Effect of Dimensionality on the Photocatalytic Behavior of Carbon–Titania Nanosheet Composites: Charge Transfer at Nanomaterial Interfaces

Due to their unique optoelectronic structure and large specific surface area, carbon nanomaterials have been integrated with titania to enhance photocatalysis. In particular, recent work has shown that nanocomposite photocatalytic performance can be improved by minimizing the covalent defect density of the carbon component. Herein, carbon nanotube–titania nanosheet and graphene–titania nanosheet composites with low carbon defect densities are compared to investigate the role of carbon nanomaterial dimensionality on photocatalytic response. The resulting 2D–2D graphene–titania nanosheet composites yield superior electronic coupling compared to 1D–2D carbon nanotube–titania nanosheet composites, leading to greater enhancement factors for CO2 photoreduction under ultraviolet irradiation. On the other hand, 1D carbon nanotubes are shown to be more effective titania photosensitizers, leading to greater photoactivity enhancement factors under visible illumination. Overall, this work suggests that carbon nanomaterial dimensionality is a key factor in determining the spectral response and reaction specificity of carbon–titania nanosheet composite photocatalysts.