Crystal Face-Dependent Behavior of Single-Atom Pt: Construct of SA-FLP Dual Active Sites for Efficient NO₂ Detection

The strong potential of platinum single atom (Pt_SA) in gas sensor technology is primarily attributed to its high atomic economy. Nevertheless, it is imperative to conduct further exploration to understand the impact of Pt_SA on the active sites. In this study, the evolution of Pt_SA on (100)CeO₂ and (111)CeO₂ is examined, revealing notable disparities in the position and activity of surface Pt_SA on different crystal planes. The Pt_SA in (100)CeO₂ surface can enhance the stability of Ce³⁺ and construct a frustrated Lewis pair (FLP) to form a double active site by combining the steric hindrance effect of oxygen vacancies, which increases the response value from 1.8 to 27 and reduce the response-recovery time from 140-192 s to 25-26 s toward five ppm NO₂ at room temperature. Conversely, Pt_SA tends to bind to terminal oxygen on the surface of (111)CeO₂ and become an independent reaction site. The response value of Pt_SA-(111)CeO₂ surface only increased from 1.6 to 3.8. This research underscores the correlation between single atoms and crystal plane effects, laying the groundwork for designing and synthesizing ultra-stable and efficient gas sensors.