Preparation And Properties Of Co Based Catalyst For Sodium Borohydride Hydrolysis

Energy as an important part in people's daily life,which is produced by burning fossils fuels,has been consumed in large quantities.With the fossil fuel resource decreasing and serious pollution caused by fossil fuel combustion,the research of new energy resources has attract more and more attention.Hydrogen is considered to be a great substitute of fossil fuels to reduce global fossil fuel consumption and global warming with high gravimetric energy density,zero emission of environment pollutants,and wide storage.Sodium borohydride as a potential material for hydrogen production has been widely investigated by researchers due to high hydrogen storage capacity and safety.In this thesis,two kinds of amorphous catalysts,Co-Cu-B and Co-Cr-B,were prepared by chemical reduction,and graphene oxide(GO)was introduced as a carrier to prepare supported Co-Cr-B/GO catalyst.The surface morphology,structure and composition,element and valence state,and specific surface area of the catalyst were characterized by TEM,SEM,XRD,XPS,BET,etc.The catalytic activity of the catalyst was tested by catalyzing the hydrolysis of NaBH4 solution.The effects of transition metal species,doping amount and graphene oxide on the hydrogen generation of NaBH4 solution hydrolysis were studied.In addition,the effects of catalyst amount,NaBH4 concentration,reaction temperature,NaOH concentration on the hydrolysis of NaBH4 solution were also researched.And the recycling performance of catalyst were investigated.The main contents were summarized as follows:(1)The ternary Co-Cu-B and Co-Cr-B catalysts was prepared by chemical reduction method,the catalyst particles were spherical.The particle size of the catalyst was reduced with the addition of a small amount of Cu and Cr,and the agglomeration of particles was suppressed,which increased the specific surface area of the catalyst.When the Cu/Co ratio was 0.05,the Co-Cu-B-1 catalyst showed the best catalytic performance,its specific surface area was 57.467 m2/g,and the hydrogen generation rate reached 1334.24 ml·min-1·g-1.When the Cr/Co ratio is 0.005,the Co-Cr-B-2 catalyst exhibited the best catalytic performance,its specific surface area was 66.402 m2/g,and the hydrogen generation rate reached 2110.4 ml·min-1·g-1.(2)The supported Co-Cr-B/GO catalyst was prepared by chemical reduction method.The addition of GO in Co-Cr-B significantly reduced the agglomeration of the catalyst.As the amount of GO.increased,the particle size of the catalyst also increased,so the specific surface area of the catalyst increased.When the amount of GO was 0.015 g,the Co-Cr-B/GO-3 catalyst expressed the best catalytic performance,its specific surface area was 76.079 m2/g,and the hydrogen generation rate reached 3284.6 ml·min-1·g-1.(3)Co-Cu-B-1,Co-Cr-B-2,Co-Cr-B/GO-3 exhibited the best catalytic activity when the NaBH4 concentration was 1.0 mol/L.It was found that adding appropriate amount of NaOH in the solution was beneficial to increasing the rate of hydrogen generation by NaBH4 hydrolysis.(4)Recycling performance of three catalysts:after 5 catalytic reactions,the performance of Co-Cu-B-1 catalyst was 64.6%of the original;the performance of Co-Cr-B-2 catalyst was 72.7%of the original;Co-Cr-B/GO-3 catalyst performance was 58.36%of the original.These catalysts behaved excellent recycling performance.