Magnetic field effects on the amount of active oxygen species released from semiconductor photocatalysts on light irradiation

在碱性条件下(pH=12.0)，用对苯二甲酸与羟基自由基反应生成高荧光的2-羟基对苯二甲酸(TAOH)的化学发光(CL)和自旋捕捉荧光技术，研究了Ag金属^(-)、Ag2O^(-)或负载AgO的TiO2光催化剂和BiVO4光催化剂悬浮液中超氧阴离子自由基(O2-)和OH自由基的产生.在TiO2光催化剂和BiVO4光催化剂上负载AgO显著增强了光致发光强度，这是由于AgO表面的热分解活性和光催化剂/Ag0界面的有效电子-空穴分离增加了负载AgO的光催化剂上的O2-生成量。另一方面，AgO对1102个样品的TAOH生成速率的负载量比BiVO_4催化剂的负载量大约三个数量级。根据7102、BiVO4和银氧化物的光致化学发光动力学和近似带边位置，讨论了这些光催化剂上产生O2-和OH自由基的性质。在光照条件下，磁场对半导体光催化剂的活性氧物种释放量没有明显影响。

Superoxide anion radical (O_(2-)) and OH radical generations in suspensions of Ag metal^(-), Ag_(2)O^(-), or AgO-loaded TiO_(2) and BiVO_(4)photocatalysts in alkaline condition (at pH=12.0) were examined by means of luminal chemiluminescence(CL) and spin-trapping fluorescence technique where terephthalic acid reacts with an OH radical to afford the highly fluorescence 2-hydmxyterephthalic acie (TAOH). The observed luminal CL intensity was remarkably enhanced by the AgO loading on TiO_(2) and BiVO_(4), This can be explained in terms of augmentation of 0_(2-) production on the AgO-loaded photocatalysts due to synergetic effects on the thermocatlytic activity on the AgO surface and efficient electron-hole separation at the photocatalyst/Ag0 interface. On the other hand, the loading effects of AgO on the TAOH formation rates for the 1102 samples were much larger than those for the BiVO_(4) catalysts by ca. three orders of magnitude. The properties of 0_(2)-and OH radical generations on these photocatalysts are discussed on the basis of the luminal CL kinetids and approximate band edge positions of 710_(2), BiVO_(4), and silver oxides. No significant magnetic field effects were observed on the amount of active oxygen species released from semiconductor photocatalysts on light irradiation.