Robust bifunctional phosphorus-doped perovskite oxygen electrode for reversible proton ceramic electrochemical cells

Driven by the demand for the sustainable regeneration of clean energy and high-efficiency low-cost energy conversion equipment, reversible proton ceramic electrochemical cells (R-PCECs), which are promising for realizing the mutual conversion between large-scale renewable electric energy and chemical energy, are receiving constant attention. Unfortunately, the sluggish activity of oxygen reduction reaction (ORR) and water oxidation reaction (WOR) for the oxygen electrode in the low and medium temperature ranges and the poor durability of reversible operation block the large-scale application of R-PCECs. Here, a novel oxygen electrode Ba_0.5Sr_0.5(Co_0.8Fe_0.2)_0.95P_0.05O_3-δ (BSCFP0.05) with high electrochemical activity and stability is developed. By partially doping non-metallic phosphorus (P) element into the B-site transition metal of the classic oxygen electrode Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF), the electronic conductivity, ions (O²⁻/H⁺) transport capacity, and hydration ability are all significantly boosted. Especially, a single cell with the BSCFP0.05 electrode achieves an excellent peak power density of 842 mW cm⁻² and an electrolysis current of −1000 mA cm⁻² at 1.3 V at 600 °C. No significant attenuation appears during continuous conversion operation between the fuel cell model and the electrolysis cell model for up to 240 h with the BSCFP0.05 oxygen electrode. These results highly promise non-metal-doped oxygen electrode materials in practical R-PCECs.