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41.
Ning Ling Jiguang Zhang Meng Wang Zhen Wang Ziyu Mi Surani Bin Dolmanan Mingsheng Zhang Bingqing Wang Wan Ru Leow Jia Zhang Yanwei Lum 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308782
Electrochemical CO2 reduction (CO2R) in acidic media with Cu-based catalysts tends to suffer from lowered selectivity towards multicarbon products. This could in principle be mitigated using tandem catalysis, whereby the *CO coverage on Cu is increased by introducing a CO generating catalyst (e.g. Ag) in close proximity. Although this has seen significant success in neutral/alkaline media, here we report that such a strategy becomes impeded in acidic electrolyte. This was investigated through the co-reduction of 13CO2/12CO mixtures using a series of Cu and CuAg catalysts. These experiments provide strong evidence for the occurrence of tandem catalysis in neutral media and its curtailment under acidic conditions. Density functional theory simulations suggest that the presence of H3O+ weakens the *CO binding energy of Cu, preventing effective utilization of tandem-supplied CO. Our findings also provide other unanticipated insights into the tandem catalysis reaction pathway and important design considerations for effective CO2R in acidic media. 相似文献
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Facile Construction of 3D Reduced Graphene Oxide Wrapped Ni3S2 Nanoparticles on Ni Foam for High‐Performance Asymmetric Supercapacitor Electrodes
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Jiqiu Qi Yuan Chang Yanwei Sui Yezeng He Qingkun Meng Fuxiang Wei Yulong Zhao Yunxue Jin 《Particle & Particle Systems Characterization》2017,34(12)
3D reduced graphene oxide (rGO)‐wrapped Ni3S2 nanoparticles on Ni foam with porous structure is successfully synthesized via a facile one‐step solvothermal method. This unique structure and the positive synergistic effect between Ni3S2 nanoparticles and graphene can greatly improve the electrochemical performance of the NF@rGO/Ni3S2 composite. Detailed electrochemical measurements show that the NF@rGO/Ni3S2 composite exhibits excellent supercapacitor performance with a high specific capacitance of 4048 mF cm?2 (816.8 F g?1) at a current density of 5 mA cm?2 (0.98 A g?1), as well as long cycling ability (93.8% capacitance retention after 6000 cycles at a current density of 25 mA cm?2). A novel aqueous asymmetric supercapacitor is designed using the NF@rGO/Ni3S2 composite as positive electrode and nitrogen‐doped graphene as negative electrode. The assembled device displays an energy density of 32.6 W h kg?1 at a power density of 399.8 W kg?1, and maintains 16.7 W h kg?1 at 8000.2 W kg?1. This outstanding performance promotes the as‐prepared NF@rGO/Ni3S2 composite to be ideal electrode materials for supercapacitors. 相似文献
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利用有限元方法对一Ku波段空间行波管收集极的热特性进行了模拟计算,得到了收集极的温度分布图。分析比较了接触热阻和热辐射对热特性的影响,结果表明接触热阻明显地阻碍了热量的散失,使收集极整体温度有一定上升,而热辐射在使收集极各部分温度降低的同时,使温度分布更均匀。运用间接法进行了热-应力耦合分析,得到了收集极的位移场分布等值线图,进而确定该收集极采用的结构在热形变方面满足散热要求;并对在轴向加矩形翅片和在径向加圆形翅片两种散热方案进行了分析,得到了各自的优缺点,为散热方案的选择提供了依据,从而可以更好地提高散热效率。 相似文献
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The mechanism of the FeCl3-catalysed cross-coupling reaction of alcohols with alkenes has been investigated using the density functional theory. All calculations were performed in liquid phase. The structures of intermediates and transition states are computed and analysed in detail. The calculations show that the entire catalytic cycle consists in three steps: (1) H-abstraction, (2) free-radical addition, and (3) hydrogen transfer. The rate-limiting step in the whole catalytic cycle is the hydrogen-abstraction step. Only the quartet potential surface is likely to play an essential role in this cross-coupling reaction. The alpha-C(sp3)–H bond of the phenylpropanol is cleaved in a homolytic fashion. Moreover, we justify the change of the oxidation state of iron along the overall reaction pathway on the basis of the computed natural population atomic charges and spin densities. Our calculated results are consistent with and provide a reliable interpretation for the experimental observations that suggest the cross-coupling reaction occurs through a radical mechanism. 相似文献
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为解决矿井中粉尘浓度测量精度低和在线监测难的问题,利用电荷感应原理设计了高精度矿井粉尘浓度传感器,使输出的感应电流与粉尘浓度之间建立了良好的线性关系;采用三级管理结构设计了分布式矿井粉尘浓度在线监控系统,系统主要由粉尘监测节点、风机控制器、数据汇聚基站、监控中心和传输网络组成;粉尘监测节点与数据汇聚基站通过ZigBee网络组成星型结构,定时采集周围环境中的粉尘浓度信息,并发送给数据汇聚基站;数据汇聚基站与监控中心采用C/S架构设计,将接收到的各监测节点数据打包后,通过局域网实时发送到监控中心的服务器上;监控中心接收、处理、分析和显示从各终端发来的数据,并将存入数据库ACCESS2003中;当某区域出现粉尘浓度过高时,会自动发出报警信号,并控制对应的风机加大排风量,使粉尘浓度保持在安全范围;通过测试实验结果表明,设计的粉尘浓度传感器具有较高的测量精度,平均误差仅为2.95%,且粉尘浓度在线监控系统工作稳定可靠。 相似文献
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Selective hydrogenation of aromatic amines,especially chemicals such as aniline and bis(4-aminocyclohexyl)methane for non-yellowing polyurethane,is of particular interests due to the extensive applications.To conquer the existing difficulties,in selective hydrogenation,,the Ru~0-Ru~(δ+)/CeO_2 catalyst with solid frustrated Lewis pairs was developed for aromatic amines hydrogenation with excellent activity and selectivity under relative milder conditions.The morphology,electronic and chemical properties,especially the Ru~O-Ru~(δ+) clusters and reducible ceria were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),sca nning electronic microscopy(SEM),X-ray photoelectron sp ectroscopy(XPS),CO_2 tempe rature programmed deso rption(CO_2-TPD),H_2 tempe rature programmed reduction(H_2-TPR),H_2 diffuse reflectance Fourier transform infrared spectroscopy(H_2-DRIFT),Raman,etc.The 2% Ru/CeO_2 catalyst exhibited good conversion of 95% and selectivity greater than 99% toward cyclohexylamine.The volcano curve describing the activity and Ru state was found.Owning to the "acidic site isolation" by surrounding alkaline sites,condensation between the neighboring amine molecules could be effectively suppressed.The catalyst also showed good stability and applicability for other aromatic amines and heteroarenes containing different functional groups. 相似文献
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引入电流负反馈会使放大电路的输出电阻变大,这种变化在实验测量时几乎没有出现。我们在分析原因后,提出了一种简单、易行的解决方案,并且对电路参数进行了合理化设计,使实验效果非常理想。 相似文献