Effective synthesis of Mg2CoH5 by reactive mechanical milling and its hydrogen sorption behavior after cycling

M.G. VERÓN; A.M. CONDÓ; F.C. GENNARI

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2013 vol. 38 p. 973 - 981

0360-3199

Mg2CoH5 was synthesized by reactive mechanical milling (RMM) under hydrogen atmosphere (0.5 MPa) from 2MgH2-Co and 3MgH2-Co mixtures, with a yield >80%. The microstructure, structure and thermal behavior of the phases formed during the processing were investigated by transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. Kinetic properties of the reaction with hydrogen of the 2MgH2-Co and 3MgH2-Co mixtures after RMM were evaluated using modified Sieverts-type equipment. The 3MgH2-Co mixture showed better properties for storage applications, with its highest rate of hydrogen absorption and desorption at 300 °C, its storage capacity of about 3.7 wt% in less than 100 seconds, and good stability after cycling. Although the starting material presents Mg2CoH5 as majority phase, the cycling leads to disproportion between Mg and Co. We obtained a mixture of Mg2CoH5, Mg6Co2H11 and MgH2 hydrides, as well as other phases such as Co and / or Mg, depending on experimental conditions.