title: Cerium oxide as a promoter for the electro-oxidation reaction of ethanol: in situ XAFS characterization of the Pt nanoparticles supported on CeO2 nanoparticles and nanorods.
abstract: In this study we probe the electrocatalytic activity of Pt nanoparticles supported on ceria nanoparticles (NPs) and nanorods (NRs) in the ethanol oxidation reaction (EOR) in alkaline media. The goal of this study was to relate morphology, support structure and composition to the EOR catalytic activity by using in situ X-ray absorption fine structure (XAFS) studies. Cyclic voltammetry experiments showed that both ceria supported catalysts (NP vs. NR) had similar peak current densities at fast scan rates, however at slow scan rates, the ceria NR catalyst showed superior catalytic activity. In situ XAFS studies in KOH showed that both ceria supported catalysts had more electron density in their d-band (with the ceria NR having more electron density overall) than ceria - free Pt/Vulcan standard. However, in an ethanol solution the ceria NR catalyst had the least electron density. We propose that this change is due to the increased charge transfer efficiency between the ceria nanorod support and platinum. In the KOH solution, the increased electron density makes the platinum less electrophilic and hinders Pt-OH bond formation. In the EtOH solution, platinum's increased nucleophilicity facilitates the bond formation between Pt and the electron deficient carbon in ethanol which in turn withdraws the electron density from platinum and increases the white line intensity as observed in the XAS measurements.
authors.affiliation: Department of Chemistry, NASA-MIRO Center for Advanced Nanoscale Materials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA. carlos.cabrera2@upr.edu.
authors.forename: Juan
authors.initials: J
authors.lastname: Corchado-García
authors.affiliation: Department of Chemistry, NASA-MIRO Center for Advanced Nanoscale Materials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA. carlos.cabrera2@upr.edu.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Betancourt
authors.affiliation: Department of Chemistry, NASA-MIRO Center for Advanced Nanoscale Materials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA. carlos.cabrera2@upr.edu.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Vélez
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Sanjaya D
authors.initials: SD
authors.lastname: Senanayake
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Dario
authors.initials: D
authors.lastname: Stacchiola
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Sasaki
authors.affiliation: Department of Chemistry, NASA-MIRO Center for Advanced Nanoscale Materials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA. carlos.cabrera2@upr.edu.
authors.forename: Maxime J-F
authors.initials: MJ
authors.lastname: Guinel
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
authors.forename: Yunyun
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
authors.forename: Chin Li
authors.initials: CL
authors.lastname: Cheung
authors.affiliation: Department of Chemistry, NASA-MIRO Center for Advanced Nanoscale Materials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA. carlos.cabrera2@upr.edu.
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Cabrera