文献类型：期刊文献

英文题名：Positron annihilation characteristics and catalytic performances of poly (vinyl alcohol) intercalated montmorillonite supported Pd-0 nanoparticles composites

作者：Zhao, Jing[1];Xu, Mengdie[1];Shu, Guiqing[1];Yang, Zhen[1];Liu, Qi[1];Zeng, Minfeng[1];Qi, Chenze[1];Cao, Xingzhong[2];Wang, Baoyi[2]

机构：[1]Shaoxing Univ, Coll Chem & Chem Engn, Zhejiang Key Lab Alternat Technol Fine Chem Proc, Shaoxing 312000, Peoples R China;[2]Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China

年份：2018

卷号：153

起止页码：164

外文期刊名：RADIATION PHYSICS AND CHEMISTRY

收录：SCI-EXPANDED(收录号：WOS:000452576200023)、、WOS

基金：This work is supported by the National Natural Science Foundation of China (Grant No. 11475114, 11875193, and 11575117), and Zhejiang Provincial Fundamental Public Welfare Research Project of China (Grant No. LGG18E030004). We are grateful to Professor Y. Lin (Institute of Materials Science and Department of Chemistry, University of Connecticut) for his valuable suggestions and discussions.

语种：英文

外文关键词：Montmorillonite; Poly (vinyl alcohol); Positron annihilation; Pd catalysis

外文摘要：The microstructure of poly (vinyl alcohol)/ montmorillonite (PVA/MMT) matrices and Pd@PVA/MMT catalytic composite was characterized by positron annihilation spectroscopy (PAS) and other techniques, such as high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), and X-ray photo electron spectroscopy (XPS). XRD and HR-TEM results showed that 20% was the saturation loading percentage of PVA intercalation into MMT. Ortho-positronium (o-Ps) annihilations were mainly distributed in the interlayer spacing of MMT and/or open spaces (free volume) of PVA. Below the saturation loading percentage of PVA 5 20%), it was found that the o-Ps annihilation lifetime became shorter after the intercalation of PVA chains into MMT layers. With further addition of PVA, the o-Ps annihilation lifetime became longer after the formation of exfoliated structure. The 20%-PVA/MMT matrix has been selected as the platform to further immobilize Pd specie for preparing novel 0.2%-Pd@20%-PVA/MMT catalytic composite. The effects of Pd immobilization on the microstructure of PVA/MMT matrices were also sensitively detected by PAS. The mean size of the micro-defects (from Tao-Eldrup model) increased from 0.28 nm (20%-PVA/MMT) to 0.29 rim (0.2%-Pd2+ @20%-PVA/MMT or 0.2%-Pd-0@20%-PVA/MMT), respectively. This increase in the size of the micro-defects of 20%-PVA/MMT matrix after Pd immobilization was mainly due to the replacement of the inter-molecular hydrogen bodings of PVA chains by the interactions formed between the PVA chains and Pd species. The prepared 0.2%-Pd-0@20%-PVA/MMT catalytic composite showed excellent catalytic efficiency and recyclability in both Heck-type and Sonogashira-type coupling reactions. The correlations between the microstructure and performance of the 0.2%-Pd-0@20%-PVA/MMT composite were thoroughly discussed.