基于低维纳米材料的能量转换与存储器件的设计

发布时间：2018-07-04 09:06

本文选题：二维超薄材料 + 电催化析氢　；参考：《中国科学技术大学》2015年博士论文

【摘要】：光电转换、电化学催化析氢和超级电容都是环境友好的能源转换、存储方式,发展具有上述性能的材料体系将极大的缓解能源危机对我们的生活和环境所造成的冲击。然而,当前具有上述性能的能源转换和存储器件仍面临着加工程序繁琐、制作成本高、性能较差等实际困难,这些问题极大的限制了其在实际中的应用。因此,设计和制备具有高性能的能量转换和存储的材料是十分必要的。由于量子尺寸效应,纳米材料往往呈现出异于相应体相材料的独特光、电、磁、热等物理、化学性能,使得我们通过设计合适的纳米结构来实现高性能能源转换与存储器件的制备。更进一步,纳米材料也为我们设计便携式的柔性、超薄的能源转换与存储器件提供了可能。本论文以多元化合物的低维纳米材料为研究对象,选取具有高光电转换、电催化析氢和超级电容性能的材料,初步探讨了它们结构与性能之间的关系,为新型能量转换和存储材料的设计提供了实验和理论基础。本论文的研究工作主要包括以下三个方面的内容：1.作者首次通过液相自组装的方法将CH3NH3PbI3沉积在柔性ITO电极上,制备成柔性的光探测器件。自制器件的光探测范围可以从紫外光区到整个可见光区,其中器件对780 nm和365 nm单色光的响应时间分别小于O.1秒和0.2秒,同时具有较高的灵敏度和优异的光响应稳定性等特点,其光响应性能远远超过目前大多数光探测器。进一步的,我们也对基于CH3NH3PbI3光探测器的光响应机理进行了研究。研究表明,肖特基势垒在光生电子-空穴对的分离过程中起着重要作用。在无光照和外加偏压情况下,器件处于平衡状态,这时在ITO电极和有机铅碘化铅钙钛矿膜或有机碘化铅钙钛矿膜内部产生肖特基势垒；而在光照(能量大于半导体带隙)和外加偏压条件下,有机碘化铅钙钛矿薄膜将吸收光子产生大量的电子-空穴对[hv→e-+h+],同时肖特基势垒产生的局部反向偏置电场不仅能够迅速分离光生电子空穴对,而且还可以减少电子、空穴的再结合率,从而增加载流子的浓度。这一过程同时也会降低肖特基势垒的有效高度,从而易于载流子的传输,显著增强器件的导电性。此外,自制的光探测器在反复弯曲变形后的光响应性能没有明显的变化,显示出优异的柔韧性和坚固性。该研究为开发低成本、易加工、高效的柔性光探测器提供了新的机遇。2.作者首次通过有机锂插层来剥离三元层状化合物Ⅰ-Cu2WS4,得到厚度仅为0.8 nm的超薄纳米片。与体相材料相比,剥离的Ⅰ-Cu2WS4纳米片具有大量暴露的表面原子、高的活性位点浓度和与电极基底接触更加紧密等优势,进而表现出较之体相材料增强的电催化产氢性能,如其阴极电流密度比体相材料提高了近74倍之多。我们通过理论计算对超薄纳米片所呈现出的高产氢性能进行了分析,分析表明较之于体相材料,Ⅰ-Cu2WS4纳米片导带边缘处的态密度明显增加,有利于在催化过程中电子的转移,进而使得Ⅰ-Cu2WS4超薄纳米片的电催化析氢反应活性明显提高。同时,通过对剥离后的Ⅰ-Cu2WS4纳米片的电催化析氢反应动力学过程的模拟,我们发现纳米片中表面的硫原子起到析氢反应活性位点的作用。Ⅰ-Cu2WS4超薄纳米片具有非常稳定的电催化产氢性能,在2000个循环后,其电流密度仍未出现明显的衰减。本工作把三元硫属化合物的超薄结构纳入电催化研究领域,不仅丰富了二维超薄纳米材料在电催化析氢领域的应用研究,同时也为设计新的电催化析氢反应催化剂以及催化活性位点的确立奠定了理论基础。3.基于对二硫化钨2H半导体相在插入有机锂剥离过程中转变为1T金属相的分析和认识,作者首次成功制备出厚度约为0.5 nm的金属相WS2(1-x)Se2x三元超薄纳米片,电阻测试表明WS0.5Se0.5超薄纳米片具有较好的导电性。通过真空抽滤法把超薄纳米片组装成取向性薄膜,并进一步组装成基于WS2(1-x)Se2x超薄纳米片薄膜的柔性全固态双电层电容器,详细研究了其在固态柔性超级电容器充放电过程中的性能。测试结果表明,三元WS2(1-x)Se2x纳米片为电极材料的全固态柔性薄膜双电层电容器显示出高达60 Fcm-2的面积比电容,且经过2000次循环充放电后电化学性能未见明显衰减。二维超薄结构同时也使器件具有良好的机械柔韧性,这对于柔性器件在实际应用中有着重要的应用价值。
[Abstract]:Photoelectric conversion, electrochemical catalytic hydrogen evolution and supercapacitor are environmentally friendly energy conversion, storage mode, and the development of the material system with the above performance will greatly alleviate the impact of the energy crisis on our life and environment. However, the current energy conversion and memory parts with the above performance are still facing the complex processing program. It is necessary to design and prepare materials with high performance energy conversion and storage. As a result of quantum size effect, nanomaterials tend to exhibit unique light, electrical, magnetic, thermal and other materials because of the quantum size effect. The chemical properties make it possible for us to achieve the preparation of high performance energy conversion and storage devices by designing suitable nanostructures. Further, nanomaterials are also possible for our design of portable flexible, ultra-thin energy conversion and memory. This paper is selected as the research object of low dimensional nanomaterials of multicomponent compounds. The materials with high photoelectric conversion, electrocatalytic hydrogen evolution and supercapacitor properties are obtained. The relationship between their structure and properties is preliminarily discussed. The experimental and theoretical basis for the design of new energy conversion and storage materials is provided. The research work of this paper mainly includes the following three aspects: 1. the author first passed the self assembly of liquid phase. The installation method deposited the CH3NH3PbI3 on the flexible ITO electrode to produce a flexible optical detector. The light detection range of the self-made device can be from the UV light region to the whole visible light region, and the response time of the devices to 780 nm and 365 nm monochromatic light is less than O. 1 and 0.2 seconds respectively, with high sensitivity and excellent light response stability. The photoresponse is far more than most of the current photodetectors. Further, we have also studied the light response mechanism based on CH3NH3PbI3 photodetectors. The study shows that the Schottky barrier plays an important role in the separation process of the photoelectron hole pair. The equilibrium state produces a Schottky barrier at the