Use of two-component methanol/glycerol solvent system as an alternative to single-component solvent systems in hydrogen production with sodium borohydride and design of phosphorus, nitrogen co-doped chitosan/kaolin composite with heterojunction as metal-free catalyst

Abstract

This study encompasses two key objectives: firstly, utilizing a two-component solvent system as an alternative to commonly used single-component solvent systems for the efficient production of hydrogen (H?) from sodium borohydride (NaBH?); and secondly, employing a phosphorus (P) and nitrogen (N)-doped chitosan/kaolin composite as a metal-free catalyst for the dehydrogenation of NaBH? within these solvent systems. For this purpose, methanol and glycerol alcohol solvents are used simultaneously in the NaBH4 solvolysis reaction for the first time in the literature. For this purpose, in the first step, optimization of methanol and glycerol mixtures for efficient H2 production is performed. The NaBH4 solvolysis reaction in methanol solvent without any catalyst takes about 15 min. However, in a 1:1 (5mL/5 mL) methanol/glycerol solution of NaBH4, this dehydrogenation reaction takes about 2.75 min. The hydrogen production rate (HGR) value obtained using 0.25 g NaBH4 with optimum methanol/glycerol at 30 °C is 36271 mLmin?1gcat?1. The activation energy for this reaction is 26.19 kJmol-1. The properties of the obtained catalyst were investigated by Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) analyses. These analyses are used to elucidate the mechanism of catalytic performance. © 2024 Hydrogen Energy Publications LLC