Engineering Multidefects on Ce_x Si_{1- x} O_{2- δ} Nanocomposites for the Catalytic Ozonation Reaction

Herein, it is shown that by engineering defects on Ce_x Si_{1- x} O_{2- δ} nanocomposites synthesized via flame spray pyrolysis, oxygen vacancies can be created with an increased density of trapped electrons, enhancing the formation of reactive oxygen species (ROSs) and hydroxyl radicals in an ozone-filled environment. Spectroscopic analysis and density functional theory calculations indicate that two-electron oxygen vacancies (O_V ⁰ ) or peroxide species, and their degree of clustering, play a critical role in forming reactive radicals. It is also found that a higher Si content in the binary oxide imposes a high O_V ⁰ ratio and, consequently, higher catalytic activity. Si inclusion in the nanocomposite appears to stabilize the surface oxygen vacancies as well as increase the reactive electron density at these sites. A mechanistic study on effective ROSs generated during catalytic ozonation reveals that the hydroxyl radical is the most effective ROS for organic degradation and is formed primarily through H₂ O₂ generation in the presence of the O_V ⁰ . Examining the binary oxides offers insights on the contribution of oxygen vacancies and their state of charge to catalytic reactions, in this instance for the catalytic ozonation of organic compounds.