有机钌螯合物/TiO_2杂化膜修饰电极上Pt纳米团簇的光电流增强效应

利用LB膜技术可控制备了纳米单层和多层的二氧化钛-有机钌螯合物杂化膜,并研究了上述无机-有机杂化膜修饰电极在Pt纳米团簇敏化后的光电流增强效应.实验结果表明:(1)纳米单层TiO2/Ru(phen)2(dC18bpy)]2+(简称为TiO2-Ru)杂化膜的平均厚度为(3.6±0.5)nm;(2)在光照条件下TiO2-Ru杂化膜能有效催化还原Pt(NH3)6]4+形成粒径位于20～160nm之间的Pt纳米团簇;(3)Pt纳米团簇的引入消除了金属钌螯合物中配体对电子传递的阻碍作用,改变了电子传递途径,从而有效减少了电子空穴对的复合,提高了Pt纳米团簇敏化的n层杂化膜修饰电极(ITO/(TiO2-Ru)n/Pt)在支持电解质中的光电流.与纳米单层TiO2-Ru杂化膜修饰的ITO电极(ITO/TiO2-Ru)相比,当工作电压为900mV时,ITO/TiO2-Ru/Pt在0.1mol·L-1的NaClO4电解质溶液中和光照(λ360nm)条件下,单位面积的光电流提高了约5倍;(4)ITO/(TiO2-Ru)n/Pt电极光电流的大小与杂化膜的层数密切相关,当TiO2-Ru杂化膜的层数从一层、二层增加到四层时,光电流呈现先升高后下降行为,这表明ITO/(TiO2-Ru)n/Pt电极的电子传递过程直接通过非电活性的二氧化钛纳米单层进行.

Enhanced Photocurrent of an ITO Electrode by the Photodeposition of Pt Nanoclusters onto a Monolayer TiO_2-Ru Complex Hybrid Film

An indium tin oxide(ITO)electrode modified with mono-/multilayer TiO_2/Ru(phen)_2(dC18bpy)]~(2+)phen=1,10.-phenanthroline,dC18bpy=4,4'-dioctadecyl-2,2'-bipyridyl]hybrid filmdenoted as ITO/(TiO_2-Ru)_n] has been prepared by a modified Langmuir-Blodgett(LB)method.The effects of Pt-photodeposition on the photocurrent of above ITO/(TiO_2-Ru)_n electrode were studied.Our experiments illustrated:(1)the single-layered hybrid film of TiO_2/Ru(phen)_2(dC18bpy)]~(2+)(denoted as TiO_2-Ru)was closely packed at a surface pressure of 25 mN·m~(-1) and had a thickness of (3.60±0.5)nm;(2)under light irradiation(λ>360nm),Pt clusters with radii of 20～160 nm were authentically observed by the reduction ofPt(NH_3)_6]~(4+) through the TiO_2-Ru hybrid film;(3)the enhanced photocurrent was achieved by depositing the Pt nanocluster onto the surface of the ITO/(TiO_2-Ru)n electrodes at the applied potential above 500 mV (vs.Ag|AgCl|KCl)under light irradiation(λ>360 nm).For example,the photocurrent of ITO/TiO_2-Ru/Pt Was increased about 5 times in comparison with an ITO/TiO_2-Ru electrode at the applied potential 900 mV when they were both in contact wilth 0.1 mol·L~(-1) NaClO_4 solution.Such a result indicates that the Pt clusters are able to hamper the combination of electron hole pairs and reduce the counterwork of insulating long alkyl chains of amphiphilic Ru(Ⅱ) complexes, and thus produce the enhanced photocurrent; (4) the photocurrent was strongly dependent on the number of TiO_2-Ru hybrid films. With the increase in the number of layers from one, two to four, the photocurrent intensity was found to firstly increase and then decrease, suggesting that the electron transfer be directly through the electrochemically inactive TiO_2 monolayer.