Construction Of Supported Cobalt-based Nanomaterials And Its Catalytic Performance For Sodium Borohydride Hydrolysis

Hydrogen energy has attracted many researchers'attention due to its importance for fuel cell vehicles and environmental protection.For the hydrolysis reaction of sodium borohydride to generate hydrogen,noble metal catalysts have high catalytic activity,but they are expensive and resources are scarce.It is the trend to develop non-noble metal catalysts,while cobalt-based catalysts have high activity and abundant resources,and stand out among many catalysts.In this thesis,three types of cobalt-based catalysts,Co@NMGC,Co-B/NGO,Ni/GF/Co-Ni-P,were prepared by chemical complexation method,in-situ reduction method and hydrothermal method,respectively.The main research contents are as follows:?1?The core-shell structure of nitrogen-doped graphitized mesoporous carbon-coated cobalt nanoparticles?Co@NMGC?was synthesized by carbonizing the ethylenediaminetetraacetic acid?EDTA?.The source acts as a nitrogen source.Comparing Co@NMGC catalysts for Na BH₄ hydrolysis at different calcination temperatures,experiments show that 500?resulted in the best catalytic activity,with a hydrogen production rate of 3575 m L min^-1 g^-1 at 25±0.1?and low activation energy of 35.2 k J mol^-1 for Na BH₄ hydrolysis.The maximum hydrogen production rate using the cobalt-based complex catalyst was about three-fold ofthe pure cobalt catalyst.The complex catalyst showed high durability,retaining 82.5%of the initial catalytic activity after 20hydrolysis cycles.Density functional theory?DFT?calculations showed that the graphitic carbon shell promoted electron penetration from the Co nanoparticles into the graphitic carbon surface,which prevented oxidation of the Co nanoparticles,conducive to improving the catalytic activity of cobalt nanoparticles.?2?Using in situ reduction method,Co-B/NGO nanocomposites were prepared by in-situ reduction of NGO and inorganic cobalt salts with sodium borohydride.As a catalyst for the hydrolysis of Na BH₄,Co-B/NGO nanocomposites have a high catalytic activity.At25?,the hydrogen production rate can reach 1736.21 m L?min^-1?g^-1,and the activation energy is only 28.01 k J mol^-1.Its excellent catalytic activity can be attributed to its large specific surface area and nitrogen doping.The Co-B/NGO nanocomposite catalyst still retains 65.76%of the initial activity after 5 cycles.?3?The CoNiP nanosheet array catalysts were successfully prepared on three-dimensional?3D?graphene foam using the hydrothermal method.These catalysts were prepared using Ni–graphene foam?Ni/GF?,comprising nickel foam as the‘skeleton'and graphene as the‘skin'.This unique continuous‘skeleton/skin'structure ensured that the catalysts had a large surface area,goodconductivity,and sufficient surface functional groups,which not only promoted in-situ CoNiP growth,but also optimized the hydrolysis process of sodium borohydride.The nanosheet arrays are fully characterized and showed excellent catalytic performance,as supported by density functional theory calculations.The hydrogen generation rate and activation energy are 6681.34 m L.min^-1?g^-1 and 31.2k J?mol^-1.Furthermore,the CoNiP catalyst retains 74.9%of the initial hydrogen generation rate remaining after 15 cycles.The catalyst shows good catalytic performance and stability.