Identification of carbon deposition and its removal in solid oxide fuel cells by applying a non-conventional diagnostic tool

Abstract

Operating solid oxide fuel cells (SOFC) in a specific industry-relevant environment can result in undesired performance alterations and subsequent morphological changes. Conventional characterization tools, such as polarization curve or electrochemical...

Fast online diagnosis for solid oxide fuel cells: Optimisation of total harmonic distortion tool for real-system application and reactants starvation identification

“…For the purpose of this type of measurements, sinusoidal current or voltage amplitude is superimposed to the system running under d.c. (direct current) conditions. The height of the amplitude can vary between 4%-5% of the d.c. load value, fulfilling the main requirement of the linearity of the system under investigation [11][12][13][14][15][16][17]. The measured impedance spectra are correlated to either different processes that occur or specific electrodes, e.g.…”

“…Thus, the main goal when applying this onlinemonitoring tool for real-system application is to not disturb the linear state, but to be able to identify non-linear mechanisms that occur in the system due to undesired failure modes. The pioneering results related to industrial-size cells with a surface of 80 cm 2 revealed very successful application of THD to identify the most relevant failure modes and degradation phenomena in SOFCs, namely (i) fuel starvation and thus implicitly Ni-reoxidation, (ii) air starvation and thus air electrode morphology changes, and (iii) carbon deposition [17,42,43]. The THD application was even helpful to identify carbon removal and SOFC performance regeneration [17].…”

“…The pioneering results related to industrial-size cells with a surface of 80 cm 2 revealed very successful application of THD to identify the most relevant failure modes and degradation phenomena in SOFCs, namely (i) fuel starvation and thus implicitly Ni-reoxidation, (ii) air starvation and thus air electrode morphology changes, and (iii) carbon deposition [17,42,43]. The THD application was even helpful to identify carbon removal and SOFC performance regeneration [17]. On the stack level, THD tool was applied to monitor the level of effective fuel utilisation [44,45].…”

Spatially Heterogeneous Chemistry Observed using NIRTI on SOFC Anodes

“…The fuel flexibility and efficiency demonstrated by SOFCs stem from their high operating temperature (600 -1000 °C), necessitated by the high activation barrier to oxide transport through the electrolyte (23). At these temperatures, the Ni based electrodes have excellent catalytic activity, although they are susceptible to a number of degradation pathways, particularly graphitic carbon formation (also referred to as coking) (7,21,(24)(25)(26)(27)(28)(29)(30).…”