Tunable polycationic organohalloysite electrocatalyst: Synthesis and characterisation

Abstract

Methylamine and 1,4-butanediol diglycidyl ether were used as monomers, in a sequential manner, to build from the surface of an aminosilane-grafted halloysite a quaternary ammonium polyelectrocatalyst. The as obtained material was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms (BET method), elemental analysis (EA), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). XRD analysis showed that the pristine halloysite was in a partial dehydrated state with a d001 value of 0.74 nm. Not only was the success of the grafting process ascertained but also the tubular nature of the used halloysite sample as seen on the SEM micrographs. The significant increase in the d value of the modified clay (H-polyQ22) suggested interlayer grafting. FTIR results showed that grafting was through OH groups, certainly interlayer, lumen and edge aluminol groups as well as defect site silanol groups. The electron transfer enhancing properties of the prepared polyelectrolyte were investigated by electrochemical impedance spectroscopy (EIS). The charge transfer resistance dropped significantly when H-polyQ22 was used as electrode modifier. The electrocatalytic behaviour of the H-polyQ22 modified electrode was further investigated using [Fe (CN)6]3− as anionic target. The halloysite polymer nanocomposite proved to be a good candidate for electrocatalysis.