<i>In Situ</i> Generated Cu/Nb Catalytic Interfaces for Enhancing MgH₂ Hydrogen Storage.

Abstract

To address the challenges of high hydrogen release temperatures, sluggish kinetics, and inadequate cycling performance of magnesium hydride (MgH₂), we developed the niobium-based bimetallic compound catalyst CuNb₂O₆ with excellent catalytic performance. It was found that the MgH₂/CuNb₂O₆ composite material achieved 4.28 wt % hydrogen uptake within 10 min at 100 °C, and even at a lower temperature of 50 °C, it has 2 wt % hydrogen absorption capacity within 60 min, showing excellent hydrogen absorption performance. For hydrogen desorption, the MgH₂/CuNb₂O₆ composite material demonstrated exceptional midtemperature hydrogen release kinetics, with 4.65 wt % hydrogen released within 20 min at 225 °C. The apparent activation energy for hydrogen release of MgH₂/CuNb₂O₆ was determined to be 50.95 kJ/mol, which was approximately 66.4% less than that of ball-milled magnesium hydride. Cyclic testing further confirmed the stability of the MgH₂/CuNb₂O₆ composite, with its hydrogen storage capacity stabilizing at 5.21 wt % after 50 cycles. Catalytic mechanism studies revealed that the MgH₂/CuNb₂O₆ composite undergoes <i>in situ</i> reconstruction of multiple-phase catalytically active species, which effectively improved the hydrogen storage performance of MgH₂. This work innovatively constructed a representative Mg₂Cu@NbO₂ heterojunction, and the results showed that hydrogen molecules were significantly activated at the interface, demonstrating the synergistic catalytic effect between the Cu and Nb species. This study provides a possible approach for designing high-efficiency catalysts for magnesium-based hydrogen storage materials.