二维纳米材料界面电荷分离策略及在太阳能转化中的应用

发布时间：2018-04-21 03:14

本文选题：二维纳米材料 + 光催化　；参考：《中国科学技术大学》2015年博士论文

【摘要】：实现光生载流子的最大化分离是提高人工太阳能转换效率的关键。本论文基于纳米固体化学原理,选择结构清晰的超薄二维纳米片为模型,结合时间分辨光谱、自旋捕获等原位表征手段,来深入理解表面微结构、有机-无机界面、小分子有机物等对半导体中光生载流子分离和迁移的影响,为设计和构筑高效的人工光催化体系提供理论支持。本论文的研究内容包括以下几个方面： 1、我们提出低维化是抑制半导体光生载流子复合的有效途径,尤其是二维纳米材料,它具有高比表面积,短载流子扩散距离,强光吸收等优势；同时其优异的力学性能满足了人们对柔性、便携式器件的需求,因此是柔性光电器件的理想载体。本工作发展了自牺牲模板法来合成非层状四方黄铜矿结构的CuInSe2超薄纳米片,高度各向异性的CuSe六方片不仅是CuInSe2形貌上的模板,而且作为结构模板用于控制CuInSe2纳米片的厚度。CuSe的(001)晶面和CuInSe2(112)晶面的原子排布匹配,为CuInSe2平行(112)晶面生长提供驱动力：同时反应过程中,在CuSe[001]方向上In取代部分Cu引入应力,使准层状结构CuSe的Se-Se键断裂,从而抑制CuInSe2纳米片沿此方向生长,实现对CuInSe2纳米片厚度的控制。CuInSe2超薄纳米片的成功合成充分验证了自牺牲模板法在控制纳米结构形貌上的优势。CuInSe2超薄纳米片-P3HT的能级交错,独特的界面结构有效促进载流子的分离,因此两者构建的杂化柔性光探测器表现出优异的光响应性能,开关比高达两个量级,响应时间达到1.7s,同时表现出优异的抗弯折性能。 2、我们提出结构明确的超薄纳米片是研究表面缺陷与材料光催化性能的理想载体。以K4Nb6O17超薄纳米片为例,我们通过可控还原过程引入表面氧空位,使其带隙降低0.2eV,从而促进了光吸收；同时,表面氧空位捕获光生电子,促进载流子的高效分离和利用。实验结果证实：含表面氧空位的K4Nb6O17超薄纳米片展示出大幅提高的光催化性能,产氢速率达到1661μmol·g-1·h-1,与无氧空位的块材相比提高了20倍,而与无氧空位的超薄纳米片相比则有6倍的提高。同时本工作中氧空位空间分布对光催化性能影响的研究解决了长期以来氧空位在光催化过程中的角色争议,体相氧空位是载流子复合的中心,而表面氧空位则促进载流子的高效分离,抑制电子-空穴复合。氧空位分布调控策略不仅为深入理解氧空位对光催化性能的影响提供新思路,而且为利用调控半导体缺陷来设计高效产氢催化剂打开切实可行的途径。 3、我们提出水溶性小分子助催化剂策略来加速光生空穴的转移。可逆氧化还原电对TFA·/TFA-使三氟乙酸(TFA)成为优异的分子助催化剂,为光生电子-空穴对提供了进一步的分离路径,从而促进光催化产氢。原位电子自旋共振(ESR)及能级对应关系显示出K4Nb6O17价带的光致空穴易与吸附的TFA阴离子反应产生TFA自由基。同时生成的高活性自由基转移空穴至甲醇,从而抑制了电子-空穴复合。此外,超快吸收光谱及稳态和时间分辨的发光光谱确认了高效的电荷分离是光催化性能大幅提高的主要因素。均相分子助催化剂不受催化剂与反应物接触面积的限制,为催化提供足够的反应位点,因此为发展高效光催化体系提供了机遇。
[Abstract]:Realizing the maximum separation of optical carrier is the key to improve the efficiency of the conversion of artificial solar energy. Based on the principle of nano solid chemistry, this paper selects the ultrathin two-dimensional nanoscale with clear structure as the model. It combines the time resolved spectrum and the spin capture in situ to understand the surface microstructures, the organic inorganic interface and the small molecules. The effects of aircraft on the separation and migration of photogenerated carriers in semiconductors provide theoretical support for the design and construction of a highly efficient artificial photocatalytic system. The contents of this paper include the following aspects:
1, we propose that low dimension is an effective way to suppress semiconductor optical carrier recombination, especially two dimensional nanomaterials. It has the advantages of high surface area, short carrier diffusion distance, strong light absorption and so on. At the same time, its excellent mechanical properties meet the needs of flexible and portable devices. Therefore, it is an ideal load of flexible optoelectronic devices. This work has developed a self sacrificial template method for the synthesis of CuInSe2 ultra-thin nanometers of non layered Quartet chalcopyrite structure. The highly anisotropic CuSe six slice is not only a template on the morphology of the CuInSe2, but also as a structural template for controlling the atomic arrangement of (001) and CuInSe2 (112) crystal surfaces of the thickness of CuInSe2 nanoscale,.CuSe. To provide driving force for CuInSe2 parallel (112) crystal surface growth: at the same time, in the course of the reaction, the In substitution of partial Cu in the direction of CuSe[001] leads to the crack of the Se-Se bond of the