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In Situ Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy of Nickel‐Catalyzed Hydrogenation Reactions
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Abstract
Synthesis methods to prepare lower transition metal catalysts and specifically Ni for Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy (SHINERS) are explored. Impregnation, colloidal deposition, and spark ablation have been investigated as suitable synthesis routes to prepare SHINERS‐active Ni/Au@SiO 2 catalyst/Shell‐Isolated Nanoparticles (SHINs). Ni precursors are confirmed to be notoriously difficult to reduce and the temperatures required are generally harsh enough to destroy SHINs, rendering SHINERS experiments on Ni infeasible using this approach. For colloidally synthesized Ni nanoparticles deposited on Au@SiO 2 SHINs, stabilizing ligands first need to be removed before application is possible in catalysis. The required procedure results in transformation of the metallic Ni core to a fully oxidized metal nanoparticle, again too challenging to reduce at temperatures still compatible with SHINs. Finally, by use of spark ablation we were able to prepare metallic Ni catalysts directly on Au@SiO 2 SHINs deposited on a Si wafer. These Ni/Au@SiO 2 catalyst/SHINs were subsequently successfully probed with several molecules ( i. e. CO and acetylene) of interest for heterogeneous catalysis, and we show that they could be used to study the in situ hydrogenation of acetylene. We observe the interaction of acetylene with the Ni surface. This study further illustrates the true potential of SHINERS by opening the door to studying industrially relevant reactions under in situ or operando reaction conditions.
Abstract
Sparking the reaction: Spark ablation is presented as a new method for the preparation of working lower transition metal catalysts supported on Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy (SHINERS)‐active Au@SiO 2 nanoparticles. The gas phase hydrogenation of acetylene is studied with in situ SHINERS over the prepared Ni catalysts, reporting the first non‐noble metal catalysis study with SHINERS.
