Kinetics and growth mechanism of electrodeposited palladium nanocrystallites

Palladium particles have been electrodeposited on AISI 316 stainless steel substrate from aqueous solution of palladium chloride. The kinetics of the electrodeposition process and growth mechanism of such three-dimensionally grown palladium particles have been studied. It has been found that the kinetics of electrodeposition of palladium follows parabolic law, which indicates involvement of instantaneous nucleation and subsequent three-dimensional growth. It was also observed that the nucleation density of palladium electrodeposits was a function of the nature of the electrode substrate. The structure, morphology, texture, chemical state, and composition of the electrodeposited palladium particles have been characterized using SEM, TEM, XPS, EDS, EBSD, and OIM. The growth of the palladium nuclei situated at the grain interior was found to be more than that at the grain boundaries on steel substrate. The micron-size electrodeposited palladium particles consisted of a number of nanocrytallites. The surface morphology of the electrodeposited palladium particles was uneven due to the preferential growth of such nanocrystallites in certain crystallographic directions. The results of the present investigation indicate that the growth of the palladium electrodeposits was limited by the diffusivity of bulky palladium tetrachloro square-planar complex from bulk solution to near the electrode surface.