Synergistic Effects of In-Situ Exsolved Ni–Ru Bimetallic Catalyst on High-Performance and Durable Direct-Methane Solid Oxide Fuel Cells

Abstract

Direct-methane solid oxide fuel cells (CH 4 -SOFCs) have gained significant attention as methane, the primary component of natural gas (NG), is cheap and widely available and the natural gas infrastructures are relatively mature. However, at intermediate temperatures (e.g., 600−650 °C), current CH 4 -SOFCs suffer from low performance and poor durability under a low steam-to-carbon ratio (S/C ratio), which is ascribed to the Nibased anode that is of low catalytic activity and prone to coking. Herein, with the guidance of density functional theory (DFT) studies, a highly active and coking tolerant steam methane reforming (SMR) catalyst, Sm-doped CeO 2 -supported Ni−Ru (SCNR), was developed. The synergy between Ni and Ru lowers the activation energy of the first C−H bond activation and promotes CH x decomposition. Additionally, Sm doping increases the oxygen vacancy concentration in CeO 2 , facilitating H 2 O adsorption and dissociation. The SCNR can therefore simultaneously activate both CH 4 and H 2 O molecules while oxidizing the CH* and improving coking tolerance. We then applied SCNR as the CH 4 -SOFC anode catalytic reforming layer. A peak power density of 733 mW cm −2 was achieved at 650 °C, representing a 55% improvement compared to that of pristine CH 4 -SOFCs (473 mW cm −2 ). Moreover, long-term durability testing, with >2000 h continuous operation, was performed under almost dry methane (5% H 2 O). These results highlight that CH 4 -SOFCs with a SCNR catalytic layer can convert NG to electricity with high efficiency and resilience.