Pt Current Collectors Artificially Boosting Si-Contaminated Praseodymium Doped Ceria Oxygen Surface Exchange Coefficients

Abstract

The chemical oxygen surface exchange coefficient (kchem ) values used to quantify and rank oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalyst performance for high-temperature, oxygen-exchange-enabled devices (such as Solid Oxide Fuel Cells, Solid Oxide Electrolysis Cells, oxygen sensors, etc.) are often determined electrically, with the aid of precious metal current collectors. In addition, due to ease of introducing siliceous contaminants during the manufacturing and operation of these devices, the performance of their oxygen exchange catalysts are often impacted by Si surface contaminants.Here, Curvature Relaxation (KR), Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS) analyses performed on Pulsed Laser Deposited thin films of the oxygen exchange catalyst Pr0.1Ce0.9O2-x (PCO) show that siliceous surface phases only a few nanometers thick are capable of 1) reducing the PCO chemical oxygen surface exchange coefficient by approximately 3 orders of magnitude and 2) approximately doubling the activation energy for oxygen incorporation and removal. Further, the results show that unpolarized platinum current collectors dramatically improve the kchem of Si-contaminated PCO by reducing the Si concentration at the PCO surface and/or diffusing into the PCO; even for PCO thin films only exposed to mild temperatures of 500 oC. This suggests that precious metal current collectors are likely responsible for some of the large kchem variation reported in the literature for “identical” materials tested under “identical” conditions. Figure 1