Silk fibroin-derived nitrogen-doped carbon quantum dots anchored on TiO2 nanotube arrays for heterogeneous photocatalytic degradation and water splitting

Bombyx mori silk, a natural nitrogen-rich biopolymer protein, is earth-abundant and sustainable. In this study, nitrogen-doped carbon quantum dots (N-CQDs) derived from Bombyx mori silk fibroin are immobilized onto TiO2 nanotube arrays (TiO2 NTAs) by a facile hydrothermal process. The resulting N-CQDs decorated TiO2 NTA heterostructures (N-CQDs@TiO2 NTAs) display a maximum incident photon-to-electron conversion efficiency (IPCE) of 32.5% under 450 nm monochromatic light in neutral solution. Compared with pristine TiO2 NTAs, the N-CQDs-decorated TiO2 NTAs demonstrate significantly improved photocatalytic efficiency during the degradation of organic contaminants. Furthermore, the constructed heterostructures are used to split water to investigate their photocatalytic promise, yielding the maximum H-2 and O-2 production rates of 30.12 and 14.96 mu mol cm(-2) h(-1), respectively. Optimizing the N-CQD coating is found to effectively tune the bandgap and up conversion capability of the heterostructures, enabling unique photon harvest and boosting photocatalytic activity. This study provides a proof of concept that nonmetal, abundant, and sustainable materials can be exploited to enhance the photocatalytic capability of TiO2, imparting a variety of unique applications such as water purification and chemical fuel production.