Spatially resolved measurements of electrochemically induced spillover on porous and microstructured Pt/YSZ catalysts

Abstract

Pt / YSZ electrodes prepared from platinum (Pt) and yttria-stabilized zirconia (YSZ) can be applied in electrocatalytic experiments for the promotion of different heterogeneously catalyzed reactions. The strong increase in catalytic activity of Pt / YSZ assemblies on electrochemical polarisation has recently been attributed to the creation of catalytically active spill-over species under non-equilibrium conditions. Our experiments combine locally resolved surface sensitive techniques (SPEM, PEEM) with electrochemical methods in order to resolve the processes at the Pt / YSZ interface and to clarify the nature of the spillover species.

Ionically Conducting Ceramics as Active Catalyst Supports

“…Subsequent PEEM work by Imbihl, Janek, and co-workers − has extracted a diffusion coefficient value of D o = (9.2 ± 1.8)10 –4 cm 2 s –1 at 670 K for the O spillover species, which is interestingly a factor of 10 3 higher than that of normally adsorbed oxygen on Pt(111) . More recently, the group of Janek has found an activation energy of 50 kJ/mol for the O spillover species. ,− An example of a PEEM observation of the spreading of spillover oxygen on a dense Pt electrode is given in Figure .…”

Effect of Electrochemical Polarization on the Emission of O[sup −] Ions from the Surface of YSZ

“…As for the variation in the work function by electrochemical polarization, it is known that the work function of metal electrodes on solid electrolytes is varied by electrochemical polarization. [17][18][19][20][21][22][23][24] Under cathodic polarization, the work function of a metal electrode is decreased, while it is increased under anodic polarization.…”

Solid electrochemical mass spectrometry (SEMS) for investigation of supported metal catalysts under high vacuum

“…Surface analysis techniques, e.g. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) [1,2], scanning photoelectron spectroscopy (SPEM) [3][4][5], photoelectron emission microscopy (PEEM) [4][5][6][7], scanning tunneling microscopy (STM), are usually coupled to electrochemistry to investigate electrochemical deposition and adsorption at the electrode while spectroscopic techniques, e.g. infrared-spectroscopy (IR), gas chromatography (GC) [8,9], mass spectrometry (MS) [8][9][10][11], are coupled to monitor (qualitatively and quantitatively) the products of an electrochemical reaction.…”

“…These techniques have allowed to propose an EPOC model based on backspillover ion promoters [8]. In order to obtain a clearer mechanistic picture of the phenomenon and demonstrate the EPOC mechanism proposed at atmospheric pressure, Imbihl et al [3][4][5][6][7] proposed to investigate EPOC under ultra high vacuum (UHV) conditions. Surface analysis tools like PEEM and SPEM were combined with success to electrochemical methods allowing the authors to directly observe the migration of O 2-promoters at the catalyst surface during an anodic polarization.…”