(Invited) In Operando Optical Studies of Solid Oxide Electrochemical Cells

Abstract

Solid oxide fuels cells (SOFCs) are promising devices for fuel flexible and efficient power generation. The high temperatures (>700 o C) required enable operation on hydrocarbon fuels but avoiding degradation by carbon deposition remains a challenge. In operando optical methods, including Raman and Fourier Transform infrared emission spectroscopy (FTIRES) and near infrared thermal imaging (NIRTI), have been developed to characterize and understand molecular and material processes in SOFCs in order to improve their performance and durability. Recent results include studies of SOFCs on methane operating under various reforming conditions. Dry reforming, using carbon dioxide, which is also simulated biogas, reveals a high degree of anode activity based on substantial cooling of the anode but also reduced carbon formation compared to unreformed methane. An intermediate amount of anode cooling and carbon formation is observed with steam reforming. Related studies have been carried out to assess the effectiveness of carbon removal by steam and carbon dioxide using a new, duplex method in which NIRTI and FTIRES are performed simultaneously. Also, NIRTI has been used in conjunction with near ambient pressure X-ray photoelectron spectroscopy (APXPS) to identify spatially resolved regions where the emission intensity changes are observed due to ceria reduction during water electrolysis. The results are consistent with the APXPS results and interpretation for the reaction. The observations also provide an example of emissivity rather than temperature changes observed with high temperature thermal imaging in solid oxide electrochemical cells.