Self-assembled FeRu bimetallic nanocatalysts for efficient and durable mutual CO–CO₂ conversion in a reversible solid oxide electrochemical cell

Herein, we report a phase-transformed fuel electrode to carry out the reversible CO–CO₂ conversion in a reversible solid oxide electrochemical cell (RSOC), which is composed of self-assembled FeRu bimetallic nanoparticles and Ruddlesden-Popper Pr_0.8Sr_1.2Fe_1−x−yRu_xMo_yO₄ (FeRu@PSFRM). Electrochemical impedance spectra and their corresponding distribution of relaxation time demonstrate that the sub-electrode reaction process in the frequency ranging 10⁰–10² Hz, including the gas adsorption, dissociation, and ionization reactions on the electrode surface, predominantly dominates the entire electrode reaction process. The single cell with the FeRu@PSFRM fuel electrode generates a maximum output power density of 170 W cm⁻² at 800°C in the solid oxide fuel cell (SOFC) mode, while yields a current density of −0.256 A cm⁻² at 1.3 V in the solid oxide electrolysis cell (SOEC) mode. In addition, the reliable reversible CO–CO₂ mutual conversion has experienced “activation-stabilization-degradation” three obvious stages in the first 42-h SOFC-SOEC cycling testing. Fortunately, the degraded fuel electrode can be regenerated by oxidizing it in the oxidizing gas and then retreating in the reductive atmosphere. Our findings reveal that the FeRu@PSFRM material generated by the in-situ exsolution technique is a promising fuel electrode candidate for efficient and durable mutual CO–CO₂ conversion in a RSOC.