Sulfur-tolerant cobalt-doped La0.3Sr0.7TiO3-d-perovskite cathode for intermediate-temperature solid oxide electrolysis cell

Abstract

Lanthanum doped strontium titanate (LST) is a perovskite cathode in Solid Oxide Electrolysis Cell (SOEC) which shows great performance in syngas production from CO2 and steam feed. However, the LST type cathode suffers from structural stability. Sulfur containing in industrial exhaust gas can affect its durability which inhibit the technology in real application. Therefore, to improve sulfur tolerance, La0.3Sr0.7Ti1-yCoyO3-δ (LSTC) by adding Co2+ metal ion at B-site when y is 0 to 20%mol was synthesized. Citrate acid-nitrate combustion method was used and the synthesized powder. LST and La0.3Sr0.7Ti0.9Co0.10O3-δ (LSTC0.10) exhibited single phase perovskite while La2O3 and La(OH)3 were observed in other samples. The electrolyte-supported cell was then fabricated instead of the cathode support to test the performance of each La0.3Sr0.7Ti1-yCoyO3-δ. The cell with the LSTC0.10 cathode shows the highest current density at 800 °C compared to the other compositions. The current density was -1.08 A/cm2 at operating voltage of 1.8 V for steam electrolysis. For steam/CO2 co-electrolysis and sulfur tolerance, The LSTC0.10/LSGM/Ag produced the highest current density (-0.91 A/cm2) at 1.8 V. However current density decreased slightly and the area specific resistance (ASR) increased when CO2 and H2S are added in feed. The electrochemical performance decreased for over operation time for 24 h. For LST/LSGM/Ag, the total polarization resistance increased from 6.02 to 8.50 Ω×cm2. And for LSTC0.10/LSGM/Ag, the total polarization resistance increased from 2.82 to 3.87 Ω×cm2