H2 generation from NaBH4 methanolysis via magnetic field sensitive ionic liquid coated silica particles as catalyst

Upon the preparation of magnetic (Fe3O4) nanoparticles (NPs), they were coated with amino-functionalized silica (SiO2@NH2) via the modified Stöber method. SiO2 coated Fe3O4 (Fe3O4@SiO2) particles and SiO2@NH2 coated Fe3O4 (Fe3O4@SiO2@NH2) particles were turned into ionic liquid (IL) colloids as Fe3O4@SiO2@NH3+Clˉ, Fe3O4@SiO2@NH3+NO3ˉ and Fe3O4@SiO2@NH3+HSO4ˉ by the treatment of Fe3O4@SiO2@NH2 with hydrochloric acid (HCl), nitric acid (HNO3) and sulfuric acid (H2SO4), respectively. The size of the prepared silica-based particles was approximately 500 nm by SEM images, and the zeta potential values varying between −59 and +26 mV. The catalytic activity performances of these silica-based particles as catalysts were investigated for H2 generation from methanolysis of NaBH4 in terms of the types of particles, reusability, recyclability, the concentration of NaBH4, and the reaction temperature. Amongst the prepared IL colloids, Fe3O4@SiO2@NH3+Clˉ particles were found to be the most effective catalysts for the methanolysis reaction of NaBH4. The maximum Hydrogen Generation Rate (HGR) value of 13188 ± 196 mL H2 g−1 min−1 was attained at 500 mM NaBH4 by using 50 mg Fe3O4@SiO2@NH3+Clˉ as catalyst at 25 °C. Additionally, turn over frequency (TOF) value was calculated as 43.1 ± 3.1 H2 mol (mol of N.min)−1 for Fe3O4@SiO2@NH3+Clˉ under the same reaction conditions. Moreover, activation energy (Ea) values for the methanolysis of NaBH4 using Fe3O4@SiO2@NH3+Clˉ particles as catalyst were found as 32.5 ± 0.5, 39.9 ± 0.3 and 24.4 ± 0.7 kJ mol−1 in the temperature range of −15-45, −30-0 and 15-45 °C, respectively, that are comparable and even better than for most of the metal nanoparticle catalysts used in NaBH4 methanolysis reactions.