Transformation of Platinum Single‐Atom Catalysts to Single‐Atom Alloys on Supported Nickel: TEM and XAS Spectroscopic Investigation

The well‐dispersed Pt atoms on Ni have shown excellent coke resistance during methane reforming. In this work, we performed detailed characterization experiments using aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy (AC‐HAADF‐STEM), and X‐ray absorption spectroscopy (XAS) to elucidate the formation of different Pt structures with respect to Pt/Ni atomic ratios. The Pt−Ni single‐atom alloys (SAAs) in Pt/Ni‐CeO2@SiO2 yolk‐shell nanotube structures are synthesized by reducing Pt single atoms supported on the NiO surface as single‐atom catalysts (SACs). Pt−Ni SAAs show Pt−Ni contribution in the first shell with the coordination number of 5 without any Pt−Pt and Pt−O interactions, implying Pt atoms are isolated on the outermost layer of Ni species. However, Pt clusters can be detected at Pt/Ni atomic ratios higher than 0.008. The well‐dispersed Pt single atoms on Ni show high activity while maintaining their structure in dry reforming of methane condition at 773 K, verifying the excellent stability of the Pt−Ni SAA morphology. Structured catalysis: The highly stable Pt single atoms on Ni surface as single‐atom alloys (SAAs) are prepared by reducing Pt single atoms supported on NiO in single‐atom catalysts (SACs). The Pt/Ni atomic ratio of 0.008 produces well‐distributed Pt−Ni SAA structured catalysts investigated by scanning transmission electron microscopy (STEM) and X‐ray absorption spectroscopy (XAS).