共查询到17条相似文献,搜索用时 15 毫秒
1.
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 (International ed. in English)》2019,58(50):18086-18095
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
2.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(9):2358-2363
Methanol synthesis by CO2 hydrogenation is a key process in a methanol‐based economy. This reaction is catalyzed by supported copper nanoparticles and displays strong support or promoter effects. Zirconia is known to enhance both the methanol production rate and the selectivity. Nevertheless, the origin of this observation and the reaction mechanisms associated with the conversion of CO2 to methanol still remain unknown. A mechanistic study of the hydrogenation of CO2 on Cu/ZrO2 is presented. Using kinetics, in situ IR and NMR spectroscopies, and isotopic labeling strategies, surface intermediates evolved during CO2 hydrogenation were observed at different pressures. Combined with DFT calculations, it is shown that a formate species is the reaction intermediate and that the zirconia/copper interface is crucial for the conversion of this intermediate to methanol. 相似文献
3.
4.
5.
Suppressing the P2–O2 Phase Transition of Na0.67Mn0.67Ni0.33O2 by Magnesium Substitution for Improved Sodium‐Ion Batteries
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Peng‐Fei Wang Ya You Dr. Ya‐Xia Yin Yue‐Sheng Wang Prof. Li‐Jun Wan Prof. Lin Gu Prof. Yu‐Guo Guo 《Angewandte Chemie (International ed. in English)》2016,55(26):7445-7449
Room‐temperature sodium‐ion batteries (SIBs) have shown great promise in grid‐scale energy storage, portable electronics, and electric vehicles because of the abundance of low‐cost sodium. Sodium‐based layered oxides with a P2‐type layered framework have been considered as one of the most promising cathode materials for SIBs. However, they suffer from the undesired P2–O2 phase transition, which leads to rapid capacity decay and limited reversible capacities. Herein, we show that this problem can be significantly mitigated by substituting some of the nickel ions with magnesium to obtain Na0.67Mn0.67Ni0.33?xMgxO2 (0≤x≤0.33). Both the reversible capacity and the capacity retention of the P2‐type cathode material were remarkably improved as the P2–O2 phase transition was thus suppressed during cycling. This strategy might also be applicable to the modulation of the physical and chemical properties of layered oxides and provides new insight into the rational design of high‐capacity and highly stable cathode materials for SIBs. 相似文献
6.
Superior Na‐Storage Performance of Low‐Temperature‐Synthesized Na3(VO1−xPO4)2F1+2x (0≤x≤1) Nanoparticles for Na‐Ion Batteries
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yuruo Qi Linqin Mu Prof. Junmei Zhao Prof. Yong‐Sheng Hu Prof. Huizhou Liu Prof. Sheng Dai 《Angewandte Chemie (International ed. in English)》2015,54(34):9911-9916
Na‐ion batteries are becoming comparable to Li‐ion batteries because of their similar chemical characteristics and abundant sources of sodium. However, the materials production should be cost‐effective in order to meet the demand for large‐scale application. Here, a series of nanosized high‐performance cathode materials, Na3(VO1?xPO4)2F1+2x (0≤x≤1), has been synthesized by a solvothermal low‐temperature (60–120 °C) strategy without the use of organic ligands or surfactants. The as‐synthesized Na3(VOPO4)2F nanoparticles show the best Na‐storage performance reported so far in terms of both high rate capability (up to 10 C rate) and long cycle stability over 1200 cycles. To the best of our knowledge, the current developed synthetic strategy for Na3(VO1?xPO4)2F1+2x is by far one of the least expensive and energy‐consuming methods, much superior to the conventional high‐temperature solid‐state method. 相似文献
7.
8.
9.
10.
Zheng Ren Venkatesh Botu Sibo Wang Yongtao Meng Wenqiao Song Yanbing Guo Ramamurthy Ramprasad Steven L. Suib Pu‐Xian Gao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(28):7351-7355
A series of large scale MxCo3−xO4 (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH4 oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions. 相似文献
11.
Metallographical and differential thermoanalytical (DTA) investigatitons indicate that the well known phosphide Co2P (Pearson code oP12, space group Pnma, Co2Si type) is not stable up to the melting point, T = 1659 K; it is therefore designated as the low‐temperature phase α‐Co2P. In the temperature range from 1428 to 1659 K, another, high‐temperature phase, designated as β‐Co2P, exists. X‐ray powder diffraction investigation of liquid quenched alloys in the composition range xP = 0.25 to 0.335, with xP as the mole fraction, show that the high‐temperature phase β‐Co2P is isotypic with Fe2P (hP9, P 6 2m). For the ideal composition Co2P, the unit cell parameters are: a = 5.742(2) Å, c = 3.457(5) Å, c/a = 0.621. Among the binary transition metal‐containing phosphides and arsenides isotypic with Fe2P, β‐Co2P is the only known high‐temperature phase and it shows (i) the highest axial ratio c/a and (ii) the “smallest” distortion of the hcp substructure formed by the transition metals atoms in the Fe2P structure type. 相似文献
12.
