Hafnia-based ferroelectrics have become a valuable class of electronic functional materials at the nanoscale, showing great potential for next-generation memory and logic devices. However, more robust ferroelectric properties and better understanding of the polarization mechanisms are currently needed both in technology and science. Herein, we report the properties of oxygen-deficient Hf0.5Zr0.5O2 films with ultralarge remanent polarization (Pr) of 387 uC cm-2 at room temperature (1 kHz). Structure characterizations identify a new ferroelectric monoclinic Pc phase in these Hf0.5Zr0.5O2 films. The in-situ STEM measurements evidence polar displacements of the oxygen atoms, which move up and down in the Pc structure under applied DC bias fields, showing a huge displacement (1.6 A). DFT calculations optimized the Pc structure and also predicted a large polarization. The coexistence of the ferroelectric monoclinic (Pc) phases and orthorhombic (Pca21) is responsible for this superior ferroelectric properties. These findings are promising for hafnia-based ferroelectric applications in integrated ferroelectric devices, energy harvesting and actuators, etc.

To address CO2 emissions caused by the overuse of fossil fuels, photocatalytic CO2 reduction from metal-organic frameworks (MOFs) to valuable chemicals is critical for energy conversion and storage. Core-shell MOFs improve interfacial interactions, increasing the number of active sites in the catalyst, thereby improving the photocatalytic reduction. In this work, the catalytic performance of Fe/Ni-MOFs toward photocatalytic CO2 reduction was improved using a bimetallic strategy. We successfully synthesized a series of Fe/Ni-MOFs with a core-shell structure using a single-step approach combined with hydrothermal synthesis. By altering the synthesis conditions of the bimetallic organic skeleton and contrasting it with a single MOF, we successfully synthesized Fe/Ni-T120 through an efficient photocatalytic reduction of CO2. The results of photocatalytic CO2 reduction experiments indicated that upon using [Ru(bpy)3]Cl2·6H2O as a photosensitizer and triethanolamine (TEOA) and acetonitrile (MeCN) as sacrificial agents, the CO evolution rate of Fe/Ni-T120 reached 9.74 mmol g-1 h-1 and the CO2 to CO selectivity reached up to 92.1%. Additionally, Fe/Ni-T120 has a broad response range to visible light, a high photocurrent intensity, good chemical stability, and strong photocatalytic efficiency, even after repeated cycles. This study proposes a straightforward method for producing adaptable and stable MOFs for effective photocatalytic CO2 reduction that is driven by visible light.

In article number 1800317, Jin-Song Hu and co-workers report a phase-controlled synthesis of 1T-MoSe2/NiSe heterostructure nanowire arrays. The conductive NiSe nanowire core can not only facilitate water dissociation and efficiently transport electrons, but also induce the formation of stable 1T-phase MoSe2 nanosheet shell for enhanced hydrogen formation, synergistically boosting the overall alkaline hydrogen evolution.

理解材料的构-效关系是功能材料领域的永恒话题,在锂离子电池材料的研究中亦是如此.因此可以看到如X射线衍射、中子衍射、核磁共振、X射线电子能谱等结构表征手段被应用于锂离子电池材料的研究中.但是因上述方法对于微观局域结构并不敏感,而给出平均的结构信息.材料的性能往往随微观结构的不同而天差地别,因此获取锂离子电池材料的微观结构信息十分重要.透射电子显微镜具有原子尺度的空间分辨能力,可以获取原子尺度上的结构扭曲和电子结构变化,在锂离子电池材料的研究中起到了至关重要的作用.本文从电子显微学和锂离子电池材料的关系入手,从基本原理和实验方法出发,为相关领域科研人员提供便利.

Lithium-ion is transferred through a variety of surfaces and interfaces in Lithium ion batteries during the process of charging and discharging.The properties of surface and interface of electrode have great influences on the power density,energy density,the rate performance,service life,as well as cycling stability.In general,the structure of surfaces and interfaces of materials are different from that of bulk,direct observation upon atomic-scale structure of electrode in different electrochemical state contributes to studying electrochemical reaction mechanism and evolution of properties and is of instructive significance to improve the properties of lithium-ion batteries.In this paper,we review the recent progress in investigations of surfaces and interfaces structure of electrode materials,introduce special interface,SEI,the phase transition of surface and doping of surface,discuss the inherent correlation between the atomic-scale structures of surfaces and interfaces of electrode materials and their performance,raise some advices to improve the performance of lithium-ion batteries and look forward to the development of lithium-ion batteries in the aspect of increasing energy density,averting side reaction of solid electrode and liquid electrolyte as well as properties improvement.

Using the first principle based on the density-functional theory, we have studied the electronic structures and optical properties of zigzag graphene nanoribbon with different Stone-Wales defects. We take two kinds of models, namely that with and without spin polarization, into consideration. The results suggest that graphene nanoribbon with symmetrical Stone-Wales defect has the concavo-convex geometry structure in the defective region without considering spin polarization, both kinds of Stone-Wales defects give rise to the charge redistribution. The spin density of graphene nanoribbon with Stone-Wales defects is obviously affected by considering spin polarization, which leads to the changes of density of states for different kinds of spin. We have further investigated the optical properties of the graphenen nanoribbons; it was found that the peaks of absorption and reflectance have significent changes in the graphene nanoribbon with the presence of Stone-Wales defects, and red shift is observed when compared with the perfect graphene nanoribbon.