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171.
Daixing Wei Yiqing Wang Prof. Chung-Li Dong Ta Thi Thuy Nga Yuchuan Shi Jialin Wang Xiaoli Zhao Prof. Fan Dong Prof. Shaohua Shen 《Angewandte Chemie (International ed. in English)》2023,62(31):e202306876
Oxide-derived Cu (OD−Cu) featured with surface located sub-20 nm nanoparticles (NPs) created via surface structure reconstruction was developed for electrochemical CO2 reduction (ECO2RR). With surface adsorbed hydroxyls (OHad) identified during ECO2RR, it is realized that OHad, sterically confined and adsorbed at OD−Cu by surface located sub-20 nm NPs, should be determinative to the multi-carbon (C2) product selectivity. In situ spectral investigations and theoretical calculations reveal that OHad favors the adsorption of low-frequency *CO with weak C≡O bonds and strengthens the *CO binding at OD−Cu surface, promoting *CO dimerization and then selective C2 production. However, excessive OHad would inhibit selective C2 production by occupying active sites and facilitating competitive H2 evolution. In a flow cell, stable C2 production with high selectivity of ∼60 % at −200 mA cm−2 could be achieved over OD−Cu, with adsorption of OHad well steered in the fast flowing electrolyte. 相似文献
172.
We study the degeneration dimension of non-archimedean analytic maps into the complement of hypersurface divisors of smooth projective varieties. We also show that there exist no non-archimedean analytic maps into where Di, 1?i?n, are hypersurfaces of degree at least 2 in general position and intersecting transversally. Moreover, we prove that there exist no non-archimedean analytic maps into when D1, D2 are generic plane curves with degD1+degD2?4. 相似文献
173.
Kateřina Plachká Veronika Pilařová Ondřej Horáček Taťána Gazárková Hana Kočová Vlčková Radim Kučera Lucie Nováková 《Journal of separation science》2023,46(18):2300431
Within this review, we thoroughly explored supercritical fluid chromatography (SFC) columns used across > 3000 papers published from the first study carried out under SFC conditions in 1962 to the end of 2022. We focused on the open tubular capillary, packed capillary, and packed columns, their chemistries, dimensions, and trends in used stationary phases with correlation to their specific interactions, advantages, drawbacks, used instrumentation, and application field. Since the 1990s, packed columns with liquid chromatography and SFC-dedicated stationary phases for chiral and achiral separation are predominantly used. These stationary phases are based on silica support modified with a wide range of chemical moieties. Moreover, numerous unconventional stationary phases were evaluated, including porous graphitic carbon, titania, zirconia, alumina, liquid crystals, and ionic liquids. The applications of unconventional stationary phases are described in detail as they bring essential findings required for further development of the supercritical fluid chromatography technique. 相似文献
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Synergetic effect of sodium borohydride (NaBH4) addition to ammonia borane (NH3BH3) hydrolysis reaction had been studied and iron-borate (FeB) was used to catalyze the reaction. Hydrogen generation performance of the hydrolysis reactions was compared for three different operating conditions: (1) in the presence of NaBH4 with FeB catalyst, (2) with FeB without NaBH4 addition and (3) in the presence of NaBH4 without FeB. It was found that addition of NaBH4 to the NH3BH3 hydrolysis reaction catalyzed by FeB resulted in the synergetic effect (synergetic factor (SF) > 0) and improved the hydrogen generation performance. Kinetic analysis showed that NaBH4 addition decreases the activation energy (Ea) from 52.11 ± 0.85 to 27.19 ± 0.44 kJ/mol. Simulation of hydrolysis kinetics curves indicated that addition of NaBH4 (the mole fraction of NaBH4 added to NH3BH3 is (1)) changed the three-dimensional diffusion mechanism to the one-dimensional one and brought on better hydrolysis properties in terms of higher hydrogen generation rate and lower induction time. 相似文献
177.
Anelise Lima de Abreu Dessimoni Leydiane de Oliveira Pereira Evanise Silva Penido Taís Regina Lima Abreu Veiga Regiane Victória de Barros Fernandes Maria Luisa Teixeira 《Analytical letters》2018,51(11):1705-1717
The use of raw materials from renewable sources by industries is essential to the sustainable development of modern society. The biodiesel produced by the transesterification of vegetable oils is a less polluting diesel fuel, but large amounts of glycerol (10% of total weight of product) are generated during the production process. The scientific community and industries of the sector know that, in the future, the amount of glycerol generated can cause a serious ecologic problem. Thus, it is essential to find alternatives for the consumption of this co-product, in its crude form and/or as high value-added derivatives. This work studied obtaining triacetate from the glycerol esterification reaction that was determined by electrospray ionization–mass spectrometry and gas chromatography–mass spectrometry. The reactions were carried out with sulfuric acid, phosphotungstic acid and in the absence of catalyst, using different acetylating agents (acetic acid and acetic anhydride). The phosphotungstic acid showed satisfactory performance in the catalytic esterification of glycerol when acetic acid and acid anhydride were used. The use of acetic anhydride as the acetylating agent favors the esterification reaction, decreasing the reaction time required for obtaining glycerol triacetate. 相似文献
178.
179.
Indolylbenzimidazole‐based ligands catalyze the coupling of arylboronic acids with aryl halides 下载免费PDF全文
A novel class of compounds bearing indole and benzimidazole rings was designed and easily synthesized from 2‐indolecarboxylic acid and o‐phenylenediamine. The catalytic system derived from a 2‐indolylbenzimidazole‐based ligand and Pd(OAc)2 in situ could lead to complete conversion of aryl bromides at 0.5 mol% Pd loading under mild reaction conditions. In the presence of a catalyst, sterically hindered biaryls were selectively generated in excellent yields by adjusting reaction parameters through the coupling of arylboronic acids with aryl halides. The efficiency of this reaction was demonstrated by its compatibility with various functional groups. 相似文献
180.
The manifestations of QCD effects on quark and gluon distribution functions of longitudinally polarized virtual photons involved
in hard collisions are investigated. It is shown that for moderate photon virtualities and in the kinematical region accessible
at HERA and LEP these effects are sizable and significantly enhance theoretical predictions based on contributions of transversally
polarized virtual photon only.
Received: 21 October 2000 / Published online: 23 January 2001 相似文献