Combining proton conductor BaZr0.8Y0.2O3-δ with carbonate: Promoted densification and enhanced proton conductivity

We report here that a carbonate can promote the densification and enhance the conductivity of a refractory proton conductor (BaZr0.8Y0.2O3-δ, BZY). Densification of BZY has been successfully demonstrated at as low as 600 °C in the presence of carbonate. The ionic conductivities of the carbonate-added BZY reach 0.33 and 0.38 S/cm at 600 °C in 3%H2O-air and in 3%H2O-H2, respectively. The observation of ionic conductivity increasing with PH2O and PH2 suggests protons as the charge carriers. A new proton transfer and exchange mechanism between oxide and carbonate phases is proposed to interpret the enhanced proton conductivity. A fuel cell based on the composite electrolyte (1 mm-thick), a LiNiO2-MPCC (Mixed Proton and Carbonate-ion Conductor) cathode, a BZY-NiO anode blocking layer and a Ni anode yields 114 mW/cm2 at 670 °C.

► Carbonate-promoted densification of refractory BaZr0.8Y0.2O3-δ ► Carbonate-enhanced proton conductivity ► New proton transfer and exchange mechanism ► Novel anode blocking layer