Size-Dependent Catalytic Activity of Monodispersed Nickel Nanoparticles for the Hydrolytic Dehydrogenation of Ammonia Borane
Size-Dependent Catalytic Activity of Monodispersed Nickel Nanoparticles for the Hydrolytic Dehydrogenation of Ammonia Borane
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DOI：
10.1021/acsami.7b14166
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发表时间：
2018-01-10
影响因子：
9.5
通讯作者：
Yu, Zhixin
中科院分区：
文献类型：
--
作者：
Guo, Kun;Li, Hailong;Yu, Zhixin
通过调节乙酰丙酮镍前驱体和三辛基膦的比例，在油胺存在下合成了粒径在4.927.4nm范围内的镍纳米粒子。X射线衍射和透射电子显微镜证实了金属Ni晶体相的形成及其单分散性。这些镍纳米粒子被发现是有效的催化剂，用于氨硼烷的水解脱氢，和它们的催化活性是依赖于尺寸。一个火山型的活动趋势，观察与8.9纳米镍纳米粒子呈现最佳的催化性能。进一步计算出8.9 nm NP催化剂的活化能和转换频率（TOF）分别为66.6 kJ中心点mol（-1）和154.2 mol（H2）中心点mol（Ni）（-1）中心点h（-1）。废催化剂的表征表明，较小尺寸的NP面临严重的团聚，导致稳定性和活性差。因此，三种碳载体材料用于分散和稳定Ni NP。这表明，负载在科琴黑（KB）上的8.9nm Ni NP表现出比负载在碳纳米管和石墨烯纳米片上的Ni NP更高的活性。通过将4.9 nm Ni NP固定到KB上进一步说明了附聚诱导的活性损失，其表现出显著增强的活性，具有447.9 mol（H2）中心点mol（Ni）（-1）中心点h（-1）的高TOF以及在氨硼烷的连续脱氢中的优异的可重复使用性。高催化性能可归因于纳米颗粒Ni的固有活性以及由于Ni/KB金属-载体的强相互作用而提高的活性和稳定性。
Nickel (Ni) nanoparticles (NPs) with controlled sizes in the range of 4.927.4 nm are synthesized by tuning the ratio of the nickel acetylacetonate precursor and trioctylphosphine in the presence of oleylamine. X-ray diffraction and transmission electron microscopy confirm the formation of the metallic Ni crystal phase and their monodispersed nature. These Ni NPs are found to be effective catalysts for the hydrolytic dehydrogenation of ammonia borane, and their catalytic activities are size-dependent. A volcano-type activity trend is observed with 8.9 nm Ni NPs presenting the best catalytic performance. The activation energy and turnover frequency (TOF) of the 8.9 nm NP catalyst are further calculated to be 66.6 kJ center dot mol(-1) and 154.2 mol(H2)center dot mol(Ni)(-1)center dot h(-1), respectively. Characterization of the spent catalysts indicates that smaller-sized NPs face severe agglomeration, resulting in poor stability and activity. Three carbon support materials are thus used to disperse and stabilize the Ni NPs. It shows that 8.9 nm Ni NPs supported on Ketjenblack (KB) exhibit higher activity than that supported on carbon nanotubes and graphene nanoplatelets. The agglomeration-induced activity loss is further illustrated by immobilizing 4.9 nm Ni NPs onto KB, which exhibits significantly enhanced activity with a high TOF of 447.9 mol(H2)center dot mol(Ni)(-1)center dot h(-1) as well as an excellent reusability in the consecutive dehydrogenation of ammonia borane. The high catalytic performance can be attributed to the intrinsic activity of nanoparticulate Ni and the improved activity and stability due to the strong Ni/KB metal-support interactions.