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21.
In this work, the substituent effects on hydrogen bonding in one kind of hydrazone-based switch are revealed. The E/Z isomerization ratios of these hydrazones and their intramolecular hydrogen bond strengths in the Z form were evaluated using NMR technique. Linear correlations between these parameters and Hammett empirical values for substituent effects are explored as well. 相似文献
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Jinghui Tu Haihong Wu Qingli Qian Shitao Han Mengen Chu Shuaiqiang Jia Ruting Feng Jianxin Zhai Mingyuan He Buxing Han 《Chemical science》2021,12(11):3937
CO2 methanation is an important reaction in CO2 valorization. Because of the high kinetic barriers, the reaction usually needs to proceed at higher temperature (>300 °C). High-efficiency CO2 methanation at low temperature (<200 °C) is an interesting topic, and only several noble metal catalysts were reported to achieve this goal. Currently, design of cheap metal catalysts that can effectively accelerate this reaction at low temperature is still a challenge. In this work, we found that the amorphous Co–Zr0.1–B–O catalyst could catalyze the reaction at above 140 °C. The activity of the catalyst at 180 °C reached 10.7 mmolCO2 gcat−1 h−1, which is comparable to or even higher than that of some noble metal catalysts under similar conditions. The Zr promoter in this work had the highest promoting factor to date among the catalysts for CO2 methanation. As far as we know, this is the first report of an amorphous transition metal catalyst that could effectively accelerate CO2 methanation. The outstanding performance of the catalyst could be ascribed to two aspects. The amorphous nature of the catalyst offered abundant surface defects and intrinsic active sites. On the other hand, the Zr promoter could enlarge the surface area of the catalyst, enrich the Co atoms on the catalyst surface, and tune the valence state of the atoms at the catalyst surface. The reaction mechanism was proposed based on the control experiments.It is discovered that an amorphous transition metal catalyst Co–Zr0.1–B–O could effectively accelerate CO2 methanation, at a rate that is comparable to or even higher than that of some noble metal catalysts under similar conditions. 相似文献
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酸性离子液体催化脂肪酸甲酯聚合制备二聚酸甲酯 总被引:1,自引:0,他引:1
以 Brönsted-Lewis 酸性离子液体为催化剂, 用于催化生物柴油中不饱和脂肪酸甲酯聚合制备二聚酸甲酯反应, 考察了催化剂种类、催化剂用量、反应温度和时间等因素对聚合反应性能的影响, 得到较佳的反应条件. 结果表明, 当以 1-(3-磺酸)-丙基-3-甲基咪唑氯锌酸盐[HO3S-(CH2)3-mim]Cl-ZnCl2 (ZnCl2 摩尔分数为 0.67) 为催化剂, 生物柴油 15 g, m(生物柴油):m(离子液体) = 15:1, 于 240 oC 下反应 6 h 时, 二聚酸甲酯收率为 63.2%, 其中三聚体含量小于 5%. 另外, 该催化剂重复使用 5 次后, 二聚酸甲酯收率仍超过 63%, 表明其具有较好的重复使用性能. 离子液体的 Brönsted 和 Lewis 酸位的协同效应显著提高了其催化活性. 相似文献
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研究了基于硅光电倍增管(SiPM)双端读出的面积为10 cm ×10 cm的薄塑料闪烁体探测器的时间性能。239Pu放射源测试结果显示:(1)在多支SiPM串连读出方式下,随着SiPM数量的增加,探测器时间分辨逐渐变好;(2)在固定12支SiPM数量不变的情况下,并联支路越多,探测器时间分辨越差;(3)采用快时间塑料闪烁体并增加其厚度,可有效提高探测器时间分辨;(4)采用比束斑尺寸更大的塑料闪烁体,可有效提高探测器时间分辨的位置均匀性;(5)对于1 mm厚的EJ232塑料闪烁体探测器,在单端12支SiPM串行连接的情况下,可获得好于131 ps的时间分辨。这一研究对RIBLL2起始时间探测器的升级改造具有重要的指导意义。 相似文献
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Xiaoqing Jiang Bingqian Zhang Guangyue Yang Zhongmin Zhou Xin Guo Fengshan Zhang Shitao Yu Shiwei Liu Shuping Pang 《Angewandte Chemie (International ed. in English)》2023,62(22):e202302462
Carbonyl functional materials as additives are extensively applied to reduce the defects density of the perovskite film. However, there is still a lack of comprehensive understanding for the effect of carbonyl additives to improve device performance. In this work, we systematically study the effect of carbonyl additive molecules on the passivation of defects in perovskite films. After a comprehensive investigation, the results confirm the importance of molecular dipole in amplifying the passivation effect of additive molecules. The additive with strong molecular dipole possesses the advantages of enhancing the efficiency and stability of perovskite solar cells (PSCs). After optimization, the companion efficiency of PSCs is 23.20 %, and it can maintain long-term stability under harsh conditions. Additionally, a large-area solar cell module-modified DLBA was 20.18 % (14 cm2). This work provides an important reference for the selection and designing of efficient carbonyl additives. 相似文献
26.
