【作者】 吴成一；

【导师】 鄢俊敏；

【作者基本信息】 吉林大学 ， 材料学， 2014， 博士

【摘要】 近年来，开发安全和高效的化学储氢材料替代传统的化石燃料引起了人们广泛的研究兴趣。水合肼(N2H4H2O)在213-392K内是无色液体、储氢量高达8.0wt%、易于储存，而且它的催化分解产物只有氮(N2)和氢(H2)，其催化分解的化学反应方程式如下：N2H4→N2(g)+2H2(g)。它的这些特点使其成为非常有应用潜力的化学储氢材料。然而，在应用过程中一定要避免它的不完全分解：3N2H4→4NH3(g)+N2(g)。研究表明，反应途径取决于催化剂的使用和反应条件。因此，研发高效的催化剂对于N2H4H2O作为储氢材料至关重要。到目前为止，Ni和贵金属(Rh，Pt)基合金相的双金属纳米催化剂被用于N2H4H2O的脱氢反应。研究表明，它们在298K时具有100%的H2选择性，但它们的脱氢反应速率很低，不能满足实际应用的需求。此外，已报道的大多数催化剂是由贵金属或很高的贵金属含量组成，由于较高的成本和资源稀缺，阻碍了它们的大规模应用。最近，非贵金属或低贵金属含量的催化剂(例如NiFe、Ni-Al2O3-HT、和NiMoB-La(OH)3)被用于催化N2H4H2O分解。然而，在室温下它们的活性很低。因此，从实际应用的角度出发，改善室温下催化剂的催化动力学性质对于发展N2H4H2O作为储氢材料是非常重要的。在这种背景下，研发一种在298K下对N2H4H2O脱氢作用具有高催化活性和100%H2选择性的低贵金属含量催化剂是一个目标。本论文主要内容如下两个部分：第一，使用共还原法在室温下合成非晶态的Co0.65Pt0.30(CeOx)0.05纳米颗粒。非晶态的Co0.65Pt0.30(CeOx)0.05纳米催化剂比结晶态的CoPt合金具有更高的催化活性。在该非晶催化剂的作用下，N2H4H2O在常温下能释放出72.1%的氢气(3.5分钟)，初始转化效率(TOF)高于结晶CoPt催化剂的TOF，而且高于所有目前报道的N2H4H2O脱氢催化剂的TOF。第二，我们合成了Ni0.90Pt0.05Rh0.05/La2O3纳米颗粒。得到的纳米颗粒的分散性很好，平均粒径尺寸为2.0nm。通过对比发现，没有使用La前驱体时，得到的Ni0.90Rt0.05Rh0.05纳米颗粒的平均粒径尺寸为3.2nm，比使用La前驱体时的粒径尺寸大。研究结果表明在合成过程中加入La(NO3)3能有效地降低纳米颗粒的尺寸，使得纳米颗粒具有更多的催化活性位。我们还研究了不同成分的NiPtRh/La2O3催化剂在298K下对N2H4H2O脱氢的催化活性。总而言之，本论文首次重点研究了Co基催化剂在N2H4H2O脱氢反应中的应用。CeOx导致的高催化活性使得N2H4H2O作为储氢材料具有很大的应用前景。当前的结果对于设计和开发下一代高效和低成本的N2H4H2O脱氢催化剂提供了新的思路，极大地推动了N2H4H2O作为储氢材料在实际生活中的应用。更多还原

【Abstract】 In recent years, discovering chemical hydrogen (H2) storage materials that can store andgenerate H2in a safe and efficient way has attracted much research interest to transform thepresent fossil fuel economy to a H2economy in recent years. Hydrazine monohydrate(N2H4H2O), which is a liquid in a wide range of temperature (213-392K) and has a H2storage capacity as high as8.0wt%, merits attention as a promising chemical H2storagematerial due to its easy recharging as a liquid and only production of nitrogen (N2) and H2via its catalytic decomposition: N2H4→N2(g)+2H2(g). However, its undesired incompletedecomposition:3N2H4→4NH3(g)+N2(g) must be avoided. Studies have shown that thereaction pathway depends on the catalyst and the reaction condition. Therefore, thedevelopment of highly efficient catalysts is quite desired for the practical application ofhydrous N2H4as a hydrogen storage material.Up to now, the bi-metallic catalysts based on the alloy phase of Ni and noble metal (Rh,Pt) in the form of nanoparticles have emerged as an important type of catalysts with100%H2selectivity at298K, But the catalytic kinetic of H2generation rate is still not satisfyingthe practical use. Recently, the catalysts using non or low noble metal including NiFe,Ni-Al2O3-HT, NiMoB-La(OH)3was applied the catalyst for the decomposition of hydrousN2H4. However, the catalysts typically show degraded catalytic activity at298K on reducingor eliminating the noble metal components. From a viewpoint of practical application, toimprove the catalytic kinetic at ambient temperature also is urgently important for thedevelopment of hydrous N2H4as a hydrogen storage material. Thus, the development of alow noble metal loading catalyst with high catalytic activity and100%H2selectivity for thedehydrogenation of N2H4H2O at298K is a desired goal.The main results obtained in the thesis are divided into four parts as following:Firstly, Amorphous Co0.65Pt0.30(CeOx)0.05NPs are successfully synthesized by a facileco-reduction method under ambient atmosphere. Amorphous Co0.65Pt0.30(CeOx)0.05NPs aresuccessfully synthesized by a facile co-reduction method under ambient atmosphere. Asresults, amorphous CoPt NPs induced on CeOxwith the TOF value of of194.8h-1caneffectively exhibit the high catalytic kinetic performance for the H2generation from hydrousN2H4at298K. Secondly, Ni0.90Pt0.05Rh0.05/La2O3catalyst are synthesized, it can be seen that the NPsare well-dispersed with an average particle size of2.0nm. In contrast, without addition of Laprecursors, the resulted Ni0.90Rt0.05Rh0.05NPs have a larger average particle size of3.2nmthan those prepared with La precursors. Therefore, it suggests that the addition of La(NO3)3during the synthetic process can effectively reduce the sizes of the NPs. we studied thecatalytic activities of the as-prepared NiPtRh/La2O3catalysts with different compositionhave been investigated toward the dehydrogenation of N2H4H2O at298K.In conclusion, this study is the first example where Co-based catalyst has been used inthe N2H4reaction system. Moreover, the high catalytic kinetic and the additional effect ofCeOxrepresent a promising step toward the practical use for H2generation from hydrousN2H4. And, the obtained promising results open new excited possibility for the developmentof next generation cost-effective and highly efficient dehydrogenation catalysts to meet therequirement of practical application of N2H4H2O.更多还原