Confinement of Mg Nanoparticles by Bituminous Coal and Associated Synergistic Hydrogen Storage Effect

Abstract

Using the coking property of bituminous coal, a nanostructured Mg-C composite hydrogen storage material was developed by ball milling and heat treatment. The heat treatment conditions and hydrogen storage behavior of the composite material were investigated. Results show that when the material is heat-treated at 550 °C under Ar atmosphere, the carbon could react with Mg to irreversibly form Mg2C3. When 1.0 MPa H2 was introduced to the heat treatment at 550 °C, the magnesium does not form Mg2C3. The resulting composite material is shown to have a globular bonded structure by scanning electron microscopy, and the Mg nanoparticles are confined by the bituminous coal. Fourier transform infrared spectroscopy and gas chromatography analysis show that the carbon could combine with hydrogen only in the presence of MgH2 under current experimental conditions. The carbon-bonded hydrogen would be released in the form of small molecule hydrocarbons such as CH4, C2H4 and C2H6. Dynamic tests show that coal carbon and magnesium absorb/desorb hydrogen at similar temperatures, which proves that there is a synergistic hydrogen storage effect between magnesium and coal carbon.