Sulphonated silica and sulphonated silica / carbon particles as efficient catalysts for hydrogen generation from sodium borohydride hydrolysis

Abstract

In the present study, silica, sulphonated silica (SS) and sulphonated silica/carbon (SSC) particles are prepared by sol-gel method using tetra-ethyl ortho-silicate and glucose as sources for silica and carbon, respectively and used as catalysts for sodium borohydride (NaBH4) hydrolysis to produce hydrogen. The acid density calculated by back titration method shows the acidic nature of SS and SSC. Further, the catalysts are characterized using FT-IR, XRD, SEM, TEM, EDAX and N2 physisorption studies. TEM and N2 adsorption/desorption studies revealed the porous nature of the particles. Further, the catalytic activities of SS and SSC are analysed towards NaBH4 hydrolysis. It is found that both SS and SSC enhance the sodium borohydride hydrolysis significantly with hydrogen generation rates of 768 and 914 mL min−1 g−1, respectively. Using Arrhenius plot, the activation energies of SS and SSC are calculated as 24.74 and 18.97 kJ mol−1, respectively. Further, thermodynamic parameters like ΔH‡, ΔS‡ and ΔG‡ of the activated complex are calculated using Erying plot. The negative ΔS‡ value suggests that the mechanism of NaBH4 hydrolysis at SS and SSC follows Langmuir-Hinshelwood associative mechanism.