The energy barrier for many of the chemical reactions is overcome by heating the reactants in the presence of a suitable catalyst, where thermal energy assists in overcoming the barrier that has been reduced during the adsorption of reactant molecules on the catalyst nanoparticle surfaces. In recent years, localized surface plasmon (LSP) resonance energy has been used to replace thermal energy to initiate reactions at low temperatures, even at room temperature. As most of the plasmonic materials, Au, Ag or Al, are not catalytically active, they have been used by decorating their particle surfaces with active catalysts such as Pt, Ni, Ru, etc. Most of the researchers so far have used optical methods to generate and measure the LSP resonance energies and the reaction products. However, the low spatial resolution, of the order of 100 nm, achievable by optical methods, does not provide sub-particle level distribution of coupling efficiency with individual resonance modes. On the other hand, high energy electrons not only excite all LSP modes simultaneously, but their coupling efficiency can also be spatially resolved. Therefore, we use a monochromated electron source in an environmental scanning-transmission electron microscope (ESTEM), combined with numerical simulations based on metal nanoparticle boundary element method (MNPBEM) and density functional theory (DFT) simulations, to characterize various LSP modes and their coupling efficiency distribution within the shape- and size- controlled nanoparticles of Au and Al in reactive environment. We demonstrate that the knowledge gained from <i>in situ</i> low-loss and core-loss EELS measurements can be used to design catalyst-plasmonic particle combination, or antenna catalyst systems for selected chemical reactions.

Electron energy-loss spectroscopy for designing plasmonic catalysts

2019 Fall National Meeting

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