Synergistic effect of sub-5 nm Fe nanoparticles supported on nanoporous carbon for catalyzing hydrogen storage properties of Mg(BH4)2

Abstract

This study investigates synergistic effects of sub-5 nm Fe nanoparticles (FeNPs) supported on mesoporous carbon (MC) for catalyzing hydrogen storage properties of Mg(BH4)2 (MBH). The study compares two methods for dispersing Fe NPs in MC: (i) ultrasonication nanoconfinement (un) and (ii) post-nanoconfinement (pn) via stirring. Based on the results, it is found that the ultrasonication nanoconfinement method can effectively disperse the FeNPs with 5 nm in MC support (FeNP-un-MC), later which can efficiently confine MBH (FeNP-un-MC@MBH system). The hydrogen (H2) desorption properties of the FeNP-un-MC@MBH system were found to be better than that of post-confinement-mediated FeNP-pn-MC@MBH system. For instance, H2 started to desorb from the FeNP-un-MC@MBH system at only 66 °C (Tonset) and reached its peak at ∼153 °C, compared to 270 °C (Tonset) and its peak ∼350 °C for pure MBH, respectively. The ultrasonication-mediated nanoconfined FeNP-un-MC@MBH system released a total of 7.01 wt% H2 within 90 min at 350 °C. The study shows that the activation energy (Ea) of FeNP-un-MC@MBH is 19.57 kJ/mol, achieved due to the improved dehydrogenation kinetics of MBH. These improvements are due to the synergistic effects of nano-compartmentalization and highly dispersed Fe NP catalyst sites in the MC support. The research emphasizes the promising application of ultrasonication-mediated nanoconfined Fe NPs in mesoporous carbon which can be used as an effective catalyst for enhancing the hydrogen storage properties of metal-based hydrides (MBH).