Regulating Charge Transfer of Lattice Oxygen in Single-Atom-Doped Titania for Hydrogen Evolution

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.     

Evaluation of radiation damage behavior in polyimide aerogel by infrared camera and photoacoustic spectroscopy

In this work, the optical absorption and thermal properties of polyimide aerogel have been investigated by Infrared Camera, ultraviolet–visible and photoacoustic spectroscopy under low energy proton irradiation. The characterization method of the infrared camera can obtain the optical absorption ratio, and meanwhile get the information of specific heat capacity. Moreover, it can acquire the nature information of damaged area rather than the overall performance. The results show an increase in optical absorption after proton irradiation, which is in good coincidence with Ultraviolet–visible spectroscopy analysis. And the specific heat capacity decreased linearly with proton fluences, which can be attributed to the irradiation damage and carbonization in polyimide aerogel. The Raman spectra suggested the cleavage of chemical bonds and carbonization in polyimide aerogel. This work provides the novel, non-destructive and sensitive methods to characterize irradiation damage of aerogel.     

机械化学法制备金属-有机骨架及其复合物研究进展

金属-有机骨架(MOFs)是由金属离子/簇和多齿状有机配体通过配位键桥联而形成的多孔晶态材料。MOFs材料具有孔隙率高、比表面积大、尺寸可调、结构易修饰、功能多样化等特点,使其在气体吸附、分离和催化等方面都具有潜在应用价值。到目前为止,在MOFs合成的几种常见方法中,机械化学法(即在无溶剂或极少量溶剂的情况下研磨固体反应物进行的反应)作为一种清洁、绿色、高效的合成手段逐渐引起人们的关注。本综述总结了近年来机械化学合成MOFs及其复合物的典型进展,目的是为机械化学法合成MOFs及其复合材料提供一个通用而易于理解的概述。目前的研究进展表明,机械化学法是一种实用且环境友好的合成方法,为低成本、宏量生产MOFs及其复合物提供了可能。     

Recent Advances in Atomic-scale Storage Mechanism Studies of Two-dimensional Nanomaterials for Rechargeable Batteries Beyond Li-ion

Developing new types of rechargeable batteries with high energy densities and low cost have received increasing attentions, aiming to reduce the dependence on high-priced lithium. Beyond Li-ion batteries, the potential alternatives including Na-ion batteries, Li-S batteries and Li-air batteries have been investigated recently, which are required to be viable for commercial applications. From this point of view, to understand the electrochemical reaction mechanisms and kinetics of these batteries has become the key challenge to make breakthroughs in the field of new energy storage. In this review, we present a critical overview of the two dimensional nanomaterials-based batteries (except Li-ion-based batteries) that could meet such demonds. To develop new energy storage devices with more promising performances, the microstructure evolution and atomic scale storage mechanism of these batteries are comprehensively summarized. In addition, the major challenges and opportunities of advanced characterization techniques are finally discussed. We do hope that this review will give the readers a clear and profound understanding of the electrochemical reaction mechanisms and kinetics of the as-discussed batteries, thus effectively contributing to the smart design of future-generation energy storage devices.     

A sonochemically promoted route to new iron pentaphenylcyclopentadienyl cationic complexes

A sonochemical procedure has enabled the synthesis of the new species (Fe(C₅Ph₅)(CO)₂(C₂H₄)]PF₆ via [Fe(C₅Ph₅(CO)₂Et]. The reactivity of the new species towards two-electron ligand exchange provides a route to a series of new cationic species [Fe(C₅Ph₅)(CO)₂L]PF₆.     

Strange saddles and the dimensions of their invariant manifolds

Nonattracting chaotic sets play a fundamental role in typical dynamical systems. They occur, for example, in the form of chaotic transient sets and fractal basin boundaries. The subject of this paper is the dimensions of these sets and of their stable and unstable manifolds. Numerical experiments are performed to determine these dimensions. The results are consistent with a conjectured formulae expressing the dimensions in terms of Lyapunov exponents and the transient life-time associated with the strange saddle.     

Quasi-wetting on a sphere

Wetting phenomena on a sphere of radius R are studied in the context of the Sullivan model. Neither a first nor a continuous transition is found for finite R. Only in the strict limit of R→∞ a second-order transition appears. For temperatures T higher than the wetting temperature in a flat geometry, T^∞_w, the thickness l of the enhanced density layer, which forms on the surface of the sphere, is for large R proportional to In R.     

Visualization of pulse sequences in frequency space,with application to INEPT and DEPT for AX systems

Visualization of pulse sequences by the vector model is inadequate when the frequency components contain contributions that do not transform as vectors. In this paper the vector model is abandoned and the INEPT and DEPT sequences are described in frequency, rather than time, space.     

Dependence of lifetime on design parameters of an nipi doping superlattice: Results of self-consistent calculations

This paper presents a scheme for calculating recombination lifetimes in a doping superlattice at arbitrary temperatures and forward biases. The scheme involves the self-consistent calculation of sub-band energies, populations and envelope functions, followed by the calculation of lifetime using overlap integrals. Results of these calculations are then presented for a variety of combinations of layer thicknesses and dopings, all at a temperature of 300 K and a forward bias of 1 V. Our results give room temperature lifetimes as high as ∼30 ms for n and p layer thicknesses of 750 Å each, i-layer thickness of 50 Å, and dopings in the n and p layers of 2×10¹⁸ cm⁻³.