Effect of Zn precursors on hydrogen storage in MWCNTs-ZnO nanocomposites

Abstract

This research included studying and preparing the complex [Zn(DMB)Cl]2 from the reaction 1 M ratio of 2,6-dimethoxybenzoic acid ligand (DMB) with one molar ratio of aqueous zinc chloride in the presence of triethylamine. This complex was diagnosed by several techniques including FT-IR, 1H NMR, elemental analysis and molar conductivity. The MWCNTS-ZnO composite was prepared by reacting the complex [Zn(DMB)Cl]2 with carbon nanotubes using an ultrasound device. The novelty of this work is mainly based on the use of zinc acetate and [Zn(DMB)Cl]2 in the preparation of MWCNTS-ZnO(acetate) and MWCNTS-ZnO(complex) nanocomposites, respectively, in order to determine the importance of raw materials and their effects on the ability to store hydrogen. Thereafter, hydrogen storage was measured as a prospective study of the MWCNTS-ZnO composites. The study proves that the maximum H2 storage was 4.3 wt% H2 using MWCNTS-ZnO(complex) at a pressure of 85 bar and a temperature of 77 K. Therefore, the kinetic and thermodynamic calculations were made for this composite to complete the study. The enthalpy value was 0.8771 KJ/(mol H2), the entropy value was 4.7029 (J/mol H2.K), and the separation factor RF was 0.168148. However, the adsorption process was compatible with the pseudo-second order reaction with a value of R2 = 0.9341. Moreover, the measurement shows that the nanocomposite has the ability to reach the highest storage value in only 30 s at a pressure of 85 bar.