Roles of Single‐Atoms and Nanoparticles of Nickel‐Based Catalysts for Oxygen‐Involved Dry Reforming of Methane at Low Temperatures

ABSTRACT Oxygen‐involved dry reforming of methane (ODRM) shows potential for converting impure CO 2 captured from air, but it suffers from low CO 2 conversion, especially at low temperatures (400°C–700°C). The optimization of catalysts via controlling the size of metal centers is significant for this reaction. Herein, we report for the first time the roles of Ni single atoms (SAs) and nanoparticles (NPs) anchored on dendritic mesoporous silica (DMS) in determining the catalytic activity for low‐temperature ODRM with different CH 4 /CO 2 /O 2 ratios. Both the single‐atoms (Ni SA /DMS) and nanoparticles (Ni NP /DMS) on DMS are highly efficient in catalyzing the reforming of CO 2 and CH 4 , with the conversions of CO 2 and CH 4 in the range of 56%–61% at 550°C. The presence of O 2 suppresses the CO 2 conversion, while the Ni SA /DMS catalyst shows higher O 2 ‐tolerance than the Ni NP /DMS, especially for the reactants with a relatively high concentration of O 2 . In addition, the Ni NPs tend to be oxidized by O 2 and favor the carbon formation, which hinders the catalytic performance during long‐term running. The Ni SAs stabilized by the interaction with DMS are highly stable under aerobic conditions and inhibit the formation of carbon deposits from CH 4 dissociation. The in situ characterizations and DFT calculations reveal that the Ni SAs show higher capacity for CO 2 dissociation but weaker ability to activate the C‐H bond of CH 4 than NPs, which contributes to the superior O 2 ‐tolerance and carbon resistant of the Ni SA /DMS catalyst. The present discovery indicates that the controlled activation of CO 2 and CH 4 is essential for designing high‐performance catalysts of ODRM.