Catalytic Membrane Nanoreactor with Cu–Ag<i><sub>x</sub></i> Bimetallic Nanoparticles Immobilized in Membrane Pores for Enhanced Catalytic Performance
Yu Chen, Senqin Fan, Jiaojiao Chen, Lei Deng, Zeyi Xiao
Abstract
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.