Synthesis And Photocatalytic Activity Of Titanium Dioxide/boron Nitride Composite Photocatalyst

With the globe industrialization, environmental pollutant problems including wastewater and organic pollutants in the atmosphere, have attracted much attention over the recent years. Many approaches have been utilized to eliminate environment pollution. Among them, environmentally friendly semiconductor-based photocatalysis shows potential application in pollution control. Titanium dioxide(TiO2) is one of the most promising semiconductor photocatalysts for the degradation of organic pollutants because of its exceptional optical and electronic properties, biological and chemical inertness, and nontoxicity. However, pure TiO2 exhibites photocatalytic activity under only ultraviolet light because of its wide band gap(Eg = 3.2 eV). Doping TiO2 with impurities such as nitrogen can efficiently extend the spectral response of TiO2 into the visible-light region, as has been proven by theoretical and experimental studies. Another effective approach to improve the photocatalytic efficiency is further increasing the specific surface area of photocatalysts. Thus, incorporation of photocatalysts with high SSA supports has been explored in this work. Many efforts have been made to load photocatalysts on various supports, revealing that supported photocatalysts have good pollutant adsorption properties, diffusion properties, and high photocatalytic activities.In this paper, we prepared a variety of BN fibre with high SSA and titanium dioxide/boron nitride composite photocatalysts. We also propose a mechanism to explain enhanced photocatalytic activity.(1) Porous boron nitride(PBN) fibre with high specific surface area was synthesized by pyrolysis method using melamine-2boron acid adducts(M·2B) as reactants at the first step, and a sol-gel route was sequently used to prepare the adsorptive TiO2/PBN composite photocatalyst. The photocatalysts were characterized by XRD, SEM, EDS, UV-Vis and BET. The results showed that PBN exhibited a tBN crystal structure with anatase TiO2 loaded on PBN fibre(TiO2/PBN). The methylene blue removing rate of TiO2/PBN could still reach 88.0% under ultraviolet irradiation.(2) An activated boron nitride(ABN) with high porosity was prepared by pyrolysis M·2B in N2 atmosphere, and fluorinated activated boron nitride(F-ABN) was obtained from by further treatment. The F-ABN was employed as supports to prepare TiO2/ABN and TiO2/F-ABN with P25 TiO2 as the starting material. Their photocatalytic activity and recycle properties were investigated. Ti O2/F-ABN exhibited higher photocatalytic activity than TiO2/ABN. The highest reaction rate of TiO2/F-ABN could reach 85.0 % in 90 min under ultraviolet irradiation.(3) Nitrogen-doped TiO2 photocatalysts using porous BN fiber as support(TiO2-xNx/BN) was synthesized from M·2B and tetrabutyl titanate. Tetrabutyl titanate was deposited onto M·2B through a hydrolytic precipitation process. After heat treatment, a novel Ti O2-xNx/BN composite photocatalysts was obtained. The photocatalytic activities of the composite in RhB degradation under visible light were investigated. The proposed mechanism of enhanced visible-light photocatalytic activity is discussed.Totally, the paper studied the adsorption and photocatalytic degradation dynamics of the different composite photocatalysts. The results revealed that compared with pure TiO2 and TiO2-x Nx, the composite photocatalysts showed enhanced photocatalytic activity probably due to the synergistic effect from BN support and TiO2 catalysts.