Ba_(0.5)Sr_(0.5)(Co_(0.8)Fe_(0.2))_(1-x)Ta_xO_(3-δ) perovskite anode in solid oxide electrolysis cell for hydrogen production from high-temperature steam electrolysis

摘要

Among perovskite anodes in solid oxide electrolysis cell (SOEC), Ba0.5Sr0.5Co0.8Fe0.2O3-delta (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 - Ba0.5Sr0.5(Co0.8Fe0.2)(1-x)TaxO3-delta (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 degrees C and H2O to H-2 ratio of 70:30). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.