Face-sharing structure perovskite air electrodes with boosted oxygen diffusion and durability for reversible protonic ceramic cells

Abstract

Reversible proton ceramic cells (R-PCCs) as highly efficient energy conversion devices can operate at intermediate to low temperatures (400–700 °C). However, the lack of high-performance air electrodes with excellent oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) performance has hindered the development of R-PCCs. In this work, we investigate a face-sharing hexagonal structure perovskite BaCo_0.6Fe_0.4O_3−δ (BCF64) as a highly electrocatalytic air electrode for R-PCCs. The results show that the R-PCCs with the BCF64 air electrode can achieve an impressive peak power density of 1.094 W cm⁻² in fuel cell mode and a current density of −2.584 A cm⁻² at 1.3 V in electrolysis mode at 600 °C. Furthermore, the cells demonstrate excellent stability, achieving 300 h of reversible cycling at 600 °C in dual-mode alternative operation and stable operation for 300 h in individual electrolysis and fuel cell modes, respectively. The density functional theory (DFT) calculations reveal that the face-sharing hexagonal BaCo_0.6Fe_0.4O_3−δ (BCF64) is conducive to decreasing the formation energy of oxygen vacancies and the proton migration energy barrier within the perovskite, thereby enhancing the electrocatalytic performance for ORR/OER processes.