Low-Temperature Photooxidation of Ethylene on Rutile TiO2(110)

Abstract

The conversion of ethylene (C₂H₄) with photocatalysis provides an alternative to traditional C₂H₄ conversion into acetaldehyde (CH₃CHO) processes in industrial production. Herein, low-temperature C₂H₄ oxidation is conducted on rutile (R)-TiO₂(110) under the third-harmonic (343 nm) and fourth-harmonic (257 nm) outputs of the laser. The results illustrate that both hole-trapped bridging oxygen (O_b^–) and Ti_5c bound oxygen adatom (O_Ti^–) are photoactive for C₂H₄ conversion. The former is strongly wavelength-dependent, which mainly induces C₂H₄ dehydrogenation into the C₂H₃^• radical, which follows an Eley–Rideal (E–R) type direct mechanism. Conversely, the latter induces two parallel reaction pathways to produce C₂H₂ via the elimination pathway and acetaldehyde (CH₃CHO) via the addition pathway. The latter pathway may undergo formation of oxometallacycle intermediates on the surface. These results not only achieve C₂H₄ direct conversion into useful partial oxidation products via photocatalysis but also further deepen the understanding of the nature of C–H activation.