Hybrid MOFs-graphene composites: Correlation between thermal transport and kinetics of hydrogen adsorption

摘要

The development of effective methods for hydrogen storage is of paramount importance in using hydrogen as a transportation fuel for on-board applications. The rate at which the hydrogen is adsorbed/desorbed on porous materials in compressed pellets is directly related to the thermal conductivity of the adsorbent. This work aims to increase the hydrogen adsorption rate in MIL-101(Cr) and MIL-100(Fe) compressed pellets by using reduced graphene oxide (rGO) as an additive, in order to get an increased thermal conductivity and thus a more efficient heat transport through the pellets. To achieve this goal, a complex study was undertaken using different techniques, namely photothermal radiometry (PTR) for thermal conductivity investigation, a volumetric home-made device for kinetic measurements and other techniques (XRD, SEM, TEM, BET, TG-DTA) for structural and morphological characterization of the samples. It has been found that the thermal conductivity of the pellets increases with the graphene addition. A significant enhancement in thermal conductivity (by factors of 4 compared to pellets without additives) is obtained and reaches a maximum of 0.58 W/mK for MIL-100(Fe) pellet (p = 0.65 g/cm(3)). The hydrogen adsorption equilibrium time in neat samples is reached in about 180 s. The presence of 10 wt% rGO in both MIL-100 and MIL-101 pellets improves the hydrogen adsorption kinetics and favors the equilibrium in shorter times, respectively 20 and 40 s, than in neat samples. The experimental data are in very good agreement with the Linear Driving Force Model (LDF) for gas adsorption kinetics. (C) 2019 Elsevier Ltd. All rights reserved.