Selective photocatalytic conversion of benzyl alcohol to benzaldehyde or deoxybenzoin over ion-exchanged CdS

The visible light absorbing CdS nanoparticles were partially modified with Au 2 S and Ag 2 S via a simple cation exchange process to prepare heterostructure photocatalysts (denoted as Au 2 S@CdS and Ag 2 S@CdS), which were employed for the conversion of aromatic alcohols to valued-added products, such as benzaldehyde and C-C coupling products, including deoxybenzoin and hydrobenzoin. When Au 2 S@CdS was used as the photocatalyst, benzaldehyde was obtained as the main product with a selectivity of 99%, and when Ag 2 S@CdS was used as the photocatalyst, deoxybenzoin was obtained as the main product with a selectivity of 95%. The critical photogenerated electron and hole transfer occurring during the photocatalytic reaction was systemically investigated by performing various control experiments and using in-situ high-resolution X-ray photoelectron spectroscopy. In addition, with the photocatalytic system proposed in this study, benzyl alcohol could be photoconverted into benzaldehyde or deoxybenzoin almost completely with high selectivity by altering the cocatalyst component via simple ion exchange. Cation-exchanged CdS exhibited selective photocatalytic conversion of benzyl alcohol, which depended on the cation species due to the efficient photogenerated electron or hole transfer processes. • The Ag + exchange in cadmium sulfide remarkably enhances the lignin model compound conversion with high selectivity. • The Ag + exchange in cadmium sulfide is employed for prompt photoexcited electron transfer to the oxidized intermediate. • The shift in the Fermi level of Ag 2 S@CdS produces a fast photoexcited electron–hole-coupled transfer.