High-Temperature Raman Spectroscopy of Solid Oxide Fuel Cell Materials and Processes

• Published in: The journal of physical chemistry. B Vol. 110; no. 35; pp. 17305 - 17308
• Main Authors: Pomfret, Michael B, Owrutsky, Jeffrey C, Walker, Robert A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.09.2006
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp063952l

Chemical and material processes occurring in high temperature environments are difficult to quantify due to a lack of experimental methods that can probe directly the species present. In this letter, Raman spectroscopy is shown to be capable of identifying in-situ and noninvasively changes in material properties as well as the formation and disappearance of molecular species on surfaces at temperatures of 715 °C. The material, yttria-stabilized zirconia or YSZ, and the molecular species, Ni/NiO and nanocrystalline graphite, factor prominently in the chemistry of solid oxide fuel cells (SOFCs). Experiments demonstrate the ability of Raman spectroscopy to follow reversible oxidation/reduction kinetics of Ni/NiO as well as the rate of carbon disappearance when graphite, formed in-situ, is exposed to a weakly oxidizing atmosphere. In addition, the Raman active phonon mode of YSZ shows a temperature dependent shift that correlates closely with the expansion of the lattice parameter, thus providing a convenient internal diagnostic for identifying thermal gradients in high temperature systems. These findings provide direct insight into processes likely to occur in operational SOFCs and motivate the use of in-situ Raman spectroscopy to follow chemical processes in these high-temperature, electrochemically active environments.