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排序方式: 共有6726条查询结果,搜索用时 15 毫秒
281.
Ding Yi Fei Lu Fengchu Zhang Shoujie Liu Bo Zhou Denglei Gao Xi Wang Jiannian Yao 《Angewandte Chemie (International ed. in English)》2020,59(37):15855-15859
Single‐atom catalysts have attracted much attention. Reported herein is that regulating charge transfer of lattice oxygen atoms in serial single‐atom‐doped titania enables tunable hydrogen evolution reaction (HER) activity. First‐principles calculations disclose that the activity of lattice oxygen for the HER can be regularly promoted by substituting its nearest metal atom, and doping‐induced charge transfer plays an essential role. Besides, the realm of the charge transfer of the active site can be enlarged to the second nearest atom by creating oxygen vacancies, resulting in further optimization for the HER. Various single‐atom‐doped titania nanosheets were fabricated to validate the proposed model. Taking advantage of the localized charge transfer to the lattice atom is demonstrated to be feasible for realizing precise regulation of the electronic structures and thus catalytic activity of the nanosheets. 相似文献
282.
Zhantao Peng Bin Di Wentao Li Dan Liu Xiaojie Wen Hao Zhu Huanjun Song Yajie Zhang Cen Yin Xiong Zhou Kai Wu 《Angewandte Chemie (International ed. in English)》2020,59(34):14321-14325
Potassium (K) cations are spontaneously formed upon thermal deposition of low‐coverage K onto an ultrathin CuO monolayer grown on Cu(110) and they were explored by low‐temperature scanning tunneling microscopy (STM) and X‐ray photoemission spectroscopy. The formed K cations are highly immobile and thermally stable. The local work function around an individual K cation decreases by 1.5±0.3 eV, and a charging zone underneath it is established within about 1.0 nm. The cationic and neutral states of the K atom are switchable upon application of an STM bias voltage pulse, which is simultaneously accompanied by an adsorption site relocation. 相似文献
283.
Tao Zhang Jingxiang Low Jiaguo Yu Alexei M. Tyryshkin Elika Mikmekov Tewodros Asefa 《Angewandte Chemie (International ed. in English)》2020,59(35):15000-15007
A mesoporous TiO2?x material comprised of small, crystalline, vacancy‐rich anatase nanoparticles (NPs) shows unique optical, thermal, and electronic properties. It is synthesized using polymer‐derived mesoporous carbon (PDMC) as a template. The PDMC pores serve as physical barriers during the condensation and pyrolysis of a titania precursor, preventing the titania NPs from growing beyond 10 nm in size. Unlike most titania nanomaterials, during pyrolysis the NPs undergo no transition from the anatase to rutile phase and they become catalytically active reduced TiO2?x. When exposed to a slow electron beam, the NPs exhibit a charge/discharge behavior, lighting up and fading away for an average period of 15 s for an extended period of time. The NPs also show a 50 nm red‐shift in their UV/Vis absorption and long‐lived charge carriers (electrons and holes) at room temperature in the dark, even long after UV irradiation. The NPs as photocatalysts show a good activity for CO2 reduction. 相似文献
284.
Hongyun Ma Hongwu Chen Mingmao Wu Fengyao Chi Feng Liu Jiaxin Bai Huhu Cheng Chun Li Liangti Qu 《Angewandte Chemie (International ed. in English)》2020,59(34):14541-14549
Capacitive energy storage has advantages of high power density, long lifespan, and good safety, but is restricted by low energy density. Inspired by the charge storage mechanism of batteries, a spatial charge density (SCD) maximization strategy is developed to compensate this shortage by densely and neatly packing ionic charges in capacitive materials. A record high SCD (ca. 550 C cm?3) was achieved by balancing the valance and size of charge‐carrier ions and matching the ion sizes with the pore structure of electrode materials, nearly five times higher than those of conventional ones (ca. 120 C cm?3). The maximization of SCD was confirmed by Monte Carlo calculations, molecular dynamics simulations, and in situ electrochemical Raman spectroscopy. A full‐cell supercapacitor was further constructed; it delivers an ultrahigh energy density of 165 Wh L?1 at a power density of 150 WL?1 and retains 120 Wh L?1 even at 36 kW L?1, opening a pathway towards high‐energy‐density capacitive energy storage. 相似文献
285.
