Facile one-step hydrothermal synthesis toward strongly coupled TiO2/graphene quantum dots photocatalysts for efficient hydrogen evolution

The coupling of semiconductor photocatalysts with graphene quantum dots (GQDs) has been proven to be an effective strategy to enhance the photocatalytic and photoelectrical conversion performances of the resulted composites; however, the preparation of semiconductor/GQDs composites usually involves several time-inefficient and tedious post-treatment steps. Herein, we present a facile one-step hydrothermal route for the preparation of GQDs coupled TiO2 (TiO2/GQDs) photocatalysts using 1,3,6-trinitropyrene (TNP) as the sole precursor of GQDs. During the hydrothermal process, TNP molecules undergo an intramolecular fusion to form GQDs, which simultaneously decorate on the surface of TiO2 nanopartides, leading to a strong surface interaction between the two components. The effective coupling of GQDs on TiO2 can effectively extend the light absorption of the TiO2 to visible region and enhance the charge separation efficiency of TiO2/GQDs composites as a result of GQDs acting as a photosensitizer and an excellent electron acceptor. These key advances make the TiO2/GQDs photocatalyst highly active towards the H-2 evolution reaction, resulting in 7 and 3 times higher H-2 evolution rate and photocurrent response at optimal GQDs content than TiO2 alone, respectively. This study provides a new methodology for the development of high-performance GQDs modified semiconductor photocatalysts for energy conversion applications. (C) 2016 Elsevier B.V. All rights reserved.