Multi-scale structural engineering of hierarchical MnO₂/Ti₃C₂T_x on hollow carbon nanofibers for enhanced supercapacitive performance

Although manganese dioxide (MnO₂) has a high theoretical specific capacitance (1370 F g⁻¹), its low electrical conductivity severely restricts its electrochemical performance. In this study, the limitation is overcome by multi-scale structural engineering. Hollow carbon nanofibers (HCNFs) are synthesized by electrospinning polyacrylonitrile (PAN), polystyrene (PS), and N, N-dimethylformamide (DMF) and annealed. In this study, a MnO₂@Ti₃C2T_x/HCNFs hierarchical heterojunction electrode was synthesized through a step-by-step approach. First, MnO₂ nanosheets were grown in situ on HCNFs, and then they were coupled with a solution of two-dimensional Ti₃C₂T_x nanosheets, ultimately forming a ternary composite structure. This ternary composite electrode exhibits excellent conductivity and reaction kinetics, thereby achieving significantly enhanced electrochemical performance. At a current density of 1 A g⁻¹, the specific capacitance is as high as 997 F g⁻¹, and at a high rate of 7 A g⁻¹, the capacity retention rate is as high as 98.2%. What is more remarkable is that the asymmetric supercapacitor assembled with it achieves a high energy density of 70.34 Wh kg⁻¹ (with a power density of 4000.16 W kg⁻¹), demonstrating great application potential. © 2026 Elsevier B.V.