Ni-MOF-74 Self-Assembled Synthesis Of Carbon-Based Nickel Nanocatalysts For Hydrogen Production Via Catalytic Decomposition Of Formic Acid

Hydrogen energy has high energy density and great application prospects in the field of new energy.Formic acid is a liquid hydrogen storage material with the advantages of high hydrogen content,easy storage and transportation.The formic acid in liquid phase catalytic dehydrogenation is one of the effective methods to obtain clean hydrogen energy.At present,there are more researches on heterogeneous noble metal catalysts catalyzing hydrogen production from formic acid,but the high cost limits the commercial application of such catalysts.Therefore,the development of non-noble metal catalysts with excellent hydrogen production performance at lower temperature is the research focus of hydrogen evolution in formic acid system.In this paper,Ni-MOF-74 is used as the precursor to synthesize non-noble metal nickel nanocatalysts for catalyzing formic acid dehydrogenation.The effects of calcination temperature and graphene oxide(GO)-mediated Ni-MOF-74 on the catalytic performance are explored.Further study the structure-activity relationship of the catalysts through different characterization methods.The main findings are shown as follows:1.Ni-MOF-74 is prepared by a one-step hydrothermal method,and the catalyst Ni@CNTs is self-assembled to synthesize carbon nanotube-confined Ni nanoparticles after high-temperature pyrolysis.Studies have shown that the ligand terephthalic acid in Ni-MOF-74 undergoes pyrolysis self-assembly to form carbon nanotubes during heat treatment under N2 atmosphere,and the coordinated Ni2+ is reduced to form metallic Ni nanoparticles.The characterization results prove that Ni nanoparticles are confined in carbon nanotubes,and the interaction between carbon nanotubes and Ni particles promotes the transfer of electrons and improves the catalytic performance.The Ni@CNTs catalysts can effectively catalyze the direct dehydrogenation of formic acid.The study finds that the synthesized Ni@CNTs-600 catalyst has the best catalytic performance for formic acid dehydrogenation,and the hydrogen yield at 50℃ is 53.8 mL·g-1·h-1.2.The Ni/CNTs-RGO catalysts are synthesized by a two-step method of hydrothermal and high-temperature heat treatment in the hydrothermal process,the layered Ni-MOF-74/RGO precursor was prepared by regulating the morphology and structure of Ni-MOF-74 by GO induction.The precursor is pyrolyzed in N2 atmosphere,the ligands in Ni-MOF-74/RGO are carbonized to form carbon nanotubes,and Ni nanoparticles are dispersed on the carbon nanotubes and RGO to prepare Ni/CNTs-RGO catalysts.Studies have shown that adjusting the ratio of Ni2+to ligand has a significant impact on the structure and performance.The interaction between Ni particles,carbon nanotubes and RGO forms a Ni-C bond,which is beneficial to improve the dehydrogenation performance of the catalyst.When the molar ratio of metal to ligand is 2:1,the catalyst has the best catalytic performance for hydrogen production.When the reaction temperature is 50℃,the hydrogen yield is 118 mL·g-1·h-1.