高温快速退火提升氧化铁光阳极光电化学水分解性能及机制研究
发布时间：2018-11-01 16:11
【摘要】：光电化学水分解是将太阳能转换成无污染的化学燃料来解决能源匮乏及环境污染的一条崭新途径。提高光阳极光生电荷的传输和转移能力是该领域研究的核心问题。本文以Fe_2O_3为光阳极,利用其较宽的光谱响应、合理的价带位置以及良好的化学稳定性等特点,重点研究高温快速退火提升Fe_2O_3光电化学水分解性能的作用机制,并协同界面修饰,进一步提高光生电子和空穴分离效率,探索提高Fe_2O_3光阳极光电化学性能的有效途径。具体研究工作如下:针对Fe_2O_3薄膜结晶性差,体内复合严重的问题,分别对FTO/Fe_2O_3光阳极进行时间相对较长的传统退火以及快速升温的高温退火。研究发现,高温快速退火能够提高氧化铁结晶性并去除部分表面态,从而提高体内电荷传输和Fe_2O_3/电解液界面电荷转移能力,增加电荷分离效率。且高温快速退火相对传统的高温退火,对FTO衬底的导电性破坏小,能够保持对电子良好的收集能力,因此FTO/Fe_2O_3光阳极展示了优异的光电化学水分解性能。针对FTO/Fe_2O_3界面处的电荷复合问题,采用层层沉积的方法在FTO/Fe_2O_3界面引入超薄的高结晶性的钛酸片层(Ti O_2NS),通过界面修饰抑制电子从FTO向Fe_2O_3反向流动引起的复合,提高光生电荷分离。接着对FTO/TiO_2/Fe_2O_3光阳极进行高温快速退火处理。研究表明,高温条件下,TiO_2NS不仅能够抑制部分电子反向流动引起的复合,而且界面处的Ti存在向Fe_2O_3中扩散的现象。Ti4+扩散到Fe_2O_3中作为施主杂质,提高载流子浓度,增大带弯,促进光生电子和空穴的分离。同时,高温快速退火能够提高Fe_2O_3结晶性,加快电荷传输,增加界面电荷转移能力,协同提高FTO/TiO_2/Fe_2O_3光阳极的光电流密度。综上所述,高温快速退火能够同时降低Fe_2O_3体内和表面电荷复合,且能实现向Fe_2O_3中的有效元素掺杂。该方法简单、易操作,可以尝试应用其它电极,或进行其它元素掺杂,在优化光电化学水分解光阳极材料的发展中具有重要意义。
[Abstract]:Photoelectrochemical water decomposition is a new way to solve energy shortage and environmental pollution by converting solar energy into non-polluting chemical fuel. Improving the transmission and transfer ability of auroral charge is the key problem in this field. In this paper, with Fe_2O_3 as the photoanode, the mechanism of improving the photo-chemical water decomposition of Fe_2O_3 by high temperature rapid annealing is studied, which is based on its wide spectral response, reasonable valence band position and good chemical stability. The efficiency of photoelectron and hole separation was further improved by synergistic interfacial modification, and an effective way to improve the photoelectrochemical properties of Fe_2O_3 photoanode was explored. The specific research work is as follows: aiming at the problems of poor crystallinity and in vivo compounding of Fe_2O_3 thin films, the traditional annealing of FTO/Fe_2O_3 photoanode and the high temperature annealing of FTO/Fe_2O_3 photoanode are carried out respectively. It is found that high temperature rapid annealing can improve the crystallinity of iron oxide and remove part of the surface state, thus improving the charge transport in vivo and the charge transfer ability at the interface of Fe_2O_3/ electrolyte, and increasing the efficiency of charge separation. Compared with the traditional high temperature annealing, the high temperature rapid annealing has little damage to the electrical conductivity of the FTO substrate, and can keep good collection ability of electrons. Therefore, the FTO/Fe_2O_3 photoanode exhibits excellent photochemical water decomposition performance. Aiming at the problem of charge recombination at the interface of FTO/Fe_2O_3, layer by layer deposition method was used to introduce ultra-thin and highly crystallized titanate lamellar (Ti O_2NS) at the interface of FTO/Fe_2O_3. The interfacial modification inhibits the recombination of electrons from FTO to Fe_2O_3 and increases the photogenic charge separation. Then the FTO/TiO_2/Fe_2O_3 photoanode was treated by high temperature rapid annealing. The results show that at high temperature, TiO_2NS can not only inhibit the recombination caused by partial reverse electron flow, but also the Ti at the interface diffuses into Fe_2O_3. Ti4 diffuses into Fe_2O_3 as donor impurity. Increasing carrier concentration, increasing band bending, and promoting the separation of photogenerated electrons and holes. At the same time, the high temperature rapid annealing can improve the crystallization of Fe_2O_3, accelerate the charge transfer, increase the interface charge transfer ability, and increase the photocurrent density of the FTO/TiO_2/Fe_2O_3 photoanode. In conclusion, high temperature rapid annealing can simultaneously reduce the internal and surface charge recombination of Fe_2O_3, and can achieve effective element doping in Fe_2O_3. The method is simple and easy to operate. It can be applied to other electrodes or doped with other elements. It is of great significance in the development of optoelectronic chemical water decomposition photoanode materials.
