Photoelectrochemistry of Pure and Core/Sheath Nanowire Arrays of Cu[sub 2]S Directly Grown on Copper Electrodes

Photoelectrochemistry (PEC) of straight and isolated Cu₂S nanowires arrayed on a copper foil is studied. A cathodic photocurrent is observed, which increases with the increasing negative bias of the film electrode, conforming to the p-type semiconducting nature of Cu₂S. PEC studies on the core/sheath nanowires of Cu₂S (Cu₂S nanowires coaled with other nanoparticles such as CdS, polypyrrole, and Au) have revealed distinctly different characteristics. Cu₂S/CdS nanowires exhibit a slightly higher photocurrent response due to the charge transfer between the p-type Cu₂S core and n-type CdS sheath, whereas the photocurrent response obtained for Cu₂S/PPy nanowires is generally an order of magnitude smaller than that for pure Cu₂S nanowires under the same bias voltage. For Cu₂S/Au nanowires, however. Au nanoparticles can readily accept the photogenerated electrons from the conduction band of Cu₂S; this redirects the electron transfer pathway and results in the anodic photocurrent response. On the basis of these findings, different photocurrent generation mechanisms are proposed.