Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

Nitrogen-doped carbon quantum dots (N-CQDs) incorporated into highly conductive transition metal nitrides offer enhanced electrochemical performance, delivering a high energy density and outstanding electrochemical stability. The present study reports a high-performance supercapacitor electrode consisting of electrophoretic anchored zero-dimensional N-CQDs with reactively cosputtered titanium chromium nitride nanopyramid (Ti–Cr–N) thin films on flexible stainless-steel mesh (SSM) substrates. The nanopyramids of N-CQDs/Ti–Cr–N offer remarkable electrochemical performance through Li+ storage, ascribed to the abundant electroactive sites and enhanced synergism between the high specific surface area of N-CQDs and higher conductivity of Ti–Cr–N. Subsequently, the N-CQDs/Ti–Cr–N/SSM electrode in a 1 M Li2SO4 aqueous electrolyte exhibits an excellent gravimetric capacitance of 393.8 F·g–1 at a specific current density of 0.32 A·g–1. Further, the N-CQDs/Ti–Cr–N/SSM heterostructure outperforms other multicationic-based supercapacitors with a maximum energy density of 41.41 Wh·kg–1 and a superior power density of 7.0 kW·kg–1. Impressive electrochemical stability of ∼88.6% is retained by the heterostructure even after 5000 continuous charge–discharge cycles. Insights into charge storage mechanisms highlight the dominance of surface-limited capacitive and pseudocapacitive kinetics, with fewer contributions from diffusion-controlled faradaic processes. Furthermore, an exemplary mechanical stability of ∼99.98% over 1200 bending cycles demonstrates the N-CQDs/Ti–Cr–N/SSM heterojunction's excellent resilient structural strength, validating the present electrode potential for high-performance flexible supercapacitor application.