one-demensional lithium motion along b-axis has been theoretical...展开更多
文摘This study investigates the effects of addition of oxygen on the oxidative dehydrogenation （ODH） of methanol when a fluorotetrasilicic mica ion-exchanged with palladium （Pd2^＋-TSM） was used as the catalyst. The reaction proceeded at a very low temperature in the presence of oxygen, and HCOOCH3 was obtained at high selectivity. By calculating the equilibrium conversion, it has been shown that substantial ODH took place for HCOOCH3 production. Consequently, this reaction would make dehydrogenation the dominant reaction at equilibrium. Not all the H dissociated from CH3OH was converted to H20 by oxidation. It has been shown that the H2O was not produced from oxidative dehydrogenation by the direct reaction of CH3OH and O2 when an attempt was made to carry out oxidative dehydrogenation using an isotope oxygen trace method in the gas phase. Therefore, when CHaOH was converted to CO2 and dehydrogenated to HCOOCH3, the C-O bonds were not dissociated.
文摘This work examines the ozone electrogeneration （OE） at a binary coating of different nominal compositions （Pt）x-（TaOy）（100-x）, where x （percentage in the precursor solution） varied between 1% and 100%, coated on titanium substrate prepared by a sol-gel technique, The OE is performed in an artificial tap water at room temperature （25 ℃）. The percentages of Pt and Tatu in the coating significantly affect the electro- catalytic activity towards oxygen evolution. The oxygen evolution was retarded to a different extent based on the electrode composition. The largest retardation was obtained at the （Pt）10-（TaOy）90 electrode （ca. 480 mV positive shift） as compared with the （Pt）100-（TaOy）0 electrode. This was reflected in a high current efficiency （CE） of OE （ca. 19.3%） at the former electrode. This value is considered to be among the highest values reported for OE at 25℃ in neutral media. The composite electrodes were characterized by voltammetric and surface techniques. A plausible explanation for the change of the efficiency of OE with the electrode composition is given based on the electrochemical results.
文摘It is well known that mineral surfaces play an important role as catalysts for abiotic polymerization of amino acids to form peptides, which are the main components of the first self-replicating system. Understanding the mechanism behind the adsorption of simple amino acids on mineral surfaces is a topic of great interest not only in field of prebiotic evolution and but also in many other branches of material sciences. Various clay minerals have been suggested for studying how organic molecules were first synthesized in a prebiotic “inorganic” environment. Among them, pyrite (FeS<sub>2</sub>) is one of the most potential minerals as it possesses a highly reactive surface to drive molecular adsorption in prebiotic chemistry reactions. Recent theoretical experiments suggest that amino acids are adsorbed on the pyrite surface depending on its surface structures. However, these results have not been tested experimentally, and the exact mechanism of the specific interactions on this mineral has not been fully resolved yet at the molecular level. In this work, through quantitative force analysis with atomic force microscope (AFM) in which a single amino acid residue was mounted on the tip apex of AFM probe, we were able to find the reaction sites and study the interaction forces between the amino acid and the pyrite surface. Our results of Raman spectroscopic studies and force measurements with a well-designed AFM probe demonstrated for the first time that pyrite provided higher adsorption probabilities of amino acid residues for the chemical reactions at surfaces.
基金supported by the Global COE Program from the Ministry of Education,Culture,Sports,Science,and Technology of Japanese Government
文摘Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and trans ? cis isomerization characteristics of azobenzenes.A blue shift in πDπ* absorption band of ortho-alkylated azobenzenes(1o and 2o) was observed together with a reduction in molar extinction coefficient in comparison with both meta-alkylated azobenzenes(4m and 5m) and 7p lacking the meta and ortho substituents.For ortho-alkylated azobenzene,photochemical trans-to-cis isomerization and thermal back cis-to-trans isomerization in solution occurred slowly when compared with 4m,5m and 7p.The half-life time of the cis form of 2o was found to be 380 h,which is about 8-50 times longer than those of comparable 4m,5m(43-13 h) and 7p(7 h).Furthermore,comparison of the molecular structure and isomerization characteristics of azobenzene thiol(2o and 5m) self-assembled monolayers on flat gold surfaces indicates that the trans-to-cis photoconversion in monolayer systems is influenced by steric hindrance and strong intermolecular interaction between azobenzene units.
文摘Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and transcis isomerization characteristics of azobenzenes.A blue shift in π-π* absorption band of ortho-alkylated azobenzenes(1o and 2o) was observed together with a reduction in molar extinction coefficient(ε) in comparison with both meta-alkylated azobenzenes(4m and 5m) and 7p lacking the meta and ortho substituents.For ortho-alkylated azobenzene,photochemical trans-to-cis isomerization and thermal back cis-to-trans isomerization in solution occurred slowly when compared with 4m,5m and 7p.The half-life time of the cis form of 2o was found to be 380 h,which is about 8-50 times longer than those of comparable 4m,5m(43-13 h) and 7p(7 h).Furthermore,comparison of the molecular structure and isomerization characteristics of azobenzene thiol(2o and 5m) self-assembled monolayers on flat gold surfaces indicates that the trans-to-cis photoconversion in monolayer systems is influenced by steric hindrance and strong intermolecular interaction between azobenzene units.
文摘1 Results As tremendous increase of interest towards the application of LiFePO4 for lithium battery cathode,the mechanism of the intrinsic transport of lithium ions and electrons in LixFePO4 is becoming the intensive and exciting research subject.In the present paper,we will mainly focus on dimension of the transport and the role of solid solution as they seem to be key issues to understand charge movement in the olivine structure.Although one-demensional lithium motion along b-axis has been theoretical...
