Why colloidal solution of PALLADIUM can absorb large volume of hydrogen gas ?

Absorption is a bulk effect whereas adsorption is a surface effect. Colloids, having large surface areas for a given volume, are excellent at adsorption.
 Palladium is the best in absorbing hydrogen gas. The rate of absorption is  affected by the physical condition of the substance. Palladium has great degree of subdivision so it has more efficient occlusive capacity.