Ti0.7W0.3O2@BiVO4 p-n复合异质结构界面光催化剂的制备及其可见光催化降解苯酚机理的研究

设计并制备了新型Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构界面光催化剂应用于可见光条件下降解模拟含苯酚污染物的废水.采用粉末X射线衍射（PXRD）、扫描电镜（SEM）、固体粉末紫外漫反射（DRS）及X射线光电子能谱（XPS）等技术表征了Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构界面的性状.结果显示BiVO₄纳米粒子均匀地分布在Ti_0.7W_0.3O₂纳米颗粒周围并构筑了稳定的p-n复合异质结构界面.Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构界面光催化剂具有更宽的可见光响应范围和更低的能带宽度.纯BiVO₄和Ti_0.7W_0.3O₂纳米颗粒的导带位置分别为-0.62 eV和0.56 eV.优化了Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构界面光催化剂降解苯酚的条件（即：pH值为4.5，催化剂用量为0.60 g·L^-1和苯酚初始浓度95 mg·L^-1），质量分数为5%Ti_0.7W_0.3O₂/BiVO₄表现出最高的苯酚催化活性且初始降解速率常数（k）为0.01137 min^-1.6次连续光催化降解苯酚后，Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构表现出良好的稳定性和可循环使用性.自由基捕获结果说明3种自由基均参加了苯酚的光催化降解过程中，且氧化能力由强到弱顺序为：羟自由基（·OH^-） > 过氧化物自由基阴离子（·O^2-） > 光生空穴（h⁺）.总有机碳结果表明苯酚在降解的过程中是先产生了中间降解产物，最后这些中间产物再矿化为无机的CO₂和H₂O.利用对苯二甲酸（TA）荧光探针证明了Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构界面光催化剂降解苯酚为羟自由基（·OH^-）机理反应；同时，利用紫外-可见光谱（UV-Vis）和高效液相色谱-质谱联用技术（HPLC-MS）探究了苯酚的中间降解产物，推测了苯酚在Ti_0.7W_0.3O₂/BiVO₄ p-n复合异质结构界面上可能的降解机理.

Preparation of Ti0.7 W0.3 O2@BiVO4 p-n compound heterostructure interfacial photocatalyst and the research on the photocatalytic degradation mechanism of phenol under the visible light

The Ti_0.7W_0.3O₂/BiVO₄ p-n compound heterostructure interfacial photocatalyst (CHIP) was designed and prepared for photocatalytic degradation of phenol pollutant in waste water. The detailed properties of the Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP were analyzed by XRD, SEM, DRS and XPS technologies, showing that BiVO₄ nanoparticles (NPs) were uniformly dispersed on the surface of Ti_0.7W_0.3O₂ NPs and formed the p-n compound heterostructure. A greatly broaden the light response range and a shorter band gap energy for Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP. The conduction band of BiVO₄ and Ti_0.7W_0.3O₂ NPs were measured based on the results of the valence band and band gap energy obtained via XPS and DRS, and then the energy level diagram of Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP was proposed. The photocatalytic degradation of phenol at Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP with different loading ratios of Ti_0.7W_0.3O₂ NPs was investigated with optimum conditions (i.e., pH of 4.5, catalyst dosage of 0.60 g·L^-1 and phenol initial concentration of 95 mg·L^-1) under the illumination of visible light. The 5wt% Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP exhibited the highest photocatalytic activity and the initial rate constant (k) was calculated as 0.01137 min^-1. After recycling six times, the Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP showed a good stability and recyclability.The capture results of free radicals showed that three kinds of free radicals have participated in the process of photocatalytic degradation of phenol, and oxidizing ability order was hydroxyl free radical (·OH^-) > superoxide anion free radical (·O^2-) > photoproduction holes (h⁺). The results of the TOC showed that phenol was first produced the intermediates, and then all the intermediates changed into inorganic finally. Hydroxyl free radical (·OH^-) involved initial reaction at the Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP was evidenced by Terephthalic Acid (TA) Fluorescence Probe. Besides, UV-Vis spectroscopy and UHPLC-MS technologies were used to analyze main intermediates of photocatalytic degradation of phenol. The probable photocatalytic degradation mechanism of phenol at the Ti_0.7W_0.3O₂/BiVO₄ p-n CHIP was also proposed.