Electroless copper plating and colloidal Pd nanoparticle impregnation were shown to greatly improve the tolerance of a multi-component AB(5)-type alloy towards air impurities. Treated alloys demonstrated improved hydrogen absorption and desorption rates and tolerance towards air impurities when exposed to 0.5 MPa initial hydrogen pressure at room temperature. In addition, the readily-activated response was retained after the treated alloys had been exposed to air for 24 h. The removal of the surface oxide species and the spillover mechanism may have accounted for the enhanced hydrogenation kinetics of the alloys after treatment. Slight degradation of the hydrogen absorption rates with increasing air exposure was observed and was attributed to limitations in the protection provided by the Pd-Cu layer, resulting in a slow growth of an oxide layer on the alloy surface, which acted as a barrier for the transport of hydrogen atoms, towards the core of the AB(5)-type alloy material after hydrogen spillover. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.