Experimental identification of the impact of direct internal and external methane reforming on SOFC by detailed online monitoring and supporting measurements

Solid Oxide Fuel Cells (SOFCs) are able to use biogas or natural gas with its main compound methane as fuel but utilization of methane bears risks which can lead to early performance loss. Application of a suitable type of methane reforming as well as online monitoring tools and a holistic knowledge about possible degradation mechanisms can limit degradation rates. Here, we compare direct internal reforming and external methane reforming on a large planar SOFC with an active area of 80cm² at different operating temperatures and methane flow rates. To do so, the measured temperature distribution, applied electrochemical impedance spectroscopy and its advanced tool distribution of relaxation times (DRT) as well as results from post mortem microscopic analysis are used. We observed that the ohmic resistance and high frequency peaks in the DRT spectra seem to be influenced not only by the average cell temperature but also by direct internal reforming (DIR) conditions. Furthermore, we observed that high temperature gradients induced by DIR could lead to or accelerate damages of the cells structure and the sealing. The results presented in this work are useful to control or manage safe SOFC operation with C containing fuels for real world SOFC applications.