Hydrogen Generation By Sodium Borohydride Hydrolysis On Co-Based Catalysts Supported On Biomass-Based Activated Carbon

Due to the expected lack of fossil fuels, the alternative new energy is imminent for human beings. Hydrogen, as a sustainable clean energy fuel in the future, attracted much attention around the world. However, the efficient and safe storage of hydrogen is still a severe constraint for hydrogen applications. NaBH4 is a promising material for hydrogen storage due to its high hydrogen storage density, high purity of hydrogen production and stable hydrolysis process. Therefore, numerous researchers explore application of NaBH4 as the source of hydrogen.For NaBH4 hydrolysis, developing a cheap and efficient catalyst is the key factor. However, there are many weaknesses such as high cost, instability, and poor activity that limit the commercialization of the existing catalysts. Therefore, this paper focuses on developing a series of catalysts to accelerate hydrogen generation by NaBH4 hydrolysis which exhibits high activity, low cost, and good stability.In this thesis, waste cotton stalks were prepared into activated carbon, and the Co-B catalysts supported on cotton stalk activated carbon (CSAC) were generated by the impregnation-chemical reduction method. By means of BET, SEM, XRD, FTIR and ICP-OES techniques, the effects of activation reaction parameters and recycle times on hydrogen generating performance of the activated carbons supported Co-B catalysts were investigated. It is indicated that the optimal activation temperature, activation time and the amount of activator (mH3PO4/mCS) for activation of cotton stalk were 500℃,1 h and 0.75, respectively. Under these conditions, the prepared Co-B/CSAC catalyst exhibited the excellent hydrogen generating performance. After five cycles, the catalyst retained 54% initial activity.The doping of additives into the catalysts and a comparison of catalytic activity between the multi-component catalyst and the Co-B catalyst were investigated. The kinetics of NaBH4 hydrolysis over Co-Ce-B/CSAC was also studied. It is indicated that the doping of Ce enhanced the performance of the catalyst greatly with the mass ratio of Ce:Co was 1:10. The Co-Ce-B/CSAC catalytic hydrolysis of NaBH4 was zero order with respect to the NaBH4 concentration, and the hydrogen generation rate decreased with an increase in the NaOH concentration. The kinetic rate equation of hydrogen generation by NaBH4 catalytic hydrolysis using the Co-Ce-B/CSAC catalyst was expressed as rH2=2.88×109exp-57.998/T/(1+0.165[NaOH]09)Co-B/CSAC catalyst was also prepared by electroless deposition method. The effects of the catalyst preparation conditions on hydrogen generating performance were studied. In addition, the reactivity and stability of the catalysts generated with two different methods were also investigated. It is demonstrated that the Co-B/CSAC prepared by electroless deposition method exhibited higher reactivity and stability. The catalyst exhibited the excellent hydrogen generating performance when the addition of Pd, NaBH4, NaOH were 0.4 g-L"1,0.51 g and 2 g, respectively.