Design,synthesis,and Catalytic Application Of Ni-CeO₂ Nanostructure

Hydrogen has been considered as a promising energy carrier in future energy society,which could satisfy the increasing demand for the sustainable and clean energy supply.However,safe and efficient storage and production technologies of hydrogen are still limited its large-scale application.Chemical hydrogen storage materials,such as hydrous hydrazine and hydrazine borane,as safety and convenient hydrogen carriers,have attracted tremendous research interest due to their high hydrogen contents,CO-free hydrogen prodcution and simple byproduct.Both hydrous hydrazine and hydrazine borane molecules contain hydrazine group,but during the decomposition of hydrazine group to generate H₂ and N₂,side reaction often occurs to generate NH₃.Obviously,from the perspective of hydrogen production,the occurrence of side reaction will greatly reduce the hydrogen production efficiency of hydrous hydrazine and hydrazine borane.Therefore,the development of highly active,highly selective,highly stable and inexpensive catalyst for decomposition of hydrazine group is the key point to promote the practical application of hydrous hydrazine and hydrazine borane as hydrogen storage materials.This thesis focuses on the design and synthesis of Ni-CeO₂ nanostructure for catalytic hydrogen prodcution from chemical hydrogen storage materials.The main research contents are given as follows:?1?Wormlike Ni-CeO₂@SiO₂ core-shell nanocatalyst with a self-assembled Ni-CeO₂ nanowires as the core and microporous silica as the shell was successfully prepared via a simple one-pot synthetic route in a reverse micelle system.The formation mechanism of novel nanostucture Ni-CeO₂@SiO₂ is discussed in detail.The obtained Ni-CeO₂@SiO₂ catalyst showed superior catalytic performance and durability for hydrogen production from hydrous hydrazine and hydrazine borane with TOF of 219.5 and 442.5 h^-1,respectively.The high catalytic performance of Ni-CeO₂@SiO₂ can be attributed to the synergistic electronic effect and strong interaction between Ni nanoparticles and CeO₂ nanowires with plenty of oxygen vacancies,as well as the unique structure effect.?2?Ni-CeO₂ nanoparticles were successfully synthesized by the introducing of CeO₂ into the active site Ni via a co-precipitation method.A series of characterization results show that the CeO₂ not only can disperse and stabilize of Ni nanoparticles,but also can provide rich defect sites of catalyst surface.Moreover,the basic sites of the catalyst can also be strengthened by the CeO₂,which is beneficial to the selective cleavage of the N-H bond in the dehydrogenation of hydrazine group.Based on the visible light response characteristics of CeO₂,for the first time,we combined traditional heterogeneous catalysis with photocatalysis and applied it to the hydrogen production performance of hydrazine borane.Compared with that under no light condition,the prepared Ni-CeO₂ nanocatalyst shows highter catalytic activity,lower activation energy and better cycling performance for the dehydrogenation of hydrazine borane under the assistance of visible light.The optical characterization results show that photo-generated electrons and hydroxyl radicals can be generated,which are beneficial to improvement of the catalyst performance and cracking of the B-N bond in the dehydrogenation of hydrazine borane under the visible light irradiation.As a results,the Ni-CeO₂ nanocatalyst can achieve a high-efficiency dehydrogenation of hydrazine borane to hydrogen under the assistance of visible light.