Study On Catalysts For Hydrogen Generation From Sodium Borohydride Hydrolysis

With the increasing worsening of energy and environment problems, hydrogen energy has become a new energy source and got more and more attention. As a convenient, practical and efficient process generating high-purity of hydrogen gas, sodium borohydride hydrolysis technology has become one of the best hydrogen resources for the proton exchange membrane fuel cells. This thesis mainly focus on the non-noble catalysts for NaBH₄ hydrolysis,including Raney metal catalyst and amorphous alloy catalyst.In this thesis, we researched the effect of Raney metal catalyst, such as NiAl alloy and CoAl alloy, on hydrogen generation by NaBH4 hydrolysis. Approprite leaching conditions were studied. The properties of Raney catalysts were characterized by means of XRD,XRF,BET,H₂-TPD etc. The results show that the BET surface area of Raney Co is lower than that of Raney Ni, however, the activity of Raney Co in NaBH4 hydrolysis is higher than that of Raney Ni , which might be concerned with the property of metal self (such as Co and Ni) and the temperature of hydrogen desorption from the surface of Raney metal.Amorphous Co-B and Co-P-B alloy particle were prepared by chemical reduction method. Sodium borohydride is the reduction agent. The structure and properties of the amorphous alloy catalysts were characterized by XRD,TEM,XPS,TPR and DSC etc. Influences of different preparation conditions on the catalysts properties have been studied. The particle size of Co-B,Co-P-B powder is 20-60nm, showing cotton wool structure, and they will be crystallized at about 300℃. Furthermore, as for the requirement of the catalyst in practical applications, the supported Co-P-B/Ni foam was also prepared. The Co-P-B/Ni foam catalyst was analyzed by SEM-EDS. This supported catalyst shows high activity and stability.The kinetics of sodium borohydride hydrolysis reaction had also been investigated in this thesis. The concentration of NaBH4 and NaOH and the reaction temperature had also been studied. The results show that at low concentration of sodium borohydride, the reaction is first order, and the performance of the system is the best when the concertrations of NaOH and NaBH4 are 5 mol·L^-1 and 1.5 mol·L^-1, respectively.