Reversible hydrogen storage in a 3NaBH4/YF3 composite

A 3NaBH4/YF3 hydrogen storage composite was prepared through ball milling and its hydrogen sorption properties were investigated. It is shown that NaBH4 does not react with YF3 during ball milling. The dehydrogenation of the composite starts at 423 °C, which is about 100 °C lower than the dehydrogenation temperature of pure NaBH4, with a mass loss of 4.12 wt%. Pressure–Composition–Temperature tests reveal that the composite has reversible hydrogen sorption performance in the temperature range from 350 °C to 413 °C and under quite low hydrogenation plateau pressures (<1 MPa). Its maximum hydrogen storage capacity can reach up to 3.52 wt%. The dehydrogenated composite can absorb 3.2 wt% of hydrogen within 5 min at 400 °C. Based on the Pressure–Composition–Temperature analyses, the hydrogenation enthalpy of the composite is determined to be −46.05 kJ/mol H2, while the dehydrogenation enthalpy is 176.76 kJ/mol H2. The mechanism of reversible hydrogen sorption in the composite involves the decomposition and regeneration of NaBH4 through the reaction with YF3. Therefore, the addition of the YF3 to NaBH4 as a reagent forms a reversible hydrogen storage composite.