Insightful understanding of the correlations of the microstructure and catalytic performances of Pd@chitosan membrane catalysts studied by positron annihilation spectroscopy

Abstract

A number of instantaneously connected free volume holes act as mass transport channels of the Pd0@CS membrane catalyst in reactions.

Positron annihilation lifetime spectroscopic analysis of Nafion and graft‐type polymer electrolyte membranes for fuel cell application

“…Note that one possible reason for the larger hole size in the mobile amorphous layers of side chains is the hole connectivity (Scheme 2B, D). [68][69][70] In this case, o-Ps atom can be formed and migrate quantum mechanically through connecting channels or from a smaller hole to a neighboring larger hole. Moreover, as can be seen in Table 3 or Table 5, the average hole size or hole diameter derived from the hole radius is higher than the d-spacing calculated from the XRD analysis (Table 1).…”

Gelatin‐pyrolyzed mesoporous N‐doped carbon supported Pd as high‐performance catalysts for aqueous Heck reactions

“…It might be attributed to the larger‐sized mesoporous structure and larger pore volumes (as confirmed by above N 2 adsorption/desorption and HR‐TEM results) formed in the cases of Pd@N‐C‐SiO 2 catalysts. As the size of the reactants of iodo benzene, n ‐butyl acrylates, and coupling products molecules are close or even bigger than 1 nm, [ 31,32 ] higher content of mesoporous structure with larger pore size of the catalysts should be definitely advantages for higher efficiency in getting access to the active sites of Pd 0 /PdO species. As shown Figure 7b, the Pd immobilization methods have great effects on the recyclability of the prepared Pd@N‐C catalysts.…”

Application Progress of PALS in the Correlation of Structure and Properties for Graphene/Polymer Nanocomposites

“…At present, the application of PALS in structure characterization for polymer composites was mainly focused on the measurement of annihilation lifetime [ 24 , 25 , 26 , 27 , 28 ]. On the one hand, the V f and f v can be calculated with the value of τ 3 , and the relationship can be established between the obtained f v and the material properties [ 29 , 30 , 31 , 32 , 33 ]. On the other hand, the β can be calculated with the value of I 2 , which can give a deep insight into the dispersion state of filler and corresponding properties [ 16 , 17 , 18 , 19 ].…”

“…Based on the free volume theory, a direct linear correlation between f v and the viscoelastic property of PC/MWCNT has been obtained using the WLF equation. In addition, based on the results of V f and f v obtained from PALS, the property change rule of many polymer composites can be explained [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. With the deepening of the investigation, a quantitative relationship between the V f , f r , and properties was established.…”