Surface modification strategies for nanoparticles based on chitosan and titanium dioxide: Catalytic properties and mechanism for sodium borohydride dehydrogenation in methanol

Abstract

Chitosan, which has important functional groups such as amino and hydroxyl, is effectively preferred for application areas. Due to its low cost and high chemical stability, titanium dioxide (TiO2) attracts great attention especially in the fields of environment and energy. Here, the green fabrication of two-stage catalyst particles by facile surface modification strategies was performed. In the first step, a hybrid material was fabricated by dispersing TiO2 nanoparticles on the chitosan polymer matrix by the calcination method. The catalytic performance can be further improved by changing the surface properties and additional defect sites by doping with green non-metallic heteroatoms. In the second stage, protonation with hydrochloric acid, nitrogen doping with ammonia and nitrogen and oxygen doping with nitric acid were applied to improve the surface properties of the hybrid material obtained by the hydrothermal method. These hybrid particles were performed for dehydrogenation (H-2) in methanol of sodium borohydride. The most effective results were obtained with chitosan-TiO2 treated with nitric acid with an HGR value of 10118 mol g(cat)(-1) min(-1). The activation energy (Ea) value was calculated as 39.25 kJmol(-1). XRD, XPS, SEM, EDS, TEM and FTIR analyses were used for the characterization of hybrid catalysts. Besides, the mechanism of H-2 release in methanol using N, O-doped chitosan-TiO2 has been proposed.