Electrochemical promotion of Pt(1 1 1)/YSZ(1 1 1) and Pt–FeOx/YSZ(1 1 1) thin catalyst films: Electrocatalytic, catalytic and morphological studies

Abstract

The electrochemical promotion of ethylene oxidation on Pt was investigated using Pt(111) thin film model catalyst–electrodes deposited on top of YSZ(111) single crystals. This is the first study involving a thin epitaxial and well-characterized catalyst system. The nearly covering Pt films were prepared by pulsed laser deposition (PLD) and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). In order to explore the influence of potentially catalytic active impurities, samples with and without FeOx dopants on the Pt catalyst surface were investigated. A major result is that most of the samples showed unequivocal electrochemical promotion of catalytic activity (EPOC). The Faradaic efficiency values Λ are typically 2.5–77 which is considerably smaller than those reported for usually investigated macroscopically porous paste electrodes (Λmax=3×105). This fact can be attributed to the much shorter three-phase boundary (tpb) length of the catalyst films. The iron-doped samples showed a permanent effect (P-EPOC). The results are discussed in terms of morphology changes and iron-doping effects. A short survey of EPOC studies using different catalyst/electrolyte preparation techniques is given.