Hydrogen absorption and desorption properties of Mg/MgH2 with nanometric dispersion of small amounts of Nb(V) ethoxide

OJEDA, XAVIER A.; CASTRO, FACUNDO J.; PIGHIN, SANTIAGO A.; TROIANI, HORACIO E.; MORENO, M. SERGIO; URRETAVIZCAYA, GUILLERMINA

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021 vol. 46 p. 4126 - 4136

0360-3199

A study to determine the optimal content of Nb(V) ethoxide required to efficiently catalyzethe H2 sorption kinetics in the Mg/MgH2 system is reported. The materials were synthesizedby hand mixing different amounts of additive (from 0.10 to 1 mol%) to pre-milledMgH2. Considering kinetics and capacity the best performance corresponds to a 0.25 mol% of Nb ethoxide concentration. With this material, a remarkable kinetic behavior withexcellent reversibility is obtained: 5.3 wt% and 5.1 wt% of hydrogen are absorbed anddesorbed respectively at 300 C in 3 min. At 250 C the material absorbs 5.2 wt% of hydrogenand releases 3.7 wt% in 10 min. Thermal desorption starts at 247 C and peaks at 268 C.The H2 sorption properties of all the materials remain unchanged after 10 cycles of absorption and desorption at 300 C, and the best material reversibly takes in and releases5.3 wt% of H2 during a 10 min combined cycle. The kinetic improvement of the hydrogendesorption and absorption properties is attributed to an enhancement of the kinetic processesthat occur on the surface of the material, due to the excellent spreading of the liquidadditive at nanometric level, as revealed by SEM/EDS and TEM/EELS.