Constructing a novel TiO2/gamma-graphyne heterojunction for enhanced photocatalytic hydrogen evolution

The use of solar energy via photocatalytic hydrogen evolution is a promising means of energy conversion. gamma-graphyne (gamma-GY), a novel large p-conjugated carbon material, for the first time, is applied to construct a heterojunction with TiO2 nanoparticles for enhanced photocatalytic hydrogen evolution. The obtained TiO2/gamma-GY photocatalysts were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy and photoluminescence spectroscopy, respectively. Enhanced photocatalytic properties were demonstrated for the as-prepared samples. The influence of the gamma-graphyne content on the photocatalytic activity was investigated. The amount of hydrogen evolved from the optimized photocatalyst reached 77.6 mmol in 4 hours, which was about 8.4-fold higher than that of pristine TiO2. This is attributed to the TiO2/g-GY heterojunction structure, which can simultaneously improve the absorption of visible light and suppress the recombination of photo-excited electron-hole pairs during the photocatalytic process. This work shows the potential of g-graphyne for application in photocatalytic hydrogen evolution.