Yuting Zhang Zelong Qiao Rui Zhang Zhengqi Wang Hui-Juan Wang Jie Zhao Prof. Dr. Dapeng Cao Prof. Dr. Shitao Wang 《Angewandte Chemie (International ed. in English)》2023,62(49):e202314539
The semiconducting properties and applications of three dimensional (3D) covalent organic frameworks (COFs) are greatly hampered because of their long-ranged non-conjugated skeletons and relatively unstable linkages. Here, a robust imidazole-linked fully conjugated 3D covalent organic framework (BUCT-COF-7) is synthesized through the one-pot multicomponent Debus-Radziszewski reaction of the saddle-shaped aldehyde-substituted cyclooctatetrathiophene, pyrene-4,5,9,10-tetraone, and ammonium acetate. The semiconducting BUCT-COF-7, as a metal-free catalyst, shows excellent two electron oxygen reduction reaction (ORR) activity in alkaline medium with high hydrogen peroxide (H2O2) selectivity of 83.4 %. When the BUCT-COF-7 as cathode catalyst is assembled into the electrolyzer, the devices showed high electrochemical production rate of H2O2 up to 326.9 mmol g−1 h−1. The accumulative amount of H2O2 could totally degrade the dye methylene blue via Fenton reaction for wastewater treatment. This is the first report about intrinsic 3D COFs for efficient electrochemical synthesis of H2O2, revealing the promising applications of fully conjugated 3D COFs in the environment-related field. 相似文献
27.
Rui Bao Zhehao Xiang Zelong Qiao Yongping Yang Yuting Zhang Prof. Dr. Dapeng Cao Prof. Dr. Shitao Wang 《Angewandte Chemie (International ed. in English)》2023,62(4):e202216751
The application of three-dimensional (3D) covalent organic frameworks (COFs) in renewable energy fields is greatly limited due to their non-conjugated skeletons. Here, we design and successfully synthesize a thiophene-enriched fully conjugated 3D COF (BUCT-COF-11) through an all-thiophene-linked saddle-shaped building block (COThTh-CHO). The BUCT-COF-11 exhibits excellent semiconducting property with intrinsic metal-free oxygen reduction reaction (ORR) activity. Using the COF as cathode catalyst, the assembled anion-exchange membrane fuel cells (AEMFCs) exhibited a high peak power density up to 493 mW cm−2. DFT calculations reveal that thiophene introduction in the COF not only improves the conductivity but also optimizes the electronic structure of the sample, which therefore boosts the ORR performance. This is the first report on the application of COFs as metal-free catalysts in fuel cells, demonstrating the great potential of fully conjugated 3D COFs as promising semiconductors in energy fields. 相似文献
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在耦合波理论的基础上,结合波导渐变曲线给出了普适高阶渐变波导设计方法,研究了95 GHz回旋管内置 TE03模式改进Dolph-Chebychev渐变波导。采用编制的数值计算程序进行优化,得到了可靠的最优几何参量,设计出了紧凑的95 GHz渐变波导。经全电磁场仿真验证,该内置渐变输出结构对杂模的抑制达30 dB,满足设计要求。回旋管的热测实验中测出的模式样图表明,所设计的内置渐变波导有效地实现了回旋管内径变化。该方法可以高效地指导高阶过模圆波导渐变结构的设计。 相似文献
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将温控结构单元聚醚链和催化氧化基团磷钨酸根共同引入到离子液体的结构中, 合成出一系列不同聚合度的十八胺类氧化-温控双功能离子液体, 并将其应用于催化O2氧化模拟柴油的脱硫反应过程, 实现了反应分离一体化, 并取得了良好的脱硫效果和催化剂循环使用效果. 该类离子液体在甲苯/正十二烷混合溶剂中具有良好的温控性能. 筛选出活性较高的离子液体催化剂, 其聚合度n=111以及烷基碳链为C12. 考察了反应温度、反应时间和氧气压力等因素对脱硫效果的影响. 在优化的反应条件(V(甲苯):V(模拟油)=1:1, T=100 ℃, t=2 h, p(O2)=2.0 MPa)下, DMF萃取一次, 脱硫率接近100%. 催化剂循环使用11次, 脱硫率仍可达到95%以上. 相似文献