Surface Spectroscopic Analysis of TiO2 and ZnO Nanoparticles Doped with Noble Metals

Abstract

Abstract: Nanoparticles (NPs) of the well-known photocatalysts TiO2 and ZnO each doped with noble metals (NM = Au, Pd, or Pt) were synthesized by applying a thermosynthetic method, and the catalytic activities of the resulting six samples were compared. After characterizing them by using high-resolution photoemission spectroscopy (HRPES), we evaluated the catalytic effects of the samples the oxidation of 4-aminothiophenol (4-ATP) by using HRPES under UV illumination and on the oxidation of 4-ATP in aqueous solution by taking electrochemistry measurements. In addition, we determined the rates of conversion of CO to CO2 in the presence of these catalysts by using a residual gas analyzer under an ultra-high vacuum condition. As a result, we found a good positive correlation between the numbers of defect structures induced by the doped noble metals and the catalytic activity, and showed that Pd-TiO2 and Pt-ZnO NPs can act as efficient catalysts due to their relatively large number of defect structures and corresponding oxygen vacancies. Graphical Abstract: [Figure not available: see fulltext.].