Tailored and Improved Protonic Conductivity through Ba(Z_xCe_10−x)_0.08Y_0.2O_3−δ Ceramics Perovskites Type Oxides for Electrochemical Devices

Acceptor-doped barium zirconate cerate electrolytes constitute prospective materials for highly efficient and environmentally friendly electrochemical devices. This manuscript employs a systematic approach to further optimize ionic conductivity in Ba(Zr_xCe_10−x)_0.08Y_0.2O_3−δ, (1≤x≤9) oxides for moderate temperature electrolysis. We found two new composition variants by fixing a cerium/zirconium ratio of 5/4 at the perovskite B-site with incremental zirconium, an observation that contrasts many reports suggesting a linear decrease in conductivity with increasing zirconium. As a result, the composition BaZr_0.44Ce_0.36Y_0.2O_3−δ demonstrates a superior ionic conductivity (10.1 mS cm⁻¹ at 500 °C) to stability trade-off whereas, BaZr_0.16Ce_0.64Y_0.2O_3−δ exhibits the highest conductivity (11.5 mS cm⁻¹ at 500 °C) among the studied pellets. The high protonic conductivity is associated with a high degree of hydration, as confirmed by thermo-gravimetric analysis. In addition, both compositions as electrolytes allow successful hydrogen production in a steam electrolyzer prototype. Electrolysis voltage as low as 1.3 V is attainable at current densities of 600 and 500 mA/cm² respectively at 600 °C, achieving 82 % current efficiencies with the later electrolyte.