Preparation Of Loaded Catalysts With Oxide Carrier And Their Catalytic Hydrogen Production Performation

The massive use of fossil fuels in recent years has brought about a large number of environmental problems,which is contrary to the current international trend of sustainable development.How to effectively use new energy to replace non-renewable resources has become one of the topics of general concern.Seeking renewable and clean energy to replace traditional fossil energy has become the focus of solving the current problems,so the development of hydrogen energy with hydrogen gas as the medium has been born.Hydrogen is attracting attention as an efficient and clean green energy source,which can be used for various purposes such as power generation or hydrogen production.Hydrogen energy is environmentally friendly and renewable,and the products are not polluting,but the performance of hydrogen is unstable under normal temperature and pressure conditions,and there are problems such as safety and application costs.Therefore,it is particularly important to study how to store and release hydrogen efficiently to meet the growing demand.Chemical hydrogen storage,as an important means of hydrogen storage,has a broad application prospect.Currently,common chemical hydrogen storage carriers include formic acid,hydrazine hydrate and ammonia borane,among which hydrazine hydrate is the most common chemical hydrogen storage material due to its low price and wide source.In this paper,hydrazine hydrate is used as a hydrogen storage carrier to generate hydrogen by decomposition,thus solving the problems of safety and efficiency in the practical use of hydrogen energy.In this paper,we investigate the catalytic performance of various structures of oxide carrier-loaded bimetallic nanoparticle catalysts for the dehydrogenation reaction of hydrazine hydrate,and further discuss the effects of different ratios of bimetallic and different temperatures on the catalytic activity of the catalysts,and determine the optimal experimental parameters by combining experimental results with theoretical analysis.The main aspects of the study are as following:（1）Two forms of La Ni O₃chalcogenide oxide materials,La Ni O₃in nanoparticle form and La Ni O₃in nanocage form,were prepared by a simple wet chemical method,and these two different forms of chalcogenide materials were used as catalyst carriers and loaded with Pt Ni bimetallic nanoparticles to study the catalytic dehydrogenation reaction of hydrazine hydrate,which can also be used to prepare other structures of oxide carriers.The method can also be used to prepare other structures of oxide carrier catalysts.It was found that among the two prepared catalysts with different morphologies,the catalyst with nano-cage type La Ni O₃as the carrier exhibited higher catalytic activity as well as H₂selectivity than the catalyst with nanoparticle morphology.The catalysts were characterized by XRD,TEM and SEM.It was found that Pt Ni nanoparticles with uniform size and particle size of about 2nm were generated on the outer surface of the nanocage La Ni O₃,and the nanoparticles prepared by chemical co-precipitation method were found to have high dispersion and purity.By optimizing the metal components,Pt_0.5Ni_0.5/La Ni O₃was found to have the relatively best catalytic activity for the dehydrogenation of hydrazine hydrate in the temperature range of 50°C with a TOF value of 1143.378 h^-1and H₂selectivity close to 100%.The catalytic performance of Pt_0.5Ni_0.5/La Ni O₃with nanocage morphology was superior to that of Pt_0.5Ni_0.5/La Ni O₃with nanoparticle morphology,with the latter having a TOF value of 904.83 h^-1.（2）A pyrochlore-type La₂Ce₂O₇oxide carrier was prepared by hydrothermal method,and then Pt Ni metal nanoparticles（NPs）were loaded onto La₂Ce₂O₇surface by Na BH₄reduction method for catalytic dehydrogenation of hydrazine hydrate.The effects of temperature,loaded metal ratio and catalytic cycle on the catalyst performance during the catalytic process were investigated,and the prepared Pt Ni/La₂Ce₂O₇hydrazine hydride dehydrogenation catalysts were characterized by SEM,XRD,XPS and TEM,and the characterization results showed that Pt Ni NPs were formed on the surface of Pt Ni/La₂Ce₂O₇carrier,and Pt Ni NPs were well dispersed on the carrier surface.The experimental results showed that Pt Ni/La₂Ce₂O₇had good catalytic activity for the decomposition of hydrazine hydrate,and among the catalysts loaded with different metal ratios,Pt_0.6Ni_0.4/La₂Ce₂O₇catalyst exhibited the relatively highest TOF value of 943.95 h^-1at 50°C.Finally,the catalytic cycling test was carried out,and the results showed that Pt_0.6Ni_0.4/La₂Ce₂O₇maintained a high catalytic activity in five consecutive catalytic cycles.（3）The bimetallic Pt Ni nanoparticles were loaded on the surface of the spinel-structured oxide Ni Co₂O₄carrier to catalyze the reaction of hydrazine hydrate dehydrogenation,and the catalytic activity and stability of the catalysts under different reaction conditions were investigated by varying the addition of different ratios of bimetallic and reaction temperatures.The characterization results showed that the ultrafine Pt Ni NPs with a particle size of 3nm were well dispersed in the spinel-structured Ni Co₂O₄carriers by the action of the bimetallic active particles and the catalyst carriers.It was found that among the prepared catalysts with different Pt Ni ratios,the Pt_0.7Ni_0.3/Ni Co₂O₄catalyst had the best catalytic activity for the dehydrogenation of hydrazine hydrate with a TOF value of 956 h^-1at 50°C.This study provides a new idea for the preparation of high-performance bimetallic nano-loaded catalysts.