AVS 65th International Symposium & Exhibition
    Fundamental Discoveries in Heterogeneous Catalysis Focus Topic Tuesday Sessions
       Session HC+SS-TuA

Paper HC+SS-TuA1
CO2 Reduction on the Surface of Cu/TiO2 NPs Supported on Graphite Studied using Ambient Pressure-XPS and Differential Electrochemical Mass Spectrometer

Tuesday, October 23, 2018, 2:20 pm, Room 201A

Session: A Tale of Two Scales: Catalytic Processes and Surface Science
Presenter: Djawhar Ferrah, University of California at Irvine
Authors: D.F. Ferrah, University of California at Irvine
A. Haines, University of California at Irvine
R.P. Galhenage, University of California at Irvine
A. Javier, California Institute of Technology
J.P. Bruce, University of California at Irvine
M. Soriaga, California Institute of Technology
J.C. Hemminger, University of California at Irvine
Correspondent: Click to Email
Metal supported on metal oxide (M1/MO) catalyst systems are widely used in industry for the hydrogen production and CO2/CO conversion to useful fuels. If incontrovertible evidence were founded for the role of the interface in the improvement of catalytic CO2 hydrogenation efficiency, it would still be an incomplete understanding on the nature of the active sites and associated reaction pathways, namely reactive species adsorption, dissociation and/or activation and intermediate formation stability. The modulation of the reaction selectivity, through the synthesis of catalysts that exhibit specific active sites, is required to design «smart » catalytic systems. Therefore, the investigation of catalytic reactions under real conditions, to illustrate the relation between properties at the atomic level of the surface and reactivity, is needed. In this context, a model catalyst based on Cu/TiO2 nanoparticles (NPs) supported on graphite (HOPG), have been synthesized and fully characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Using physical vapor deposition (PVD), a high density of 15 nm TiO2 NPs are deposited on HOPG and are used to support Cu NPs. TEM studies reveal that most of the TiO2 NPs have a rutile structure and display mainly (110) vicinal surface, which is favorable for CO2 adsorption. A formation of thin layer of graphitic carbon at surface of TiO2 NPs is also reported. Photodeposition of Cu on TiO2 NPs by irradiating the band gap of TiO2 in a CuCl2 solution has been studied. In the present work, two different catalytic aspects for CO2 reduction on CuOx/TiO2 NPs on HOPG systems will be reported: (1) thermocatalytic CO2 hydrogenation and (2) electrochemical CO2 hydrogenation. Efforts have been devoted to exploring different surface chemistry effects, as well as the oxidation states of Cu NPs (Cu2O, Cu, and Cu2O@Cu) with diameters ranging from 2 to 5 nm and TiO2 surface encapsulation with thin layer of graphited carbon, on the CO2 reduction mechanism in the temperature range of 300-550 K using Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) at the National Synchrotron Light Source II (NSLS-II). Similarly, the CO2 reduction on CuOx/TiO2 NPs on HOPG electrodes in aqueous KHCO3 has been investigated using a Differential Electrochemical Mass Spectrometer (DEMS) to evaluate the reaction products. Ongoing Infrared reflection-absorption spectroscopy (IRRAS), and AP-XPS experiments on electrochemical CO2 reduction will be introduced.