Isolated Zr Surface Sites on Silica Promote Hydrogenation of CO 2 to CH 3 OH in Supported Cu Catalysts
Year: 2018
Type: article
Abstract: Copper nanoparticles supported on zirconia (Cu/ZrO 2 ) or related supported oxides (Cu/ZrO 2 /SiO 2 ) show promising activity and selectivity for the hydrogenation of CO 2 to CH 3 OH. However, the role of the support remains controversial because most spectroscopic techniques provide information dominated by the bulk, making interpretation and formulation of structure–activity relationships challenging. In order to understand the role of the support and in particular of the Zr surface species at a molecular level, a surface organometallic chemistry approach has been used to tailor a silica support containing isolated Zr(IV) surface sites, on which copper nanoparticles (∼3 nm) are generated. These supported Cu nanoparticles exhibit increased CH 3 OH activity and selectivity compared to those supported on SiO 2, reaching catalytic performances comparable to those of the corresponding Cu/ZrO 2 . Ex situ and in situ X-ray absorption spectroscopy reveals that the Zr sites on silica remain isolated and in their +4 oxidation state, while ex situ solid-state nuclear magnetic resonance spectroscopy and catalytic performances show that similar mechanisms are involved with the single-site support and ZrO 2 . These observations imply that Zr(IV) surface sites at the periphery of Cu particles are responsible for promoting CH 3 OH formation on Cu–Zr-based catalysts and provide a guideline to develop selective CH 3 OH synthesis catalysts.
DOI: 10.1021/jacs.8b05595
Institutions: ETH Zurich, Paul Scherrer Institute
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2884737359