Hydrogen desorption behavior of vanadium borohydride synthesized by modified mechano-chemical process

Abstract

The vanadium borohydride was synthesized by a mechano-chemical milling method and its hydrogen desorption performance was evaluated. The effect of cooling during milling process on the hydrogen desorption behavior was also investigated. Nearly pure hydrogen was detected using a mass spectrometer coupled with a simultaneous thermal analyzer. Thermogravimetric method was conducted to determine the initial desorption temperature and the amount of hydrogen released from the hydride. The initial desorption temperature of vanadium borohydride was found below 100 °C, with an enthalpy change of 25.4 kJ/mol V(BH 4) 3. The amount of hydrogen released from the hydride prepared by milling but without cooling was 0.25 wt%, while that prepared with controlled cooling at 20 °C was 1 wt%. A beneficial effect of enhanced hydrogen release to 2.2 wt% from borohydride was found if multi-walled carbon nanotubes (MWCNTs) were added as an additive.