ITO electrode and the organic lead perovskite perovskite film or the organic lead perovskite perovskite membrane, and the organic lead perovskite film will produce a large number of electron hole pairs of [hv to e-+h+], while the light (energy is greater than the semiconductor band gap) and the applied bias conditions, and at the same time the Schottky potential The local reverse bias electric field produced by the base can not only quickly separate the photoelectron hole pair, but also reduce the electron and hole re binding rate, thus increasing the concentration of the loading stream. This process also reduces the effective height of the Schottky barrier, thus it is easy to transmit the carrier and significantly enhance the electrical conductivity of the device. In addition, self-made. The photodetector has no obvious change in light response performance after repeated bending and deformation, showing excellent flexibility and robustness. This study provides a new opportunity for the development of low cost, easily machinable and efficient flexible photodetectors..2. authors first use organic lithium intercalation to peel off three element layered compound I -Cu2WS4, and get the thickness only. The ultra-thin nanoscale of 0.8 nm. Compared with the bulk material, the stripped I -Cu2WS4 nanoscale has a large number of exposed surface atoms, high concentration of active sites and more close contact with the electrode substrate, and then shows the performance of electrocatalytic hydrogen production enhanced by the bulk phase material, as the cathode current density is nearly 74 higher than that of the bulk material. More than three times. We analyzed the high hydrogen performance of ultra-thin nanoscale by theoretical calculation. The analysis showed that the density of state of I -Cu2WS4 nanometers increased obviously at the edge of the lead band compared with the bulk phase material, which was beneficial to the transfer of electrons during the catalytic process, and then the electrocatalytic hydrogen evolution of I -Cu2WS4 ultra-thin nanoscale nanoscale was alive. At the same time, through the simulation of the kinetic process of the electrocatalytic hydrogen evolution reaction of the peeled I -Cu2WS4 nanoscale, we found that the sulfur atoms in the surface of the nanoscale played a role in the active site of the hydrogen evolution reaction. I -Cu2WS4 ultra-thin nanoscale has a very stable electrocatalytic hydrogen production performance and its current density after 2000 cycles. The ultrathin structure of the three sulfur compounds has been incorporated into the field of electrocatalysis, which not only enriches the application of two-dimensional ultrathin nanomaterials in the field of electrocatalytic hydrogen evolution, but also lays a theoretical foundation for the design of new catalytic hydrogen evolution catalysts and the establishment of catalytic active sites. For the analysis and understanding of the transformation of two tungsten sulfide 2H semiconductor phase to 1T metal phase during the insertion of organic lithium, the author successfully prepared WS2 (1-x) Se2x three element ultra-thin nanometers of WS2 (1-x) Se2x with a thickness of about 0.5 nm. The resistance test showed that the ultra-thin nanoscale of WS0.5Se0.5 had better conductivity. The film is assembled into an orientable film and is further assembled into a flexible all solid state double layer capacitor based on WS2 (1-x) Se2x thin film. The performance of a solid state flexible supercapacitor in charge and discharge process is studied in detail. The test results show that the three element WS2 (1-x) Se2x nanometers are all solid state flexible thin film double layers of the electrode materials. The area of up to 60 Fcm-2 is higher than the capacitance, and the electrochemical performance is not obviously attenuated after 2000 cycles of charge and discharge. The two dimensional ultrathin structure also makes the device have good mechanical flexibility, which is of great value for the practical application of the flexible devices.
【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】：TB383.1

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