Abundant interfacial and intrinsic oxygen vacancies enabling small nickel/ceria nanocrystal efficient CO2 methanation.

Small nano-sized Ni/CeO 2 -S catalyze air-level CO 2 hydro-methanation. Here, Ni/CeO 2 -S has double defect synergistic effect, highly dispersed active Ni species, enhanced H spillover and efficient CO 2 adsorption and activation capability. [Display omitted] • Ni/CeO 2 -S (<5 nm) shows superior CO 2 methanation performance. • Enhanced CO 2 methanation due to Ni-O x -Ce interfaces, O vacancies, dispersed Ni, and H spillover. • In-situ DRIFTS reveals a unique Formate pathway on Ni/CeO 2 -S. • Ni/CeO 2 -S shows excellent durability in 100-h continuous CO 2 methanation. Smaller nano-sizes typically result in supported catalysts with abundant interfacial and intrinsic oxygen vacancies for better adsorption and activation of small molecules, including CO 2 , leading to improved efficiency of CO 2 methanation. Here, Ni/CeO 2 -S with the smaller nano-size of around 4.2 nm is used to catalyze CO 2 methanation, which exhibits significantly enhanced activity compared to larger nano-sized Ni/CeO 2 -L catalyst, even surpassing the most majority of previously reported catalysts using CeO 2 as the support or Ni as the active metal. The coexistence of interfacial defects and intrinsic oxygen vacancies allows for enhanced adsorption and activation of CO 2 molecules as well as H spillover, resulting in such improved CO 2 methanation. In-situ DRIFTS demonstrate a nearly sole Formate pathway on Ni/CeO 2 -S for efficient CO 2 hydrogenation. This research provides valuable insights into the reaction mechanism over a small nanosize supported catalyst. [ABSTRACT FROM AUTHOR]