Superior reusability of metal catalysts prepared within poly(ethylene imine) microgels for H2 production from NaBH4 hydrolysis

Polyethylene imine (PEI) particles were synthesized by a microemulsion polymerization technique, and were used as template for metal nanoparticle preparation. The PEI particles were loaded with Co(II), Ni(II) and Cu(II) ions from water and with CoCl2, NiCl2 and CuCl2 from ethanol and treated with NaBH4 to reduce the corresponding metal nanoparticles in situ. The PEI-M (Co, Ni, and Cu) composites were used in hydrogen generation from the hydrolysis of NaBH4 and NH3BH3 (AB). The PEI-Co composite catalyst system had better catalytic performances in the hydrolysis reactions of NaBH4 and AB than the other metal containing composites. The turnover frequency (TOF) value of PEI-Co in the hydrolysis of AB was found to be almost 12.5 fold more than NaBH4 hydrolysis. It is reported here that the PEI template offered better characteristics than the other templates providing many advantages; for example, the metal loading capacity of PEI increased by sequential loading and reduction cycles, and very high conversion (100%) and activity (100%) were obtained when PEI-Ni was used in fifteen consecutive runs for NaBH4 hydrolysis. The PEI-M composites have mild activation energy in comparison to the literature but better, more flexible characteristics, and very fast kinetics in AB hydrolysis.