结构可控的表面镍物种在二氧化碳加氢及其光分解水反应特性的研究

发布时间：2018-04-13 15:02

  本文选题：结构可控 + 镍物种　； 参考：《兰州大学》2016年博士论文

【摘要】：本论文以结构可控的表面镍物种催化剂在二氧化碳甲烷化反应和可见光催化分解水制氢体系中的应用为研究切入点,基于金属有机框架(MOFs)材料设计并构建了高分散、高活性的非贵金属镍基催化剂。此外,本论文还系统地研究了在CO_2甲烷化反应和光催化制氢反应中,表面镍物种的构效关系,取得了以下创新性成果:1.Ni-Ru/γ-Al_2O_3催化剂表面活性物种的调控与CO_2甲烷化性能的研究系统的考察了不同浸渍方法制备的CO_2甲烷化催化剂的构效关系。研究发现催化剂10Ni-1.0Ru在共浸渍制备过程中,Ru存在表面偏析现象,使得Ru更加容易还原成金属态,并提供更多的活性物种,使得10Ni-1.0Ru表现出更高的活性与更好的稳定性。此外,基于催化剂的表征,本文提出CO_2在催化剂10Ni-1.0Ru表面产生甲烷的机理,CO_2在Ru表面活化形成COads和Oads,最终在Ni表面的氢物种与Ru表面碳物种形成甲烷。2.基于MOF-5构建高分散的纳米Ni基催化剂及其催化CO_2甲烷化性能的研究利用原位浸渍还原法合成了一系列低温条件下对CO_2甲烷化具有高活性的Ni@MOF-5催化剂。此催化剂比传统方法制备的10Ni/SiO_2催化剂展示了更高的催化活性。基于BET,TEM和化学吸附表征等技术对催化剂10Ni@MOF-5的结构和状态表征,发现Ni在大比表面积的MOF-5(~2961 m2/g)上具有高分散(~41.8%)和小尺寸(~9nm)特性。催化剂10Ni@MOF-5在320°C时,CO_2转化率达到75.09%,CH4选择性为100%。此外,该催化剂也展示了高稳定性与选择性,在100h内几乎没有失活。3.Ni助剂晶面对Ni@MOF-5表面电荷转移行为及其可见光催化制氢性能影响的研究基于金属有机框架MOF的高比表面积特性构建了一系列高分散、小尺寸、高活性的光催化分解水产氢非贵金属催化剂Ni@MOF-5。Ni@MOF-5与贵金属催化剂Pt@MOF-5具有相同的产氢过电位(-0.37V),但Ni@MOF-5表现出更高的产氢活性、稳定性、荧光寿命和光电流。在430nm波长下,催化剂Ni@MOF-5的最高AQE为16.7%。此外,对Ni@MOF-5催化剂中Ni NPs不同晶面电荷转移行为与光催化产氢性能的研究发现Ni NPs暴露出的(111)晶面相比(200)晶面更利于产氢和电荷转移。4.基于MIL-101构建低氢吸附自由能的Ni-Mo合金簇助催化剂及其可见光催化制氢性能的研究采用DFT和FMO计算分析得到单金属镍簇的氢吸附自由能为537 kJ·mol-1,而合金簇MoNi4具有更低的氢吸附自由能(458kJ·mol-1)。我们通过双溶剂法制备了高活性、高稳定性的光催化分解水产氢非贵金属助催化剂NiMo@MIL-101。在可见光条件下,在EY敏化体系中,通过对比单金属助催化剂(Ni@MIL-101和Mo@MIL-101)产氢活性发现,合金催化剂NiMo@MIL-101展示出最高的产氢活性(2h内产氢总量达到1480.4μmol,pH 7)和高的表观量子效率(75.7%,520nm)。催化剂NiMo@MIL-101也存在最大的光电流、低的产氢过电位(-0.51V)和长的荧光寿命(1.57ns)。正是因为MoNi4纳米合金簇具有低的氢吸附自由能才导致高的光催化产氢活性。
[Abstract]:In this paper, the application of surface nickel species catalyst with controllable structure in methanation of carbon dioxide and visible light catalytic decomposition of water for hydrogen production was studied. Based on organometallic framework MOFs, high dispersion was designed and constructed.Highly active non-noble metal nickel-based catalysts.In addition, the structure-activity relationships of nickel species on the surface of CO_2 methanation and photocatalytic hydrogen production have also been systematically studied.The following innovative results were obtained: 1. The structure-activity relationship between the surface active species of Ni-Ru-Al _ 2O _ 3 catalyst and the methanation performance of CO_2 was investigated systematically. The structure-activity relationship of CO_2 methanation catalysts prepared by different impregnation methods was investigated.It is found that the surface segregation of Ru in the co-impregnation process of catalyst 10Ni-1.0Ru makes it easier to reduce Ru to metal state and provide more active species, which makes 10Ni-1.0Ru exhibit higher activity and better stability.In addition, based on the characterization of the catalyst, the mechanism of methane production from CO_2 on the surface of the catalyst 10Ni-1.0Ru is proposed. CO-2 is activated on the surface of Ru to form COads and Oads.The hydrogen species on the surface of Ni and the carbon species on the surface of Ru form methane. 