Design, Synthesis, And Performance Investigation Of Hydrous Hydrazine Dehydrogenation Catalysts

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: N2H4â†'N2(g)+2H2(g). However, its undesired incompletedecomposition:3N2H4â†'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.