LAUSR

We demonstrate a simple template‐free green method to prepare copper oxide (CuO) nanoporous material using copper acetate as a single precursor with Piper nigrum (Indian black pepper) dried fruit extract as a reducing medium under microwave irradiation. The surface properties and morphology of the obtained CuO material were assessed using powder X‐ray diffractometer, X‐ray photoelectron spectrometer, field‐emission scanning electron microscope with elemental mapping analysis, focused ion beam high‐resolution transmission electron microscope, and N2 adsorption‐isotherm techniques. The characterization results reveal that the prepared CuO is a single monoclinic crystalline phase, and nanoporous in morphology with a specific surface area of 81.23 m2 g−1 and containing pore sizes between 3–8 nm. Nanoporous CuO showed excellent electrochemical energy storage performance with the specific capacitance of 238 Fg−1 at 5 mVs−1 when compared with commercially available CuO (75 Fg−1). Also, nanoporous CuO showed efficient desalting performance in the capacitive deionization system. This eco‐friendly synthesis derived nanoporous CuO can be applied as high‐performance supercapacitor material for high‐energy storage devices and desalination processes.