Room‐Temperature Electrochemical Assembly of Copper/Cuprous Oxide Nanocomposites

Abstract

Nanocomposite films of copper metal and cuprous oxide, Cu.O, are electrodeposited at room temperature from alkaline solutions of copper(Il) lactate. The electrode potential oscillates spontaneously if the films are deposited galvanostatically. The oscillation period is a function of pH, varying from 69 seconds at pH 8.7 to 11 seconds at pH 9.7. No oscillations are observed if the pH is below 8.5 or above 10. The phase composition of films deposited at 0.5 mNcm z is a function of pH. The composition varies from nearly pure copper (93 mole%) at pH 8, to 42 mole% copper at pH 9.5, to pure cuprous oxide when the pH exceeds 10. The observation of quasi-periodic potential oscillations suggests that the nanocomposites are layered. The calculated faradaic thickness of cuprous oxide is 5-8 nm, and the thickness of the copper layer is 1-11 nm. The thickness of each of the layers increases as the pH is lowered.

Electrochemical self-assembly of Cu/Cu2O nanowires

“…2(a)] compared to 0.1-2.2 mA/cm 2 in Ref. 9. It is interesting to note that the upper current densities in the oscillating range were almost the same for planar substrate and nanoporous media, independent of the pore size.…”

“…Oscillation phenomena were reported for a wide range of deposition current density and for a pH range of 8.5-10. 9 Two different mechanisms have been proposed to account for the oscillating phenomena. 9 First, the formation and breakdown of rectifying Cu 2 O/solution interface have been invoked as probable sources of potential oscillations.…”

“…It was recently demonstrated that layered structures of copper/cuprous oxide can be prepared by electrodeposition. 9,10 The fabrication of multilayers by electrodeposition is usually made by pulsing the applied potential or current during the growth. However, it was shown that, when appropriate solution and pH is used, the electrode potential may spontaneously oscillate when a fixed current is applied.…”

Interfacial stability of electrodeposition of cuprous oxide films

“…6 As seen in Fig. 7, changing values of U, and by extension changing current, does not change the frequency very significantly.…”

“…Switzer and co-workers [1][2][3][4][5][6] have deposited such films using electrochemical means. Typically, the bath is made by dissolving 90 g of CuSO 4 •5H 2 O in 150 ml of 85% lactic acid and neutralized with 450 ml of 5M NaOH.…”