Ru-based Catalysts For Catalytic Hydrogen Production Ammonia-borane Hydrolysis

Hydrogen energy is considered as a clean renewable energy source.Ammonia-borane?AB?has been regard as one of the most important promising chemical hydrogen storage materials with respect to its nontoxicity,environmentally benign and high hydrogen content.However,it is relatively stable at room temperature and very difficult to achieve rapid hydrolysis for hydrogen prodction.To improve the rate of hydrolysis and recyclability for hydrogen production of AB,Ru-based catalysts were synthesized by a simple method of in situ reduction in this thesis.In addition,we used porous carbon materials as carriers and PVP as stabilizer to increase the activity of catalysts.The structure of as-prepared catalysts of Ru/NPC,Ru/GC,Ru/BC-1 was characterized by BET,XRD,TEM,XPS,SEM and ICP.Their catalytic activities for AB hydrolysis and the mechanism of the reaction were systematically studied.The main results are as follows:1)By using glucose as carbon source and hydrochloride semicarbazide as nitrogen source,the nitrogen-doped porous carbon?NPC?materials were synthesized by hydrothermal method and the following calcination under inert atmosphere.Then,Ru/NPC catalyst was synthesized by in situ reduction.As-prepared Ru/NPC catalyst efficiently catalyzes the hydrolysis of AB at room temperature.The hydrogen production reaction is completed within 90 s with the turnover frequency?TOF?for hydrogen production of 813mol_H2·mol_Ru^-1·min^-11 and the activation energy?E_a?of 24.95 kJ·mol^-1.Moreover,Ru/NPC can be recycled with a well-maintained performance.After five cycles,the catalytic activity is corresponded to 67.3%of the initial catalytic activity.2)The ginkgo leaf-derived porous carbon?GC?materials were synthesized by low temperature carbonization,chemical activation and calcination at high temperature by using ginkgo leaves as a carbon source.Then Ru/GC catalyst was synthesized by in situ reduction.The as-prepared Ru/GC catalysts for AB hydrolysis exhibit high activity(TOF=921 mol_H2·mol_Ru^-1·min^-1)and low activation energy(E_a=23.86 kJ·mol^-1).Moreover,Ru/GC shows fairly good recyclability with 58%of the initial catalytic activity after five cycles.The decrease of catalytic activity could be attributed to the agglomeration of the metal particles after multiple catalysis.3)By using bamboo leaves as carbon source,hydrochloride semicarbazide as nitrogen source,we synthesized the bamboo leaf-derived porous carbon?BC?through calcination at high temperature under an inert N₂ atmosphere.To improve the cycle stability of the catalyst,PVP was added as stabilizer for Ru nanoparticles.Then we changed the amount of PVP to synthesize the Ru/BC catalyst.Ru/BC-1 exhibits high activity(TOF=718 mol_H2·mol_Ru^-1·min^-1)and low activation energy(E_a=22.8 kJ·mol^-1).Moreover,the catalyst exhibits considerably good recyclability with 55.6%of the initial catalytic activity retained after ten experimental cycles.The good cycle performance can be attributed to the fact that the PVP can stabilize the presence of Ru metal particles on the support.