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31. Understanding the Impact of Peripheral Substitution on the Activity of Co Phthalocyanine in Sulfur Reduction Catalysis.

Author

Zhao, Xinhong, Zhang, Yukun, Liu, Weizhe, Zheng, Zhiqiang, Fu, Zhanghua, Chen, Chuanzhong, and Hu, Cheng

Subjects
SULFUR, CATALYSIS, LITHIUM sulfur batteries, ELECTRONIC modulation, ELECTRIC potential, AMINO group, SULFUR cycle
Abstract

Catalytic materials are effective in promoting sulfur utilization in lithium‐sulfur batteries. Co phthalocyanine (CoPc) presents a unique planner single‐molecular structure with a highly active Co‐N4 center for sulfur reduction catalysis. The high flexibility of phthalocyanines offers rich opportunities for electronic structure modulation toward enhanced catalytic activities. To guide future design and screening, this study aims to understand the impact of peripheral substitution, the most common method to obtain CoPc derivatives, by examining two typical substituents: the electron‐withdrawing nitro and electron‐donating amino groups. Co tetranitrophthalocyanine (CoTnPc) presents a significantly higher activity in promoting the liquid‐solid transition process than Co tetraaminophthalocyanine (CoTaPc). Substitution alters the stable binding geometry of Li2S4 by influencing the electrostatic potential and Li─bond, making the Co─S bond energetically favorable with the bridging S atoms on CoTnPc. CoTnPc also enables a greater electron donation from the S 3pz orbital to the singly occupied Co 3dz2${d}_{{z}^2}$ orbital, significantly weakening the bridging S─S bond to enhance the reactivity of Li2S4 for the subsequent liquid‐solid transition. A framework of theoretical calculation is tested, providing descriptors for the screening of related materials. The potential of CoPc derivatives is demonstrated by pouch cells with CoTnPc under high sulfur loading and limited electrolyte addition. [ABSTRACT FROM AUTHOR]

Published
2024
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41. Microstructure and wear resistance of composite coating by laser cladding Ni60A/B4C pre-placed powders on Ti-6Al-4V substrate

Author

Zhang Hongxia, Yu Huijun, and Chen Chuanzhong

Subjects
composite coating, hardness, laser cladding, microstructure, wear resistance, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

The composite coatings were fabricated by laser cladding Ni60A/B4C pre-placed powders on the surface of Ti-6Al-4V alloy for improving wear resistance and hardness of the substrate. In this research, the composite coatings were studied by means of X-ray diffraction, scanning electron microscope and energy dispersive spectrometer. The sliding wear tests were performed using MM200 wear test machine. The hardness of the coatings was tested by HV-1000 hardness tester. After laser cladding, it was found that there was a good metallurgical bond between the laser cladding coating and Ti-6Al-4V substrate. The composite coatings were mainly composed of the matrix of γ-Ni and a little Ni3Ti and the reinforcements of TiB2, TiC and CrB. The hardness of the sample of Ni60A-5B4C was approximately 2.5–3.5 times that of the Ti-6Al-4V substrate. The hardness of the sample of Ni60A-10B4C was 30% higher than that of sample 1. The wear resistance of samples 1 and 2 were 11 times and 10 times that of the substrate, respectively.

Published
2017
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