Hierarchical pore engineering in waste-derived carbons for supercapacitors: bridging the performance gap from three-electrode evaluation to practical two-electrode devices

) often fail to deliver superior device performance. Particular attention is given to the roles of pore accessibility, ion transport limitations, electrolyte-pore matching, and the trade-off between porosity and electrical conductivity. The effectiveness of hierarchical pore architectures and heteroatom doping is critically reassessed, distinguishing genuine performance enhancements from overstated effects. Finally, design principles for developing device-relevant carbon electrodes are proposed, emphasising accessible porosity, optimised pore connectivity, and realistic testing conditions. Practical challenges related to scalability, reproducibility, and environmental impact are also discussed. This review provides a comprehensive framework for transitioning from inflated laboratory metrics to reliable, high-performance supercapacitor devices based on waste-derived carbons.