Structural and impedance analysis of copper doped LSM cathode for IT-SOFCs

Copper-doped lanthanum strontium manganite (LSM) system, La0.8Sr0.2Mn1−xCuxO3−δ (0 ⩽ x ⩽ 0.3), was synthesized using the EDTA-combined citrate process and their characteristics were investigated for solid oxide fuel cell (SOFC) cathode applications. In all compositions, a single perovskite phase was obtained after calcination at 750 °C for 10 h. The maximum electrical conductivity at elevated temperatures was obtained at a composition of x = 0.2 (190 S cm−1 at 750 °C), whereas the sample with x = 0.3 showed the minimum value (100 S cm−1 at 750 °C). The increase in electrical conductivity with increasing Cu contents was attributed to a charge compensating transition of the Mn3+–Mn4+ and the reason for the decreased value, at x = 0.3, is mainly due to the presence of a second phase. The cathode area specific resistance of the sample with x = 0.2 was 4.3 Ω cm2 at 750 °C, which is lower than that of LSM (x = 0). The enhanced performance with the addition of Cu can be explained by the additional Mn4+ promoting the formation of surface oxygen vacancies when Mn4+ is converted to Mn3+ at high temperatures. Copper ion doping at the B-site of LSM affects the formation of oxygen vacancies, which can enhance the oxygen reduction reaction.

► Cu-doped LSM with perovskite structure was synthesized using EDTA combined citrate process.
► The compositions with 0 ⩽ x ⩽ 0.2 showed enhanced electrical conductivity with addition of Cu ion.
► The enhanced ASR was observed with addition of Cu.
► Copper ion doping at the B-site of LSM affected the formation of oxygen vacancies.