| With the energy crisis and the increasing environmental pollution caused by the exhaustion of fossil fuels,the development and utilization of new energy have drawn much attention.Hydrogen has been widely regarded as an ideal new energy carrier in the future because of the high energy density and no pollution of combustion products.However,the challenges in economy and engineer to safe and efficient storage of hydrogen are still crucial barriers for large-scale practical applications of hydrogen energy.Hydrous hydrazine?N2H4·H2O?is a promising chemical hydrogen storage material due to the high hydrogen contents of 8 wt%,low cost and stable under the atmosphere.Moreover,as a liquid-phase material,hydrous hydrazine has the potential to take advantage of the existing liquid-based distribution infrastructure,more competitive than solid chemical hydrogenstorage materials such as sodium borohydride?NaBH4?and ammonia borane?NH3BH3?derivatives.However,NH3 is always generated in the decomposition of N2H4.For the sake of hydrogen production,it is desirable to develop novel catalysts for efficient N2H4 dehydrogenation.This thesis mainly focuses on the preparation,characterization,and catalytic performance of La?OH?3 supported Pt-based bimetallic nanocatalysts.The main contents are as follows:Previous works reported that non-noble metal Co is effective to decomposition of N2H4 but only a low catalytic performance.Here,highly efficient CoPt NPs supported on La?OH?3 were firstly prepared by facile immersion process.Compared to pure CoPt NPs,the La?OH?3 nanosheet anchored CoPt NPs possess a smaller particle size and higher dispersion.The introduction of La?OH?3 lead to a strong interaction with CoPt,through which the electronic property of surface CoPt is modified.Besides,a large number of strong basic sites on the La?OH?3 surface is also beneficial for cleavage of N-H bond.Consequently,the resultant CoPt/La?OH?3 nanocomposite exhibits remarkable catalytic performance for decomposition of N2H4,giving a TOF value as high as 2400 h-1 at 50?.Especially,CoPt/La?OH?3catalyst can be easily separated by a magnet from reaction systemand the recycled catalyst exhibits excellent reusability.Most of the catalysts for decomposition of N2H4 show poor catalytic activity without addition of NaOH.However,the presence of NaOH will corrode the installations.The ultrafine NiPt-Ni?OH?2 bimetallic nanocatalyst was successfully in-suit prepared and loaded on La?OH?3 by using NaOH to precipitate Ni2+and Pt2+to generate hydroxide and then adding NaBH4 to reduce the mixtures.The characterization results indicate that the NiPt-Ni?OH?2 NPs with a size of 1.89 nm are succefully loaded on the La?OH?3.It is found that the presence of minor Ni?OH?2 in NiPt-Ni?OH?2 NPs can increase the number of basic sites in NiPt-Ni?OH?2 NPs,which is conducive to the selective cleavage of N-H bond.Consequently,NiPt-Ni?OH?2/La?OH?3 show the highest catalytic performance in neutral condition with a TOF of 303.2 h-1 and 95% H2 selectivity.After 5 cycles,the NiPt-Ni?OH?2/La?OH?3 show excellent durability with the unchanged H2 selectivity. |
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