Active catalytic species generated in situ in zirconia incorporated hydrogen storage material magnesium hydride
D. Pukazhselvan, K. S. Sandhya, Devaraj Ramasamy, A.L. Shaula, Igor Bdikin, Duncan P. Fagg
Abstract
This study explores how zirconia additive interacts with MgH2 to improve its hydrogen storage performance. Initially it is confirmed that the zirconia added MgH2 powder releases hydrogen at a temperature of about 50 °C below that of the additive free MgH2. Subsequent tests by X ray diffraction (XRD) and infrared (IR) spectroscopy techniques reveal that the ZrO2 mixed MgH2 powder contains ZrHx (2 <x> 1.5) and MgO secondary phases. This observation is supported by the negative Gibbs free energy values obtained for the formation of ZrH2/MgO from ZrO2/MgH2 powder samples. An X ray photoelectron spectroscopy (XPS) study reveals that apart from Zr4+cations, Zr2+ and zero valent Zr exist in the powder. Atomic force microscopy (AFM) study reveals that the average grain size is 20 nm and the elemental line scan profiles further proves the existence of oxygen deficient Zr bearing phase(s). This study strengthens the belief that functional metal oxide additives in fact chemically interact with MgH2 to make active in-situ catalysts in the MgH2 system.