Co-Electrolysis of Steam and Carbon Dioxide in Solid Oxide Cells

Reduction of H 2 O and CO 2 as well as oxidation of H 2 and CO was studied in a Ni/YSZ electrode supported Solid Oxide Cell (SOC) produced at DTU Energy conversion (former Risø DTU).Even though these Ni/YSZ based SOCs were developed and optimized for fuel cell use, they can work as reversible SOCs in mixtures of H 2 O, H 2 , CO 2 and CO.From polarization (i-V) and electrochemical impedance spectroscopic characterization, it is evident that, electrochemical reduction of both CO 2 and H 2 O occurs during coelectrolysis of H 2 O and CO 2 in these Ni/YSZ based SOC.During co-electrolysis, the equilibrium of the water gas shift reaction is reached, and CO is therefore produced via the water gas shift reaction also.Significant differences during oxidation/reduction in H 2 O -H 2 and CO 2 -CO mixtures were observed implying that different reaction mechanisms apply for the mixtures.