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

The electrochemical promotion of ethylene oxidation on Pt was investigated using Pt(1 1 1) thin film model catalyst–electrodes deposited on top of YSZ(1 1 1) 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.

Galvanostatic transient experiments for the partly porous Pt PLD film (Pt3) at 648 K (top), and (bottom) SEM images of the film after the electropromotion experiments (dark areas are holes).Figure optionsDownload as PowerPoint slideResearch highlights▶ Electrochemical promotion (EPOC) of ethylene oxidation on partly porous Pt(1 1 1) deposited on YSZ(1 1 1). ▶ Reversible EPOC obtained only with porous and clean Pt(1 1 1) catalyst. ▶ Fe doping of Pt catalyst leads to irreversible permanent EPOC.