The thermodynamics of hydrogen absorption/desorption by Pd–Co alloys

Abstract

The thermodynamics of Pd–Co–H(D) systems have been investigated using H 2(D 2) pressure–composition isotherms and reaction calorimetry. The enthalpies for hydrogen solution and hydride formation decrease in magnitude with increase of X Co and, because of this, the hydrogen pressures at a given value of H/ M increase with X Co. This behavior is consistent with the decrease of the unit cell size with increase of X Co for these random solid solution fcc Pd–Co alloys. Repeated hydride formation and decomposition at ambient temperature without intermediate annealing treatments, causes the plateau pressures to converge thereby decreasing the extent of hysteresis.