Fig. 1: Characterization of single-atom catalysts.

a AC-STEM image of 3 wt% Pt/ceria prepared via atom trapping. Particle A is oriented along the [112] zone axis resulting in strong contrast from the Ce atom columns, while the ceria particle in the boxed region is oriented off the zone axis making it easier to detect the Pt single atoms, which appear as bright dots. The boxed region is 5 nm × 5 nm in size and contains 25 Pt atoms, consistent with the overall loading of 1 Pt atom/nm². Surface steps are a common feature of ceria polyhedral particles and are likely sites for strong binding of Pt single atoms. The figure content is adapted with permission from Kunwar et al.⁶. Copyright (2019) American Chemical Society. b CO oxidation reactivity of Pt, Pd, and Rh single-atom catalysts prepared via atom trapping. The catalysts contain identical molar loading equivalent to 1 wt% Pt/CeO₂ (0.88 mol% of Pt, Pd, or Rh and 99.12 mol% CeO₂). The CO oxidation was performed using 20 mg of catalyst, with 1 ml/min of CO, 1.5 ml/min of O₂, and 75 ml/min of helium. The samples were heated to 300 °C at 2 °C/min and cooled back down to room temperature in the reaction mixture to test for reproducibility. The data shown represent the third run. The catalysts are stable and each of them contain exclusively atomically dispersed metal species located on the surface of the ceria. The figure content is adapted with permission from Alcala et al.¹². Copyright (2021) Elsevier, Inc.