【学位授予单位】：东北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ116.21
本文编号：2304433
[Abstract]:Photoelectrochemical water decomposition is a new way to solve energy shortage and environmental pollution by converting solar energy into non-polluting chemical fuel. Improving the transmission and transfer ability of auroral charge is the key problem in this field. In this paper, with Fe_2O_3 as the photoanode, the mechanism of improving the photo-chemical water decomposition of Fe_2O_3 by high temperature rapid annealing is studied, which is based on its wide spectral response, reasonable valence band position and good chemical stability. The efficiency of photoelectron and hole separation was further improved by synergistic interfacial modification, and an effective way to improve the photoelectrochemical properties of Fe_2O_3 photoanode was explored. The specific research work is as follows: aiming at the problems of poor crystallinity and in vivo compounding of Fe_2O_3 thin films, the traditional annealing of FTO/Fe_2O_3 photoanode and the high temperature annealing of FTO/Fe_2O_3 photoanode are carried out respectively. It is found that high temperature rapid annealing can improve the crystallinity of iron oxide and remove part of the surface state, thus improving the charge transport in vivo and the charge transfer ability at the interface of Fe_2O_3/ electrolyte, and increasing the efficiency of charge separation. Compared with the traditional high temperature annealing, the high temperature rapid annealing has little damage to the electrical conductivity of the FTO substrate, and can keep good collection ability of electrons. Therefore, the FTO/Fe_2O_3 photoanode exhibits excellent photochemical water decomposition performance. Aiming at the problem of charge recombination at the interface of FTO/Fe_2O_3, layer by layer deposition method was used to introduce ultra-thin and highly crystallized titanate lamellar (Ti O_2NS) at the interface of FTO/Fe_2O_3. The interfacial modification inhibits the recombination of electrons from FTO to Fe_2O_3 and increases the photogenic charge separation. Then the FTO/TiO_2/Fe_2O_3 photoanode was treated by high temperature rapid annealing. The results show that at high temperature, TiO_2NS can not only inhibit the recombination caused by partial reverse electron flow, but also the Ti at the interface diffuses into Fe_2O_3. Ti4 diffuses into Fe_2O_3 as donor impurity. Increasing carrier concentration, increasing band bending, and promoting the separation of photogenerated electrons and holes. At the same time, the high temperature rapid annealing can improve the crystallization of Fe_2O_3, accelerate the charge transfer, increase the interface charge transfer ability, and increase the photocurrent density of the FTO/TiO_2/Fe_2O_3 photoanode. In conclusion, high temperature rapid annealing can simultaneously reduce the internal and surface charge recombination of Fe_2O_3, and can achieve effective element doping in Fe_2O_3. The method is simple and easy to operate. It can be applied to other electrodes or doped with other elements. It is of great significance in the development of optoelectronic chemical water decomposition photoanode materials.
【学位授予单位】：东北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ116.21
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