Abstract
N-doped graphene (NG)/TiO2composites were prepared by a two-step hydrothermal method using HF as the surface etchant and urea as the nitrogen source. The morphology, structure, and bonding conditions of the NG/TiO2composites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy. The effects of NG on the lifetime of photogenerated electron-hole pairs, adsorption capacity, and photocatalytic activity of the composite photocatalysts were also investigated. The photocatalytic activity was evaluated under ultraviolet light and sunlight irradiation. The recovery testing was completed under ultraviolet light irradiation. The results show that TiO2was uniformly loaded on the NG surface by chemical bonding. The introduction of NG effectively inhibited the recombination of photogenerated electron-hole pairs and improved both the adsorption capacity and photocatalytic activity of the composites. The 7 wt % NG/TiO2showed the best adsorption capacity of methyl orange (MO). The best photocatalytic activity occurred for 5 wt % NG/TiO2composites, and after four recovery tests, the photocatalytic degradation of MO under 60 min ultraviolet light irradiation exceeded 90%.
Highlights
In recent years, TiO2 has become widely used in the field of photocatalysis because of its strong oxidizing ability, high chemical stability, low cost, nontoxicity, and environmental friendliness [1, 2]
Comparing N-doped graphene (NG)/TiO2 with two other photocatalysts (RGO/TiO2 [9] and N-TiO2/RGO [29]) under the same conditions, the results showed that NG/TiO2 exhibited the highest degradation efficiency for methyl orange (MO). e main reasons are as follows: (1) NG had a large specific surface area and an extremely high electron mobility. e combination of NG and TiO2 significantly increased the specific surface area and electron mobility of the catalyst
NG/TiO2 composites were successfully synthesized by a twostep hydrothermal method with HF as the surface etchant and urea as the nitrogen source of NG. e morphology was optimal, and the chemical bond between NG and TiO2 resulted in a firm loading
Summary
TiO2 has become widely used in the field of photocatalysis because of its strong oxidizing ability, high chemical stability, low cost, nontoxicity, and environmental friendliness [1, 2]. The recombination rate of photoexcited charge carriers is high, so the quantum efficiency of TiO2 is low. Graphene is a two-dimensional carbon material formed by a single layer of C atoms with sp hybridization It has high conductivity, high stability, and a large specific surface area (theoretical value of 2630 m2/g). NG can provide a carrier for TiO2 photogenerated electrons, reduce the recombination of photoexcited carriers, and improve the efficiency of photocatalytic reactions. Yan et al [8] prepared RGO/TiO2 composites with high photocatalytic performance by a two-step hydrothermal method. Based on this previous work, the raw materials. Journal of Chemistry were modified and new NG/TiO2 composites were synthesized by a two-step hydrothermal method. Ti(SO4) was used as the titanium source, urea as the nitrogen source, and HF as the surface etchant. e samples were characterized by various methods to determine the morphology and structure of NG/TiO2. e effects of introducing NG on photogenerated electron-hole pair lifetimes, adsorption performance, and photocatalytic performance were studied. e photocatalytic properties of the composites for the degradation of methyl orange (MO) were tested under UV and sunlight conditions, and the catalysts were tested several times to investigate their cyclability
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