2.Preparation of highly dispersed Nano-Ni-based Catalysts based on MOF-5 and their Catalytic Properties for CO_2 methanation A series of Ni@MOF-5 catalysts with high activity for CO_2 methanation at low temperature were synthesized by in-situ impregnation reduction method.The catalytic activity of this catalyst is higher than that of 10Ni/SiO_2 catalyst prepared by traditional method.Based on the characterization of the structure and state of the catalyst 10Ni@MOF-5 by BET-TEM and chemisorption, it is found that Ni has the characteristics of high dispersion 41.8% and small size (9nm) on the MOF-5(~2961 m2 / g with large specific surface area.At 320 掳C, the conversion of the catalyst 10Ni@MOF-5 was 75.09 and CH4 selectivity was 100.In addition, the catalyst also showed high stability and selectivity.Charge transfer behavior on the Surface of Ni@MOF-5 and its effect on visible Light Catalytic hydrogen production; A series of high dispersions and small sizes were constructed based on the high specific surface area characteristics of organometallic frame MOF.The non-noble metal catalyst Ni@MOF-5.Ni@MOF-5 has the same hydrogen production potential as the noble metal catalyst Pt@MOF-5, but Ni@MOF-5 exhibits higher hydrogen production activity, stability, fluorescence lifetime and photocurrent.The maximum AQE of the catalyst Ni@MOF-5 is 16.7g at 430nm wavelength.In addition, the charge-transfer behavior and photocatalytic hydrogen production properties of Ni NPs on different crystal planes in Ni@MOF-5 catalyst were studied. It was found that the exposed surface of Ni NPs was more favorable for hydrogen production and charge transfer than that of #number0#).Construction of Ni-Mo Alloy Cluster Cocatalyst with low hydrogen adsorption Free Energy based on MIL-101 and its performance in visible Light Catalytic hydrogen production; calculated and analyzed by DFT and FMO, the hydrogen adsorption free energy of single metal nickel cluster was 537 kJ mol -1, while that of alloy cluster MoNi4 was lower than that of single metal nickel cluster.The free energy of hydrogen adsorption is 458 kJ mol-1.A high activity and high stability photocatalytic catalyst NiMoR MIL-101 was prepared by double solvent method for the catalytic decomposition of aquatic hydrogen.The catalyst NiMo@MIL-101 also has the largest photocurrent, low hydrogen overpotential (-0.51V) and long fluorescence lifetime (1.57nsg).It is due to the low hydrogen adsorption free energy of MoNi4 nanoclusters that the photocatalytic activity of hydrogen production is high.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O643.36;TQ116.2
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本文编号：1745008