Abstract
The metal–support interaction (MSI) has a remarkable effect on the catalytic properties, but how to precisely modulate its degree remains a huge challenge. Herein, polyvinylpyrrolidone (PVP) with three different molecular weights (MWs) (24, 58, and 130 kDa) was used as a capping agent to fabricate Ag nanoparticles (NPs) supported on ZrO2. The physiochemical properties of the catalysts were characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), and Fourier transform infrared (FT-IR) techniques. The impacts of MSI on the catalytic activity and reaction kinetics for aerobic oxidation of 5-hydroxymethylfurfural (HMF) were investigated. The results showed that the introduction of PVP with various MWs could efficiently tailor the interfacial interactions and charge transfers (CT) among PVP, the support, and Ag NPs, thereby affecting the oxidation activity of HMF. The turnover number (TON) for HMF oxidation decreases in the order of unsupported colloidal Ag clusters > Ag/ZrO2 (58,000) > Ag/ZrO2 (130,000) > Ag/ZrO2 (24,000) > Ag/ZrO2. The reason for this large difference in the catalytic activity for HMF oxidation is that various MWs of PVP result in a change of MSI, thereby facilitating CT from PVP to Ag metal sites. This study offers a new strategy for modulating MSI by varying the MW of capping agents, thereby tuning the catalytic properties in the oxidation of HMF.
Highlights
The catalytic activity of metal nanoparticles (NPs) highly depends on their particle size, shape, and surface composition [1,2,3]
X-ray Photoelectron Spectroscopy (XPS) was employed to reveal the effect of PVP molecular weights (MWs) on the interaction between PVP and ZrO2
After the introduction of PVP, shifts of the binding energies related to theNa3ndomtartaenriaslist2io02n0s, 1w0,exrFeOoRbPsEeErvReRdE.VMIEWoreover, it was found that the binding energy assigned to 36d3o/f2 11 shifted from 374.0 eV for Ag/ZrO2 to 373.6 eV for Ag/ZrO2 (24,000), and further shifted to 373.3 eV for
Summary
The catalytic activity of metal nanoparticles (NPs) highly depends on their particle size, shape, and surface composition [1,2,3]. Metal–support interaction (MSI) has significant impacts on catalytic properties due to electronic effect, geometric effects, and so on [1,4,5,6,7]. Colloidal metal NPs have attracted considerable attention, because the usage of organic ligands (often referred to as stabilizers and capping agents) can precisely control particle size, shape, and surface composition [2]. Skurai et al investigated the impact of PVP chain length on the catalytic activities of Au nanoclusters capped by PVP [11] They revealed that long-chain PVP results in highly entangled structures through entanglement of the Au nanocluster surface, which increases the electronegativity at the cluster’s surface [11]. A deep understanding of the role of PVP in the catalytic activity of supported colloidal NPs has not yet been elucidated
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