Colourless block‐shaped crystals of [(NH4)2(2.2.2‐cryptand)2][P2S8] ( 1 ) and [(NH4)2(18‐crown‐6)2][P2S8]·H2O ( 2 ) could be obtained by the reaction of an aqueous solution of ammonium hexathiohypodiphosphate, (NH4)4P2S6·2 H2O, with sulfur and 2.2.2‐cryptand or 18‐crown‐6. The crystal structures of both compounds have been determined by single‐crystal X‐Ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group C2/c with a = 2032.7(2), b = 1243.6(2), c = 2244.6(2) pm, β = 98.64(1)°, and Z = 8, whereas compound 2 crystallizes also monoclinic in the space group P21/c with a = 2121.3(2), b = 865.5(1), c = 2345.4(2) pm, β = 91.96(1)°, and Z = 4. It could be established that the title compounds contain a new type of six‐membered [1,2‐P2S4] ring with P – P bond and three S – S linkages. The tetrahedral environment of each phosphorus is completed by a (formally) single and double bonded sulfur atom attached externally to the [1,2‐P2S4] ring. These terminal PS2 units are mesomerically stabilized according to their P – S distances. FT‐IR and FT‐Raman spectra of the title compounds are recorded and interpreted. 相似文献
13.
Theeranuch Nachaithong Pairot Moontragoon Prasit Thongbai 《Molecules (Basel, Switzerland)》2022,27(18)
The (Zn, Nb)-codoped TiO2 (called ZNTO) nanopowder was successfully synthesized by a simple combustion process and then the ceramic from it was sintered with a highly dense microstructure. The doped atoms were consistently distributed, and the existence of oxygen vacancies was verified by a Raman spectrum. It was found that the ZNTO ceramic was a result of thermally activated giant dielectric relaxation, and the outer surface layer had a slight effect on the dielectric properties. The theoretical calculation by using the density functional theory (DFT) revealed that the Zn atoms are energy preferable to place close to the oxygen vacancy (Vo) position to create a triangle shape (called the ZnVoTi defect). This defect cluster was also opposite to the diamond shape (called the 2Nb2Ti defect). However, these two types of defects were not correlated together. Therefore, it theoretically confirms that the electron-pinned defect-dipoles (EPDD) cannot be created in the ZNTO structure. Instead, the giant dielectric property of the (Zn0.33Nb0.67)xTi1−xO2 ceramics could be caused by the interfacial polarization combined with electron hopping between the Zn2+/Zn3+ and Ti3+/Ti4+ ions, rather than due to the EPDD effect. Additionally, it was also proved that the surface barrier-layer capacitor (SBLC) had a slight influence on the giant dielectric properties of the ZNTO ceramics. The annealing process can cause improved dielectric properties, which are properties with a huge advantage to practical applications and devices. 相似文献
14.
15.
16.
Patrick Esch Moritz Fischer Sven Heiles Mathias Schfer 《Journal of mass spectrometry : JMS》2019,54(12):976-986
This contribution is part of our ongoing efforts to develop innovative cross‐linking (XL) reagents and protocols for facilitated peptide mixture analysis and efficient assignment of cross‐linked peptide products. In this report, we combine in‐source Paternò‐Büchi (PB) photo‐chemistry with a tandem mass spectrometry approach to selectively address the fragmentation of a tailor‐made cross‐linking reagent. The PB photochemistry, so far exclusively used for the identification of unsaturation sites in lipids and in lipidomics, is now introduced to the field of chemical cross‐linking. Based on trans‐3‐hexenedioic acid, an olefinic homo bifunctional amine reactive XL reagent was designed and synthesized for this proof‐of‐principle study. Condensation products of the olefinic reagent with a set of exemplary peptides are used to test the feasibility of the concept. Benzophenone is photochemically reacted in the nano‐electrospray ion source and forms oxetane PB reaction products. Subsequent CID‐MS triggered retro‐PB reaction of the respective isobaric oxetane molecular ions and delivers reliably and predictably two sets of characteristic fragment ions of the cross‐linker. Based on these signature ion sets, a straightforward identification of covalently interconnected peptides in complex digests is proposed. Furthermore, CID‐MSn experiments of the retro‐PB reaction products deliver peptide backbone characteristic fragment ions. Additionally, the olefinic XL reagents exhibit a pronounced robustness upon CID‐activation, without previous UV‐excitation. These experiments document that a complete backbone fragmentation is possible, while the linker‐moiety remains intact. This feature renders the new olefinic linkers switchable between a stable, noncleavable cross‐linking mode and an in‐source PB cleavable mode. 相似文献