A catalytic mechanism investigation of TiF3 on hydriding/dehydriding properties of Mg85Cu5Ni10 alloy

Abstract

In this research, Mg₈₅Cu₅Ni₁₀–x wt% TiF₃ (x = 0, 2, 4, 6, 8) alloys were synthetized via ball milling and the catalytic mechanism of TiF₃ on hydrogenation and dehydrogenation of Mg₈₅Cu₅Ni₁₀ was studied. The microstructure, hydriding/dehydriding kinetics and thermodynamics of the alloys were discussed in detail. The TiF₃ catalyzed alloys have faster hydriding/dehydriding kinetics and lower thermodynamic stability. After hydrogen absorption and desorption, TiF₃ decomposes into TiH₂ and MgF₂. TiF₃, TiH₂ and MgF₂ promote to forming crystal defects, dislocations, grain boundaries and nanocrystals which are advantageous to speeding up the rate of hydrogen absorption and desorption. The dehydrogenation activation energy E_a(de) and dehydrogenation enthalpy ΔH(de) are reduced to 81.462 from 116.767 kJ mol⁻¹ and 72.456 from 93.372 kJ mol⁻¹ respectively by 6 wt% TiF₃. An appropriate amount of TiF₃ can improve the hydriding/dehydriding kinetics and thermodynamics of Mg₈₅Cu₅Ni₁₀.