Micro-solid oxide fuel cells using free-standing 3 mol.% yttria-stabilised-tetragonal-zirconia-polycrystal electrolyte foils

Ultrathin 3 mol.% yttria-stabilised-tetragonal-zirconia-polycrystal (Y-TZP) foils with thicknesses of 1–10 μm are fabricated by a new wet-chemical processing route. The foils are free-standing, semi-transparent and flexible. The in-plane electrical conductivity of the Y-TZP foil is 0.03 S m−1 at 500 °C. Cross-plane impedance measurements with sputtered Pt electrodes yield two arcs, of which the high-frequency arc is attributed to the ohmic resistance of the electrolyte and the low-frequency arc to the electrode–electrolyte interface. A symmetrical micro-solid oxide fuel cell (SOFC) is designed using this ultrathin free-standing Y-TZP foil as the electrolyte and sputtered Pt electrodes. An open-circuit voltage of 0.98 V and a maximum power density of 12 mW cm−2 are measured at 500 °C. These results prove the feasibility of this approach to the fabrication of miniaturised planar SOFCs without the need for microfabrication.

► Ultrathin 1–10 μm yttria-stabilised-tetragonal-zirconia-polycrystal (Y-TZP) foils. ► Free-standing Y-TZP foils as electrolyte in micro-solid oxide fuel cells (micro-SOFC). ► Y-TZP foil has an in-plane electrical conductivity of 0.03 S m−1 at 500 °C. ► Micro-SOFC with an OCV of 0.98 V and a max. power density of 12 mW cm−2 at 500 °C. ► New approach to the fabrication of micro-SOFCs without any microfabrication.