Ag-BiVO_4复合光催化剂的制备及其可见光光催化机理的研究

Preparation of Ag-BiVO_4 Composite and Its Photocatalytic Oxidation Mechanism

BiVO4是一种优良的可见光光催化剂,但是低电荷分离效率和表面吸附性差能严重地制约了其光催化活性的提高.我们通过简单易行的一步水热法制备了银-钒酸铋复合光催化剂(Ag-BiVO4).通过XRD、EDS、XPS、SEM、DRS、PL和BET等手段对其结构和光化学性质进行了详细表征.结果表明,银以Ag和Ag2O的形态存在于催化剂表面.在可见光照射下(λ≥420nm),以染料罗丹明B(Rhodamine B,RhB)和无色小分子水杨酸(Salicylic acid,SA)为模型污染物,考察了Ag-BiVO4和BiVO4的光催化活性.结果表明:Ag的引入能有效提高BiVO4的可见光催化活性,当Ag掺杂量为1.44%时,其光催化效率最高.吸附实验表明Ag的存在极大地加强了RhB在光催化剂表面的吸附.进一步实验表明Ag2O和Ag的相互协同作用使Ag/Ag2O-BiVO4可见光催化活性得到显著提高,其中Ag2O因与BiVO4形成p-n型异质结对其催化活性起到主导作用.

It is reported that,as an excellent visible light photocatalyst,the photocatalytic activity of BiVO4 was seriously restricted due to the low efficiency of charge separation and surface adsorption capacity. One step hydrothermal method was used to prepare Ag-BiVO4 composite photocatalyst,which was detailedly characterized by X-ray diffraction（ XRD）,energy dispersive spectrometer（ EDS）,X-ray photoelectron spectroscopy（ XPS）,scanning e lectron microscope（ SEM）,UV-Vis diffuse reflectance spectroscope（ DRS）,photoluminescence（ PL） and brunauer-emmett-teller（ BET）. The results showed that both Ag and Ag2O coexsit on the surface of BiVO4. The photocatalytic activity of BiVO4 and Ag-BiVO4 catalyst was evaluated by the degradation of Rhodamine B（ Rh B） and Salicylic acid（ SA） under visible-light（ λ≥420 nm）. It was illustrated that the optimal catalytst Ag-BiVO4（ 1.44% Ag doping amount） could significantly promote the visible-light photocatalytic performation. Adsorption experiments indicated the presence of Ag greatly strengthened the adsorption of Rh B on the surface of the photocatalyst. Further experiments showed that the high-efficiently photocatalytic performance of Ag-BiVO4 derived from the coordination of Ag2O and Ag,and Ag2O played an leading role due to the information of p-n heterojunction with BiVO4.