Active Sites of supported bimetallic nano-Catalysts

Dynamic Structural Changes of Active Sites in Pt–Ni Bimetallic Catalysts Revealed by a Multimodal Approach

Supported alloy nanoparticle catalysts have been widely used for heterogeneous catalysis, with applications in reforming processes, selective hydrogenation/oxidation, and other important reactions in both the petroleum and fine chemical industries. Understanding the atomic structures adopted by supported metal nanoparticles in the environments of their use (‘in operando’) provide a key to understanding their catalytic properties. Based on an advanced multimodal analytical approach - including in situ X-ray Absorption Spectroscopy (XAS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and ex-situ aberration corrected Scanning Transmission Electron Microscopy (STEM) - complex reactions occurring between the bimetallic nanoclusters and the support are documented under operando conditions. Bimetallic nanoparticles possessing an intermetallic structure that are conjoined with Ni-rich, metal-silicate substrate species are identified. The intermetallic structure formed by these ∼1 nm sized Pt-Ni clusters, once driven to a specific composition in their active state, provides a heretofore unrecognized heterometallic structure that sustains the exceptionally high activity and selectivity seen in reverse Water Gas Shift reaction.