Chemical stability and electrochemical properties of CaMoO3−δ for SOFC anode

In an effort to develop alternative anode materials based on mixed conducting ceramics capable of offering high mixed ionic–electronic conductivity, stability to redox cycles, and limited activity for carbon formation to Ni/YSZ cermets, CaMoO3 ceramics for application as a solid oxide fuel cell (SOFC) anode material were synthesized as a function of temperature and oxygen partial pressure (pO2). CaMoO3 perovskite-dominant powders were obtained by reducing the CaMoO4 showing a structure of orthorhombic unit cells with the following lattice parameters: a = 5.45 Å, b = 5.58 Å, and c = 7.78 Å. The equilibrium total conductivity of CaMoO3, measured by DC 4-probe method in 5% H2/balance N2 condition (pO2 ≈ 10−22 atm) at various temperatures, decreased with increasing temperature below 400 °C, indicating metallic properties with an activation energy of 0.028 eV. Between 400 °C and 600 °C, the equilibrium total conductivity slightly increased, and finally sharply decreased at 800 °C. The Mo metal precipitation during measurement was thermodynamically proved by the predominance diagram for CaMoO3. Finally, a fuel cell with CaMoO3 anode exhibited poor performance with a maximum power density of only 14 mW/cm2 at 900 °C, suggesting that further research is needed to enhance the ionic conductivity and thus improve the catalytic properties.