Lattice Incorporation of Cu²⁺ into the BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3−δ Electrolyte on Boosting Its Sintering and Proton-Conducting Abilities for Reversible Solid Oxide Cells

Lattice modification by incorporating heteroatoms could effectively and precisely tune their intrinsic properties to get improved sinterability and electrochemical performance. Here, by introducing Cu2+ into the interstitial position of a ABO3-type perovskite, a 2 times higher protonic conductivity (1.9 × 10–2 S cm–1 at 700 °C) and low-temperature (1200 °C) sinterability were achieved for the BaCe0.68Zr0.1Y0.1Yb0.1Cu0.02O3−δ (BCZYYC2) electrolyte, compared to the precursor electrolyte. Meanwhile, the modified BCZYYC2 also exhibits excellent chemical stability in high-temperature and high-humidity conditions, as well as good compatibility with the components of cell. When used as the electrolyte in reversible fuel cell (FC)/electrolysis cell (EC) operational modes, the reversible solid oxide cell with the BCZYYC2 electrolyte illustrates prominent FC (0.85 W cm–2 at 700 °C) and EC (−1.96 A cm–2 at 700 °C and 1.3 V) performances with high film–electrolyte conductivity (8.7 × 10–3 S cm–1 at 700 °C). Additionally, an obvious increase in current density is observed during the short-term stability test, which has shown great promise for their practical application.