It is well established that Cu is an important metal for both the thermocatalytic and electrochemical reduction of CO2. However, the nature of the active Cu species has been debated with some studies showing that Cu0 is active for both of these processes while others report that stabilizing Cu+ results in enhanced catalytic activity and is critical in achieving stable adsorption of CO2 onto the surface of the Cu-based catalyst. For bulk Cu electrodes, Cu+ species would be reduced to Cu0 under electrochemical CO2 reduction potentials but metal oxide supports could play a critical role in the stabilization of Cu+. While metals on metal oxide supports have been widely studied, there still remains a dispute as to the role of the oxide supports and the surface oxidation state of the active metal and its efficacy in the reduction of CO2. In this context, we have designed and characterized a model catalytic system consisting of Cu-based nanoparticles (NPs) deposited on TiO2 NPs in an effort to investigate the fundamental aspects of the thermocatalytic and electrochemical reduction of CO2. TiO2, a reducible metal oxide, serves as a suitable metal oxide support as it is capable of exchanging oxygen and has the ability to stabilize partially oxidized Cu-based NPs. A high density of rutile TiO2 NPs have been deposited on a plasma treated inert highly oriented pyrolytic graphite (HOPG) substrate by physical vapor deposition (PVD). Using photodeposition, small Cu-based NPs are selectively deposited onto the TiO2 NPs and fully characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The thermocatalytic activity for the CO2 reduction reaction under H2 was evaluated with synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS) where we observed intermediate formation and changes in the oxidation state of the Cu-based NPs. Electrochemical CO2 reduction studies were carried out in an aqueous KHCO3 solution saturated with CO2 and the reaction products were determined using differential electrochemical mass spectrometry (DEMS). Ongoing electrochemical studies are being performed in order to investigate the stability of the Cu/TiO2 NPs under negative potentials.

Cu nanoparticles on metal oxide nanoparticle model catalysts: Synthesis, characterization and reactivity

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.