Synthesis of enhanced imidazolium ionic liquid and amino immoblised mesoporous silica supported ruthenium nanoparticle for H2 generation from NaBH4

Abstract

The new supported mesoporous nanoparticles RuNPs, decorated as RuNPs@[KIT-6]-NH₂ 4 and RuNPs@[KIT-6]-NH₂-imid 5, were synthesized by a chemical modification of silica surface procedure utilizing the [KIT-6] 1, then RuCl₃.3H₂O reduced by sodium borohydride. RuNPs 4 and 5 were characterised by ²⁹Si solid-state NMR, SEM, XPS, and TEM. The influence of different factors, for example, reaction time, temperature, catalyst loading, and concentration of NBH₄, were examined to achieve the best catalytic conditions. RuNPs 4 and 5 catalyse the release of H₂ from sodium borohydride with remarkable proficiencies, and RuNP 5 catalyst was found to be more effective than its counterpart 4. The hydrolytic reaction generates H₂ in the presence of (2 mg, 0.18 mol) of catalyst 5 at 20 °C conducting 163.3 mole_H2 mol_cat⁻¹ min⁻¹ of TOF. The study of kinetics discovered that the hydrogen generation process is first order with activation energy E_a of 35.7 kJ mol⁻¹ for both catalysts 5 and 4. The RuNPs 5 efficacy for the H₂ production reaction of NaBH₄ was conducted in D₂O and H₂O showed that the catalytic process is significantly more rapid in water than in D₂O indicating the solvent isotope KIE k_H/k_D = 1.5 which is consistent with the determination step of rate includes cleavage of O–H of H₂O. This difference in this initial value of rate may be due to not occurring the bond cleavage of B–OD in the determination step of rate. Furthermore, the good repeatability of catalytic hydrolysis for RuNPs based [KIT]-NH₂-imid mesoporous silica 5 retains 87% of the primary catalytic activity after the 4th runs.