TiN catalyst for the reversible hydrogen storage performance of sodium alanate system

Abstract

A TiN catalyst was used to synthesize NaAlH₄via the mechanical milling of a NaH–Al mixture under 2 MPa hydrogen pressure. The dehydrogenation thermodynamics and kinetics of the as-synthesized TiN-doped NaAlH₄ were systematically investigated. Thermodynamic analyses show that the dehydrogenation rate clearly increases with a corresponding increase of dehydrogenation temperature. The apparent activation energy (E_a) for the first step is estimated to be 45.15 kJ mol⁻¹ by using the Arrhenius equation. The dehydrogenation and hydrogenation behaviors of TiN-doped NaAlH₄ are investigated under different hydrogen pressures using high-pressure differential scanning calorimetry (HP-DSC). Interestingly, the onset dehydrogenation temperature of TiN-doped NaAlH₄ is lowered to about 100 °C with a peak of 138.05 °C. X-Ray diffraction and XPS results reveal that the TiN nanopowders possess excellent catalytic stability.