Various amine functionalized halloysite nanotube as efficient metal free catalysts for H 2 generation from sodium borohydride methanolysis

Abstract In this work, naturally available clay, halloysite (Hal) nanotube was modified systematically with various types and number of amine groups containing modifying agents and used as catalyst in the methanolysis of sodium borohydride (NaBH4) for hydrogen (H2) production. The modifying agents such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tris(2-aminoethyl)amine (TAEA), and polyethyleneimine (PEI) were used in Hal nanotube modification followed by protonation with HCl treatments. Various parameters affecting the H2 production rate such as the types of modification agents and/or catalyst types, NaBH4 amount, and the reaction temperature were investigated. The methanolysis of NaBH4 catalyzed by PEI modified and protonated Hal nanotube (H-PEI(750.000)-Hal nanotube) was found to follow first order reaction kinetic with respect to NaBH4 concentration. Interestingly, superior catalytic performances in comparison to the literature for the similar studies were obtained with 16.44 kJ/mol, 14.05 kJ/mol, and 196.46 J/mol·K of activation energy, enthalpy and entropy, respectively for NaBH4 methanolysis catalyzed by H-PEI(750.000)-Hal nanotubes. The hydrogen generation rate of 2218 mL/min·g that is comparable to the most of metal nanoparticle catalysts for H-PEI(750.000)-Hal nanotube catalyst was obtained.