Excellent catalysis of Mn(3)O(4) nanoparticles on the hydrogen storage properties of MgH(2): an experimental and theoretical study

Recently, transition metal oxides have been evidenced to be superior catalysts for improving the hydrogen desorption/absorption performance of MgH(2). In this paper, Mn(3)O(4) nanoparticles with a uniform size of around 10 nm were synthesized by a facile chemical method and then introduced to modify the hydrogen storage properties of MgH(2). With the addition of 10 wt% Mn(3)O(4) nanoparticles, the MgH(2)–Mn(3)O(4) composite started to release hydrogen at 200 °C and approximately 6.8 wt% H(2) could be released within 8 min at 300 °C. For absorption, the completely dehydrogenated sample took up 5.0 wt% H(2) within 10 min under 3 MPa hydrogen even at 100 °C. Compared with pristine MgH(2), the activation energy value of absorption for the MgH(2) + 10 wt% Mn(3)O(4) composite decreased from 72.5 ± 2.7 to 34.4 ± 0.9 kJ mol(−1). The catalytic mechanism of Mn(3)O(4) was also explored and discussed with solid evidence from X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) studies. Density functional theory calculations revealed that the Mg–H bonds were elongated and weakened with the doping of Mn(3)O(4). In addition, a cycling test showed that the hydrogen storage capacity and reaction kinetics of MgH(2)–Mn(3)O(4) could be favourably preserved in 20 cycles, indicative of promising applications as a solid-state hydrogen storage material in a future hydrogen society.