Co-electrolysis of H2O and CO2 in a solid oxide electrolysis cell with hierarchically structured porous electrodes

Abstract

A solid oxide electrolysis cell with novel asymmetric-porous structured electrodes has been fabricated by the combination of freeze-drying tape-casting and impregnation methods. The electrodes possess unique channel-like pores with nano- or sub-micron-sized catalysts homogeneously coated on the inner face of the porous scaffold. The straight channel-like pores in the electrodes facilitate mass transport while the nano- or sub-micron-sized catalysts promote the electrode electrochemical reactions. The cell demonstrates low electrode polarization resistance values of 0.27, 0.19 and 0.14 Ω cm² at OCV in 50 vol% H₂O–25 vol% H₂–25 vol% CO₂ at 800, 850 and 950 °C, respectively. The cell DC voltage–current density dependence is generally linear at all temperatures, and high current densities of 0.8, 1.1 and 1.66 A cm⁻² for 50 vol% H₂O–25 vol% H₂–25 vol% CO₂ co-electrolysis have been obtained with 1.30 V applied voltage at 800, 850 and 900 °C, respectively. Compared to that of the cell fabricated by conventional or phase-inversion methods, the mass transportation limitation phenomenon in the porous electrodes is mitigated and cell performance is greatly improved.