Si纳米线/ZnFe_(2)O_(4)/AgBr光催化剂的构建及其磁场可调控性能

Construction of Si Nanowire/ZnFe_(2)O_(4)/AgBr Photocatalyst and Its Magnetic Field Tunable Performance

采用金属辅助化学刻蚀法和水热法制备了Si纳米线/ZnFe_(2)O_(4)/AgBr复合光催化剂,考察了Si纳米线/ZnFe_(2)O_(4)/AgBr在磁场作用下的光催化性能。结果表明:Si纳米线/ZnFe_(2)O_(4)/AgBr复合光催化剂在未使用HNO_(3)溶液浸泡且无磁场作用时的光电流密度为0.25 mA/cm^(2),开启电压为0.4 V;Si纳米线/ZnFe_(2)O_(4)/AgBr复合材料在合成时表面会产生Ag,采用HNO_(3)溶液将其浸泡除去Ag,浸泡后光电流密度为0.07 mA/cm^(2),相比于未使用HNO_(3)溶液浸泡时的光电流密度明显下降,这是由于Ag具有传输电子与空穴的能力,可加快ZnFe_(2)O_(4)和Si纳米线间光生电子和光生空穴对的分离,从而提高光电流密度;当外加80000 A/m磁场时,其光电流密度增加至0.2 mA/cm^(2),开启电压为0.28 V,表明磁场可显著提高该复合光催化剂的光催化效率。Si纳米线/ZnFe_(2)O_(4)/AgBr界面处的能带弯曲加快了光生载流子的传输,减少了光生空穴与光生电子间的复合,使更多的电子和空穴可参与到光催化过程中,进而提高了体系的光催化性能。在光催化过程中,外加磁场使体系所产生的光生载流子可以更快速地传输至光催化剂表面,进一步增强体系的光催化效率。

Si nanowires/ZnFe_(2)O_(4)/AgBr composite photocatalysts were prepared by metal-assisted chemical etching and hydrothermal method,and the photocatalytic performance of Si nanowires/ZnFe_(2)O_(4)/AgBr under magnetic field were investigated.The results show that in the condition of no HNO_(3)solution and no magnetic field,the photocurrent density of Si nanowires/ZnFe_(2)O_(4)/AgBr composite photocatalyst is 0.25 mA/cm^(2)and the opening voltage is 0.4 V.Ag can be produced on the surface of Si nanowires/ZnFe_(2)O_(4)/AgBr composites during synthesis,and removed by immersion in HNO_(3)solution.The photocurrent density after immersion is 0.07 mA/cm^(2),which is significantly lower than that without immersion in HNO_(3)solution.This attributes to the ability of Ag to transport electrons and holes,which can accelerate the separation of photogenerated electrons and photogenerated hole pairs of ZnFe_(2)O_(4)and Si nanowires,thus improving the photocurrent density.When applying an external magnetic field of 80000 A/m,the photocurrent density is increased to 0.2 mA/cm^(2)and the turn-on voltage is 0.28 V,indicating that the magnetic field can significantly improve the photocatalytic efficiency of composite photocatalyst.The band bending at the Si nanowires/ZnFe_(2)O_(4)/AgBr interface have sped up the transport of photogenerated carriers,and reduced the recombination between photogenerated holes and photogenerated electrons,so that more electrons and holes can participate in the photocatalytic process,thereby improving the photocatalytic performance of the system.In the process of photocatalysis,the external magnetic field enables the photogenerated carriers produced by the system to be transmitted to the surface of the photocatalyst more rapidly,which further enhances the photocatalytic efficiency of the system.