Ni/YSZ solid oxide fuel cell anodes operating on humidified ethanol fuel feeds: An optical study

Direct internal steam reforming of ethanol fuel in solid oxide fuel cells (SOFCs) has been investigated using near-infrared thermal imaging. Thermal data are correlated to electrochemical analyses, post-mortem photographs of the cells and gas-phase infrared (FTIR) spectroscopy. These techniques allow for an understanding of how gas-phase composition and electrical conditions affect the fuel chemistry on the anode, specifically with regards to carbon formation. Ethanol flows that are humidified to H2O:C2H5OH ratios of 1.58, 1.27, and 1.12 at 700, 750, and 800 °C, respectively, result in far less anode damage than dry ethanol. However, subtle spatial variations in anode surface temperature indicate that damage occurs at temperatures below 800 °C. FTIR spectra of the fuel feed reaching the anode show that internal steam reforming occurs both in the gas phase and at the anode catalyst. Thermal imaging and post-mortem analysis confirm that humidified ethanol flows at 800 °C form negligible amounts of carbon deposits in polarized cells, resulting in minimal anode deterioration. These results serve as benchmark data for the further development of direct, internal reforming SOFC systems, especially in smaller, portable systems. The H2O:C2H5OH ratio used in this work is well below the >3:1 ratios suggested elsewhere.

► Direct steam reforming of C2H5OH in SOFCs investigated by NIR thermal imaging.
► Humidified fuel flows result in far less damage to the anode than dry ethanol.
► Imaging and spectroscopy characterize reforming in the gas phase and at the anode.
► Limiting carbon formation with <3:1 H2O:C2H5OH is promising regarding logistics.
► Real-time analysis of SOFC failure demonstrates diagnostic capabilities of imaging.