Preparation and photocatalytic efficiency of graphitic carbon nitride/silver-titanium dioxide composite

Abstract

This research aimed to synthesize high efficiency UV-visible light responsive g-C₃N₄/Ag-TiO₂ composite photocatalysts. The photocatalysts preparation method was classified into 3 parts. The first part was to study the influence of calcination temperature, %Ag loading content, and types of reducing agent on the photocatalytic performance of achieved Ag-TiO₂. The second part, effect of calcination temperatures and soaking time on preparation of high performance g- C₃N₄ photocatalysts under visible light irradiation were studied. Finally, the g- C₃N₄/Ag-TiO₂ composite was synthesized. Then, the photocatalytic performance of prepared photocalysts were investigated through cationic and anionic dye degradation under both UV and visible light irradiation. The photocatalyst’s characteristics such as crystallinity, morphology, optoelectronic properties, and surface properties were well characterized. Likewise, the oxidation state of Ag existing in the prepared composites were clearly investigated by using the X-ray absorption near edge structure (XANES). Moreover, the X-ray photoelectron spectroscopy (XPS) was applied for further confirmation of chemical surface properties. The result showed that the optimal condition for preparation of Ag-TiO₂ was 2 wt.% of Ag loading by using NaBH4 as reducing agent without calcination, while a high performance g- C₃N₄ was achieved by calcining urea at 600 °C for 4 hours. It was obtained that the optimal ratio of g- C₃N₄ to Ag-TiO₂ in g- C₃N₄/Ag-TiO₂ composite was 2 to 1 which possessed the highest photocatalytic performance in anionic/cationic dye degradation under both UV and visible light irradiation. It could degrade 10 mg/L of rhodamine B dye under UV and visible light irradiation for 95.01 % within 60 min and 99.74 % within 15 min, respectively, by using 0.05 g of photocatalysts. In addition, for methyl orange degradation efficiency, as prepared g- C₃N₄/Ag-TiO₂ presented 62.32% within 30 min and 65.71% within 15 min under UV and visible light irradiation, respectively. The results suggested that preparation of photocatalyst as heterostructured g- C₃N₄/Ag-TiO₂ composite could improve photocatalysis activity of g- C₃N₄ under both UV and visible light irradiation. Further, the light-responsive region of Ag-TiO₂ was extended to UV-visible light by using as heterostructured composite. Hence, it was worth noting that the g- C₃N₄/Ag-TiO₂ can possibly be applied as the promising photocatalyst materials.