【作者】 张成龙；

【导师】 卫敏；

【作者基本信息】 北京化工大学 ， 化学工程（专业学位）， 2015， 硕士

【摘要】 近几十年,能源危机成为全球关注的问题,开发利用新能源已经成为国内外研究的热点,光电化学(PEC)分解水制氢为人类获取新能源提供了一种有效的方法。传统的光电阳极材料主要是以Ti02,ZnO, WO3等为代表的半导体氧化物材料,但这些传统光电阳极材料存在着可见光利用率低、光生电子-空穴易复合和量子效率低等问题,限制了它们的近一步应用。本文在传统的光电阳极材料ZnO, WO3基础上,通过构筑ZnO纳米阵列多级结构、沉积贵金属金纳米颗粒和引入水滑石(LDH)助催化剂等方法,在提高活性位,抑制电子-空穴复合,扩大光谱吸收以及提高水氧化动力学等方面实现了对光电阳极材料的优化,提高了光电化学分解水的性能。同时,通过DFT理论计算的方法对光电阳极材料在光电化学分解水的过程中一些机理进行了探索。具体研究内容如下：1、通过水热法合成了ZnO NR@NP核壳阵列,研究表明ZnONR@NP核壳阵列多级结构有利于ZnO活性位点的暴露,提高了光电化学分解水的效率。进一步用Au纳米颗粒进行修饰后,Au-ZnO NR@NP阵列光电流有很大提高,在电压0.6 V vs. Hg/Hg2Cl2下光电流密度为1.47 mA·cm-2,而ZnO NR@NP阵列为1.17 mA·cm-2。 Au-ZnONR@NP光电化学分解水性能的增强是由于金纳米颗粒形成电子陷阱抑制了ZnO光生电子-空穴对的复合,同时,金纳米颗粒的SPR效应提高了可见光的利用率。密度泛函理论(DFT)计算进一步证明ZnO的光激发电子容易转移到Au纳米颗粒上。该工作提供了一个有效的制备贵金属／半导体多级结构纳米阵列的方法。2.通过电合成的方法实现了NiFe-LDH纳米片在W03纳米线阵列上的有序生长,并探究了在光电化学分解水方面NiFe-LDH与W03之间的协同作用。W03本身具有光催化性能,NiFe-LDH具有优良的电催化性能,两者结合形成的WO3@NiFe-LDH核壳纳米阵列显著增强了光电化学分解水的性能。NiFe-LDH壳作为助催化剂增加了整个体系的反应动力学,同时抑制了W03电子-空穴对的复合。本论文提出了一个制备半导体氧化物和LDH复合多级纳米阵列材料的方法,其显著提高了半导体金属氧化物的PEC分解水性能。更多还原

【Abstract】 With increasing concern on the reduction of global fossil fuels, considerable efforts have been committed to exploit alternative energy sources in the past several decades. Photoelectrochemical (PEC) water splitting provides a renewable and environmentally friendly energy conversion method. The conventional photoelectrodes is metal oxide semiconductors, such as ZnO, TiO2, WO3. However, these photoelectrodes usually suffers from the limited surface area, less efficiency in light capture and unsatisfied electron-hole separation. Based on the conventional photoelectrodes, this thesis realize the optimization of photoanode material by constructing ZnO core-shell hierarchical nanostructure, deposition of precious metals and introducing cocatalyst NiFe-LDH because of the increased active site exposure, inhibited electronic-hole recombination, expanded light absorptionas well as the improved water oxidation kinetics. Furthermore, the mechanism of the photoelectrochemical water splitting on the photoanode material has been studied by DFT theory calculation.The detailed content is as follows:1. ZnO nanorod@nanoplatelet (NR@NP) core-shell arrays have been synthesized via a facile hydrothermal method. The resulting ZnO NR@NP nanoarray exhibits promising behavior in photoelectrochemical water splitting, which can be attributed to the core-shell hierarchical nanostructures which facilitates the exposure of active sites. By a further modification using Au nanoparticles, the obtained Au-ZnO NR@NP demonstrates a largely enhanced photocurrent density of 1.47 mA-cm-2 at 0.6 V, much large than that of ZnO NR@NP core-shell arrays (1.17 mA-cm-2). Au nanoparticles as electron traps inhibit ZnO electronic-hole recombination. In addition, the surface-plasmon-resonance effect of Au nanoparticles facilitates utilization of visible light. Density functional theory (DFT) calculations further confirm that the photogenerated electrons of ZnO transfer to Au, which suppresses the recombination of electron-hole pairs. Therefore, this work provides a facile and cost-effective strategy for the construction of hierarchical metal/semiconductor nanoarrays, which can be potentially used in the field of energy storage and conversion.2. WO3@NiFe-LDH core-shell nanoarrays have been synthesized by electrochemical deposition method. The combination of these two photoelectrodes material significantly enhances the performance of photoelectrochemical water splitting. Typically, WO3 has photocatalytic properties, while NiFe-LDH shell acts as cocatalyst which increases water oxidation kinetics and suppresses the recombination of electron-hole pairs. This work provides a facile strategy for the construction of hierarchical core-shell nanoarrays, which can be potentially used in the PEC water splitting.更多还原