Chemical hydrogen storage and release properties using redox reaction over the Cu-added Fe/Ce/Zr mixed oxide medium

Abstract

The chemical hydrogen storage (hydrogen reduction) and release (water-splitting oxidation) properties of the Cu-added Fe/Ce/Zr mixed oxide medium were investigated. The media with Cu content ranging from 0 to 5 wt% were prepared by a co-precipitation method using urea as a precipitant. The hydrogen reduction and the water-splitting oxidation on the medium were tested by temperature programmed reduction/oxidation (TPR/TPO) and repeated isothermal redox cycles at 550 °C for reduction and 350 °C for oxidation. The initial reduction rates and oxidation rates of the media increased with increasing the amount of the Cu additive. In addition, the reactivity of the medium for water-splitting oxidation was enhanced as the CeO 2/ZrO 2 ratio increased. Especially, the Fe-based mixed oxide medium with Cu/CeO 2/ZrO 2 contents of 3/30/10 wt% (Cu(3%)-Fe-CeO 2/ZrO 2(3/1)) showed superior performance in chemical hydrogen storage and release. As the results of isothermal redox cycles using the medium, the total amount of hydrogen evolved in water-splitting oxidation was maintained at ca. 8.5 mmol g −1-medium (ca. 1.8 wt% hydrogen storage amounts on the basis of the total medium) over 15 repeated redox cycles.