钨掺杂g-C_(3)N_(4)薄膜电极的制备及光电性能研究

Preparation of Tungsten-doped g-C_(3)N_(4) Film Electrode and Its Photoelectric Properties

采用高温液相生长法制备了不同钨(W)掺杂量的W/g-C_(3)N_(4)薄膜电极,并通过SEM、XRD、FTIR、UV/vis DRS、XPS等手段对薄膜电极进行表征。结果表明,掺杂的W以W^(0)、WO_(2)和WO_(3)等多种形态存在。将W/g-C_(3)N_(4)薄膜电极用作光阳极,进行交流阻抗测试、光电流密度测试以及降解亚甲基蓝实验,与g-C_(3)N_(4)薄膜电极相比,W/g-C_(3)N_(4)薄膜电极对可见光的响应能力明显增强,其中当Na_(2)WO_(4)与g-C_(3)N_(4)的掺杂比为1∶50时光电流密度可提高至原来的2.2倍。通过添加自由基捕获剂探究W/g-C_(3)N_(4)薄膜电极对亚甲基蓝的催化氧化机理,发现掺杂W之后,W/g-C_(3)N_(4)薄膜电极光生电子空穴对的分离效果提高,而且电子的迁移能力增强,因此光生电子能更多、更快地迁移到阴极铂丝,被O_(2)捕获生成·O_(2)^(-)并最终生成·OH来降解亚甲基蓝;此外,WO_(3)同样具有光催化活性,在可见光下可以生成光生电子空穴对,也可以提供电子被O_(2)捕获并最终生成·OH来降解亚甲基蓝。

W/g-C_(3)N_(4)film electrodes with different tungsten(W)doping contents were prepared by high temperature liquid-based reaction.Then,the film electrodes were characterized by SEM,XRD,FTIR,UV/vis DRS and XPS.The doped tungsten existed in various forms such as W^(0),WO_(2)and WO_(3).The W/g-C_(3)N_(4)film electrode was used as a photoanode for electrochemical impedance spectroscopy(EIS)test,photocurrent density test and methylene blue degradation experiment.Compared with g-C_(3)N_(4)film electrode,the photoelectric response of W/g-C_(3)N_(4)film electrode to visible light was obviously enhanced.When the doping ratio of Na_(2)WO_(4) and g-C_(3)N_(4)was 1∶50,the photocurrent density of W/g-C_(3)N_(4)film electrode was 2.2 times that of g-C_(3)N_(4)film electrode.The mechanism of W/g-C_(3)N_(4)film electrode for catalytic oxidation of methylene blue was investigated by adding free radical trapping agent.After doping tungsten,the separation of photoelectron hole pair in W/g-C_(3)N_(4)film electrode was improved,and the electron migration ability was enhanced.Therefore,more photoelectron migrated faster to the cathode platinum,which was captured by O_(2)to generate·O_(2)^(-)and eventually to generate·OH to degrade methylene blue.In addition,WO_(3)also had photocatalytic activity to generate photoelectron hole pairs under visible light,and could also provide electrons to be captured by O_(2)and eventually generate·OH to degrade methylene blue.