Ultrasmall graphitic carbon nitride quantum dots decorated self organized TiO2 nanotube arrays with highly efficient photoelectrochemical activity
Abstract In the present study, a novel graphitic carbon nitride quantum dots (CNQDs) modified TiO 2 nanotube arrays (NTAs) photoelectrode was successfully synthesized by a simple two step method which includes an electrochemical anodization technique followed by a facile organic molecular linkage. The successful modification of TiO 2 by CNQDs was found to improve the photoelectrochemical activity significantly because of enhanced light absorption and improved separation of photo generated electron hole pairs. The optimized CNQDs/TiO 2 NTAs showed nearly 3.5 fold photocurrent of that from TiO 2 NTAs alone at 0.3 V vs Ag/AgCl and the maximum photoconversion efficiency reaches up to 0.63% in neutral solution under simulated solar light irradiation. Furthermore, the prepared CNQD/TiO 2 NTAs demonstrated superior photoelectrocatalytic activity and stability in the degradation of RhB, with kinetic constants 3.0 times of that from TiO 2 NTAs. The hydroxyl and superoxide radicals were proved to be the dominant active radicals during pollutants degradation. Additionally, the prepared CNQD/TiO 2 sample was used as photoanodes for direct photoelectrochemical water splitting to produce H 2 and O 2 under simulated solar light illumination, achieving a H 2 production rate with 22.0 mmol h 1 cm 2 at 0.3 V vs Ag/AgCl.