用复合电沉积方法制备了(Ni-Mo)/TiO₂薄膜电极, 以扫描电子显微镜(SEM)、X射线衍射(XRD)、拉曼光谱(Raman Spectra)和紫外-可见漫反射光谱(DRS)对薄膜的表面形貌、晶相结构和光谱特性进行了表征, 在负偏压和可见光作用下, 以罗丹明B为模拟污染物研究了薄膜的光电催化性能. 采用电化学技术和向溶液中加入活性物种捕获剂的方法对薄膜光电催化降解机理进行了探索. 结果表明: (Ni-Mo)/TiO₂薄膜是由粒径为50～100 nm的TiO₂纳米粒子相和纳米晶Ni-Mo固溶体相构成的复合薄膜. 薄膜具有较高的光电催化活性, 在-0.4 V偏压和可见光照射下反应60 min, 复合薄膜光电催化罗丹明B (c=5 mg/L)的降解率是多孔TiO₂(P25)/ITO纳米薄膜的1.56倍. 复合薄膜电极中Ni-Mo纳米晶合金对溶解氧和激发电子还原反应的催化作用是光电催化降解活性提高的重要原因. 通过调节外加偏压, 可以控制电极溶液界面间染料与活性氧化物种的存在形式及其相互作用, 是研究可见光催化降解反应历程的有效方法. 在负偏压和可见光作用下, 羟基自由基和染料正离子自由基对染料的光电催化降解有决定性作用.

In the purpose of preparing highly efficient film photocatalyst and exploring rule of semiconductor photocatalytic and photoelectrocatalytic degradation of organic pollutants, (Ni-Mo)/TiO₂ composite thin films were prepared by composite electroplating at a constant current. The depositing conditions of (Ni-Mo)/TiO₂ film were as follows: suspension quantity of TiO₂ in solution was 6.0 g/L; pH value in solution was 10.5; electrodepositing time and current density were 15 min and 95 mA/cm², respectively. The surface morphology, phase structure, and spectral characteristics of the thin film were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectrum and ultraviolet-visible diffuse reflectance spectroscopy (DRS), respectively. Its photoelectrocatalytic properties were evaluated with Rhodamine B as a model compound under the conditions of negative bias and visible light. Using electrochemical technique and adding active species scavenger to the solution, the mechanism of photoelectrocatalytic degradation for the film were explored. The results indicate that the (Ni-Mo)/TiO₂ film consists of crystalline grains of TiO₂ in the size range of 50～100 nm and the nano-crystalline of Ni-Mo in solid solution. The (Ni-Mo)/TiO₂ film is photoelectrocatalytically more active than TiO₂/ITO (indium tin oxide) film. Reacting 60 min under the negative bias of -0.4 V and visible light irradiation, the photoelectrocatalytic degradation rate of (Ni-Mo)/TiO₂ film is 1.56 times as much as that of porous TiO₂(Degussa P25)/ITO film. The improvement in photoelectrocatalytic degradation activity for the composite film could be mainly attributed to the catalysis of Ni-Mo in the composite film for the reaction of excited electrons with oxygen. By adjusting the applied bias, the existing forms of the dye and active oxygen species at the electrode/electrolyte surface and their interactions can be controlled. It is the efficient method to study the visible light catalytic degradation reaction mechanism. Both the hydroxyl radical and the dye cationic radical have a decisive role on the photoelectrocatalytic degradation of dyes under the conditions of negative bias and visible light.