Dual oxygen modulation approach through basicity enhancement and vacancy engineering for high-efficiency CO₂ reduction in solid oxide electrolysis cells

Solid oxide electrolysis cells (SOECs) offer significant potential for the efficient and low-cost conversion of CO₂ into valuable chemical fuels. However, the inadequate stability and electro-catalytic activity of cathode towards the CO₂ reduction reaction (CO₂RR) hamper its further development and application. Herein, Nb element is introduced and used to modify the Sr₂Fe_1.5Mo_0.5O_6-δ matrix perovskite oxide. Notably, a single cell with Sr₂Fe_1.5Mo_0.4Nb_0.1O_6-δ cathode exhibits significantly enhanced current density of 2.20 A cm⁻² at 1.6 V and 800 ℃ for CO₂ electrolysis and exhibits good stability after 160 h continuous test. The improvement originates from the synergistic interplay between optimized lattice oxygen basicity and increased oxygen vacancy concentration induced by the lower electronegativity of Nb incorporation. Density Functional Theory calculations further confirm the formation energy of oxygen vacancies is reduced and the energy barrier for CO₂ adsorption/dissociation is lowered after Nb doping, thereby realizing the faster CO₂ reduction reaction kinetics.