Research Progress of Hydrogen Production from Hydrous Hydrazine Decompo-sition Catalyzed by Metal Catalysts
Hydrogen is an efficient and clean new energy,and it is expected to occupy an important position in the future energy field.Developing safe and efficient hydrogen storage materials is the key to realize large-scale practical application of hydrogen energy.Hydrous hydrazine(N2H4·H2O)is a promising hydrogen storage material because of its high hydrogen storage content(8％)and conve-nient transportation and storage.The research show that the appropriate metal catalyst can effectively reduce the reaction energy barrier of hydrous hydrazine decomposition and hydrogen production,and significantly increase the dehydrogenation rate of hydrous hydra-zine.Therefore,the development of efficient dehydrogenation catalyst under mild conditions has become a research hotspot of hydrous hydrazine as a hydrogen storage material.In this paper,the decomposition and dehydrogenation mechanism of hydrous hydrazine were briefly introduced,and the research progress of hydrous hydrazine dehydrogenation catalyst system in recent years was systematically expounded,and the strategies to improve the catalytic performance of the catalyst were analyzed.Essentially,the catalytic decomposi-tion reaction path of N2H4 mainly depended on the cleavage sequence of N-N bond and N-H bond.The purpose of the prepared cata-lyst was to promote the cleavage of N-H bond.In recent years,the research on dehydrogenation catalysts of hydrous hydrazine had ex-perienced metal nanoparticles,composite oxides and metal-supported catalysts.Metal nanoparticles were usually synthesized by co-re-duction method,some of which could selectively decompose hydrous hydrazine,but the overall catalytic performance was poor.This was because the free metal nanoparticles were easy to agglomerate,which reduced the specific surface area and active sites of the cata-lyst,resulting in the decline of catalytic performance.Although the addition of surfactant could avoid the aggregation of metal nanopar-ticles,it would cover the active sites on the surface of the particles,which could not fundamentally improve the catalytic performance.Relatively speaking,as a catalyst in strong alkaline environment,composite oxide could achieve 100％selectivity of hydrogen produc-tion,and its catalytic performance was considerable,but there were some problems such as low strength and easy change of metal va-lence.Supported catalyst was to load metal nanoparticles on the carrier/carrier surface,which not only ensured the good dispersion of active metal nanoparticles,but also provided excellent catalytic performance stability for nano-catalyst.In addition,the carrier would have a synergistic effect with metal nanoparticles,and sometimes the carrier could provide a suitable chemical environment for the re-action,which was conducive to improving the catalytic activity and hydrogen production selectivity of the catalyst.With the deepening of scholars'research and understanding on the mechanism of hydrogen production by catalytic decomposition,the nano-catalyst devel-oped showed extremely high catalytic activity for hydrogen production by catalytic decomposition of hydrous hydrazine.After continu-ous exploration,the researchers summarized the following design strategies that affect the catalytic performance of the catalyst:build-ing alloy structure,create a suitable chemical environment for nano-catalyst,introducing strong metal-carrier interaction(SMSI)and optimizing the synthesis method to increase the surface area and active sites.
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