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

Abstract

Layered perovskite SrGdNi x Mn 1-x O 4±δ 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 SrGdNi x Mn 1-x O 4±δ (x = 0.2, 0.5, and 0.8) materials revealed that significant exsolution of Ni nanoparticles occurred in SrGdNi 0.2 Mn 0.8 O 4±δ (SGNM28) in H 2 at over 650 °C. Consistently, the SGNM28 on the LSGM electrolyte showed low electrode polarization resistance (1.79 ω cm 2 ) in H 2 at 800 °C. Moreover, after 10 redox cycles at 750 °C, the electrode area specific resistance of the SGNM28 anode in H 2 increased only 0.027 ω·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 °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 (∼ 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.