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Xiangsi Liu Wenhua Zuo Bizhu Zheng Yuxuan Xiang Ke Zhou Zhumei Xiao Peizhao Shan Jingwen Shi Qi Li Guiming Zhong Riqiang Fu Yong Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18254-18263
Sodium layered P2‐stacking Na0.67MnO2 materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn4+/Mn3+ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn3+, we obtain the low cost pure P2‐type Na0.67AlxMn1?xO2 (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na+ layer thus producing a remarkable rate capability of 96 mAh g‐1 at 1200 mA g‐1. 相似文献
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Aisulu Aitbekova Emmett D. Goodman Liheng Wu Alexey Boubnov Adam S. Hoffman Arda Genc Huikai Cheng Lee Casalena Simon R. Bare Matteo Cargnello 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17612-17618
Catalytic CO2 reduction to fuels and chemicals is a major pursuit in reducing greenhouse gas emissions. One approach utilizes the reverse water‐gas shift reaction, followed by Fischer–Tropsch synthesis, and iron is a well‐known candidate for this process. Some attempts have been made to modify and improve its reactivity, but resulted in limited success. Now, using ruthenium–iron oxide colloidal heterodimers, close contact between the two phases promotes the reduction of iron oxide via a proximal hydrogen spillover effect, leading to the formation of ruthenium–iron core–shell structures active for the reaction at significantly lower temperatures than in bare iron catalysts. Furthermore, by engineering the iron oxide shell thickness, a fourfold increase in hydrocarbon yield is achieved compared to the heterodimers. This work shows how rational design of colloidal heterostructures can result in materials with significantly improved catalytic performance in CO2 conversion processes. 相似文献
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Siddarth Narasimhan Stephan Scherpe Alessandra LuciniPaioni Johan vanderZwan Gert E. Folkers Huib Ovaa Marc Baldus 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13103-13107
Elucidating at atomic level how proteins interact and are chemically modified in cells represents a leading frontier in structural biology. We have developed a tailored solid‐state NMR spectroscopic approach that allows studying protein structure inside human cells at atomic level under high‐sensitivity dynamic nuclear polarization (DNP) conditions. We demonstrate the method using ubiquitin (Ub), which is critically involved in cellular functioning. Our results pave the way for structural studies of larger proteins or protein complexes inside human cells, which have remained elusive to in‐cell solution‐state NMR spectroscopy due to molecular size limitations. 相似文献
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Minghui Zhu Pengfei Tian Ravi Kurtz Thomas Lunkenbein Jing Xu Robert Schlgl Israel E. Wachs Yi‐Fan Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9181-9185
The commercial high‐temperature water‐gas shift (HT‐WGS) catalyst consists of CuO‐Cr2O3‐Fe2O3, where Cu functions as a chemical promoter to increase the catalytic activity, but its promotion mechanism is poorly understood. In this work, a series of iron‐based model catalysts were investigated with in situ or pseudo in situ characterization, steady‐state WGS reaction, and density function theory (DFT) calculations. For the first time, a strong metal‐support interaction (SMSI) between Cu and FeOx was directly observed. During the WGS reaction, a thin FeOx overlayer migrates onto the metallic Cu particles, creating a hybrid surface structure with Cu‐FeOx interfaces. The synergistic interaction between Cu and FeOx not only stabilizes the Cu clusters, but also provides new catalytic active sites that facilitate CO adsorption, H2O dissociation, and WGS reaction. These new fundamental insights can potentially guide the rational design of improved iron‐based HT‐WGS catalysts. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(3):883-887
The coordination of N‐heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the 13C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC PdII complex. NMR studies after 13CO adsorption established that the KS shifts the 13C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight‐shifted to 600 ppm for 13C‐labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car–Purcell–Meiboom–Gill (CPMG) echo train acquisition NMR experiments. 相似文献
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Negative Thermal Expansion in the Metal–Organic Framework Material Cu3(1,3,5‐benzenetricarboxylate)2
Yue Wu Atsushi Kobayashi GregoryJ. Halder VanessaK. Peterson KarenaW. Chapman Nina Lock PeterD. Southon CameronJ. Kepert 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2008,120(46):9061-9064
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Using renewable green hydrogen and carbon dioxide (CO2) to produce methanol is one of the fundamental ways to reduce CO2 emissions in the future, and research and development related to catalysts for efficient and stable methanol synthesis is one of the key factors in determining the entire synthesis process. Metal nanoparticles stabilized on a support are frequently employed to catalyze the methanol synthesis reaction. Metal-support interactions (MSIs) in these supported catalysts can play a significant role in catalysis. Tuning the MSI is an effective strategy to modulate the activity, selectivity, and stability of heterogeneous catalysts. Numerous studies have been conducted on this topic; however, a systematic understanding of the role of various strengths of MSI is lacking. Herein, three Cu/ZnO-SiO2 catalysts with different strengths of MSI, namely, normal precipitation Cu/ZnO-SiO2 (Nor-CZS), co-precipitation Cu/ZnO-SiO2 (Co-CZS), and reverse precipitation Cu/ZnO-SiO2 (Re-CZS), were successfully prepared to determine the role of such interactions in the hydrogenation of CO2 to methanol. The results of temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) characterization illustrated that the MSI of the catalysts was considerably affected by the precipitation sequence. Fourier transform infrared reflection spectroscopy (FT-IR) results indicated that the Cu species existed as CuO in all cases and that copper phyllosilicate was absent (except for strong Cu-SiO2 interaction). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2O chemical titration results revealed that strong interactions between the Cu and Zn species would promote the dispersion of Cu species, thereby leading to a higher CO2 conversion rate and improved catalytic stability. As expected, the Re-CZS catalyst exhibited the highest activity with 12.4% CO2 conversion, followed by the Co-CZS catalyst (12.1%), and the Nor-CZS catalyst (9.8%). After the same reaction time, the normalized CO2 conversion of the three catalysts decreased in the following order: Re-CZS (75%) > Co-CZS (70%) > Nor-CZS (65%). Notably, the methanol selectivity of the Re-CZS catalyst was found to level off after a prolonged period, in contrast to that of Co-CZS and Nor-CZS. Investigation of the structural evolution of the catalyst with time on stream revealed that the high methanol selectivity of the catalyst was caused by the reconstruction of the catalyst, which was induced by the strong MSI between the Cu and Zn species, and the migration of ZnO onto Cu species, which caused an enlargement of the Cu/ZnO interface. This work offers an alternative strategy for the rational and optimized design of efficient catalysts. 相似文献
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Hydrogenation of CO2‐Derived Carbonates and Polycarbonates to Methanol and Diols by Metal–Ligand Cooperative Manganese Catalysis
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M. Sc. Viktoriia Zubar Dr. Yury Lebedev Dr. Luis Miguel Azofra Prof. Dr. Luigi Cavallo Dr. Osama El‐Sepelgy Prof. Dr. Magnus Rueping 《Angewandte Chemie (International ed. in English)》2018,57(41):13439-13443
The first base‐metal‐catalysed hydrogenation of CO2‐derived carbonates to alcohols is presented. The reaction proceeds under mild conditions in the presence of a well‐defined manganese complex with a loading as low as 0.25 mol %. The non‐precious‐metal homogenous catalytic system provides an indirect route for the conversion of CO2 into methanol with the co‐production of value‐added (vicinal) diols in yields of up to 99 %. Experimental and computational studies indicate a metal–ligand cooperative catalysis mechanism. 相似文献