表面修饰纳米TiO2光催化动力学及EIS分析

采用溶胶-凝胶法以掺杂Fe3+和沉积Ag做表面修饰,制备了TiO2、0.03%Fe3+-TiO2、3%Ag-TiO2三种纳米材料工作电极,并用XRD表征了膜的晶相结构和晶粒尺寸.考察了膜电极催化降解反应.以高压汞灯为光源,通过紫外-可见分光光度计测定证实RhB在催化剂作用下的光催化动力学为一级反应,反应速率常数及在同一实验条件下的降解率依TiO2、0.03%Fe3+-TiO2、3%Ag-TiO,的顺序增大.用IM-6e电化学阻抗仪进行了电化学阻抗谱(EIS)的测量,设计了模拟电路并得到了拟合值.在实验的扫描范围内(10-5-105Hz)发现此光催化反应的速控步为电荷转移过程,得到的Nyquist图的圆弧半径及其模拟阻值大小与光催化降解动力学常数及降解率变化趋势相反.

Photocatalytic dynamics and EIS analysis of nanocrystalline TiO2 by surface modification

Three working electrodes of nano-scale TiO2(TiO2,0.03%Fe3+-TiO2,3%Ag-TiO2) are prepared by sol-gel method and by surface modification with Fe3+ -doping or Ag-deposition. Crystal structures and crystalline grain dimensions of membrane are characterized by XRD and catalytic decomposition on the membrane electrodes is studied. By using the high - pressure mercury lamp as the light source and with the determination by UV -VIS spectrometry, it is proved that photocatalysis - decomposition dynamics of Rhodamine B is the first order reaction and that rate constants increase according to different catalysts used under the same conditions, i. e. TiO2<0. 03%Fe3+-TiO2<3%Ag - TiO2. EIS is measured, simulated circuits are designed, and fitting constants are obtained by the IM -6e. Within the scanning region of experiments (10-1 -105 Hz), it is found that the electron transfer process is the rate control step in the photocatalytic reaction. The change of arc radii of Nyquist graph and simulated impedance values are reverse to the trend of decomposition rate constants and decomposition ratios.