Electrochemical Study of the Versatility of a Solid Cell Working both as Fuel Cell and Electrolysis Modes

A Ni/Yttria-stabilized zirconia (YSZ) cell with a (La 0.60 Sr 0.40) 0.95 Co 0.20 Fe 0.80 O 3- cathode is tested both in fuel cell and electrolysis modes. In fuel cell mode under dry air and wet H 2 , the cell is operated between the Open Circuit Voltage and 0.4 V and reaches 330 mW cm-2 at 850°C for 157 mL min-1 H 2 supply. The influence of temperature and air or hydrogen flow rate is studied, and impedance measurements show that below 0.8 V the electrolyte becomes the more resistive part of the cell. Nevertheless, fuel utilization yields are higher under oxygen or hydrogen depletion. If it is possible at 750°C to work at low voltage during several hours in the entire voltage range, the voltage decrease must be limited at 850°C. The cell can also be operated under wet air. The same cell can be operated in electrolysis mode, and a power density of 340 mW cm-2 can obtained at 0.3V/OCV under 100 mL min-1 wet (3% H 2 O) 5% H 2-95% Ar mixture on the fuel side and dry or wet 100 mL min-1 air flow on the air side. Nevertheless, bubbling air providing the air electrode in salt water has an irreversible detrimental effect on the cell.