Investigation into the effect of Fe-site substitution on the performance of Sr2Fe1.5Mo0.5O6−δ anodes for SOFCs

Abstract

Ni-substituted Sr₂Fe_1.5−xNi_xMo_0.5O_6−δ (SFNM) materials have been investigated as anode catalysts for intermediate temperature solid oxide fuel cells. Reduced samples (x = 0.05 and 0.1) maintained the initial perovskite structure after reduction in H₂, while metallic nickel particles were detected on the grain surface for x = 0.2 and 0.3 using transmission electron microscopy. Temperature programmed reduction results indicate that the stable temperature for SFNM samples under reduction conditions decreases with Ni content. In addition, X-ray photoelectron spectroscopy analysis suggests that the incorporation of Ni affects the conductivity of SFNM through changing the ratios of Fe³⁺/Fe²⁺ and Mo⁶⁺/Mo⁵⁺. Sr₂Fe_1.4Ni_0.1Mo_0.5O_6−δ shows the highest electrical conductivity of 20.6 S cm⁻¹ at 800 °C in H₂. The performance of this anode was further tested with electrolyte-supported cells, giving 380 mW cm⁻² at 750 °C in H₂, hence demonstrating that Ni doping in the B-site is beneficial for Sr₂Fe_1.5Mo_0.5O_6−δ anode performance.