Enhanced Stability of Atomically Dispersed Pd Catalysts via Ionic Liquid Layer Deposition for Selective Acetylene Hydrogenation to Ethylene in Excess Ethylene

A series of TiO₂-supported Pd catalysts with different amounts of ionic liquid (IL) were synthesized for the selective hydrogenation of acetylene to ethylene in excess ethylene. CO Fourier transform infrared spectroscopy (FTIR), high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS) suggested that the Pd species in the catalysts synthesized via the strong electrostatic adsorption (SEA) method exist predominantly as isolated atoms on TiO₂ independent of the presence of the IL. Using a combination of FTIR and XPS, it was found that IL deposition on Pd catalysts induces a change in the electronic structure of atomically dispersed Pd atoms. The IL-modified catalysts exhibited improved stability in acetylene hydrogenation compared to IL-free catalysts owing to their higher coke resistance. Thus, this study provides a novel synthetic strategy based on IL deposition for improving the coke resistance and stability of atomically dispersed catalysts.