Comparison of Carbon Deposition and Removal from Ni-YSZ and Ni-BCZY Composites Using Operando Optical Methods

Abstract

In this study, 50%-50% Ni-8YSZ and Ni-BCZY27 composites were exposed to CH4 in the absence and presence of H2O. Carbon deposition at 750 °C and carbon removal were estimated by exposure to steam using operando vibrational emission spectroscopy and thermal imaging. Carbon removal reveals more CO2 + CO formation from Ni-8YSZ compared to Ni-BCZY27, suggesting more carbon on the surface of the former. Carbon removal from composites exposed to CH4 alone indicates limited formation and fast depletion of CO over Ni-BCZY27. Over Ni-8YSZ, CO and CO2 depletion is gradual and sustained, suggesting carbon formation over Ni-BCZY27 is restricted and full oxidation readily occurs. Methane cracking over Ni-8YSZ is accompanied by more cooling compared to Ni-BCZY27. Wet reforming results in similar cooling over Ni-8YSZ and Ni-BCZY27. The results are discussed in the context of recent work using operando spectroscopies of fuel utilization over Ni-8YSZ SOFCs.