表面相变及Pt负载的BiOBr纳米片的协同光催化效应

Effect of Surface Phase Transition and Pt Loading of BiOBr Nanosheets on Synergistic Photocatalysis

通过热处理手段考察了BiOBr纳米片的表面相变过程。通过XRD,Raman,SEM,TEM,UV-Vis-DRS等手段对不同热处理温度下样品的结构进行表征。结果表明,高温热处理下(≥400℃),BiOBr相向Bi24O31Br10相转变,可形成BiOBr/Bi24O31Br10异质结。通过气相乙醛的降解,并与商用P25 TiO2做比较来评估催化剂的光催化性能,测得活性顺序为:P25 TiO2>BiOBr>BiOBr/Bi24O31Br10。能带结构分析可知BiOBr与Bi24O31Br10间形成I型异质结不利于电荷分离,因而活性降低。然而,当同样条件下于上述催化剂表面负载Pt后,测得光催化活性顺序为:(BiOBr/Bi24O31Br10)-Pt>BiOBr-Pt>P25 TiO2-Pt。(BiOBr/Bi24O31Br10)-Pt的最高活性归因于BiOBr/Bi24O31Br10异质结与Pt负载的协同分离光生载流子过程,即与BiOBr/Bi24O31Br10界面的光生空穴转移,BiOBr/Pt及Bi24O31Br10/Pt界面的光生电子转移、累积及开启双电子还原O2的一系列过程有关。

BiOBr nanosheets were synthesized by solvent thermal technique and their phase transition behavior was studied under thermal treatment. The structure was characterized by XRD, Raman, SEM, TEM and UV-Vis- DRS techniques. The results illustrate that BiOBr has transformed to Bi24O31Br10 upon calcination above 400℃ and BiOBr/Bi24O31Br10 surface phase junction is formed. The photocatalytic activity of as-obtained catalysts was tested via degradation of gaseous acetaldehyde and compared with the reference P25 TiO2. The activity decreases with the increase of temperature, and the tested activity follows the order： P25 TiO2〉BiOBr〉BiOBr/Bi24O31Br10. The energy band structure analysis demonstrates that the decreased activity of BiOBr/Bi24O31Br10 is due to the inefficient charge separation induced by the type I heterojunction between BiOBr and Bi24O31Br10. Interestingly, when Pt loading on the surface of aforementioned catalyst via photoreduction of H2PtCl6 under UV light, the activity order is： （BiOBr/Bi24O31Br10）-Pt 〉BiOBr-Pt 〉P25 TiO/-Pt. We believe that the activity order may be attributed to enhanced charge separation efficiency induced by the synergistic effect between BiOBr/Bi24O31Br10 heterojunction and Pt loading.