Fei Lu Ding Yi Shoujie Liu Fei Zhan Bo Zhou Lin Gu Dmitri Golberg Xi Wang Jiannian Yao 《Angewandte Chemie (International ed. in English)》2020,59(40):17712-17718
A dual‐site catalyst allows for a synergetic reaction in the close proximity to enhance catalysis. It is highly desirable to create dual‐site interfaces in single‐atom system to maximize the effect. Herein, we report a cation‐deficient electrostatic anchorage route to fabricate an atomically dispersed platinum–titania catalyst (Pt1O1/Ti1?xO2), which shows greatly enhanced hydrogen evolution activity, surpassing that of the commercial Pt/C catalyst in mass by a factor of 53.2. Operando techniques and density functional calculations reveal that Pt1O1/Ti1?xO2 experiences a Pt?O dual‐site catalytic pathway, where the inherent charge transfer within the dual sites encourages the jointly coupling protons and plays the key role during the Volmer–Tafel process. There is almost no decay in the activity of Pt1O1/Ti1?xO2 over 300 000 cycles, meaning 30 times of enhancement in stability compared to the commercial Pt/C catalysts (10 000 cycles). 相似文献
286.
287.
Dr. Luis Martín-Gomis Sairaman Seetharaman David Herrero Prof. Dr. Paul A. Karr Prof. Dr. Fernando Fernández-Lázaro Prof. Dr. Francis D'Souza Prof. Dr. Ángela Sastre-Santos 《Chemphyschem》2020,21(20):2254-2262
The effect of donor-acceptor distance in controlling the rate of electron transfer in axially linked silicon phthalocyanine-C60 dyads has been investigated. For this, two C60-SiPc-C60 dyads, 1 and 2 , varying in their donor-acceptor distance, have been newly synthesized and characterized. In the case of C60-SiPc-C60 1 where the SiPc and C60 are separated by a phenyl spacer, faster electron transfer was observed with kcs equal to 2.7×109 s−1 in benzonitrile. However, in the case of C60-SiPc-C60 2 , where SiPc and C60 are separated by a biphenyl spacer, a slower electron transfer rate constant, kcs=9.1×108 s−1, was recorded. The addition of an extra phenyl spacer in 2 increased the donor-acceptor distance by ∼4.3 Å, and consequently, slowed down the electron transfer rate constant by a factor of ∼3.7. The charge separated state lasted over 3 ns, monitoring time window of our femtosecond transient spectrometer. Complimentary nanosecond transient absorption studies revealed formation of 3SiPc* as the end product and suggested the final lifetime of the charge separated state to be in the 3–20 ns range. Energy level diagrams established to comprehend these mechanistic details indicated that the comparatively high-energy SiPc.+-C60.− charge separated states (1.57 eV) populated the low-lying 3SiPc* (1.26 eV) prior returning to the ground state. 相似文献
288.
A fully-coupled model for a piezoelectric hetero-junction subjected to a pair of stresses is proposed by discarding the depletion layer approximation. The effect of mechanical loadings on PN junction performance is discussed in detail. Numerical examples are carried out for a p-Si/ZnO-n hetero-junction under a pair of stresses acting on the ntype ZnO portion near the PN interface, where ZnO has the piezoelectric property while Si is not. It is found that the bottom of conduction band is lowered/raised near the two loading points due to the decrease/increase in the electron potential energy there induced by a tensile-stress mode via sucking in majority-carriers from two outside regions, which implies appearance of a potential barrier and a potential well near two loading points. Furthermore, the barrier height and well depth gradually become large with increasing tensile stress such that more and more electrons/holes are inhaled in loading region from the n-/p-zone, respectively. Conversely, rising/dropping of conduction band bottom is brought out near the two loading points by a compressive-stress mode due to the increase/decrease in the potential energy of electrons by pumping out the majority-carriers from the loading region to the two outside regions. Therefore, a potential well and a potential barrier are induced near the two loading points, such that more and more electrons/holes are driven away from the loading region to the n-zone/p-zone, respectively, with the increasing compressive stress. These effects are important to tune the carrier recombination rate near the PN interface. Thus, the present study possesses great referential significance to piezotronic devices. 相似文献
289.
Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed. 相似文献
290.
卤键是一种新的分子间非共价作用力,它存在于卤素原子(路易斯酸)和具有孤电子对的原子或π-电子体系(路易斯碱)之间,在超分子化学、材料科学、生物识别和药物设计等领域已经显示出独特的优势。本文主要从卤键的特征和在化学传感和分子识别中的应用以及发展前景等几方面进行了介绍,期望引起人们对卤键的更多关注。 相似文献