Anode degradation via carbon growth from hydrocarbon fuels has presented a major hurdle for solid oxide fuel cell (SOFC) development. While all hydrocarbons and even the simplest (e.g. methane) are known to form carbon, steam reforming can be an effective vehicle to mitigate carbon formation during operation. Recently techniques that directly probe anode chemistry have seen some advancement, but the complex reforming mechanisms of the anode remain difficult to quantify. Yet, an empirical approach with minimal ambiguity is needed to understand conditions that influence fuel chemistry and anode stability. The current work describes experiments that simultaneously probe 1) reforming/electrochemical products and 2) temperature gradients on Ni/YSZ (yttrium stabilized zirconia) anodes of working cells. These observations are made possible by an in operando duplex technique that utilizes Fourier transform emission spectroscopy (FTIRES) to measure mid-infrared emissive signatures of anode species while near infrared (NIR) thermal imaging simultaneously measures temperature changes with high temporal and spatial resolution. Measurements are collected while an SOFC is operated with steam/methane at 700 °C and under different loads. Related measurements assess carbon removal using steam, indicating that the rate of carbon removal is related to the operational temperature. This conclusion is supported by direct, simultaneous observation of COx gasification products (FTIRES) and anode temperature changes (NIR thermal imaging). Furthermore, surface cooling during steam reforming is different from cooling measured during carbon gasification. These studies show that the steam reforming mechanism during cell operation may be more complex than simple removal of carbon deposits to COx reformates. Ultimately, the goal of these studies is to understand heterogeneous reforming mechanisms under a variety of hydrocarbon fuels, with particular regard to how these are modulated by electrochemical load.

In-operando, optical investigations of carbon gasification by steam in solid oxide fuel cells

251st National Meeting (2016)

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