Speciation analysis applied to the electrodeposition of precursors of neodymium cuprate and related phases First application of speciation modelling to a solution not at equilibrium

Abstract

We report the first time that speciation analyses have been used to explain the distribution of products obtained by a system not at equilibrium: films of insoluble metal hydroxide have been obtained by cathodic electroprecipitation from aqueous solutions containing the nitrate salts of Nd³⁺ and Cu²⁺. Variation in film composition is achieved by manipulating deposition parameters, such as deposition voltage V_a and solution composition. The variations are caused by changes at the electrode/solution interface and differences in the solution- and solid-phase speciation characteristics of the two metals and their hydroxides.

The experimental compositions of the Nd–Cu hydroxides are correlated with thermodynamic formation constants β, and with calculations of concentrations obtained using speciation analyses. The accuracy of the predicted compositions is taken to verify the model of electroprecipitation.