A panchromatic graphite-derived-carbon-dot TiO2 photocatalyst: Broad visible light absorption via ligand-to-metal charge transfer

In recent decades, solar-to-chemical conversion catalysts for energy and environmental applications have drawn significant attention. Catalysts composed of nano-size TiO2 and various dye-based photosensitizers can absorb solar light efficiently and produce promising photocatalysts, but their photoactive region is limited. In this study, we demonstrate that nanocomposites composed of graphite-derived carbon dots (GCDs) and TiO2 are capable of ligand-to-metal charge transfer (LMCT), which was active across the entire visible-light spectrum. The effect of GCDs on the photocatalytic activity of TiO2 was determined through the production of hydrogen peroxide and the degradation of pollutants. On the basis of chemical and optical investigation, we demonstrate the formation of an LMCT band in the TiO2/GCD nanocomposites, which are responsible for photoactivation below the bandgap of each component. Our research provides conclusive evidence for the presence of the LMCT band in TiO2/GCD and reveals a novel method for expanding the light-absorption spectrum of the photocatalyst.