A Highly Active and Redox-Stable SrGdNi0.2Mn0.8O4 +/-delta Anode with in Situ Exsolution of Nanocatalysts

Abstract

Layered perovskite SrGdNixMn1-xO4 +/-delta phases were evaluated as new ceramic anode materials for use in solid oxide fuel cells (SOFCs). Hydrogen temperature-programmed reduction (H-2-TPR) analysis of the SrGdNixMn1-xO4 +/-delta (x = 0.2, 0.S, and 0.8) materials revealed that significant exsolution of Ni nanoparticles occurred in SrGdNi0.2Mn0.8O4 +/-delta (SGNM28) in H-2 at over 650 degrees C. Consistently, the SGNM28 on the LSGM electrolyte showed low electrode polarization resistance (1.79 Omega cm(2)) in H-2 at 800 degrees C. Moreover, after 10 redox cycles at 750 degrees C, the electrode area specific resistance of the SGNM28 anode in H-2 increased only 0.027 Omega.cm(2) per cycle (1.78% degradation rate), indicating excellent redox stability in both reducing and oxidizing atmospheres. An LSGM-electrolyte-supported SOFC employing an SGNM28-Gd-doped ceria anode yielded a maximum power density of 1.26 W cm(-2) at 850 degrees C, which is the best performance among the SOFCs with Ruddlesden-Popper-based ceramic anodes to date. After performance measurement, we observed that metallic Ni nanoparticles (similar to 25 nm) were grown in situ and homogeneously distributed on the SGNM28 anode surface. These exsolved nanocatalysts are believed to significantly enhance the hydrogen oxidation activity of the SGNM28 material. These results demonstrate that the SGNM28 material is promising as a high catalytically active and redox-stable anode for SOFCs.