Synergistic modulation of oxygen vacancies and electronic structure for efficient CO₂ electroreduction in perovskite cathodes

The development of efficient cathode materials for high-temperature CO₂ electrolysis in solid oxide electrolysis cell (SOEC) is critically limited by insufficient CO₂ adsorption and sluggish interfacial reaction kinetics. Herein, Ti⁴⁺ is introduced into Sr₂Fe_1.5Mo_0.5O_6-δ perovskite oxide to simultaneously regulate oxygen vacancy and electronic structure. The valence mismatch between Ti⁴⁺ and Mo⁶⁺ thermodynamically promotes oxygen vacancy formation, while the d⁰ electronic configuration of Ti enhances the electron-donating capability of lattice oxygen. Experimental results demonstrate that Ti⁴⁺ doping increases oxygen vacancy concentration and enhances oxygen transport kinetics. Combined with density functional theory calculations, Ti⁴⁺ doping is found to improve the electron density of oxygen ions adjacent to oxygen vacancies and enhance CO₂ adsorption capability, as indicated by the more negative adsorption energy from −0.76 to −1.48 eV, thereby facilitating electron transfer and promoting carbonate intermediate formation. The optimized cathode delivers a current density of 1.62 A·cm⁻² at 1.8 V while maintaining a near-unity Faradaic efficiency. The single cell operates steadily for 120 h and no noticeable deterioration is observed during electrolysis. These results demonstrate that Ti⁴⁺ incorporation effectively regulates oxygen vacancy chemistry and lattice oxygen electronic structure, providing a robust design strategy for enhancing the electrochemical conversion of CO₂ in SOEC cathodes.