Fabrication And Performance Investigation Of Catalysts For Hydrogen Generation From Formic Acid/Ammonia Borane

Hydrogen energy,as an energy carrier for the future,is an ideal clean energy and is known as"the energy of the future of mankind".High-capacity hydrogen storage materials composed of small molecules,such as metal complex hydrides,nitrogen-based compounds,boron-based compounds,etc.,with high hydrogen storage density,good stability and safety,are prospective for the development of hydrogen storage materials.Formic acid?HCO₂H,FA?,non-toxic,and abundant in source,can generate H₂ by dehydrogenation reaction under the action of catalyst.Ammonia borane?NH₃BH₃,AB?is a stable solid at room temperature and non-toxic,with a high energy density?19.6 wt%?superior to other hydrogen storage materials.Whether FA or AB,the efficiency of hydrogen generation reaction mainly depends on the selection of catalyst.Therefore,the development of high-efficiency,low-cost catalysts to further improve the hydrogen generation efficiency of FA and AB under mild conditions is the key point to promot the practical application of FA and AB as hydrogen storage materials.In this paper,we will focus on the application of several catalysts in the hydrogen generation reaction of hydrogen storage materials.The research contents mainly including the following three aspects:1.We prepared MIL-101-NH₂ with high specific surface area by solvothermal and post-treatment methods,and then prepared MIL-101-NH₂ supported CrPd nanocomposites by impregnation and one-step co-reduction methods.The obtained CrPd nanoparticles are uniformly distributed on the MIL-101-NH₂ substrate with an average particle size of 2.6nm.Compared with Cr_0.4Pd_0.6/MIL-101,Cr_0.4Pd_0.6/MIL-101-NH₂ exhibits excellent activity and 100%hydrogen selectivity in catalyzing hydrogen generation from FA decomposition reaction,and the initial turnover frequency?TOF?is as high as 2009 mol H₂·mol Pd^-1·h^-1,which is higher than most of the heterogeneous catalysts under similar reaction conditions.The excellent catalytic performance of CrPd/MIL-101-NH₂ is attributed to the fact that-NH₂ modified MIL-101 can serve as electron donor for the active component of the catalyst,and the electron-rich metal active component has more It is beneficial to the cleavage of O-H bond in FA.Moreover,-NH₂ functionalized MIL-101can effectively immobilize metal precursor by synergistic effect,which leads to the formation of uniform dispersion of metal nanoparticles,and then leads to the increases of the concentration of the active site of the FA decomposition reaction.2.We successfully immobilized the ultrafine particle size and well dispersed CrPd nanoparticles on the?-cyclodextrin silicon derivative?M-?-CD-A?by wet chemical method.Due to the strong metal-organic interface interaction between CrPd nanoparticles and M-?-CD-A,the prepared Cr_0.4Pd_0.6/M-?-CD-A exhibits high catalytic performance for FA dehydrogenation.the time for completing reaction is only required 4.5 minutes,and the initial turnover frequency?TOF?is as high as 5771 mol H₂ mol Pd^-1 h^-1,without any additives at 323 K,which is much higher than those obtained for most of the reported heterogeneous catalysts under similar conditions.3.We prepared amorphous CoB-based catalysts with different B contents and tested their catalytic performance for hydrogen generation of AB hydrolysis.The results show that CoNiB-h nanoparticles prepared by in-situ synthesis possess higher B content than CoNiB-1 prepared by pre-synthesis.The TOF value of Co_0.7Ni_0.3B-h(30.9 mol H₂ mol metal^-1·min^-1)is much higher than that of Co_0.7Ni_0.3B-l(4.3 mol H₂ mol metal^-1·min^-1)for the AB hydrolysis reaction.The excellent catalytic performance of CoNiB-h is mainly due to its relatively high B content and good dispersibility in the absence of any surfactant and support.