Carbon Tolerant Electrodes for SOFC and Reversible SOFC (RSOFC) Cells Operating on Carbon Containing Fuels

Abstract

Solid Oxide Fuel Cells (SOFC) and Electrolyzers (SOEC) hold great potential for the security of energy sector, providing solutions for efficient power generation and production of hydrogen and synthesis gas. A challenging barrier for the successful implementation of SOFC and SOEC technologies, remains the long term stability under realistic operating conditions by the effective control and minimization of degradation due to carbon built up. The problem arise from the fact that the commonly used anode cermets, e.g. Ni-YSZ and Ni-GDC, are prone to carbon deposition onto nickel, as a result of the Boudouard reaction (CH4cracking, disproportionation of CO), leading to low activity and fast degradation. In this study, a class of Au-modified commercially available NiO/GDC and NiO/YSZ cermet powders has been developed and studied for their performance and tolerance to carbon deposition, operating as SOFC anodes for CH4 steam reforming, as well as bi-functional electrodes in a Regenerative SOFC operating on the CO2 cycle (SOEC mode: electrolysis of CO2, SOFC mode: electrochemical reaction of CO and oxygen for power generation). In- situ HT-XRD tests revealed that the presence of Au, in an optimum nominal loading of 3wt%, affects the Ni crystal phase and has a significant positive effect in inhibiting carbon deposition. The results from cell testing in the temperature range of 800-1000°C, showed promising, stable performance of electrodes under carbon forming conditions (e.g. H2O/CH4=0.25, CO or CO/CO2mixtures of 0.7/0.3). The work is supported by the FCHJU project T-CELL (298300).