Tunable Selectivity of Photocatalytic Benzyl Alcohol Transformation over Ag-Ion-Exchanged CdS Nanowires

Existing methods for the photocatalytic transformation of aromatic alcohols to value-added products via C–C cross-coupling are inefficient and insufficiently selective. Herein, a series of cadmium sulfide nanowires (CdS NWs) loaded with Ag2S (denoted as Ag2S@CdS NWs) are constructed via a simple Ag+ exchange protocol for the photocatalytic transformation of benzyl alcohol. We successfully demonstrated that the selectivity toward specific products in the photocatalytic transformation of benzyl alcohol over Ag+-exchanged CdS NWs is controlled by varying the amount of exchanged Ag+ ions. Notably, the product of the photocatalytic reaction was dependent on the amount of Ag+ ions exchanged: with a Ag+ exchange of <5 mol %, the C–C coupling product was obtained with >90% selectivity and >95% transformation yield owing to photoinduced electron transfer from the conduction band of CdS to Ag2S. Conversely, with a Ag+ exchange of >7 mol %, a cocatalyst in which Ag2S and Ag are mixed was produced, and benzaldehyde was obtained with >90% selectivity and >90% transformation yield because of photoinduced hole transfer from the valence band of CdS to Ag2S/Ag. This study proves that Ag2S@CdS NWs can be used as a basis for the development of heterojunction photocatalysts for the conversion of aromatic alcohols into value-added products via C–C cross-coupling reactions or photooxidation toward aromatic aldehyde.