Effect of Current Collecting Materials on the Performance of the Double-Perovskite Sr2MgMoO6-δ Anode

The performance of the double-perovskite Sr 2 MgMoO 6-δ (SMM) anode was investigated with the La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 3-δ (LSGM) electrolyte-supported cells in both wet H 2 and CH 4 at 800°C, using current-collecting materials Au, Ag and Pt paste/mesh as well as La 0.3 Sr 0.7 TiO 3-σ (LST). SMM was found to be compatible chemically with these current collectors, i.e. no new phase was formed in all the mixtures of the SMM and current collector powders after exposure at 800°C in Ar+5%H 2 for 50 h. The cell performance in H 2 with different current collectors followed the order of Pt > LST > Ag (≈Au) initially and changed with time due to the sintering/spreading of the paste and the change in contact area. The presence of Pt on the anode side led to the highest anodic activity and cell performance in both H 2 and CH 4 , due to its high catalytic activity in both fuels. In the absence of Pt, La 0.4 Ce 0.6 O 2-σ (LDC), which was used as a buffer layer between the SMM anode and the LSGM electrolyte, dominated the anodic activity in H 2 , and the cell performance difference could be largely explained by current collection efficiency variation with the different current collectors. In CH 4 , the power output was negligible for all the Pt-free cells. We conclude that the double-perovskite SMM possessed very poor intrinsic catalytic activity for oxidation of both H 2 and CH 4 . Impregnation of the SMM anode with catalytically-active metal/alloy particles might be an attractive approach to improve the overall performance of this oxide anode system.