Preparation Of Composite Cobalt-based Catalysts And Their Performance In Catalytic Hydrogen Of Production From Sodium Borohydride

NaBH₄ has the advantages of abundant hydrogen storage density,high purity of hydrogen production and controllable hydrolysis process as an integrated material for hydrogen production and storage,which has a good development prospect.However,NaBH₄ hydrolysis at room temperature suffers from problems such as slow reaction,and the selection of a suitable catalyst is beneficial in facilitating the hydrolysis reaction.Based on the research status and development trend of the literature on hydrogen production by hydrolysis of NaBH₄,three cobalt-based catalysts,Co-Cr-B/NG,Co-Mo-B/N-PCN and Co-Ru-B/SiCN,were prepared by electrostatic spinning,high-temperature calcination and chemical reduction,and their morphology,structure,hydrogen production performance and mechanism were investigated in this paper.The work is as follows:（1）A cobalt-chromium-boron loaded nitrogen-doped graphene（Co-Cr-B/NG）catalyst was prepared by in situ reduction and a"valence band center"descriptor based on the valence band spectroscopy has proposed.The valence band centers are found to change with different ratios of Cr doping and to show a volcano plot relationship with the catalytic activity of the catalyst.The best catalytic activity of the Co-Cr-B/NG catalyst is achieved when the ratio of Cr/（Cr+Co）is 4%,with the hydrogen production rate of 2231.7m L·min^-1·g^-1 and the activation energy of 38.41 k J·mol^-1.（2）Nitrogen-doped porous carbon nanofiber N-PCN carriers were obtained by electrostatic spinning and calcination using polyacrylonitrile（PAN）and polystyrene（PS）as raw materials.Then Co-Mo-B nanoparticles were uniformly and stably loaded onto the N-PCN carriers by impregnation and in situ reduction to obtain amorphous structured Co-Mo-B/N-PCN catalyst.SEM and TEM experimental results demonstrate that the nitrogen-doped porous carbon nanofibers promote the uniform distribution of Co-Mo-B particles.Compared to N-PCN,Co-B,Co-Mo-B and Co-B/N-PCN catalysts,Co-Mo-B/N-PCN has the best catalytic activity.At room temperature,Co-Mo-B/N-PCN produced hydrogen at a rate of 3159.2 m L·min^-1·g^-1 and an activation energy of 34.75k J·mol^-1.（3）The Co-Ru-B/SiCN catalyst was prepared by electrostatic spinning and high-temperature carbon thermal reduction of silicon nitride（SiCN）nanofibers,and Co-Ru-B nanoparticles are uniformly and stably loaded on SiCN carrier by in situ reduction.The specific surface area of the prepared rod-shaped Co-Ru-B/SiCN catalyst reached 124.5715 m²·g^-1 and the pore size reached 0.599701 cm³·g^-1.The large specific surface area and pore size provided channels for metal transport and increased the contact area for the reaction between the catalyst and the NaBH₄ solution.When the ratio of Ru/（Ru+Co）is 5%,the Co-Ru-B/SiCN catalyst has the best catalytic activity.At room temperature,the hydrogen production rate of Co-Ru-B/SiCN catalyst was 3716.4m L·min^-1·g^-1 and the activation energy was 33.92 k J·mol^-1.