quasi layered structure CuSe, thereby inhibiting the growth of the CuInSe2 nanoscale along this direction, and realizing the successful synthesis of the.CuInSe2 ultra-thin nanoscale with the thickness of CuInSe2 nanoscale. The advantages of self sacrificing template method in controlling the nanostructure morphology are interlaced, and the unique interface structure can effectively promote the separation of carriers. Therefore, the hybrid flexible photodetectors have excellent optical response performance. The switch ratio is up to two orders, the response time is up to 1.7s, and the table is at the same time. Excellent bending resistance.
2, we propose that ultrathin nanoscale is an ideal carrier for the study of surface defects and photocatalytic properties of materials. Taking K4Nb6O17 ultra-thin nanoscale as an example, we introduce surface oxygen vacancies by controlled reduction process to reduce the band gap of 0.2eV and thus promote optical absorption; at the same time, surface oxygen vacancies capture photoelectrons to promote carriers. The experimental results show that the K4Nb6O17 ultra-thin nanoscale containing the surface oxygen vacancy shows a significant enhancement in the photocatalytic performance, the hydrogen production rate reaches 1661 Mu mol. G-1. H-1, which is 20 times higher than that of the non oxygen vacant bulk, while the oxygen vacancy is 6 times higher than that of the ultra-thin nanoscale without oxygen vacancy. The study of the influence of spatial distribution on the photocatalytic activity has solved the role controversy in the photocatalytic process for a long time. The oxygen vacancy of the bulk is the center of the carrier recombination, while the surface oxygen vacancy promotes the efficient separation of the carrier and inhibits the recombination of the electron hole. The effect of catalytic performance provides a new idea and opens a feasible way to design efficient hydrogen production catalyst by controlling semiconductor defects.
3, we propose a water-soluble small molecular cocatalyst strategy to accelerate the transfer of photogenerated holes. Reversible oxidation-reduction electricity makes TFA. /TFA- an excellent molecular cocatalyst for three FLUOROACETIC acid (TFA), which provides a further separation path for photoelectron hole pairs, thus promoting the photocatalytic hydrogen production. In situ electron spin resonance (ESR) and energy level pairs The relationship shows that the photoinduced cavitation of the K4Nb6O17 valence band is easy to react with the adsorbed TFA anion to produce TFA radical. Meanwhile, the high active free radical transfer cavitation to methanol, which inhibits the electron hole recombination. In addition, the ultra fast absorption spectrum and the steady and time resolved luminescence spectra confirm that the efficient charge separation is photocatalytic. The main factor that can be greatly improved. The homogeneous molecular cocatalyst is not limited by the contact area between the catalyst and the reactant, and provides sufficient reaction sites for the catalysis, thus providing an opportunity for the development of the high effective photocatalytic system.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TK511;TB383.1

【共引文献】