Preparation and characterization of silver-modified La_(0.8)Sr_(0.2)MnO_3 cathode powders for solid oxide fuel cells by chemical reduction method

摘要

Herein a chemical reduction method is proposed in order to modify the solid oxide fuel cells (SOFC) traditional cathode material La_(0.8)Sr_(0.2)MnO_(3-x) (LSM). Silver nanoparticles were prepared by the reduction of ammoniacal silver nitrate with ascorbic acid in dilute aqueous solutions containing PVP. The obtained LSM-Ag composite powders were characterized by XRD, SEM, EDX, and STEM. The results showed that the LSM-Ag composite powder possess an elaborated fine structure with a homogeneous distribution of Ag and LSM, which effectively shortens the diffusion pathway for electrons and adsorbed oxygen. The electrochemical performance of the LSM-Ag cathode with different Ag loadings was investigated. A cathode loading with 1 wt.% Ag exhibited an area specific resistance as low as 0.45 n cm~2 at 750 ℃, compared to around 1.1 Ω cm~2 for a pure LSM electrode. Similarly an anode-supported SOFC with 1 wt.% Ag in the cathode shows a peak power density of 1199 mW cm~(-1) higher than the value of 717 mW cm~(-1) achieved for a similar cell with a LSM cathode. Increasing the Ag loading is shown to have an insignificant effect on improving electrocatalytic performance at 750 ℃, however it can increase output power at 650 ℃.