In situ formation of cocatalytic sites boosts single-atom catalysts for nitrogen oxide reduction
Tuesday, 2023/02/28 | 08:16:40
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Pengfei Wang, Guoquan Liu, Zhifei Hao, He Zhang, Yi Li, Wenming Sun, Lirong Zheng, and Sihui Zhan PNAS; February 14, 2023; 120 (8) e2216584120 SignificanceThe use of oxide-supported isolated Pt single atoms as catalytic active sites is of interest due to their maximum atom utilization efficiency and unique catalytic properties for the removal of NOx. However, relationships between the structure of active center, the dynamic response to environments, and catalytic functionality have proved difficult to experimentally establish. This research reveals that the in situ formation of adjacent cocatalytic sites boosts single-atom catalysts for the conversion of NOx during the catalytic reaction of NOx reduction with H2. The presence of cocatalytic sites tunes and optimizes the catalytic performance at the atomic scale that can benefit the environment and human health by removing NOx efficiently. AbstractNitrogen oxide (NOx) pollution presents a severe threat to the environment and human health. Catalytic reduction of NOx with H2 using single-atom catalysts poses considerable potential in the remediation of air pollution; however, the unfavorable process of H2 dissociation limits its practical application. Herein, we report that the in situ formation of PtTi cocatalytic sites (which are stabilized by Pt–Ti bonds) over Pt1/TiO2 significantly increases NOx conversion by reducing the energy barrier of H2 activation. We demonstrate that two H atoms of H2 molecule are absorbed by adjacent Pt atoms in Pt–O and Pt–Ti, respectively, which can promote the cleave of H–H bonds. Besides, PtTi sites facilitate the adsorption of NO molecules and further lower the activation barrier of the whole de-NOx reaction. Extending the concept to Pt1/Nb2O5 and Pd1/TiO2 systems also sees enhanced catalytic activities, demonstrating that engineering the cocatalytic sites can be a general strategy for the design of high-efficiency catalysts that can benefit environmental sustainability.
See https://www.pnas.org/doi/10.1073/pnas.2216584120
Figure 1: HAADF-STEM characterization of Pt1/TiO2. (A and E) HAADF-STEM images of fresh Pt1/TiO2 (A) and used Pt1/TiO2 (E). (B–D) In situ HAADF-STEM images and relevant intensity profiles of Pt1/TiO2 without reaction in Ar atmosphere at 125 °C (1 bar). (F–H) In situ HAADF-STEM images and relevant intensity profiles of Pt1/TiO2 under the reaction at 125 °C (NO:H2 ~ 1:1, 1 bar). (I–L) EDS mapping of used Pt1/TiO2. (M and N) The intensity profiles obtained in A and E, respectively.
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