Room Temperature Hydrogen Storage in a Metal-Organic Framework-Derived Carbon-Based Hybrid Material

Abstract

In addressing the global demand for clean and renewable energy, hydrogen stands as a promising candidate for many fuel cell applications. In order to use it at an industrial scale, researchers must develop practical and efficient storage systems that fulfill the targets stated by the US Department of Energy. Among the storage systems that have emerged in the past decades, porous materials have attracted researchers interest due to their light weight, fast sorption kinetics, total reversibility and mass production capacity. They however store only a small amount of hydrogen at room temperature. In order to overcome that drawback related to the storage capacity, researchers have been synthesizing hybrid materials as they could show enhanced characteristics which would lead to an enhanced storage.Hybridizing can be achieved by including metal nanoparticles into the porous materials so that spillover can occur: dissociation of the hydrogen molecule on the metal followed by migration and further diffusion on the porous material. This phenomenon, well established in the catalyst field, remains however highly controversial in hydrogen storage as some authors reported huge enhancement while others noticed bare or no enhancement at all. Such discrepancies in the literature suggest a high dependency of spillover occurrence with the hybrid material characteristics and hence will persist until the true conditions, which favor enhancement, as well as the mechanism, get revealed. Numerous reports about different materials under different conditions could then lead to a better understanding of that phenomenon. Many porous materials have been studied to show an enhancement resulting from the metal doping. When seeking for an enhancement, it might be more interesting to choose the material which stores an appreciable amount of hydrogen, if not the highest, but quite surprisingly, no research has been done on MDCs, highly porous carbon materials with exceptional hierarchical porosity and high SSA, which store the highest amount of hydrogen in their structure at room temperature and 100 bar.Moreover, the electronic state of the doping metal has not been studied either in spite of the relative importance of the metal form or the oxide form in hydrogenation processes. Previous works did not outline which state of the metal was expected to play a role in the enhancement process, or actually did. This work then aims to give the first evidence of the feasibility of MDC hybridization by platinum particles, which will be wanted to be in a metal form. A special care will be given to the synthesis method as MDCs synthesis requires harsh thermal treatment that might be disadvantageous to the Pt particles. The obtained results showing an increased storage capacity of the hybrid material compared to the pristine one, together with fast kinetics and total reversibility, will be presented in this work. Before that, the different hydrogen storage systems will be briefly reviewed in a first step, the state of the arts of storage enhancement by metal doping will be presented in a second step and a deeper explanation of the purpose of this work as well as the experimental methods explanation will be given afterwards.