Enhancing The Activity Of Nickel Catalysts Based On Hydrotalcite Precursors And Cocatalysts

In this work,Ni Fe double hydroxide-graphene composites are used as precursors,a series of Ni Fe alloy nanoparticles were prepared by pyrolysis of the precursor at high temperature in inert atmosphere.A series of researches have been carried out on the preparation of Ni Fe alloy nanocomposites catalysts for ammonia borane hydrolysis.The structure of synthesized Ni Fe alloy catalysts were N-doped carbon coated Ni Fe alloy nanoparticles grown on graphene nanosheets.The synthesis process of Ni Fe double hydroxide-graphene composites are through self-polymerization of dopamine under alkaline conditions and following hydrothermal method.During the hydrothermal reaction,Ni and Fe ions precipitate in an alkaline aqueous solution caused by urea hydrolysis.After filtration,freeze-drying collection,then the obtained precursor was pyrolyzed under nitrogen.Carbon in graphene and dopamine at as reducing agents in order to restore Ni Fe double hydroxide-graphene composite precursors the original preparation alloy nanoparticles with high dispersity,dopamine forms nitrogen-doped carbon shells during pyrolysis.Ni Fe alloy nanocomposites with different proportions were prepared by adjusting the amount of nickel salt and iron salt.The prepared Ni Fe alloy nanocomposites were characterized and then tested for catalytic ammonia borane hydrolysis performance.The performance test experiment results showed that adding certain amount of iron could improve the catalytic activity of nickel.The reason is that the doping of iron in nickel can effectively optimize the electronic of nickel.At the same time,when the iron content is optimized,the catalyst has high activity for hydrogen production of ammonia borane.Based on density functional theory（DFT）,the change of strain before iron doping after doping to form Ni Fe alloy were calculated.DFT calculations also describes the adsorption and activation of both NH₃BH₃and water molecules.theoretical calculations show that the activation effect on ammonia borane molecules and water molecules induced at the active interface constructed between nickel and iron is the key factor to produce excellent catalytic performance.The possible mechanism of hydrogen production of ammonia borane catalyzed by Ni Fe alloy nanocomposites was proposed.According to the experimental data and theoretical calculation,the higher activity of the prepared catalyst is the result of the synergistic action of nickel and iron.Graphene with high specific surface area as the carrier promotes the formation of small size Ni Fe alloy nanoparticles.Meanwhile,the introduction of graphene oxide and dopamine carbon materials further enhanced the catalytic activity of Ni Fe alloy nanoparticles.Without the addition of graphene oxide and dopamine,the corresponding contrast materials were prepared,and the activity and corresponding tests were carried out at the same time.The performance test experiment results showed that the simultaneous existence of graphene oxide and dopamine had a great influence on the morphology and activity of the catalyst.The introduction of graphene oxide increases the apparent catalytic activity from TOF value of 4.41 to23.25 min^–1at 298 K.The magnetic property of resultant catalysts promotes its separation from the reaction system by adopting an external magnet,making reuse more convenient compared to other catalysts.The strategy used for this research work offers a new idea for the synthesis of bimetallic nanoalloy and indicates its promising potential for industrial applications.