Pressurization of solid oxide fuel cells for innovative energy systems with ultra-low CO2 emissions

Integrating solid oxide fuel cells (SOFCs) in power generation cycles is a prominent solution to decarbonize the energy sector. Accordingly, novel power cycles require operating the SOFCs stack at high pressure and high fractions of CO2 in the oxidant stream, to ease coupling with oxy-combustion cycles designed for CO2 capture. Here, we study the performance and durability of state-of-the-art Ni-YSZ anode-supported button SOFCs, with YSZ electrolyte and LSCF-GDC/LSC composite cathode (La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O2-δ/La0.6Sr0.4CoO3-δ), operated at 31 bar and 700°C for 170 h, with a cathodic O2/CO2 feed mixture (21% O2 and 79% CO2) and anodic 3% humidified hydrogen. The interaction between this O2/CO2 mixture and the cathode's perovskites is also investigated with time-resolved in situ XRD synchrotron experiments, performed at 31 bar and 700°C. Pressure boosts the SOFC's performance, more than doubling the current density at 0.7 V (from 266.4 mA/cm2 at 1 bar to 645 mA/cm2 at 31 bar). Conversely, CO2 leads to tolerable performance loss due to SrCO3 formation (−0.16%/h current density decay at 0.85 V), followed by stabilization within 85 h. Modelling shows that the beneficial effect of pressure is due to accelerated anodic kinetics, which prevail over the inhibition of the cathodic kinetics caused by CO2.