Copper Crystallization from Aqueous Solution: Initiation and Evolution of the Polynuclear Clusters

Abstract

The initial steps of copper electrocrystallization process from aqueous solutions have been studied at DFT level of theory. It has been shown that Cu(H2O) unit is the final product of Cu2+-ions electroreduction. From this particle clusters Cun·aq are formed and grow. Aggregation of copper atoms to the Cun·aq clusters consists of two steps. The first step includes condensation of Cu(H2O) units to hydrated clusters Cun(H2O)n (n = 2–6). At the second step bonding of Cu(H2O) particles is accompanied by dehydration of clusters yielding Cun(H2O)m structures (n > m). Cluster Cu7·aq has been singled out as key structure based on calculated values of energies and Cu–Cu bond distances of Cun·aq clusters. This cluster is of D5h symmetry which is typical for copper microcrystals formed from aqueous solutions in electrocrystallization processes on foreign surface. This key particle could be considered as a critical nucleus. Number of copper atoms therein matches average dimension of critical nucleus.