Fabrication Of Efficient Visible Light Photocatalyst Based On Conducting Polymers And Their Performance In Photodegradation Of Pollutants

Photocatalysis is one of the attractive efficient environmental pollution control technique due to its environmental friendly property, excellent photocatalytic activity and potential in solar useless. However, there are two problems for the mostly studied photocatalyst TiO2, which were the vital factors to the further development of photocatalysis. One is the limitation of utilization of visible light; another one is low quantum efficiency. Conducting polymers (CPs) was a unique organic semiconductor, which possesses efficient visible light absorption and charge transfer ability. The separation of photogenerated charge could be facilitated when CPs combined with other semiconductors owing to the heterojunction built between them; on the other hand, the visible light harvest efficiency of photocatalyst could be enhanced by employing the multiple scattering effect, reflection effect and slow photons effect of photonic crystals and mesoporous core-shell microspheres structure. The synergy of the two factors as stated above would enhance the efficiency of photocatalysis under visible light irradiation. In this dissertation, the following work has been done:(1) Photonic crystal coupled TiO2/P3HT hybrid photocatalyst on FTO substrate (Bilayer TiO2/P3HT) were fabricated by the combination of template method, liquid phase deposition method, spin coating and dipping method. The Bilayer TiO2/P3HT was composed of inverse opal TiO2 layer and TiO2 nanoparticle layer. The inverse opal TiO2 was regular with FCC. The TiO2 nanoparticle layer was composed of TiO2 nanoparticle with diameter in the range 5-25 nm. After modification with P3HT, the Bilayer TiO2/P3HT composite photocatalyst was still in anatase. Moreover, the visible light absorption of Bilayer TiO2/P3HT was more intensive than the conventional NP-TiO2/P3HT in the range of 400-650 nm because of the reflection effect and slow photos effect of inverse opal TiO2. The result of photocatalytic degradation of MB under visible light irradiation illustrated that the pseudofirst-order kinetic constant using the Bilayer TiO2/P3HT was 2.08 times as great as that using NP-TiO2/P3HT. The photocatalytic mechanism of photodegradation of MB was discussed.(2) PANI modified core-shell mesoporous TiO2 microspheres (PANI/M-TiO2) were fabricated by the combination of hydrothermal method and chemisoroption method. The morphology of PANI/M-TiO2 was microspheres with unique core-shell structure..The specific surface area of PANI/M-TiO2 was 125 m2/g. The PANI/M-TiO2 composite photocatalyst with the mass proportion of 6% showed the best photocatalytic peformance. The visible light absorption of 6% PANI/M-TiO2 was more intensive that of conventional PANI/NP-TiO2 because of the multireflection effect and large surface area of PANI/M-TiO2. The result of photocatalytic degradation of RhB and 4-CP under visible light irradiation illustrated that the pseudofirst-order kinetic constant using the 6% PANI/M-TiO2 was 5.04 times and 2.03 times as great as that using conventional PANI/NP-TiO2, respectively. The photocatalytic mechanism of photodegradation of RhB and 4-CP was discussed.(3) The graphene oxide and graphitic carbon nitride (g-C3N4/GO) was prepared by directly heating melamine and ultrasonic adsorption method. The g-C3N4 was composed of graphite-like stacking of the tri-s-triazine units. The GO displayed flake-like shapes of with wrinkles and ripples. The surface of GO contained much functional groups, such as-COOH,-OH,-C-O-C-. After ultrasonic adsorption, g-C3N4 combined with GO via strong bonds. The absorption of g-C3N4/GO was more intensive than that of g-CsN4. Moreover, efficient photocharge separation process occured in the g-CsN4/GO composite photocatalyst. The result of photocatalytic degradation of RhB under visible light irradiation illustrated that the pseudofirst-order kinetic constant using the g-C3N4/GO was 3.80 times as great as that using conventional g-C3N4.The results of the experiments in this dissertation demonstrated that the visible light absorption of photocatalyst could be harvested efficiently via the construction of photocatalyst with suitable morphology and structure; the heterojunction built between CPs and other semiconductors benefited the separation of photogenerated charge. The synergy effect of the two aspects could enhance the efficiency of photocatalysis under visible light irradiation, which supplied feasible approaches for the design and fabrication of efficient visible light photocatalyst, and promoted the application and development of photocatalytical technology further.