Owing to their rapid charge-discharge, extremely low maintenance, high power density, versatile operating temperatures and durability, supercapacitors are widely used as electrochemical storage devices in advanced energy applications. In recent years, transition metal oxides, especially nano-textured CuO structures have gained much attention as a low cost and widely available electrode material for supercapacitors. However, the existing techniques for developing nano-textured CuO involve a large number of processing steps through multiple chemical treatments. Further, the performance of nano-structured copper oxides needs to be significantly enhanced to make them commercially viable. Here, we report a facile, two step approach comprising surface activation through thermomechanical treatment and electrochemical dealloying of a Cu-Zn alloy for developing a 3-dimensional hierarchical CuO microstructure. Surface activation prior to dealloying significantly accelerates the reaction kinetics and the hierarchical microstructure comprising micro and nano-scale porosity develops in a few seconds only. Electrochemical studies revealed that the surface activated electrode possesses a high areal capacitance of 1.68 F cm−2at a current density of 5 mA cm−2, exhibits an excellent cycling stability with 90% retention for 5000 cycles at a current density of 15 mA cm−2and a high energy density of 0.33 mW h cm−2. The reported specific capacitance is one of the highest values obtained for copper-based alloys which is attributed to its unique 3D hierarchical microstructure that favours rapid ion intercalation and the increased surface area for energy storage. Electrochemical analysis indicates intercalation pseudo-capacitance as the primary charge storage mechanism. The current approach is highly generic and can be applied for a wide number of material systems which signifies its huge potential in the emerging field of advanced supercapacitors, and portable and flexible electronics. © The Royal Society of Chemistry 2021.