460024 Enhanced Electro-Kinetics of CO2 Generation for Ethanol Oxidation Using Catalysts with a Partially Oxidized Pt and Rh Core and a SnO2 Shell

Wednesday, November 16, 2016
Grand Ballroom B (Hilton San Francisco Union Square)
Guangxing Yang, Chemical Engineering, University of New Hampshire, Durham, NH and Xiaowei Teng, Department of Chemical Engineering, University of New Hampshire, Durham, NH

Direct ethanol fuel cell (DEFC) is a promising technology for generating electricity via the electro-oxidation of liquid ethanol. Its implementation requires the development of anode catalysts capable of producing CO2 and yielding 12-electron transfer through breaking C-C bond of ethanol. To evaluate the capability to break C-C bond over catalysts, here we designed an electrochemical cell equipped with a CO2 microelectrode, through which CO2 partial pressure and current density could be obtained simultaneously. Then CO2 generation rate and selectivity as functions of potential were calculated in 0.5M H2SO4/0.5 M ethanol solution. In this work, the Pt/Rh/Sn catalysts with different Pt and Rh ratios were synthesized using surfactant free approach. Reduced Pt/Rh/Sn samples were prepared by reducing the as-made Pt/Rh/Sn catalysts in H2/Ar mixture. Both as-made and reduced samples were characterized by transmission electron microscopy (TEM), scanning transmission electron microscope-electron energy loss spectroscopy (STEM-EELS), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). We demonstrated that the as-made sample was the tri-phase PtRhOx-SnO2 catalysts with a partially oxidized Pt and Rh core and a SnO2 shell, and the reduced sample was the bi-phase PtRh-SnO2 catalysts with a metallic PtRh alloy core and a SnO2 shell. The comprehensive kinetics studies showed that PtRhOx-SnO2 catalysts coincided with a 2.5-fold increase in the CO2 generation rate towards ethanol oxidation reaction at 0.35V, compared with PtRh-SnO2 and commercial Pt. PtRhOx-SnO2 also exhibited lower onset potential of CO2 generation and higher CO2 selectivity than PtRh-SnO2. These in situ studies provided insight on the design of a new genre of electro-catalysts with a partially oxidized noble metal.

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