Achieving excellent and durable CO₂ electrolysis performance on a dual-phase fuel electrode in solid oxide electrolysis cells

Conversion of CO₂ into valuable chemicals through solid oxide electrolysis cells (SOECs) is a promising technology towards efficient utilization of CO₂ and reducing its emission. However, the well-established Ni-cermet fuel electrode is not applicable for high-concentration or pure CO₂ electrolysis due to the Ni oxidation and coking issues. Here, we report that a novel nominal Pr_0.2Ca_0.8Fe_0.8Ni_0.2O_3-δ perovskite fuel electrode, which is self-assembled into Pr(Ca)Fe(Ni)O_3-δ perovskite and Ca₂Fe₂O₅ brownmillerite dual-phase composite during the calcination process, possesses efficient CO₂ electrolysis activity. The presence of Ca₂Fe₂O₅ with abundant oxygen vacancies significantly improves CO₂ chemical adsorption and activation and Pr(Ca)Fe(Ni)O_3-δ serves charge carrier matrix, and consequently leads to a high CO₂ reduction reaction rate constant of 1.104 × 10⁻⁴ cm⁻¹ at 800 °C as determined by the electrical conductivity relaxation method. The electrochemical performance of pure CO₂ electrolysis is investigated in model SOECs, exhibiting an excellent current density of 0.648 Acm⁻² at 1.5 V and 800 °C. Moreover, the cell shows no noticeable degradation under two constant current densities of 0.421 Acm⁻² at 800 °C and 0.3 Acm⁻² at 700 °C for nearly a total of 300 h. The present study reveals a novel strategy to develop dual-phase Pr(Ca)Fe(Ni)O_3-δ-Ca₂Fe₂O₅ materials as a reliable electrode for pure CO₂ electrolysis. © 2021 Elsevier B.V.