Preparation Of Supported Rhodium Catalysts And Performance Investigation For The Dehydrogenation Of Ammonia Borane

Ammonia borane（AB）has been considered as one of the leading contenders in promising storage materials for various applications because it presents a high hydrogen content（19.6 wt%）,high stability,and non-toxicity under ambient conditions.Hydrogen generation from the hydrolysis of AB over heterogeneous catalysts is essential for practical applications.However,most catalysts reported in literature are low-activity and poor cycle performance.We are devoted in the synthes-is of Rh catalysts,the characterization of the samples and the study of catalysts performance in order to synthesis high-performance catalysts for dehydrogenation in AB.The main contends and results are as follows:（1）N-doped graphene-like meso-macroporous carbons（GMCs）with unique layered structure was obtained by soft template method,and Rh/GMCs catalysts are synthesis by impregnation-reduction method.TEM characterization results showed that the particle size of the 4 wt%Rh/GMCs-40-800 catalyst was 1.8±0.6 nm.The results show that the dehydrogenation rate of AB is proportional to the mass of the catalyst and the concentration of AB and it is volcanic type with the mass ratio of melamine to glucose.In addition,4 wt%Rh/GMCs-40-800 catalysts show superb catalytic activity with a record turnover frequency value（TOF）of 645.3 min^-1at 283K and retain 100%active after ten runs of dehydrogenation of AB.It is currently reported in the literature that this type of catalyst has the highest stability.（2）Rh nanoparticles with various mass ratios immobilized on melamine-urea-formaldehyde carbons（MUFCs）that obtained by hard template method were success-fully synthesized by impregnation-reduction method.The microstructure was charact-erized by XRD,XPS,TEM.The resulting 3 wt%Rh/M₁₀UFCs-6-750 and 3 wt%Rh/M₁₀UFCs-6-800 catalysts had a measured TOF of 473.5 min^-1and 1290.7 min^-1,repectively.This catalyst could also be reused ten times and reserving 66.7%of 3wt%Rh/M₁₀UFCs-6-750 initial catalytic activity.The large surface area and abundant nitrogen-functional species of MUFCs facilitate dispersion of Rh nanoparticles on their surface,providing numerous catalytically active sites for AB dehydrogenation,thereby leading to high catalytic activity and better cycle performance.This result provides a theoretical basis for the large-scale application of hydrogen energy.