Effect of the TiO2-carbon interface on charge transfer and ethanol photo-reforming

Carbonaceous materials have been widely used in photocatalysis to solve the drawback of rapid electron-hole recombination rate of semiconductors such as titania. To further understand the charge separation mechanism and its effect on the ethanol photoreforming hydrogen production, two types of carbon-titania hybrid material systems were studied. One of them is multi-walled carbon nanotube-titania nanoparticles (MWCNT-TiO2) prepared by a sol-gel synthesis method, which according to previous studies should facilitate the migration of electrons from TiO2 to MWCNT. The second system is based on a two-dimensional carbon (exfoliated carbon, 2DC) and titania nanosheet (TNS), synthesized through a hydrothermal route that enabled the formation of strong interaction between the carbon and the {001} facets of the TNS. Our results demonstrate that this unique design promotes the migration of the photogenerated holes from the TNS to the expanded carbon. Steady state photoluminescence studies indicate that the recombination rate in both cases decreases benefiting from the spatial separation of photogenerated carriers, resulting in enhanced photocatalytic activity. The present study provides a comprehensive understanding of the charge separation mechanism and its effect on ethanol photoreforming hydrogen production in carbon-titania hybrid material systems and clearly highlights the need for further research to investigate the charge transfer in these kinds of hybrid materials.