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231.
《Comptes Rendus Chimie》2014,17(9):890-893
Iodine catalyzes the cyclocondensation of various aldehydes with resorcinol to give tetrameric cyclic products, resorcinarenes. Through the reaction of resorcinol with aromatic aldehydes, the product is obtained as a mixture of two isomers, the all-cis isomer (rccc) and the cis-trans-trans isomer (rctt), whereas a single diastereomer, the all-cis, is formed with aliphatic aldehydes. Besides excellent isolated yields, the use of iodine makes this procedure simple, convenient, cost-effective and practical. 相似文献
232.
Multi-walled carbon nanotubes (MWNTs) were modified by oxyfluorination treatment at several different temperatures of 20, 100, 200, and 300 °C. The changes of surface properties of oxyfluorinated MWNTs were investigated using X-ray photoelectron spectroscopy (XPS) method. As a result, it was found that surface fluorine contents were varied with changing an oxyfluorination temperature and showed a maximum value at 100 °C. By changing the treatment temperature in the process of oxyfluorination for carbon supports, the surface characteristics of MWNTs had been modified, resulting that the size and loading content of deposited Pt on the modified carbon supports could be changed. Consequently, Pt deposited MWNTs that were treated at 100 °C (Pt/100-MWNTs) showed the best electroactivity among samples. The enhanced electroactivity was dependent on the higher surface area of electrochemical reaction for metal catalyst, which was related to the particle size and the morphology of the deposited particle catalysts. 相似文献
233.
Dr. Dong Cao Dr. Zhirong Zhang Yahui Cui Runhao Zhang Prof. Lipeng Zhang Prof. Jie Zeng Prof. Daojian Cheng 《Angewandte Chemie (International ed. in English)》2023,62(9):e202214259
The construction of highly active, durable, and cost-effective catalysts is urgently needed for green hydrogen production. Herein, catalysts consisting of high-density Pt (24 atoms nm−2) and Ir (32 atoms nm−2) single atoms anchored on Co(OH)2 were constructed by a facile one-step approach. Remarkably, Pt1/Co(OH)2 and Ir1/Co(OH)2 only required 4 and 178 mV at 10 mA cm−2 for hydrogen evolution reaction and oxygen evolution reaction, respectively. Moreover, the assembled Pt1/Co(OH)2//Ir1/Co(OH)2 system showed mass activity of 4.9 A mgnoble metal−1 at 2.0 V in an alkaline water electrolyzer, which is 316.1 times higher than that of Pt/C//IrO2. Mechanistic studies revealed that reconstructed Ir−O6 single atoms and remodeled Pt triple-atom sites enhanced the occupancy of Ir−O bonding orbitals and improved the occupation of Pt−H antibonding orbital, respectively, contributing to the formation of the O−O bond and the desorption of hydrogen. This one-step approach was also generalized to fabricate other 20 single-atom catalysts. 相似文献
234.
Dr. Haobo Li Prof. Yan Jiao Prof. Kenneth Davey Prof. Shi-Zhang Qiao 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216383
The design of heterogeneous catalysts is necessarily surface-focused, generally achieved via optimization of adsorption energy and microkinetic modelling. A prerequisite is to ensure the adsorption energy is physically meaningful is the stable existence of the conceived active-site structure on the surface. The development of improved understanding of the catalyst surface, however, is challenging practically because of the complex nature of dynamic surface formation and evolution under in-situ reactions. We propose therefore data-driven machine-learning (ML) approaches as a solution. In this Minireview we summarize recent progress in using machine-learning to search and predict (meta)stable structures, assist operando simulation under reaction conditions and micro-environments, and critically analyze experimental characterization data. We conclude that ML will become the new norm to lower costs associated with discovery and design of optimal heterogeneous catalysts. 相似文献
235.
Yuanyuan Yang Cejun Hu Dr. Jieqiong Shan Chuanqi Cheng Prof. Lili Han Prof. Xinzhe Li Ruguang Wang Prof. Wei Xie Prof. Yao Zheng Prof. Tao Ling 《Angewandte Chemie (International ed. in English)》2023,62(20):e202300989
Decarbonizing N2 conversion is particularly challenging, but essential for sustainable development of industry and agriculture. Herein, we achieve electrocatalytic activation/reduction of N2 on X/Fe−N−C (X=Pd, Ir and Pt) dual-atom catalysts under ambient condition. We provide solid experimental evidence that local hydrogen radical (H*) generated on the X site of the X/Fe−N−C catalysts can participate in the activation/reduction of N2 adsorbed on the Fe site. More importantly, we reveal that the reactivity of X/Fe−N−C catalysts for N2 activation/reduction can be well adjusted by the activity of H* generated on the X site, i.e., the interaction between the X−H bond. Specifically, X/Fe−N−C catalyst with the weakest X−H bonding exhibits the highest H* activity, which is beneficial to the subsequent cleavage of X−H bond for N2 hydrogenation. With the most active H*, the Pd/Fe dual-atom site promotes the turnover frequency of N2 reduction by up to 10 times compared with the pristine Fe site. 相似文献
236.
