Initiation: A Critical Step for High Activity and Stability in Ni‐Based Methane Dry Reforming Catalysts Supported on <i>θ</i> ‐Al ₂ O ₃

Abstract

ABSTRACT Ni‐based catalysts are extensively studied for the dry reforming of methane (DRM), which converts CO 2 and CH 4 —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 ‐Al 2 O 3 ‐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.