The exceptional performance of the plasmonic Au-Fe/TiO2 nanocatalysts achieved by O2 plasma activation

Abstract

The plasmonic Au-based bimetallic nanocatalysts have the potential to exhibit superior visible-light (VL) photocatalytic activity, and their performance in reaction is greatly dependent on the method of activation. Herein, Au-Fe/TiO2 nanocatalysts are prepared by a modified incipient wetness impregnation method with the precursors of HAuCl4 and FeCl3. The visible-light activities of the samples activated by calcination at 300 °C, 50%H2/Ar plasma and O2 plasma are compared using CO oxidation. Au-Fe/TiO2 activated by O2 plasma has the most exceptional performance with a CO conversion of 90%. The samples are characterized by transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectra, and CO chemisorption. It is found that O2 plasma restructures nano Au and Fe on the TiO2 support into Au-Fe alloy, preventing nano Au particle size increase. The Au-Fe alloy nanoparticles on TiO2 has a narrow size distribution and are approximately 4 nm in size. Many surface oxygen species on Au-Fe alloy are observed, as well as a unique board peak assigned to CO adsorption, and they can improve the activity and stability of Au-Fe alloy in CO oxidation. Finally, a reaction mechanism of Au-Fe/TiO2 activated by O2 plasma for CO oxidation is developed. This research demonstrates that the treatment of O2 plasma is an available approach to producing efficient Au-Fe plasmonic nanocatalysts.