Thermodynamic Calculations of Hydrogen Storage on Ultrasound-Assisted Synthesis of Boehmite–Graphene

Abstract

This research include an industrial step, which is the synthesis of the inorganic–organic nanocomposite using ultrasound as a rapid and one-step method, which is done by mixing boehmite with graphene oxide and then reacting them with the help of ultrasound with a capacity of 750 watts and a time not exceeding 10 min. The resulted product are then reacted with hydrazine hydrate to give boehmite–graphene nanocomposite. The materials are characterized using XRD, which prove the presence of boehmite and graphene without any structural change, indicating the physical decoration between them. Furthermore, the TEM measurement proves the presence of a graphene sheet with a thickness of one sheet carrying on its surface nanoboehmite particles that are no larger than 30 nm. Moreover, the composite is used to store hydrogen at four different temperatures (77–273 K). It is observed that the composite has the ability to store approximately 5.9 wt% at 77 K, which deceases with the increase in temperature until it reaches its lowest levels at 273 K with a storage value of 0.6 wt%, noting that the study is done at a pressure of 90 bar. Moreover, the thermodynamic properties of the storage process are studied, which prove that the enthalpy value is equal to 0.101788 (KJ/mol H₂), and the entropy value is 5.96878 (J/mol H₂. K), indicating the physical bonding of hydrogen.