Reduced gas diffusion resistance via modification of negatrode morphology for steam/CO2 co-electrolysis SOEC

Abstract

Solid oxide electrolysis cells (SOECs) exhibit remarkable efficiency in the production of syngas, a mixture of hydrogen and carbon monoxide, owing to their ability to electrolyze steam and carbon dioxide simultaneously. However, the polarization resistance associated with the gas diffusion process in the negatrode (fuel electrode) increases with increasing CO₂ concentrations during steam/CO₂ co-electrolysis. To reduce the gas diffusion resistance in negatrode-supported microtubular SOECs, acrylic resin and graphite are employed as pore formers in the negatrode. Replacing acrylic resin with graphite pore formers enhances the current density from 0.477 to 0.544 A cm⁻² at H₂O/CO₂ = 2 and 700 °C owing to 22 % reduction in the polarization resistance associated with the gas diffusion process at low frequencies below 10 Hz. Focused ion beam-scanning electron microscopy analysis reveals that the fraction of small-pores (less than 2 μm in diameter) is higher in the cell employing the graphite pore former, which helps decrease the polarization resistance associated with the gas diffusion process in the negatrode. Thus, optimizing the negatrode microstructure is crucial to enhancing the performance of co-electrolysis SOECs.