Blue TiO₂ with tunable oxygen-vacancy defects for enhanced photocatalytic diesel oil degradation

The proliferation of marine petroleum exploitation has culminated in the undesired release of oils into the aquatic ecosystem, causing detrimental environmental effects. Photocatalysis proffers a solution to degrade recalcitrant diesel oil utilizing abundant solar energy, in which TiO₂ is the perennial photocatalyst of choice. However, it suffers from the low utilization of the light spectrum and the rapid recombination of photogenerated charge carriers. In this work, oxygen-vacancy-rich blue TiO₂ was employed to overcome the shortcomings of TiO₂ in diesel oil degradation which has historically not been attempted. These oxygen vacancies induce favourable mid gap states to extend the optical absorption capabilities and enrich the photocatalyst charge density. Additionally, oxygen vacancies enhance the separation of electron hole pairs by acting as trap states, evident from increased trap-mediated capture fluorescence. Consequently, a 1.60-fold enhancement of diesel oil degradation performance compared to pristine TiO₂ was observed. Mechanistic insights revealed the restructuring of diesel alkane distribution upon degradation corollary to the cleavage of hydrocarbon chains, illustrating that short alkanes experience a greater susceptibility to degradation compared to long alkanes. GC–MS analysis elucidates that shorter chained alkanes, alkenes, alcohols and cycloalkanes were produced as a product of the degradation.