可见光响应型金属纳米催化剂的设计合成及其在催化储氢材料放氢中的应用

发布时间：2018-05-17 14:28

本文选题：氢能 + 化学储氢材料　；参考：《内蒙古大学》2017年博士论文

【摘要】：随着化石资源日渐枯竭,利用高效的能源科学与技术,开发"绿色燃料"具有重要意义,而氢是应对目前能源危机和环境污染问题的理想替代能源之一。在以氢为基础的能源体系中,开发便于运输和贮存的高性能储氢材料并探索节能条件下氢的高效释放是未来实现"氢能经济"的关键。甲酸(HCOOH)和硼烷氨(NH3BH3)分别含有4.4 wt%和19.6 wt%的氢,是有广阔应用前景的化学储氢材料。针对这两种储氢材料放氢过程中存在的关键共性科学问题,即催化剂活性低、催化剂昂贵,本论文根据光催化的方式能够提高催化剂活性的原理,通过引入具有表面等离子体共振(SPR)效应的非活性金属、调控半导体载体的微结构、利用非贵金属(Fe、Co、Ni)纳米粒子的光热效应,设计合成了一系列可见光响应的负载型金属纳米催化剂,并系统研究了催化剂以太阳光为驱动力催化分解HCOOH和NH3BH3的放氢性能。主要结果如下:(1)利用具有SPR效应的特定金属如Au在光激发下能够产生自由电子的特性,设计合成了一系列氧化石墨烯(GO)负载的双金属AuPd纳米催化剂,并研究了其室温光催化分解HCOOH的放氢性能。结果表明,催化剂中AuPd纳米粒子以合金形式存在,可见光照射下Au上的电子能够有效转移到Pd的表面,这使得AuPd合金催化剂中Pd的固有室温放氢活性显著增强,其中Au1Pd2/GO的转换频率(TOF)达954.2 h-1。此外,调整入射光的波长范围和强度可以调控催化剂的放氢活性,随着波长范围的扩大和光强增强,催化剂的放氢活性明显提高。(2)利用半导体结构决定相应催化剂光催化性能的特点,设计合成了微结不同的多孔半导体氮化碳(C3N4),以它们为载体制备了一系列廉价过渡金属(Co、Ni)纳米催化剂,并研究了催化剂在可见光照射下室温催化分解NH3BH3放氢性能。结果表明,通过控制含氮小分子母体的结构和比例,实现了少片多孔氮化碳微结构的可控合成,进而调控了它们的光响应特性和相应催化剂可见光催化放氢活性。其中,Co基催化剂的最高TOF达到111.1 min-1,是目报道的室温催化分解NH3BH3放氢中最高的。改变入射光的波长范围和强度可调控催化剂的光催化放氢活性,说明可见光照射的确可以提高催化剂中廉价属纳米粒子表面的电子密度,进而提高其催化放氢活性。另外,催化剂具有的放氢循环稳定性。(3)利用特定金属纳米粒子的光热效应、金属有机框架(MOF)与金属纳米子的相互作用,设计合成了一系列MIL-53负载的廉价过渡金属(Fe、Co、N纳米催化剂,并研究了它们光热催化分解NH3BH3的放氢性能。结果表明,催剂在光热条件下的放氢活性大幅增加,这说明在光热条件下光电子参与并促了催化放氢反应,其中Co/MIL-53和Ni/MIL-53催化剂的光热催化活性比相温度下的暗催化活性分别提高了 0.73倍和1.94倍,它们的TOF分别达到257.min-1 和 529.4 min-1。
[Abstract]:With the depletion of fossil resources, it is of great significance to develop "green fuel" by using efficient energy science and technology. Hydrogen is one of the ideal alternative energy sources to deal with the current energy crisis and environmental pollution. In the energy system based on hydrogen, it is the key to realize "hydrogen energy economy" in the future to develop high performance hydrogen storage materials which are convenient for transportation and storage and to explore the efficient release of hydrogen under the condition of energy saving. HCOOH) and NH _ 3BH _ 3) contain 4.4 wt% and 19.6 wt% hydrogen, respectively, so they are promising chemical hydrogen storage materials. In view of the key common scientific problems in the dehydrogenation process of these two hydrogen storage materials, that is, the catalyst activity is low and the catalyst is expensive, this paper can improve the principle of catalyst activity according to the way of photocatalysis. By introducing inactive metal with surface plasmon resonance (SPR) effect to regulate the microstructure of semiconductor carrier, the photothermal effect of non-noble metal FeCoCoNi) nanoparticles was studied. A series of supported metal nanocrystalline catalysts with visible light response were designed and synthesized. The dehydrogenation properties of HCOOH and NH3BH3 were systematically studied. The main results are as follows: 1) A series of graphene oxide supported bimetallic AuPd nanocatalysts have been designed and synthesized by using the characteristic that certain metals with SPR effect such as au can produce free electrons under photoexcitation. The dehydrogenation properties of HCOOH photocatalytic decomposition at room temperature were also studied. The results show that the AuPd nanoparticles in the catalyst exist in the form of alloy, and the electrons on au can be transferred to the surface of PD effectively under visible light irradiation, which makes the intrinsic room temperature dehydrogenation activity of PD in the AuPd alloy increase significantly. The conversion frequency of Au1Pd2/GO is 954.2 h ~ (-1). In addition, adjusting the wavelength range and intensity of the incident light can regulate the dehydrogenation activity of the catalyst. With the increase of the wavelength range and the intensity of the light, The photocatalytic properties of the corresponding catalysts are determined by the semiconductor structure. A series of cheap transition metal (CoCoN) nanocatalysts with different microjunction porous semiconductor carbon nitride (C _ 3N _ 4N _ 4N _ 4) have been prepared. The catalytic properties of the catalysts for the decomposition of NH3BH3 at room temperature under visible light irradiation have been studied. The results show that by controlling the structure and proportion of nitrogen-containing small molecular matrix, the controllable synthesis of porous carbon nitride microstructures has been realized, and their photoresponse characteristics and visible light catalytic dehydrogenation activity of the corresponding catalysts have been regulated. The maximum TOF of Co-based catalyst is 111.1 min-1, which is the highest in the room temperature catalytic decomposition of NH3BH3 dehydrogenation. The photocatalytic dehydrogenation activity of the catalyst can be controlled by changing the wavelength range and intensity of the incident light, which indicates that visible light irradiation can increase the electron density of the cheap nanoparticles in the catalyst, and then improve the catalytic dehydrogenation activity of the catalyst. In addition, the hydrogen removal cycle stability of the catalyst. 3) based on the photothermal effect of specific metal nanoparticles and the interaction between metal-organic framework (MOF) and metal nanoparticles, a series of cheap transition metal catalysts supported by MIL-53 have been designed and synthesized. Their photothermal decomposition of NH3BH3 was studied. The results show that the catalytic activity of the catalyst increases greatly under the photothermal condition, which indicates that photoelectron participates in the catalytic dehydrogenation reaction under the photothermal condition. The photothermal catalytic activity of Co/MIL-53 and Ni/MIL-53 was 0.73 times and 1.94 times higher than that of dark catalyst at phase temperature, respectively, and their TOF reached 257.min-1 and 529.4 min-1 respectively.
【学位授予单位】：内蒙古大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36

【相似文献】