Magnesium tuned triple conductivity and bifunctionality of BaCo0.4Fe0.4Zr0.1Y0.1O3-δ perovskite towards reversible protonic ceramic electrochemical cells

The performance of reversible protonic ceramic electrochemical cells (R-PCECs) was significantly limited, due to lack of suitable air electrode materials specifically designed to match proton conducting electrolyte. Here, we report by doping a small amount of magnesium (5 %), a phase-pure triple conducting Ba(Co0.4Fe0.4Zr0.1Y0.1)0.95Mg0.05O3-δ (BCFZYM) perovskite is developed as an air electrode for R-PCECs. The doping of 5 % Mg effectively enhances oxygen/steam surface exchange, oxygen-ion and proton conductivity, consequently significantly improves catalytic oxygen reduction and evolution reactions (ORR/OER) activities over protonic electrolytes. R-PCECs with the BCFZYM display excellent performances in both fuel cell (850 mW cm-2 at 600 °C) and electrolysis modes (−1244 mA cm-2 at 1.3 V at 600 °C). In addition, the R-PCECs show favorable stability in cycling (110 h), electrolysis (200 h) and fuel cell modes (300 h), demonstrating that BCFZYM air electrode has excellent operating stability.