Graphene quantum dots to enhance the photocatalytic hydrogen evolution efficiency of anatase TiO2 with exposed {001} facet

Abstract

Hydrogen evolution through photocatalysis is promising with respect to the environmental problems and challenges of energy shortage that we encounter today. In this paper, we have combined graphene quantum dots (GQDs) and {001} faceted anatase TiO₂ (with an exposed percentage of 65–75%) together for effective photocatalytic hydrogen evolution. A series of characterizations including X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and UV-visible absorption spectroscopy have been carried out to study the structure of the as-prepared GQDs/{001}TiO₂ composite. It turns out that GQDs could be effectively decorated on {001}TiO₂ sheet without changing its intrinsic structure. With an optimum loading amount of GQDs (0.5 wt% to {001}TiO₂), GQDs/{001}TiO₂ exhibits a hydrogen evolution efficiency 8 times higher than that of bare {001}TiO₂, which is a significantly more obvious improvement than many other photocatalytic systems relevant to GQDs and TiO₂ hybrids. In addition, GQDs/{001}TiO₂ could stand long-term photocatalytic experiments. Photocurrent tests show that such an improvement of the photocatalytic efficiency over GQDs/{001}TiO₂ may originate from a higher charge separation efficiency. The present study could offer reference for the construction of photocatalytic hydrogen evolution systems with low cost and long term stability.