Enhanced Hydrogen Production from DNA-Assembled Z-Scheme TiO₂-CdS Photocatalyst Systems

A wide range of inorganic nanostructures have been used as photocatalysts for generating H₂. To increase activity, Z-scheme photocatalytic systems have been implemented that use multiple types of photoactive materials and electron mediators. Optimal catalysis has previously been obtained by interfacing different materials through aggregation or epitaxial nucleation, all of which lowers the accessible active surface area. DNA has now been used as a structure-directing agent to organize TiO₂ and CdS nanocrystals. A significant increase in H₂ production compared to CdS or TiO₂ alone was thus observed directly in solution with no sacrificial donors or applied bias. The inclusion of benzoquinone (BQ) equidistant between the TiO₂ and CdS through DNA assembly further increased H₂ production. While the use of a second quinone in conjunction with BQ showed no more improvement, its location within the Z-scheme was found to strongly influence catalysis. TiO₂ and CdS nanocrystals were organized into a Z-scheme photosynthesis system by using DNA as a structure-directing agent. Increased H₂ production from water splitting was observed compared to either the photocatalyst alone or dispersed mixtures of the two. The inclusion of the electron mediator benzoquinone equidistant between the TiO₂ and CdS through DNA assembly further increased H₂ production.