<p>Electrochemically anodized Cupric Oxide (CuO) nanostructures possess excellent potential for multifunctional applications like ethanol sensing, hydrophobic coatings, and photoelectrochemical water splitting. CuO nanowires and nanoflakes were prepared at different anodization times (0.5, 1, 2, and 3&#xa0;h) and characterized for their structural and functional properties in this work. X-ray diffractometer validated the monoclinic CuO phase, and Field emission scanning electron microscopy (FESEM) indicated a morphology transition from nanowires to nanoflakes with increasing anodization time. X-ray photoelectron spectroscopy (XPS) analysis identified Cu²⁺ ions, and Photoluminescence spectroscopy identified defect states. Among the samples, 1&#xa0;h anodized CuO nanoflakes had good ethanol sensing performance with a sensitivity of 273 µA mM⁻¹&#xa0;cm⁻² and a broad detection range (0.5–7&#xa0;mM) due to their high surface area. Wettability tests indicated that 2&#xa0;h anodized samples were strongly hydrophobic with a contact angle of 140.81°. Photocurrent measurements in Xenon light showed that 1&#xa0;h anodized nanoflakes provided the maximum photocurrent density of 0.937&#xa0;mA&#xa0;cm⁻², showing their efficiency for photoelectrochemical water splitting. This study highlights that anodization time is critical for tuning CuO nanostructures for desired functionalities. The cost-effective and facile fabrication process further favours their suitability for sensing, environmental, and energy-related applications.</p> Graphical Abstract <p></p>