氧化锌基光子晶体的界面结构设计及光电化学活性研究
发布时间：2018-10-17 14:46
【摘要】：光电化学水解产氢是决当前能源与环境问题的理想技术之一,广受国内外学者关注。一个完整的光电化学水解产氢过程包括以下三个步骤:光能捕获、光生电荷产生与转移、电极界面处的氧化还原反应。反蛋白石结构的光子晶体一方面可以由于光子在其内部发生的多重折射和衍射增强了基体对光子的捕获,另一方面由于较短的载流子传输路径,提升了光生电子和空穴的分离效率。因此,光子晶体是一种理想的光电化学水解产氢的纳米结构。ZnO由于环境友好、形貌可控、资源丰富,被认为是合适的光电化学水解产氢的半导体材料。但ZnO较宽的禁带宽度(3.2eV),限制了其在光电化学水解产氢方面的进一步应用。本论文通过界面结构设计调控ZnO基光子晶体的光电化学活性,提高光子捕获效率及载流子分离效率,具体研究结果有如下:1.利用层层自组装的方法制备了三维有序堆积的聚苯乙烯(Polystyrene Sphere,PS)微球薄膜,以此为模板浸入氧化锌前驱体溶液,通过高温煅烧除去PS微球得到ZnO光子晶体。之后浸入铁盐的前驱体溶液,利用高温条件下的固相反应原位合成三维多孔结构ZnO/ZnFe_2O_4光子晶体。分析了不同浸入次数对光子晶体形貌和性质的影响,探索了最佳性能参数。利用固相转化反应制备的复合光子晶体界面电阻较小,光生载流子的迁移速率快,ZnO和ZnFe_2O_4能带结构匹配,提高了光生电子与空穴的分离效率。复合光子晶体展示出优异的光电转换效率,在偏压为0.38V无助催化剂存在的条件下高达0.81%几乎是纯的氧化锌的6倍。制备的光电极光稳定性很好,经过十个小时的持续光照光电流还保持了95.1%(在相同条件下衰减了 89%)。展示出了良好的光电催化性能和优异的稳定性。通过DFT理论计算和电化学性能分析,很好的佐证了较快的载流子动力学促进了 ZnO/ZnFe_2O_4反蛋白石结构光电极性能的提升。2.以ZnO光子晶体为前驱体,通过阴阳离子交换的方法原位制备了全光谱响应的ZnO/CdSe复合光子晶体。这种三维多孔结构的复合光子晶体对光子的捕获从紫外区拓宽到了近红外区,低的界面电阻提高了光生载流子的转移与分离。在波长小于400nm光的辐射下,ZnO/CdSe复合光子晶体光电流可高达17.5 mA cm~(-2),并且样品展现了令人满意的光稳定性。ZnO/CdSe复合光子晶体的产氢速率为148μmol cm~(-2)h~(-1),法拉第效率高达95%以上。相较于在相似条件下文献中报道的结果,我们制备的三维多孔结构的ZnO/CdSe复合光子晶体体现了优异的竞争力。这为制备可实际应用的高活性和稳定性的光电极提供了新的思路。
[Abstract]:Photochemical hydrolysis of hydrogen production is one of the ideal technologies to solve the current energy and environmental problems, and has been widely concerned by scholars at home and abroad. A complete photochemical hydrolysis process for hydrogen production consists of three steps: photoenergy capture, photogenerated charge generation and transfer, and redox reaction at the electrode interface. On the one hand, photonic crystals with inverse opal structure can enhance the capture of photons due to the multiple refraction and diffraction of photons in their interior, on the other hand, because of the short carrier transmission path, The separation efficiency of photogenerated electrons and holes is improved. Therefore, photonic crystal is an ideal nano-structure of photochemical hydrolysis for hydrogen production. ZnO is considered to be a suitable semiconductor material for photochemical hydrolysis of hydrogen because of its friendly environment, controllable morphology and abundant resources. However, the wide band gap (3.2eV) of ZnO limits its further application in photochemical hydrolysis to produce hydrogen. In this paper, the photochemical activity of ZnO based photonic crystal is regulated by interface structure design, and the photonic capture efficiency and carrier separation efficiency are improved. The results are as follows: 1. Three-dimensional ordered polystyrene (Polystyrene Sphere,PS) microspheres were prepared by layer-by-layer self-assembly method, which were used as templates to immerse in zinc oxide precursor solution, and ZnO photonic crystals were obtained by calcination of PS microspheres at high temperature. After soaking in the precursor solution of iron salt, three-dimensional porous ZnO/ZnFe_2O_4 photonic crystals were synthesized in situ by solid state reaction at high temperature. The effects of different immersion times on the morphology and properties of photonic crystals were analyzed and the optimum performance parameters were explored. The interface resistance of photonic crystals prepared by solid phase conversion reaction is small, the transfer rate of photogenerated carriers is fast, the band structure of ZnO and ZnFe_2O_4 is matched, and the separation efficiency of photogenerated electrons and holes is improved. The composite photonic crystal exhibits excellent photoelectric conversion efficiency, which is almost 6 times that of pure zinc oxide at a bias voltage of 0.38 V in the presence of a helpless catalyst. The photo-electric auroral stability is very good. After 10 hours of continuous illumination, the photocurrent is kept at 95.1% (the attenuation is 89% under the same conditions). Good photocatalytic performance and excellent stability are shown. Through DFT theory calculation and electrochemical performance analysis, it is well proved that faster carrier dynamics can promote the improvement of optoelectronic pole performance of ZnO/ZnFe_2O_4 reverse opal structure. 2. Using ZnO photonic crystal as precursor, ZnO/CdSe composite photonic crystal with full spectral response was prepared in situ by anion exchange method. The photonic trapping of this three-dimensional porous composite photonic crystal extends from the ultraviolet region to the near infrared region, and the low interfacial resistance increases the transfer and separation of photogenerated carriers. The photocurrent of ZnO/CdSe composite photonic crystal can reach 17.5 mA cm~ (-2) under the radiation of wavelength less than 400nm, and the sample shows satisfactory photostability. The hydrogen production rate of ZnO/CdSe composite photonic crystal is 148 渭 mol cm~ (-2) h ~ (-1), and the Faraday efficiency is over 95%. Compared with the results reported in the literature under similar conditions, the ZnO/CdSe composite photonic crystals with three dimensional porous structures exhibit excellent competitiveness. This provides a new idea for the preparation of highly active and stable photoelectrodes which can be applied in practice.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O734
