Heteroatom modified polymer immobilized ionic liquid stabilized ruthenium nanoparticles: Efficient catalysts for the hydrolytic evolution of hydrogen from sodium borohydride

Ruthenium nanoparticles stabilised by polymer immobilized ionic liquids catalyse the hydrolytic release of hydrogen from sodium borohydride. The composition influences performance and ruthenium an amine-decorated imidazolium-based immobilised liquid ([email protected]2-PIILS) was most efficient with a maximum initial turnover frequency (TOF) 177 moleH2.molRu−1.min−1, obtained at 30°C catalyst loading 0.08 mol%; markedly higher than that 69 molH2.molRu−1.min−1 5 wt% Ru/C one highest to be reported for RuNP catalyst. apparent activation energy (Ea) 38.9 kJ mol−1 hydrolysis NaBH4 catalysed [email protected]2-PIILS is lower other RuNPs, which consistent its efficacy. Comparison rates in H2O D2O gave primary kinetic isotope effect (kH/kD) 2.3 supports mechanism involving rate limiting oxidative addition O-H bonds strongly hydrogen-bonded surface-coordinated [BH3H−]—-H2O ensemble. involvement borohydride further supported inverse 0.65 comparison NaBD4 under conditions catalysis i.e., high hydride/catalyst mole ratio. Interestingly though, when conducted dilute solution ratio 1 2.72 obtained; this would more concerted both B-H bond step, possibly via addition-hydride transfer Catalyst stability reuse studies showed retained 71% activity over five runs; gradual drop TOF run number appears due passivation borate by-product as well increase viscosity reaction mixture rather leaching