Influence Of Graphene Load Non-noble Metal Catalysts On The Properties Of Products Borohydride Hydrogen

Borohydride is a kind of solid state hydrogen storage compounds with high hydrogen content and tunable hydrogen release properties.Because of good stability,sodium borohydride（Na BH₄,10.7 wt.%）and ammonia borane（NH₃BH₃,19.6 wt.%）are being groomed as candidates.Catalysts act as an “on/off” switch during hydrogen release of Na BH₄.By controlling the reaction conditions,reaction rate can be effective control.This paper studies on the preparation of transition metal catalyst and the effect of the catalyst on hydrolysis of borohydride.Simultaneously,we studied on the influence of the preparated variety novel transition metal catalysts using in hydrolysis under different conditions.Three-dimensional graphene oxide（3DGO）prepared by hydrothermal have both functional groups on the surface of two-dimensional graphene oxide and three-dimensional structure.Using chemical reduction we obtain the Co@3DGO catalyst.Micro-structure analysis show that the agglomeration of Co particles are reduced,and particles size are shrinking from about 40-50 nm to 20 nm.At 298 K,the hydrogen generation rate（HGR）of Na BH₄ can reach up to 4394 11min2--××MHgm L.As well as the reaction activation energy is 37.43 k J?mol^-1.It is found that when hydrogen reaction at a high generation rate,large number of air bubbles accompanied generate from the catalyst surface.Hydrogen bubbles expand rapidly which has great effect on the structure of the catalysts and lead to the reunion of catalyst metals and collapse of carrier structure.Thus concentration of Na OH within the scope of 0.25 M to 0.05 M,the cyclicity of catalyst increases with the decrease of the concentration of Na OH.We add another kind of transition metal Mo into the active component and use chemical reduction method to reduce Co2+ and Mo6+ together to the surface of 3DGO.This two metles work together shows that when the molar ratio of Co and Mo is 7:3 written as Co_0.7 Mo_0.3@3DGO has the best activity.Under the same condition,the activity is 1.6 times higher than the catalyst of Co@3DGO which can reach 7023.311min2--××MHgm L.The reaction activation energy is 35.6 k J?mol^-1.In order to increase the defect of graphene oxide and anchor active component,we use oxide etching method to preparate the porous oxide graphene（PGO）.We introduce the porous graphene oxide（PGO）as the carrier modified by oxide etching method,and prepare the catalyst Co@PGO.The hydrogen generation rate（HGR）of Na BH₄ can reach up to 595511min2--××MHgm L and the reaction activation energy is 55.2 k J?mol^-1.After five circles,catalyst activity can retain 72.9% of the first lap.The HGR of AB can reach up to 10730.911min2--××MHgm L.The reaction activation energy of AB hydrolysis is 41.95 k J?mol^-1.