The excellence of La(Sr)Fe(Ni)O3 as an active and efficient cathode for direct CO2 electrochemical reduction at elevated temperatures

Abstract

To effectively reduce and utilize the atmospheric CO₂, electrochemical conversion of CO₂ into CO using an efficient and stable cathode in a high temperature solid oxide electrolyzer has attracted extensive interest. A composite cathode based on lanthanum nickelate potentially opens up the possibility for CO₂ electrolysis. Herein, we developed a new Ni-doped La(Sr)FeO_3−δ material, which has been firstly fabricated as a cathode for CO₂ electrolysis in a solid oxide electrolysis cell (SOEC). The ultra-low total polarization resistance, together with an impressive current density of 1.21 A cm⁻² at a potential of 1.55 V and 850 °C, demonstrates the superior electrocatalytic activity of La_0.6Sr_0.4Fe_0.8Ni_0.2O_3−δ (LSFN) for stably and effectively promoting the cathodic kinetics for the CO₂ electrolytic reaction. Moreover, an ultra-high Faraday efficiency of ∼99.7% was achieved at an applied potential of 1.0 V (vs. OCV) and 850 °C. The comparable cell performance for CO₂ electrolysis benefits from the extension of the reactive sites due to the improved mixed ionic and electronic conductivity and accelerated adsorption and diffusion of the adsorbed active species, resulted from the high oxygen vacancy introduced on the LSFN backbone surface. Besides the comparable electrochemical performance, the excellent redox reversibility between the reduction and re-oxidation as well as considerable coking tolerance towards CO-enriched gas reveals that this newly prepared La(Sr)Fe(Ni) is a potential cathode material for SOEC, particularly for a direct carbon-abundant cell.