Maodi Wang Huicong Dai Prof. Qihua Yang 《Angewandte Chemie (International ed. in English)》2023,62(39):e202309929
The regeneration of the reduced form cofactor NAD(P)H is essential for the extra-cellular application of bio-reduction, which necessitates not only the development of efficient artificial NAD(P)H regeneration catalytic system but also its well compatibility with the cascade enzymatic reduction system. In this work, we reported the preparation of a metal nanoparticle (NP) and metal complex integrated core-shell nanoreactor for H2-driven NAD(P)H regeneration through the immobilization of a Rh complex on Ni/TiO2 surface via a bipyridine contained 3D porous organic polymer (POP). In comparison with the corresponding single component metal NPs and the immobilized Rh complex, the integrated catalyst presented simultaneously enhanced activity and selectivity in NAD(P)H regeneration thanks to the rapid spillover of activated H species from metal NPs to Rh complex. In addition, the size-sieving effect of POP precluded the direct interaction of enzyme and Rh complex confined in the pores, enabling the success coupling of core-shell nanoreactor and aldehyde ketone reductase (AKR) for chemoenzymatic reduction of acetophenone to (R)-1-phenylethan-1-ol. This work provides a strategy for the rational manipulation of multicomponent cooperation catalysis. 相似文献
237.
Meng Yang Dr. Jiafeng Yu Dr. Anna Zimina Dr. Bidyut Bikash Sarma Dr. Lakshmi Pandit Prof. Dr. Jan-Dierk Grunwaldt Ling Zhang Prof. Hengyong Xu Prof. Dr. Jian Sun 《Angewandte Chemie (International ed. in English)》2023,62(7):e202216803
Active Zn species in Cu-based methanol synthesis catalysts have not been clearly identified yet due to their complex nature and dynamic structural changes during reactions. Herein, atomically dispersed Zn on ZrO2 support is established in Cu-based catalysts by separating Zn and Zr components from Cu (Cu−ZnZr) via the double-nozzle flame spray pyrolysis (DFSP) method. It exhibits superiority in methanol selectivity and yield compared to those with Cu−ZnO interface and isolated ZnO nanoparticles. Operando X-ray absorption spectroscopy (XAS) reveals that the atomically dispersed Zn species are induced during the reaction due to the strengthened Zn−Zr interaction. They can suppress formate decomposition to CO and decrease the H2 dissociation energy, shifting the reaction to methanol production. This work enlightens the rational design of unique Zn species by regulating coordination environments and offers a new perspective for exploring complex interactions in multi-component catalysts. 相似文献
238.
239.
Dr. Shuhao An Xuewen Li Shuaishuai Shang Dr. Ting Xu Dr. Shuai Yang Dr. Cheng-Xing Cui Prof. Changjun Peng Honglai Liu Prof. Qing Xu Prof. Zheng Jiang Prof. Jun Hu 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218742
Two-dimensional covalent organic frameworks (2D COFs) are often employed for electrocatalytic systems because of their structural diversity. However, the efficiency of atom utilization is still in need of improvement, because the catalytic centers are located in the basal layers and it is difficult for the electrolytes to access them. Herein, we demonstrate the use of 1D COFs for the 2e− oxygen reduction reaction (ORR). The use of different four-connectivity blocks resulted in the prepared 1D COFs displaying good crystallinity, high surface areas, and excellent chemical stability. The more exposed catalytic sites resulted in the 1D COFs showing large electrochemically active surface areas, 4.8-fold of that of a control 2D COF, and thus enabled catalysis of the ORR with a higher H2O2 selectivity of 85.8 % and activity, with a TOF value of 0.051 s−1 at 0.2 V, than a 2D COF (72.9 % and 0.032 s−1). This work paves the way for the development of COFs with low dimensions for electrocatalysis. 相似文献
240.
Prof. Lu-Hua Zhang Yangting Jia Jiayu Zhan Guomeng Liu Dr. Guanhua Liu Prof. Fei Li Prof. Fengshou Yu 《Angewandte Chemie (International ed. in English)》2023,62(22):e202303483
Electrochemically converting NO3− into NH3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO3− is still suffering from low activity and/or selectivity. Herein, B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO3− reduction reaction (NO3RR) with dilute NO3− concentration (≤100 ppm NO3−−N). Notably, a linear relationship was established by plotting NH3 yield vs. the oxidation state of Cu, indicating that the increase of Cu+ content leads to an enhanced NO3−-to-NH3 conversion activity. Under a low NO3−−N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO3−-to-NH3 conversion at −0.55 to −0.6 V vs. RHE, and a record-high NH3 yield of 309 mmol h−1 gcat−1, which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h−1 gcat−1). This research provides an effective method for conversion of dilute NO3− to NH3, which has certain guiding significance for the efficient and green conversion of wastewater in the future. 相似文献