A catalytic membrane nanoreactor (CMNR) with Cu–Agx (where x is the millimolar concentration of AgNO3) bimetallic catalysts immobilized in membrane pores has been fabricated via coupling flowing synthesis and replacement reaction. Surface characterization by transmission electron microscopy (TEM) gives obvious evidence of the formation of Cu–Ag bimetallic core–shell nanostructures with Ag islands deposited on the Cu core metal. An apparent high shift phenomenon for the Cu element and a low shift phenomenon for the Ag element was determined by X-ray photoelectron spectroscopy (XPS), indicating a close interaction with the transfer of electron density from the Cu atom to the Ag atom. The hydrogenation catalysis of p-nitrophenol (p-NP) was tested to evaluate the catalytic performance. During the catalytic process, the Cu core acts as an electron-deficient site to adsorb and activate the −NO2 group for p-NP, and the Ag shell is beneficial for enhancing active H spilling to the Cu surface and then performing hydrogenation. A volcano-shaped apparent reaction rate constant can be achieved, which rises initially with the increasing Ag content and subsequently drops with a further increase in the Ag content. The highest value of 1071 min–1 can be achieved for CMNR immobilized with Cu–Ag2 owing to the suitable adsorption activation behavior and the best hydrogen spillover behavior.
In this article, the effect of the distinctiveness and arrangements on the plasmonic resonance of Cu–Ag system were studied by finite element method , and the effect of morphologies on the plasmonic properties of Cu@Ag core@shell NPs and Cu–Ag corn-cob liked NPs was investigated by experiment. For Cu@Ag core-shell structure, as the fixed thickness of Ag-shell at 10 nm, the dipole plasmon resonance gradually blue-shifts with increasing the radius of Cu core, and as the fixed radius of Cu-core at 50 nm, the feature peak shows a red-shift and broadening with increasing the thickness of Ag shell. For Cu–Ag corn-cob structure, the feature for different Ag coverage are similar to each other and most of the them follow the blue-shifted tendency with the increase the degree of Ag-coverage. Furthermore, as the regular-shaped structure increases (form trigonal to spherical), the plasmon resonance gradually blue shifts, and finally, we use two parameters to describe the different idealized Cu–Ag structure: separation, exterior contact, intersection and core@shell. The combined information from our simulation and experiment will give guidelines for choosing adequate particles when aiming at certain plasmonic properties.
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