Understanding the Metal-Support Interaction between Cu and Reducible Metal Oxides during CO2 Hydrogenation through the Use of Well-Defined Surface Models

• Applicant: Professor Dr. Deven Estes
• Subject Area: Technical Chemistry
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 444948747

Hydrogenation of CO2 (derived from climate neutral sources) to methanol using green-energy sources could be a way of producing sustainable fuels. However, the current catalytic systems for hydrogenating CO2 to methanol, typically consisting of Cu nanoparticles supported on a reducible metal oxide, such as ZnO or ZrO2, are not active enough to be used in such an industrial process. This may be due to a low number of active sites on the surface. These active sites are thought to consist of reduced Zn or Zr sites created through a Strong Metal-Support Interaction (SMSI) in the vicinity of Cu defects. Understanding this SMSI is vital to improving these catalysts. Once we understand the origin of this metal-support interaction, we can increase the number of active sites and thereby the catalytic activity. In this proposal, I describe the development and synthesis of well-defined models of the potential active sites, both homogeneous and on metal oxide surfaces, in order to investigate the SMSI in these catalysts. In section one, we will examine the electrocatalytic activity of molecular complexes containing Zr-O-Zr bridges for CO2 reduction, as molecular models of hydrogen spillover onto the ZrO2 surface. In the second section, reduced Zn and Zr sites will be synthesized directly on the surfaces of ZnO and ZrO2 through the use of Surface Organometallic Chemistry and their reactivity examined by DRIFTS and TPR-MS. In the third section, the reactivity of ZrO2 and ZnO with molecular models of Cu particles, such as Stryker's reagent [HCu(PPh3)]6, will be examined by NMR, UV-Vis, IR, and EPR in the presence and absence of CO2 as a model of the SMSI. In the final stage, we will use the synthetic methods developed thus far to synthesize active sites directly on the surfaces of known catalysts, a strategy termed Active Site Enrichment (ASE). With this method, it will be possible to increase the number of active sites on a working catalyst via simple post-synthetic treatments.

• DFG Programme: Research Grants