Promoting C─C Coupling via Photocatalytic Desulfurization Through Controlled Reduction of TiO 2 Nanoparticle Catalyst

This work examines the effect of defect engineering on the photocatalytic desulfurization of methyl thioglycolate and its downstream C─C coupling with styrene using modified TiO 2 nanoparticles. Fully oxidized nanoparticles show high desulfurization yields (97.7%) but poor C─C coupling selectivity (14.5%) due to a lack of surface defects. Controlled reduction in NH 3 atmosphere at mild temperatures (300–400 °C) introduces surface defects (Ti 3+ centers and oxygen vacancies) without modifying the bulk lattice. These surface defects stabilize intermediate carbon radicals, dramatically increasing C─C coupling yields to over 84%. Higher reduction temperatures (≥500 °C) severely diminish photocatalytic activity by depletion of surface Ti 4+ sites and eventual transformation into crystalline TiN. The study highlights the critical role of surface chemistry tuning in balancing photocatalytic activity and selectivity.