Properties and characteristics of hydriding alloys are strongly dependent on surface compositions and morphologies. For instance, oxides such as La203 on AB5 alloys and ZrO2 on AB2, AB, and body-centered-cubic (BCC) alloys act as the barriers for the conversion of molecular and ionic hydrogen to atomic hydrogen at the surface, thus reducing the kinetics in both the gas-solid and electrochemical reactions.
Alloy surfaces chemically treated by an aqueous F-ion containing solution have been developed to solve such problems. F-treated surfaces exhibit significantly improved characteristics in regard to the hydrogen uptakes and the protection against impurities and electrolyte solution. In addition, highly conductive metallic Ni layers can be formed on the surface of the alloy particles by the fluorination.
The authors report the properties and characteristics of fluorinated hydriding alloys, mainly of a typical AB2 Laves phase material which represents the difficult activation characteristics and poor long-term durability during electrochemical charge/discharge cycles.