Enlarging the Three-Phase Boundary to Raise CO₂/CH₄ Conversions on Exsolved Ni-Fe Alloy Perovskite Catalysts by Minimal Rh Doping

Exsolved Ni-Fe alloy perovskite catalysts exhibit remarkable coking resistance during C-H and C-O activation. However, metallic utilization is typically incomplete, resulting in relatively low catalytic activity. Herein, we investigated minimal doping with Rh to boost the catalytic activity in the dry reforming of methane by promoting exsolution and enlargement of the three-phase boundary between the alloy, support, and reactants. The Rh influences the formation of the Ni-Fe alloy, as revealed by X-ray diffraction, and promotes the individual and collective CH4 and CO2 conversions, as revealed by packed bed reactor runs, temperature-programmed surface reactions, and in situ infrared spectroscopy. A minimal 0.21 wt % Rh addition enlarges the three-phase boundary while improving oxygen mobility and storage. The oxygen mobility is responsible for promoting CH4 dissociation and dynamic removal of carbon-containing intermediates, such that the catalyst remains stable for over 100 h under both 1 and 14 bar.