Reversible solid oxide cells (SOCs) are unique devices that perform interconversion between chemical energy (particularly hydrogen) and electricity, providing efficient energy storage for site-specific and weather-dependent solar and wind resources. One of the key requirements for achieving high-performance reversible SOCs is the development of highly active bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we investigate a La0.2Sr0.8Co0.8Fe0.2O3−δ(LSCF2882) material as a novel oxygen electrode for reversible SOCs at intermediate temperatures. Unlike most widely used La0.6Sr0.4Co0.2Fe0.8O3−δ(LSCF6428) with a rhombohedrally distorted perovskite structure, LSCF2882 possesses a simple cubic perovskite structure with a symmetric BO6octahedral network. Furthermore, the 3D bond valence sum calculation of the LSCF2882 structure suggests a reduction in oxygen ion conduction barrier energy. Oxygen surface exchange (kchem) and diffusion (Dchem) coefficients of LSCF2882 determined by electrical conductivity relaxation are consistently remarkably higher by >2 and 20 times compared to those of LSCF6428 at 700 °C, respectively. This result is further supported by a 43% reduction in the oxygen vacancy formation energy of LSCF2882 determined from density functional theory calculations. The reversible SOCs with LSCF2882 oxygen electrodes greatly outperform LSCF6428 cells in both fuel cell (2.55 W cm−2) and electrolysis mode (2.09 A cm−2at 1.3 V) at 800 °C, with excellent reversible cycling stability. Our findings strongly suggest that LSCF2882 is a promising candidate as a bifunctional oxygen electrode for high performance reversible SOCs at reduced temperatures.
|Number of pages||15|
|Journal||Journal of Materials Chemistry A|
|State||Published - 7 Mar 2021|
Bibliographical noteFunding Information:
This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2019M3E6A1103944, 2021M3H4A1A01002695 and 2020R1A2C2010690). This work was also supported by the Global Frontier R&D Program of the Center for Multiscale Energy Systems funded by the National Research Foundation under the Ministry of Science and ICT, Republic of Korea (2014M3A6A7074784).
© The Royal Society of Chemistry 2021.