Initiation: A Critical Step for High Activity and Stability in Ni-Based Methane Dry Reforming Catalysts Supported on...

Ni-based catalysts are extensively studied for the dry reforming of methane (DRM), which converts CO₂ and CH₄-the two most abundant greenhouse gases-into syngas for downstream chemical synthesis. The harsh reaction conditions required for DRM lead to coking, metal aggregation. Although multiple mechanisms have been proposed, the molecular-level understanding of the reaction remains debated. Here, we report the synthesis of θ-Al₂O₃-supported Ni DRM catalysts via surface organometallic chemistry (SOMC) and report its outstanding activity and stability. The resulting Ni nanoparticles remain highly dispersed, with an average size of 5.3 ± 1.3 nm even after reduction at 900°C. This model catalyst exhibits distinct temperature-dependent behavior during DRM, with marked structural and mechanistic differences observed within a narrow 50°C range. In situ x-ray absorption spectroscopy (XAS) and ex situ synchrotron x-ray diffraction (XRD) reveal a dynamic induction process involving rapid Ni oxidation, followed by reduction and carbon insertion into the Ni lattice at 850°C, forming a carbide-like NiC_x phase. At 800°C, incorporation of carbon is limited, thus leading to surface coking and catalyst deactivation. Furthermore, gas-switching experiments confirm the importance of a carbide cycle at 850°C, enabling continuous carbon removal and sustained catalytic stability.