Zanyu Chen,Jiugang Hu,Shijun Liu,Hongshuai Hou,Guoqiang Zou,Wentao Deng,Xiaobo Ji
Vanadium oxides are considered as promising cathode materials for aqueous zinc ions batteries (AZIBs). However, the long diffusion distance, low diffusion coefficient, and strong electrostatic interactions with divalent Zn 2+ in bulk vanadium oxide restrict their practical application. In this work, vanadium oxide nanofibers with physical and chemical defects were facilely fabricated by electrospinning for the application in AZIBs. The hierarchical framework exhibits structure stability during insertion/ extraction processes of zinc ions, and the extracted zinc ions are easily confined in the caverns of porous fibers to shorten the diffusion paths. Furthermore, the electrochemical reaction mechanism was verified by using in situ Raman and ex situ XPS and HRTEM, demonstrating a co-insertion mechanism of zinc ions and H + . The cathode shows a fast activation process, exhibiting a high capacity of 256 mAh g −1 at 1 A g −1 , and the capacity fading of only 17% is observed after 1000 cycles at 5 A g −1 . The outstanding electrochemical performances and efficient Zn 2+ transportation can be attributed to the synergism of physical and chemical defects. This strategy of dual defects may provide new insights into the improvements of AZIBs performance.
Li Zhang,Melissa Berteau-Rainville,Tianshu Zhai,Yuhao Wang,Qi Wang,Ingo Salzmann,Steffen Duhm
The energy-level alignment (ELA) at interfaces ubiquitous in organic optoelectronic applications is decisive for the device performance. Due to the notoriously low density of free charge carriers in organic thin films, the ELA at organic––inorganic interfaces is determined by gap states and/or tailing states of the frontier molecular orbitals, that is, the highest occupied molecular orbital and the lowest unoccupied molecular orbital (LUMO). Informed by modeling defect energies on the density-functional theory level, it is deduced from ultraviolet and X-ray photoelectron spectroscopy data that chemical-defect induced gap states lead to the substrate-independent pinning of the Fermi level ( E F ) to the LUMO for 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile thin films. For 5,6,11,12,17,18-hexaazatrinaphthylene thin films, the ELA is instead governed by tailing states due to energetic disorder, which put the E F closer to midgap position. It is highlighted in the study that the susceptibility of conjugated organic material to forming chemical and structural defects is key for the ELA at interfaces and, therefore, must be considered in the synthesis of novel materials and their processing into functional structures.
The optical properties of colored cool pigments including their color and solar reflectance are predominantly governed by chemical defects.In this study, a series of yellow cool pigments SrCe 1-x Tb x O 3 (x = 0–0.3) and SrCe 0.7-x Tb 0.3 Y x O 3 (x = 0–0.1) were synthesized via the solid-state reaction based on defect engineering. The effects of chemical defects on their optical performance were systematically investigated. Tb doping extends the absorption edge of the pigments to the visible region beyond 500 nm, thereby imparting a distinct yellow hue to the pigment. However this doping process simultaneously introduces oxygen vacancy defects and facilitates the coexistence of mixed-valence cations (Ce 4+ /Ce 3+ and Tb 4+ /Tb 3+ ) within the host lattice. This results in pronounced tail absorption that compromises both color properties and solar reflectance. To address this issue, yttrium was introduced as a co-dopant following the charge compensation principle which effectively suppressed defect formation and reduced tail absorption intensity. This co-doping strategy successfully achieved a synergistic optimization of pigment color and solar reflectance. The optimized pigments exhibited a high b* value of 75 and an exceptional near-infrared reflectance of95.33 %. The simulation experiment revealed that coating based on the as-prepared pigment exhibited an internal surface temperature reduction of 15.5 °C compared to the conventional cement coating. These findings underscore that optimizing color and solar reflectance through chemical defect regulation represents a feasible approach for preparing high-performance colored cool pigments.
危险品化学品经营许可证（带存储）