Synthesis, Characterization Of Several Vanadium Oxides Nanomaterials And Their Application In Catalytic Degradation Of Dyes

Textile industry effluents contain a variety of complex and hard to degrade pollutants such as dyes that may cause significant water pollution when they are released to our environment. Therefore, to synthesize a highly effective catalyst for treating textile dye wastewater is still a challenge and has important scientific significance and application prospects.Semiconductor photocatalysts have been extensively studied in recent decades, and have been applied in numerous areas, such as water treatment, air purification, decomposition of water into hydrogen, etc. However, most of photocatalysts work under ultraviolet light. Thereinto, nano-TiO2has been extensively studied as an effective photocatalyst, but it is not a good candidate under visible light irradiation. Therefore, it is still a challenge to synthesize a highly effective catalyst for treating textile dye wastewater under visible light. Vanadium oxides semiconductor materials have received significant attention recently because of their distinctive structural versatility and novel applications in catalysis, high-energy lithium batteries, electric field-effect transistors, chemical sensors/actuators and electrochemical devices. Nevertheless, a few studies about using vanadium oxides in photocatalytic degradation of organic pollutants have been reported.In this thesis, several kinds of vanadium oxide nanomaterials were synthesized via hydrothermal method, and their photocatalytic or electrochemical properties were studied. The main results are as follows:1. The ammonium vanadium oxide cross-like nanobelt arrays with bamboo mat center were synthesized via hydrothermal method using NH4VO3as precursors in presence of sodium carboxymethyl cellulose (CMC), the soft template, at160℃for6h. The synthesized-products were characterized by XRD, FE-SEM, TEM, SA-ED, HRTEM, and FT-IR. The effects of CMC concentration, pH value and temperature on the product morphology were investigated. It showed that pH value plays a crucial role in the formation of cross-like nanobelt arrays. Based on the results of time dependent experiments, the growth process of the cross-like NH4V4O10nanobelt arrays is proposed. Furthermore, the mixed valance state vanadium oxide nanobelt arrays were obtained by calcination of the cross-like NH4V4O10nanobelt arrays at400℃for40min and its capability of catalytic degradation of rhodamine B with oxygen in aqueous under UV/vis light irradiation was studied and compared with anionic dyes. Besides, the influence of temperature on the photocatalytic degradation was also investigated. The result showed that the degradation efficiency of rhodamine B catalyzed by the calcinated product was about95%at pH6.8and75℃for3h and30min, suggesting it is a candidate of efficient catalysts for the photocatalytic degradation of rhodamine B under visible light irradiation.2. Single-crystalline MnV2O6V2O5cross-like nanobelt arrays were successfully synthesized by hydrothermal reaction. The products were characterized by XRD, TEM and HR-TEM. The effects of the reaction conditions such as pH, V5+/Mn2+ratio, carboxymethyl cellulose concentration and reaction time on the morphology of the products were studied. The band gap of the as-prepared products was calculated via diffuse reflectance spectral analysis and their activity of photocatalytic oxidation was evaluated by photodegradation of methylene blue under visible-light irradiation. The results showed that the degradation efficiency of methylene blue catalyzed by the calcinated products is remarkably enhanced due to Mn doping, suggesting that MnV2O6.V2O5cross-like nanobelt arrays are a good candidate for visible-light-driven photocatalysts.3. VO2(B) hollow like-nanosphere material was synthesized via a facile one-step hydrothermal process using vanadium oxalate as precursors in the presence of water-benzyl alcohol. Effects of vanadium oxalate concentration, existence of benzyl alcohol and its concentration, and addition of hydrogen peroxide on the morphologies of as-prepared products were investigated. The as-synthesized products were characterized by XRD, FE-SEM, TEM, HR-TEM and FT-IR. Based on the results of time dependent experiments, the growth process of VO2(B) hollow like-nanosphere were proposed. The inside-out Ostwald ripening is responsible for the growth of spherical particles and the formation of hollow like-nanosphere. In addition, the electrochemical properties of VO2(B) like-nanosphere at various reaction times were compared by using cyclic voltammogram.