Thin film proton conducting membranes for micro-solid oxide fuel cells by chemical solution deposition

作者：Engels J; Griesche D; Waser R; Schneller T^*

来源：Thin Solid Films, 2017, 636: 446-457.

DOI：10.1016/j.tsf.2017.06.038

• Proton conducting material
• Yttrium-doped barium zirconate
• Chemical solution deposition
• Spin coating
• Thin-film electrolyte
• Solid oxide fuel cell

Micro solid oxide fuel cells (mu-SOFC) were manufactured with perovskite type proton conductors on silicon substrates and with structured Pt-grid electrodes. In order to miniaturize the mu-SOFCs and to shorten the ion path through the electrolyte, the thin film proton conductors were only similar to 510 nm thick. The thin films consist of 10 mol% yttrium-doped BaZrO3 (BZY10) and they were deposited by means of chemical solution deposition (CSD). CSD was applied, because it represents a highly attractive fabrication method, considering the relatively low investment costs and flexibility with regard to stoichiometry. The backsides of the mu-SOFCs on the substrates were opened by wet chemical and plasma etching to form the freestanding membranes. The completed mu-SOFCs resist up to a temperature of 450 degrees C. Their electrical properties, such as permittivity, and resistivity were investigated. By means of electrochemical impedance spectroscopy (EIS) in the temperature range of 100 degrees C to 450 degrees C, the resistivity properties and the activation energies of the model mu-SOFC were studied with humid hydrogen in nitrogen at the anode and different oxygen partial pressures at the cathode. The results provide a clear hint for a dominating protonic defect transport mechanism in the electrolyte. In the 450 degrees C measurement, the model mu-SOFCs reached an open circuit voltage of 600 mV with 100% oxygen at the cathode and humid hydrogen in nitrogen at the anode.