Regulating catalytic activity with geometry distortion of Sr2FeMoO6 anode

The strong coupling between functional properties and geometry distortion is acknowledged as a distinctive feature of ABO₃ perovskite. In particular, defect chemistry has been suggested as a critical factor affecting electrochemical reaction. In order to unravel the microscopic link between geometry distortion and catalytic activity of perovskite electrode, the electrochemical performance of Sr₂(Fe_0.9V_0.1)MoO₆ (S(FV)M) and Sr₂Fe(Mo_0.9V_0.1)O₆ (SF(MV)) anodes is investigated in this work. From S(FV)M to SF(MV), FeO₆ octahedral evolves from being stretched to being compressed, while MoO₆ octahedral evolves from being flattened to being expanded. Accompanied with such distortion, S(FV)M anode holds much higher content of oxygen vacancy than SF(MV) anode. Consequently, S(FV)M anode exhibits rapid oxygen ion diffusion in EIS test. Besides, the higher conductivity of S(FV)M is also conducive to the charge-transport process. Thus, the electrochemical reactions on S(FV)M anode proceed rapidly and excellent performance is obtained. At 850 ℃, the maximum power densities of S(FV)M- and SF(MV)- based cell is 810 mW·cm^-2 and 547 mW·cm^-2 respectively, i.e. the difference attains ⁓ 32.4%. Above results demonstrate the critical role of geometry distortion on electrochemical activity of Sr₂FeMoO₆ electrode. The innovation of this work is that simple structural distortion is introduced by doping the same element into different sub - lattice, excluding the influence of other factors, such as different electronegativity, ionic radius or chemical character. What´s more, understanding the critical role of geometry distortion is beneficial to achieving the highly active and durable catalysts for SOFC.