Tuning Band Gaps and Photoelectrochemical Properties of Electrodeposited CuO Films by Annealing in Different Atmospheres

Abstract

The band gaps and photoelectrochemical properties of electrodeposited CuO films were tuned through annealing as-electrodeposited films in different atmospheres at various temperatures. The direct band gaps of the CuO film descended from 1.80 eV for as-electrodeposited film to 1.76 eV for the film annealed in O2 at 300 °C or 1.64 eV for the film annealed in N2 at 300 °C. The stable photocurrent density for CuO electrode annealed in O2 at 300 °C measured at −0.4 V vs Ag/AgCl under a simulated sun light reached to 0.44 mA cm−2 while the value was only 0.29 mA cm−2 for the electrode annealed in N2 in a solution with 10 mM potassium ferricyanide, 10 mM potassium ferrocyanide, and 0.5 M Na2SO4. The mechanism for photoresponse enhancement was studied and could be due to faster charge transfer and higher doping density for the CuO film annealed at 300 °C in O2.