| Hydrolysis of sodium borohydride(NaBH4)is an efficient and safe way of hydrogen generation.However,the strong reducibility of NaBH4 makes the stability of catalytic materials being highly required.In this paper,Co-MOF derived Co@C nanomaterials and ZIF-67@GO composites were prepared and used as the catalysts for hydrolysis of NaBH4.Co-MOF precursors were firstly synthesized by solvothermal method.Then,the Co@C catalysts were obtained by pyrolysis the Co-MOF precursors at different temperatures in nitrogen atmosphere.The results of XRD,BET,SEM,HRTEM and XPS characterizations show that the as-prepared Co@C catalysts are composed of MOF-dernved carbon and Co nanoparticles.The Co@C catalysts display high catalytic activity toward NaBH4 hydrolysis for hydrogen generation.Particularly,Co@C-700 exhibits the highest activity and good stability with 93.1%of its initial activity maintained after five cycles.The good stability of Co@C is attributed to the high dispersion of Co over carbon matrix.The behavior and kinetics of NaBH4 hydrolysis over Co@C were also studied.The results show that the reaction is first-order reaction with respect to the amount of catalyst and pseudo first-order reaction with respect to the concentration of NaBH4 under the experimental conditions.The activation energy of the reaction is 56.9 kJ.mol-1.(?)ZIF-67 and ZIF-67@GO composites were prepared at room temperature and utilized for the hydrolysis of NaBH4 to produce hydrogen.It was found that the doping of graphene oxide can obviously promote the catalytic performance of ZIF-67.The XRD,BET,Raman and SEM characterization results indicate that the graphene oxide doping significantly affects the structure of ZIF-67.The CV and LSV electrochemical analyses show that an appropriate doping of graphene oxide can improve the electron migration rate in the reaction.A mechanism model of NaBH4 hydrolysis was proposed based on the electron transfer and step-by-step substitution reaction. |
