Preparation Of TiO₂/CNTs Composites By Microwave-Assisted Method And Its Photocatalytic Properties Under Visible Light

Photocatalysis technology takes an important place in solving the increasing severe environmental pollution. Photocatalysis technology can realize a reaction proceeding under normal pressure and temperature. Among numerous semiconductor photocatalysts, TiO2 enjoys great popularity due to its high activity, good thermal properties and low price. However, there is still some weakness in the application of TiO2, such as the narrow light corresponding range and high recombination rate of photo-generated current and hole. All these weakness limit large-scale application of TiO2 in industry.To solve this problem, researchers have put forward many feasible methods for TiO2 modification. In addition, Microwave-assited heating method has a lot of advantages such as rapid volumetric heating, acceleration of the reaction rates, products form and particle control synthesis. TiO2/CNTs composites were prepared by microwave-assisted method in this study. The photocatalytic activity of TiO2 was improved by synergistic effect between TiO2 and carbon nanotube. The main contents of this study are as following:(1) CNTs pretreatment was conducted by H2O2 and HNO3 mixed solution in microwave-assisted heating condition to remove impurities such as amorphous carbon, nano-carbon particles. The surface of CNTs is very smooth with little dangling-bond which make CNTs difficult bond with other matrix. After pretreatment by H2O2 and HNO3 mixed solution, more -COOH and -OH were formed in surface of CNTs. Moreover, the dispersibility of CNTs after pretreatment was improved which is seen from FESEM images.(2) TiO2/CNTs composites were prepared with microwave-assisted heating method by (NH4)2TiF6 in low price as Ti source, H3BO3 as F- consumption reagent, CNTs as TiO2 carrier. The influence of the ratio of H3BO3/(NH4)2TiF6, microwave preparation temperature, microwave preparation time, concentration of H3BO3 and (NH4)2TiF6 and pH on the crystalline form of TiO2 and loading effect on the surface of CNTs were discussed. The results indicated that the ratio of H3BO3/(NH4)2TiF6, microwave-assisted preparation temperature, microwave-assisted preparation time, concentration of H3BO3 and (NH4)2TiF6 and pH could all influence the growth of TiO2 and the sythesis effect of TiO2/CNTs composites. The best process condition was H3BO3/(NH4)2TiF6=2:1, heating (50min,60min) under 90?, pH=2.(3) TiO2/CNTs composites potocatalytic activity was evaluated by photocatalysis degradation by Rhodamine B. The influence of the ratio of H3BO3/(NH4)2TiF6, microwave preparation temperature, microwave preparation time, concentration of H3BO3 and (NH4)2TiF6 and initial concentration of Rhodamine B on the photocatalytic activity of TiO2 was investigated. The results indicated that the photocatalytic activity of TiO2/CNTs composites was highly improved compared with pure TiO2 and P25, and all the factors above could influence the photocatalytic activity of TiO2. Suitable photocatalytic condition could degrade organic pollutants efficiently and played a role as catalyst to a maximum extent. The best condition for TiO2/CNTs composites to degrade Rhodamine B was H3BO3/(NH4)2TiF6=2:1, heating (50min,60min) under 90?, initial concentration of Rhodamine B is 1×10-4 mol/L.In this study, a novel microwave-assisted heating method was used to prepare TiO2/CNTs composites. The photocatalytic activity of TiO2 was improved by recombination with CNTs. The whole process was simple, efficient and without pollution, which is a feasible microwave-assisted heating method worth improving and developing for TiO2/CNTs composites preparation.