Deposition of Nickel on Electrodeposited Cu2O Films at Potentials More Positive than the Nernst Potential of Ni2+/Ni0

Abstract

Deposition of nickel on electrodeposited Cu2O films was investigated at potentials more positive than the estimated Nernst equilibrium potential of Ni2+/Ni0 for the purpose of developing a monolayer deposition method that will act as a protective and catalytic overlayer on the oxide films. Cu2O films were subjected to 0.08 mM nickel acetate solutions for 60 s at potentials more positive than the estimated Nernst equilibrium potential of Ni2+/Ni0. The quantities of Ni recovered from the Cu2O films were determined by atomic absorption spectrometry. The oxidation state of Ni deposited on the Cu2O was determined to be +3 via X-ray photoelectron spectroscopy. The absence of evidence of reduction of Ni2+ to Ni0 suggests that the nature of the nickel deposition is adsorption, and it is not characterized as underpotential deposition. Photoelectrochemical measurements showed that deposited Ni protected Cu2O films from the photodecomposition to Cu0 by interfering with H+ binding to the O2− surface sites, and indicated the possibility of catalytic activity of deposited nickel for H+ reduction. The catalytic activity of deposited nickel was explained by the shift of the Cu2O Fermi level by 50 mV in negative direction upon nickel deposition.