Building efficient and durable 3D nanotubes electrode for solid oxide electrolytic cells

Solid oxide electrolytic cells (SOEC) have great potential in CO₂ conversion and energy storage. However, commercial application of SOEC is still challenging due to the sluggish rate of CO₂ electrochemical reduction caused by the arduous activation and limited CO₂ adsorption on cathode surface. In this study, synergetic regulation strategy on intrinsic catalysis activity and surface amelioration is proposed to improve the CO₂ adsorption capacity and increase the adsorption sites. This strategy is demonstrated in a Cu-doped three-dimensional (3D) porous Sr₂Fe_1·3Cu_0·2Mo_0·5O_6−δ(SFCuM) nanotube cathode. The results indicate that SFCuM nanotube shows more oxygen vacancies and excellent oxygen ion conduction. At the same time, the nanostructure provides a larger three-phase reaction interface and more reaction sites for CO₂ reduction reaction (CO₂RR). Benefiting from these merits, the maximum electrolytic current density of the designed SFCuM electrode can be improved to 1.68 A cm⁻² at 750 °C and the related polarization resistance can be lowered to 0.59 Ω cm². In addition, the porous SFCuM nanotube electrode also showed good stability at a constant electrolytic voltage of 1.5 V, with no performance decay during continuous 200-h operation. Such a synergetic regulation strategy may provide some new insight on catalyst design and modification for high-activity CO₂RR electrode.