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

Abstract

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 H2 when ZrO2@Nb2CTx is used as the catalyst, which is far smaller than the case of ZrO2 (94.8 kJ/mol H2) and Nb2CTx MXene (125.6 kJ/mol H2). 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 °C and within 900 s even at 240 °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.