High catalytic activity of Fe-based perovskite fuel electrode for direct CO2 electroreduction in SOECs

A solid oxide electrolysis cell (SOEC) can effectively convert greenhouse gas CO2 to fuel gas CO by using renewable electricity and industrial waste heat for sustainable development. However, this state-of-the-art Ni-based ceramic fuel electrode suffers from the degradation of coking deposition and Ni aggregation in CO2 atmosphere. Herein, we report Nb substitution for ferrite-based perovskite oxides La0.6Sr0.4Fe1-xNbxO3-delta (x = 0, 0.05, 0.1, 0.15, LSFNbx) as potential fuel electrodes for the direct electrolysis of CO2 in SOEC. Doping Nb into Fe site greatly enhances the redox stability of LSF and restrains the surface Sr segregation under oxidizing/reducing condition. Among the samples, LSFNb0.1-GDC (La0.6Sr0.4Fe0.9Nb0.1O3-delta-Gd0.1Ce0.9O2-delta) presents the lowest polarization resistance under different applied voltages at 800 degrees C. Distribution of re-laxation times analysis shows that Nb doping could significantly improve the catalytic activity in CO2 reduction reaction and accelerate surface adsorption/dissociation. Meanwhile, the electrolyte-supported single cell with LSFNb0.1-GDC fuel electrode achieves a current density of 0.85 A cm(-2) at 1.5 V and 800 degrees C, which is 25% higher than that of LSF. Moreover, the LSFNb0.1-GDC single cell presents good stability at a constant voltage of 1.2 V for 40 h, demonstrating excellent coking resistance for pure CO2 electrolysis. This work suggests that Nb doping is a promising strategy to enhance the redox stability and catalytic activity of ferrite-based perovskite fuel electrode for SOEC. (C) 2021 Elsevier B.V. All rights reserved.