Mg–B–Reduced Graphene Oxide Nanocomposites with Negligible Incubation Time for Hydrogen Release

Abstract

Depleting fossil fuels and greenhouse emissions render hydrogen (H) a promising alternative for powering automobiles. MgH2 with its promising H‐weight capacity ≈7.6 wt% can be used for this purpose. However, it exhibits long incubation times with no significant H‐release during the early stages. The present Mg–B–reduced graphene oxide (rGO) nanocomposites can reduce such incubation time drastically. Herein, Mg, rGO, and elemental B as a light weight catalyst at various proportions (viz. B/C (from rGO) weight ratios of 0, 0.09, 0.22, 0.36, and 0.90) are used to synthesize Mg–B–rGO nanocomposites by ball milling. They are eventually subjected to hydrogen uptake at ≈320 °C and PH2 ≈ 15 bar followed by H‐release in vacuum. The nanocomposite with B/C ≈ 0.22 exhibits remarkably negligible incubation time (≈43 s) vis‐à‐vis ≈11 min by B/C = 0. This B/C ≈ 0.22 nanocomposite experiences charge (electron) transfer from Mg and B to C, located external to MgH2 unit cell. This causes Mg←H→B “Tug‐of‐war” within MgH2 unit cell, containing B in its interstitials (due to ball milling) and shrinking it. This leads to “structural catalysis” of H‐release, understood by X‐ray photoelectron, valence band, Raman spectra, and novel electron density maps. These novel materials can alleviate the need for activation cycles for their application.