Nankai University

About: Nankai University is a education organization based out in Tianjin, China. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 42964 authors who have published 51866 publications receiving 1127896 citations. The organization is also known as: Nánkāi Dàxué.

Transition metal vanadium oxides and vanadate materials for lithium batteries

Abstract: Transition metal vanadium oxides and vanadates have been widely investigated as possible active materials for primary and rechargeable lithium batteries. As compared to the classic lithium-insertion compounds such as LiCoO2, the composite vanadium oxides and vanadates have the prominent advantages of high theoretical capacities owing to multistep reductions and more electron transfer upon lithium intercalation. This short review presents a survey of recent advances made in the application of transition metal vanadium oxides and vanadates. Particularly, the structure, synthesis and electrochemical properties of silver vanadium oxides (e.g., AgVO3, Ag2V4O11 and Ag4V2O6F2) and copper vanadates (e.g., CuV2O6, Cu2.33V4O11 and Cu1.1V4O11) are discussed, with the illustration of the effect of crystal structure, composition, and morphology on the battery performance. Benefits gained from reducing the particle size have been particularly demonstrated.

Realization of broadband cross-polarization conversion in transmission mode in the terahertz region using a single-layer metasurface

Abstract: We present the design specifications and in-depth analysis of a terahertz (THz) broadband cross-polarization converter composed of a single-layer metasurface. This device can convert linearly polarized light into its cross-polarization in transmission mode. Different from other polarization conversion devices, this effect results from the suppression and enhancement for different electric components. The broadband characteristic is also achieved by specific partial symmetries designed in the structure. The proposed polarization converter can aid in the development of novel plasmonic polarization devices, and can help to overcome certain limitations of the customary designs that have been proposed thus far.

Rechargeable Room-Temperature Na-CO2 Batteries.

Abstract: Developing rechargeable Na–CO2 batteries is significant for energy conversion and utilization of CO2. However, the reported batteries in pure CO2 atmosphere are non-rechargeable with limited discharge capacity of 200 mAh g−1. Herein, we realized the rechargeability of a Na–CO2 battery, with the proposed and demonstrated reversible reaction of 3 CO2+4 Na↔2 Na2CO3+C. The battery consists of a Na anode, an ether-based electrolyte, and a designed cathode with electrolyte-treated multi-wall carbon nanotubes, and shows reversible capacity of 60000 mAh g−1 at 1 A g−1 (≈1000 Wh kg−1) and runs for 200 cycles with controlled capacity of 2000 mAh g−1 at charge voltage <3.7 V. The porous structure, high electro-conductivity, and good wettability of electrolyte to cathode lead to reduced electrochemical polarization of the battery and further result in high performance. Our work provides an alternative approach towards clean recycling and utilization of CO2.

Fine-particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Abstract: . pH is an important property of aerosol particles but is difficult to measure directly. Several studies have estimated the pH values for fine particles in northern China winter haze using thermodynamic models (i.e., E-AIM and ISORROPIA) and ambient measurements. The reported pH values differ widely, ranging from close to 0 (highly acidic) to as high as 7 (neutral). In order to understand the reason for this discrepancy, we calculated pH values using these models with different assumptions with regard to model inputs and particle phase states. We find that the large discrepancy is due primarily to differences in the model assumptions adopted in previous studies. Calculations using only aerosol-phase composition as inputs (i.e., reverse mode) are sensitive to the measurement errors of ionic species, and inferred pH values exhibit a bimodal distribution, with peaks between −2 and 2 and between 7 and 10, depending on whether anions or cations are in excess. Calculations using total (gas plus aerosol phase) measurements as inputs (i.e., forward mode) are affected much less by these measurement errors. In future studies, the reverse mode should be avoided whereas the forward mode should be used. Forward-mode calculations in this and previous studies collectively indicate a moderately acidic condition (pH from about 4 to about 5) for fine particles in northern China winter haze, indicating further that ammonia plays an important role in determining this property. The assumed particle phase state, either stable (solid plus liquid) or metastable (only liquid), does not significantly impact pH predictions. The unrealistic pH values of about 7 in a few previous studies (using the standard ISORROPIA model and stable state assumption) resulted from coding errors in the model, which have been identified and fixed in this study.