Compositing Of Cobalt-boron Noncrystal And Carbon Nanomaterials And Their Related Hydrogen Storage And Hydrogen Production Properties

With the increasing demand for energy,the storage capacity of traditional fossil fuels is drastically reduced.Hydrogen energy attracts the eyes of the world cause for its characteristic of green,environmental friendly and efficient.It is considered as an important source of energy in the future.The safety of the storage and transportation,the low cost and high efficiency preparation are the preconditions for its widely application.In the aspect of hydrogen storage,the traditional methods have many disadvantages such as high energy consumption and large container quality.In the field of hydrogen production,the technologies include biomass hydrogen production,natural gas cracking hydrogen production,photolysis and electrolysis of water and so on.Some results show that cobalt-based compounds have excellent electrochemical hydrogen storage properties and catalytic activity for hydrogen evolution and the research of cobalt-boron compounds used in the electrochemical hydrogen storage and electrolysis of water has attracted great interest from researchers and gradually become a hot research spot.In this paper,amorphous carbon-boron compound-modified carbon nanocomposites is prepared by an efficient,low-cost and simple method.Mainly includes the following two aspects:1.Graphene(GR)composite(Co-B-GR)modified by amorphous cobalt-boron compound is prepared by high-energy ball milling,the electrochemical hydrogen storage property of Co-B-GR is also studied.First,the amorphous cobalt boron precursor is obtained by putting cobalt powders blended together with boron powders after ball-milling at a speed of 800 r for 10 h.After that,graphene is prepared by sodium reduction of ethanol.Finally,the graphene was mixed with the above amorphous cobalt boron precursor ball-milled at 600 r for 5 h to obtain Co-B-GR.The micro-component and structure of Co-B-GR is analyzed by X-ray photoelectron spectroscopy(XPS),Raman spectroscopy,Fourier transform infrared(FTIR)spectroscopy and transmission electron microscopy(TEM,HRTEM).The results show that the boron atom in the amorphous cobalt boron replaces the carbon atom in the six-membered ring of graphene,and the hybridization between amorphous cobalt-boron/grapheme compound is realized.The stable structure model of Co-B-GR is established by density functional theory(DFT)in simulation.Based on this model,the electrochemical hydrogen storage mechanism of Co-B-GR is analyzed theoretically.The results of electrochemical hydrogen storage test and infrared spectroscopy show that there are different hydrogen adsorption sites in Co-B-GR materials under the mechanism we propesed before and Kubas enhanced adsorption,and the hydrogen storage capacity of the Co-B-GR material can reach 710 mAh/g(2.68 wt.%).2.The multi-walled carbon nanotubes(MWCNTs)were used as "molecular sieves”to prepare Co2B monolayers by high energy ball milling process,and the electrocatalytic hydrogen evolution of the materials is studied.ended together with boron powders after ball-milling at a speed of 600 r for 15 h.Then,the multi-walled carbon nanotubes was mixed with the above amorphous cobalt boron precursor ball-milled at 300 r for 6 h to obtain(MWCNT/Co2B-M).The micro-component and structure of MWCNT/Co2B-M composite is analyzed by X-ray photoelectron spectroscopy(XPS),Raman spectroscopy(Raman)and transmission electron microscopy(TEM,HRTEM).The results show that the lattice distortion of the multi-walled carbon nanotubes(MWCNTs)and the position of intercalation of Co2B molecules in the composites are analyzed by HRTEM.We see that the multi-wall carbon nanotubes(MWCNTs)wall of nanotubes is broken and the lattice is distorted,and the amorphous cobalt-boron compound adheres to the outer surface of the multi-walled carbon nanotubes,and the Co2B molecules along the multi-walled carbon nanotube.Infiltrate and intercalate the layers through the crack.Compared with MWCNT/Co2B composite,MWCNT/Co2B-M composite has a better electrocatalytic hydrogen evolution property,and the initial hydrogen evolution overpotential is-83 mV,the cathodic current density is 10 mA/cm2,the overpotential is-116 mV and the tafel slope is 99 mV/decade.The initial hydrogen evolution potential of MWCNT/Co2B is-103 mV,the overpotential is-167 mV and the tafel slope is 130 mV/decade at the cathode current density of 10 mA/cm2.