Dual-Doping Strategy for Lowering the Thermal Expansion Coefficient and Promoting the Catalytic Activity in...

Lowering the thermal expansion coefficient (TEC) and promoting the catalytic activity of cobalt-based perovskite air electrodes is crucial for efficient solid oxide cells (SOCs) devices. However, the co-achievement of both merits has usually been largely compromised in most scenarios. Herein, a dual-doping strategy to manipulate the properties of perovskite cobaltate electrocatalyst is reported in which a high valence element of Ta⁵⁺ is incorporated into B-site to significantly suppress the dynamic reduction of Co⁴⁺ species and reduces the TEC value from PrBaCo₂O_5+δ (PBC, 17.8 × 10^⁻6 K^-1) to PrBaCo_1.96Ta_0.04O_5+δ (PBCT, 12.5 × 10⁻⁶ K^-1) and suppresses the oxygen loss in SOCs operation condition, revealing the improved structural stability. Meanwhile, the Ca²⁺ is doped into A-site of Ta-incorporated candidate, further decreasing the covalency of Co─O bonds and facilitating the formation of oxygen vacancies, benefiting the oxygen exchange kinetics and leading to a low polarization resistance of 0.026 Ω cm² (800 °C) in as-prepared PrBa_0.8Ca_0.2Co_1.96Ta_0.04O_5+δ (PBCCT) electrode. The cell with PBCTT demonstrates remarkable robustness during a 50 h thermal cycling test (25 cycles). Moreover, it delivers a high current density of 1.44 A cm⁻² (1.6 V, 800 °C), as well as attractive durability over 100 h for pure CO₂ electrolysis.