Ex situ synthesis and characterization of a polymer-carbon nanotube-based hybrid nanocatalyst with one of the highest catalytic activities and stabilities for the hydrolytic dehydrogenation of hydrazine-borane at room temperature conditions.

Abstract

In this study, a facile ex situ synthesis of a polyaniline-multiwalled carbon nanotube-based Pt nanocatalyst (Pt@PANI-MWCNT) with an average particle size of 3.18\u202f±\u202f0.12\u202fnm was performed successfully. The obtained Pt@PANI-MWCNT nanocatalysts were isolated from the solution medium by centrifugation and then were characterized by spectroscopy and microscopy methods. The characterization studies showed that the prepared Pt nanoparticles were formed on PANI-MWCNT surface, and H2 evolution was obtained by the dehydrogenation of hydrazine-borane in water as a model reaction under room temperature conditions, with the help of the synthesized nanocatalyst. It was observed that the Pt@PANI-MWCNT nanocatalyst had a very high catalytic activity for the hydrolytic dehydrogenation of hydrazine-borane and generated 2.95\u202fmol of H2 for 1\u202fmol of hydrazine-borane. The initial turn-over frequency (TOFinitial) value of the prepared nanocatalyst for the model reaction at room temperature conditions was found to be 168.5\u202fmin-1. The calculations for the kinetics of the hydrolytic dehydrogenation reaction showed that the hydrazine-borane catalytic reaction kinetics are first order, with respect to the catalyst concentration; several activation parameters, such as entropy (ΔS#, app\u202f=\u202f-72.11\u202f±\u202f3\u202fJ/mol K), enthalpy (ΔH#, app\u202f=\u202f43.5\u202f±\u202f2\u202fkJ/mol) and activation energy (Ea,app\u202f=\u202f45.5\u202f±\u202f2\u202fkJ/mol), of the catalytic reaction with the Pt@PANI-MWCNT nanocatalyst were calculated using these kinetic data.