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

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 (Ob–) and Ti5c bound oxygen adatom (OTi–) 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.