纳米尺度TiO_2微粒多孔膜电极光电化学

Photoelectrochemical Studies on the Electrode of Nano-structured TiO_2 Porous Film

用光电流作用谱、光电流-电势图和瞬态光电流谱等光电化学方法研究了TiO2多孔膜电极在含不同氧化还原体系的电解质溶液中的光电转换过程.结果说明TiO2多孔股为n-型半导体，其禁带宽度为3.26eV.当在电解质溶液中加入醌二苯酸（BQ／HQ），TiO2多孔膜电极的光电流作用谱形基本与没加氧化还原对时类似。在可见光区的光电流拖尾是由于醌被光激发，然后给出电子到TiO2多孔膜导带而产生阳极光电流.而在电解质溶液中加入Fe（CN）3-6-／4-时，TiO2多孔膜电极的光电流作用谱有明显的改变.除了在小于380nm短波区有光电流峰外，还在400-600nm的可见光区观察到宽的光电流峰，大大增加了光电流转换效率.同时在小于-0.2V下为阳极光电流，在-0.2V～0.3V电势区间为明显阴极光电流，在大于0.3V下可观察到较弱的阳极光电流.当电极电势大于-0.2V时，光电流瞬态谱在开始光照时有一阴极瞬态光电流尖峰，然后转变为阳极稳态光电流.这是因为当电极电势较负时，Fe（CN）4-6与TiO2的电子传递络合物可以吸收光子，光生电子迅速注入TiO2导带，然后还原溶液中的而产生阴极光电流.

The photoinduced elcctron transfer process of the TiO2 porous film in the electrolytes containing different redox couples was invcstigated using photoelectrochedrical techniques. The photocurrent acti0n spectra, the potential dcpcndence of photocurrent and the photocurrent transients indicate that the TiO2 porous film shows characteristics of sedriconductor of n-type with an optical gap of 3.26eV.After adding quinllydrone (BQ/HQ) in the clectrolyte, the photocurrcnt action spectrunl is similar to tl1at without redox couple and the photocurrent tail in the visible region is due to the injection of clectron of excitcd statc of p-benzoquinone to the conduction band of TiO2 porous film.After adding in the electrolyte, the photocurrent action spectrum is obviously differcnt from that without rcdox couple. In addition to the photocurrent peak in the region of wavelength less that 380nm, a wide peak is observcd in the visible region of 400-600nm which increitses the efficiency of light-electric conversion. The photocurrent is anodic at the potential more negative than 0.2V. becomes cathodic at the potential of 0.2~0.3V and is anodic again but weak at potential more positive than 0.3V. At the potential more positive than -0.2V.a cathodic spike is observed on the photocurrent transicnts plot at the moment of light-on, and later transforms into anodic steady state photocurrent, which can be interpreted that the rapid injection of the photoinduced electron of the charge-transter complex of . in the conduction band ofTiO2 porous film, and then reduces in the electrolyte.