Reversible Operation of Metal Supported Solid Oxide Cells

Abstract

Solid oxide cells (SOCs) can operate in fuel cell and electrolysis mode. This option allows for production of electricity and heat from a green fuel in fuel cell mode and for storage of electricity as gas or use as fuel in electrolysis mode. Demonstration of reversible SOCs has progressed over the last few years. Increase of lifetime and reduction of costs are major factors for successful commercialization. In metal supported SOCs (MSCs) the thickest layer in the cell, the support layer of a few hundred µm, uses metal instead of Ni/YSZ cermet as in state-of-the-art (SoA) fuel electrode supported cells, thereby enabling a significant cost reduction. The present study investigates SoA Ni/YSZ SOCs and MSCs, fabricated by tape casting, lamination, and screen-printing, in reversible operation at 650oC in 50/50 steam/hydrogen. In the initial few hundred hours, the degradation rate in electrolysis mode is smaller on a MSC compared to a SoA Ni/YSZ cell, while they are comparable in fuel cell mode. According to electrochemical impedance evaluation, the degradation is due to a simultaneous increase of the serial and polarization resistances in the MSC, while it is mainly due to an increase of the polarization resistance in the SoA cell.