Abstract
The sol immobilisation technique, in which a stabilising ligand (such as polyvinyl alcohol or polyvinyl pyridine) can be used to tune metal particle size and composition, has become a valuable method of making supported nanoparticle catalysts. An unfortunate consequence of the stabilising ligand is that often access of reactant molecules to the metal nanoparticle surface is impeded. Several methods have been proposed for the removal of these ligands, though determination of the degree of their success is difficult. Here, we demonstrate the use of in situ infrared and UV-Vis spectroscopy to elucidate the access of carbon monoxide to the surface of Au/TiO2 catalysts before and after various ligand removal treatments. These were contrasted with a catalyst prepared by deposition precipitation prepared in the absence of stabilising ligand as a control. Changes were observed in the infrared spectrum, with the wavenumber of carbon monoxide linearly bonded to Au for catalysts shifting before and after ligand removal, which correlated well with the activity of the catalyst for carbon monoxide oxidation. Also the extent of shifting of the Au surface resonance plasmon band on the addition of carbon monoxide, observed by UV-Vis, also correlated well with catalyst activity. These simple methods can be used to determine the quantity of exposed metal sites after a ligand removal treatment and so determine the treatments effectiveness.
Highlights
Supported gold catalysts have received considerable attention in the last decade, with the number of related publications increasing significantly since the seminal work by Haruta on sub-ambient CO oxidation and Hutchings on acetylene hydrochlorination.[1,2] Supported gold catalysts have since been reported for many reactions, such as epoxidation,[3] hydrogen peroxide synthesis,[4] selective oxidation of hydrocarbons[5] and alcohols.[6]
In addition we applied the same protocol for Au/TiO2 catalysts prepared with polyvinyl pyridine (PVP) capping agent
1 wt% Au/TiO2 made by sol immobilization and stabilised by polyvinyl alcohol (PVA) (SI-PVA) or PVP (SI-PVP) were both treated with water at 90 1C for a range of times
Summary
Supported gold catalysts have received considerable attention in the last decade, with the number of related publications increasing significantly since the seminal work by Haruta on sub-ambient CO oxidation and Hutchings on acetylene hydrochlorination.[1,2] Supported gold catalysts have since been reported for many reactions, such as epoxidation,[3] hydrogen peroxide synthesis,[4] selective oxidation of hydrocarbons[5] and alcohols.[6]. It is known that both sol-immobilization and deposition precipitation techniques provide particles with a low aspect ratio and with similar particle size distributions.[41,42,44] The similar particle sizes observed by TEM (Table 1) for these catalysts correlate well with the literature and the relative invariance of SPR position observed by UV-Vis. The position of the SPR band for all catalysts did not change position (within error) after the water treatment (Fig. 3).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