本文编号：2277016
[Abstract]:Photochemical hydrolysis of hydrogen production is one of the ideal technologies to solve the current energy and environmental problems, and has been widely concerned by scholars at home and abroad. A complete photochemical hydrolysis process for hydrogen production consists of three steps: photoenergy capture, photogenerated charge generation and transfer, and redox reaction at the electrode interface. On the one hand, photonic crystals with inverse opal structure can enhance the capture of photons due to the multiple refraction and diffraction of photons in their interior, on the other hand, because of the short carrier transmission path, The separation efficiency of photogenerated electrons and holes is improved. Therefore, photonic crystal is an ideal nano-structure of photochemical hydrolysis for hydrogen production. ZnO is considered to be a suitable semiconductor material for photochemical hydrolysis of hydrogen because of its friendly environment, controllable morphology and abundant resources. However, the wide band gap (3.2eV) of ZnO limits its further application in photochemical hydrolysis to produce hydrogen. In this paper, the photochemical activity of ZnO based photonic crystal is regulated by interface structure design, and the photonic capture efficiency and carrier separation efficiency are improved. The results are as follows: 1. Three-dimensional ordered polystyrene (Polystyrene Sphere,PS) microspheres were prepared by layer-by-layer self-assembly method, which were used as templates to immerse in zinc oxide precursor solution, and ZnO photonic crystals were obtained by calcination of PS microspheres at high temperature. After soaking in the precursor solution of iron salt, three-dimensional porous ZnO/ZnFe_2O_4 photonic crystals were synthesized in situ by solid state reaction at high temperature. The effects of different immersion times on the morphology and properties of photonic crystals were analyzed and the optimum performance parameters were explored. The interface resistance of photonic crystals prepared by solid phase conversion reaction is small, the transfer rate of photogenerated carriers is fast, the band structure of ZnO and ZnFe_2O_4 is matched, and the separation efficiency of photogenerated electrons and holes is improved. The composite photonic crystal exhibits excellent photoelectric conversion efficiency, which is almost 6 times that of pure zinc oxide at a bias voltage of 0.38 V in the presence of a helpless catalyst. The photo-electric auroral stability is very good. After 10 hours of continuous illumination, the photocurrent is kept at 95.1% (the attenuation is 89% under the same conditions). Good photocatalytic performance and excellent stability are shown. Through DFT theory calculation and electrochemical performance analysis, it is well proved that faster carrier dynamics can promote the improvement of optoelectronic pole performance of ZnO/ZnFe_2O_4 reverse opal structure. 2. Using ZnO photonic crystal as precursor, ZnO/CdSe composite photonic crystal with full spectral response was prepared in situ by anion exchange method. The photonic trapping of this three-dimensional porous composite photonic crystal extends from the ultraviolet region to the near infrared region, and the low interfacial resistance increases the transfer and separation of photogenerated carriers. The photocurrent of ZnO/CdSe composite photonic crystal can reach 17.5 mA cm~ (-2) under the radiation of wavelength less than 400nm, and the sample shows satisfactory photostability. The hydrogen production rate of ZnO/CdSe composite photonic crystal is 148 渭 mol cm~ (-2) h ~ (-1), and the Faraday efficiency is over 95%. Compared with the results reported in the literature under similar conditions, the ZnO/CdSe composite photonic crystals with three dimensional porous structures exhibit excellent competitiveness. This provides a new idea for the preparation of highly active and stable photoelectrodes which can be applied in practice.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O734
【参考文献】
相关期刊论文 前1条
1 李珩;王京霞;王荣明;宋延林;;三维胶体光子晶体对光的调控与应用研究[J];化学进展;2011年06期
，本文编号：2277016
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