Determination of Stability Constants of Copper(II)–Lactate Complexes in Cu 2 O Electrodeposition Baths by UV-vis Absorption Spectra Factor Analysis

Abstract

© The Author(s) 2019. The stability constants of highly concentrated copper(II)–lactate alkaline aqueous solutions for Cu2O electrodeposition were determined by factor analysis of UV-vis absorption spectra. The stability constant is 107.05 ± 0.05 for the chemical equilibrium expression CuL2 + OH– = Cu(H–1L)L– + H2O, while that for the chemical equilibrium expression Cu(H–1L)L– + OH– = Cu(H–1L)22– + H2O is 105.05 ± 0.05; here, L– is the lactate ion (CH3CH(OH)COO–) and H–1L2– is the deprotonated lactate ion (CH3CH(O–)COO–). By refining the potential–pH and pH speciation diagrams for the Cu–lactate–H2O system, it appears that the pH dependence of the preferential orientation of Cu2O is due to differences in the dissolved species.