Effect of annealing on the electrodeposited Cu2O films for photoelectrochemical hydrogen generation

Cu2O films were electrodeposited on stainless steel substrates followed by Ar annealing for photoelectrochemical hydrogen generation. Plating variables including time and pH for the plating bath were explored to obtain desirable film qualities. X-ray diffraction (XRD) patterns indicated that the as-deposited Cu2O films exhibited preferred orientations in (200) and (111) planes from the plating bath of pH 9 and pH 11, respectively. Images from scanning electron microscope (SEM) revealed pyramid-like grains in 1 µm size for the Cu2O films from pH 9 plating bath and large plate-like grains in 3–8 µm size from pH 11 plating bath. Identical results from SEM and XRD were obtained from the Cu2O films at longer plating time. After annealing at 350 °C for 30 and 60 min, the Cu2O phase was nicely maintained but SEM images demonstrated coarser grains. Photoelectrochemical activity for H2 generation was obtained on the Cu2O films before and after annealing by recording relevant photoelectrochemical currents at − 0.3 V in 0.5 M aqueous Na2SO4 solution. For the Cu2O films from both baths, substantial increments in photoelectrochemical current were observed for the annealed samples as opposed to as-deposited ones. The largest photoelectrochemical current was obtained at 0.143 mA/cm2 from the Cu2O film of pH 9 plating bath with 60 min annealing, which exhibited a 560% increase over the as-deposited sample. We attributed the enhanced photoelectrochemical current to the improved crystallinity and reduced defects for the annealed Cu2O films.