Effects of Hydroxylation on PbS Quantum Dot Sensitized TiO₂ Nanotube Array Photoelectrodes

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• 作者：Zhongqing Liu^a ; ^{liuzq_hgxy@scu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; ^{lzq_301@126.com" class="auth_mail" title="E-mail the corresponding author} ; Bin Wang^a ; Jianchun Wu^b ; Qiang Dong^a ; Xiaoming Zhang^a ; He Xu^a
• 关键词：NaOH pretreatment ; Transient photovoltage ; Interfacial kinetics ; First principle simulation.
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：1 January 2016
• 年：2016
• 卷：187
• 期：Complete
• 页码：480-487
• 全文大小：1962 K

文摘

The contact state at the heterojunction interfaces greatly influences the interfacial kinetics of the photoinduced charge carriers. In this study, we used a facile NaOH pretreatment to replenish the hydroxyl groups lost during the heat treatment for crystallization of TiO₂ nanotube arrays (TNAs) prepared via anodic oxidization. By reacting the carboxylic acid groups of thioglycolic acid (TGA) with the TiO₂ surface hydroxyl groups, TGA molecules were covalently linked to the TiO₂ surface and then PbS quantum dots (QDs) were anchored onto the TNAs via the successive ionic layer adsorption and reaction (SILAR) method. The sample microstructure and photoelectrochemical properties were analyzed with X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM),current–voltage characteristics (J–V), electrochemical impedance spectroscopy (EIS), transient photovoltage plots and Mott-Schottky curves. The contact state and electrostatic potential distribution between TiO₂ {1 0 1} and PbS {1 1 1} planes were estimated by using first principle simulation. It was found that the NaOH pretreatment could enhance the crystallization degree of PbS QDs, decrease the crystal face mismatch, dangling bond density and the interfacial resistance between PbS QDs and TiO₂, and accelerate the interfacial separation and transfer of photoinduced charge carriers. The first principle calculations demonstrated that the PbS QDs and TiO₂ interfacial contact was strengthened, and the built-in electric field was induced from TiO₂ {1 0 1} towards PbS {1 1 1}. These combined effects apparently improved the device photoelectrochemical performance. Compared to the sample without pretreatment, the specimen pretreated with NaOH demonstrated 19.96% and 29.93% increases in peak photoconversion efficiency after five and ten cycles of SILAR deposition, respectively.