Potential dependent growth of Cu(OH) ₂ nanostructures on Cu and their thermal conversion to mixed-valent copper oxides p-type photoelectrode

Herein, we report the anodic growth of nanostructured Cu(OH) ₂ thin films on the copper surface by potentiostatic and potentiodynamic methods. The phase formation, crystalline feature, morphology and the progressive growth of Cu(OH) ₂ thin films were controlled by the applied potential and concentrations of alkali utilized in anodization process. Electrochemical investigations suggest the rapid growth of Cu(OH) ₂ and passivation at higher anodization potentials. In contrast, the lower anodization potentials favours the progressive growth of Cu(OH) ₂ nanorod like features. The thermal treatment of Cu/Cu(OH) ₂ reveals the formation of crystalline mixed copper oxide film with predominantly Cu ₂ O phase at 673 K and 773 K. Photoelectrochemical investigations of these copper oxide thin films exhibit the p-type behavior with repeatable photovoltage (55 mV) and stable photocurrent responses (20–60 μA cm ⁻² ). The hydrogen evolution studies show better activity with nanostructured Cu(OH) ₂ and copper oxides than with aggregated thin films and bare substrate.