Ba0·5Sr0·5(Co0·8Fe0.2)1-xTaxO3-δ perovskite anode in solid oxide electrolysis cell for hydrogen production from high-temperature steam electrolysis

Among perovskite anodes in solid oxide electrolysis cell (SOEC), Ba_0·5Sr_0·5Co_0·8Fe_0·2O_3-δ (BSCF) has gained much attention due to its dominantly high performance. However, the BSCF still suffers from chemical instability. In this study, the B-site of BSCF is partially substituted by a higher valence Ta⁵⁺ (5, 10, 15 and 20 mol%) to improve its structural stability - Ba_0·5Sr_0·5(Co_0·8Fe_0.2)_1-xTa_xO_3-δ (BSCFTax, 0 ≤ x ≤ 0.20). It is found that doping with higher valence Ta⁵⁺ increases both chemical stability and electrochemical performance of BSCF. Although the BSCFTa0.10 shows the lowest oxygen vacancies indicating by the ratio of adsorbed oxygen vacancies (O_adsorbed) to lattice oxygen (O_lattice), the electrochemical performance increases. The decrease in Co³⁺/Co⁴⁺ ratio results in increasing electronic conductivity in the anode. It is likely that proper amount of Ta⁵⁺ doping provide a balance between ionic and electronic conductivity in the anode and improved electrochemical performance. The symmetrical half-cells with electrolyte support (BSCFTa/YSZ/BSCFTa) are fabricated to determine the area specific resistance (ASR) and activation energy of conduction - BSCFTa0.10 shows the best performance. Cathode-supported Ni-YSZ/YSZ/BSCFTa0.10 also shows higher durability than Ni-YSZ/YSZ/BSCF (operating at current density ?0.45 A cm^?2 in electrolysis mode, 80 h, 800 °C and H₂O to H₂ ratio of 70:30).