Anchoring Mo single atoms on N-CNTs synchronizes hydrogenation/dehydrogenation property of Mg/MgH2

Abstract

MgH2 has attracted substantial consideration mainly due to its sufficient content and high gravimetric density etc. However, its high thermodynamic stability and poor dynamics hinder its practical application. N-doping carbon nanotubes (N-CNTs) supported Mo single atoms (MoSA-N-CNTs) was constructed to facilitate the hydrogenation/dehydrogenation properties of the Mg/MgH2 system. According to the synergistic effect of N-CNTs nanoconfinement and MoSA catalysts, Mg@MoSA-N-CNTs can absorb 7.37 wt.% H2 during the milling within 15 h and the corresponding activation energy for hydrogenation can be reduced to 21.2 kJ·mol−1. MgH2 @MoSA-N-CNTs releases 7.23 wt.% H2 at 325 ℃ for 5 min, nearly 3 times pristine MgH2. Meanwhile, its initial dehydriding temperature decreases from 265.7°C to 204.6°C, and its apparent activation energy for dehydrogenation also greatly decreases from 108.6 kJ/mol to 68.4 kJ/mol. The above values are much lower than the pure MgH2. The synergistic effect mechanism of N-CNTs and MoSA on hydrogenation/dehydrogenation properties of Mg/MgH2 is proposed systemically. It is revealed that the MoSA and the N-CNTs not only accelerate H2 dissociation and diffusion but also effectively prevent the Mg/MgH2 nanoparticles agglomeration. The above results highlight the great promise of Mg/MgH2 @MoSA-N-CNTs composite for high-performance Mg-based hydrogen storage materials.