High photoelectrochemical activity of CuO nanoflakes grown on Cu foil

CuO is a narrow band gap p-type semiconducting material having a wide range of applications. However, it is quite challenging to obtain phase pure CuO nanostructures grown directly on Cu substrate as most of the synthesis techniques like thermal oxidation results in the formation of additional Cu₂O phase. In this work, we report the growth of CuO nanoflakes without the formation of Cu₂O by a facile two-step synthesis process which consist of electrochemical anodization of Cu foil followed by low-temperature hydrothermal treatment at 100 °C. The phase purity of the sample is confirmed through XRD, XPS, and HRTEM. Further, photocurrent response of the sample is evaluated, and a rapid thermal treatment was used to improve the photo-response without altering the phase and morphology of the CuO nanoflakes. Such a process at 400 °C for 10 s resulted in a high photocurrent density of −4.6 mAcm⁻² (at 0.05 V vs. RHE under AM 1.5G conditions). Electrochemical impedance spectroscopy and Mott Schottky analysis shows the direct role of rapid thermal treatment in increasing the charge carrier density of the sample.