Dual Cells with Mixed Protonic-Anionic Conductivity for Reversible SOFC/SOEC Operation

The dual cell concept is a novel design for solid oxide fuel cells operating at intermediate temperature. The cell comprises a series of five layers with different compositions, alternating two dense electrolytes and three porous layers, i.e. the outer electrodes and a central membrane. The dual cell concept makes it possible to separate the compartment for water formation from both fuel and oxidant chambers. Such a three-chamber configuration gives many advantages related to fuel dilution, materials corrosion, and reversibility between fuel cell and electrolyser operational modes (SOFC/SOEC) at high temperature. Dual conductivity (protonic/anionic) can be achieved by joining two dense BaCe0.85Y0.15O3-δ (BCY) and Ce0.85Y0.15O2-δ (YDC) electrolytes through a porous ceramic central membrane made up of both materials. Complete anode-supported dual cells have been fabricated by a combination of pressing, casting, printing, wet spraying, and plasma spraying techniques. Electrochemical tests carried out by impedance spectroscopy showed the feasibility of the concept and successful reversible operation of the dual cell. The fabrication route, the microstructural and electrochemical testing results are reported in this work, and partially compared to simulated results from an electrochemical model developed describing the dual cell concept.