ZrO2@Nb2CTx composite as the efficient catalyst for Mg/MgH2 based reversible hydrogen storage material

While Mg/MgH2 system has a high hydrogen storage capacity, its sluggish hydrogen desorption rate has hindered practical applications. Herein, we report that the hydrogen absorption and desorption kinetics of Mg/MgH2 system can be significantly improved by using the synergetic effect between Nb2CTx MXene and ZrO2. The catalyst of Nb2CTx MXene loading with ZrO2 (ZrO2@Nb2CTx) is successfully synthesized, and the dehydrogenation activation energy of MgH2 becomes as low as 60.0 kJ/mol H-2 when ZrO2@Nb2CTx is used as the catalyst, which is far smaller than the case of ZrO2 (94.8 kJ/mol H-2) and Nb2CTx MXene (125.6 kJ/mol H-2). With the addition of ZrO2@Nb2CTx catalyst, MgH2 can release about 6.24 wt.% and 5.69 wt.% of hydrogen within 150 s at 300 degrees C and within 900 s even at 240 degrees C, respectively. Moreover, it realizes hydrogen absorption at room temperature, which can uptake 2.98 wt.% of hydrogen within 1800 s. The catalytic mechanism analysis demonstrates that the in-situ formed nanocomposites can weaken the Mg-H bonding and provide more hydrogen diffusion channels, enabling the dissociation and recombination of hydrogen under milder reaction conditions. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.