Oxygen electrode reactions of doped BiFeO3 materials for low and elevated temperature fuel cell applications

Abstract

Perovskite-based catalysts have been considered as candidate bifunctional electrocatalysts for oxygen evolution (OER) and reduction reactions (ORR) for unitized regenerative fuel cells (URFCs), because of their excellent catalytic activity and durability at low temperature. Furthermore, perovskite-structured materials can be utilized as an oxygen electrode material for solid oxide fuel cells (SOFCs) at even elevated temperatures due to their distinctive layered structure, providing great flexibility regarding the modification of their electronic configurations. Herein, we investigate whether alkaline earth metal-doped bismuth iron oxides (Bi_0.6M_0.4FeO₃, M = Ba, Sr, Ca, and Mg) can act as both bifunctional catalysts for URFCs and cathode materials for SOFCs. Among these, Bi_0.6Ca_0.4FeO₃ (BCFO) exhibits remarkable OER and ORR catalytic performances, with better long-term stability than that of a pristine BiFeO₃ (BFO) catalyst in alkaline media at room temperature. Moreover, the DC conductivity of BCFO is more than 2 to 3 orders of magnitude higher than that of the BFO material at 500–700 °C for SOFCs. In addition, BCFO has a α_TEC value of 12.4 × 10⁻⁶ K⁻¹ at 25–650 °C, which is near those of yttria-stabilized zirconia and rare-earth-doped ceria electrolytes. Hence, BCFO demonstrates potential as an oxygen electrode material for operation at room and elevated temperatures.