Electrochemical activation-induced electronic structure modulation of ZnMn-Ni/graphene scaffolds for high-performance asymmetric supercapacitor

Abstract

In this work, Zn–Mn incorporated three-dimensional porous Ni/graphene composite electrodes (NGZn x Mn y , x/y = 1/1, 1/3, and 1/5) were systematically developed to elucidate the synergistic effects of Zn/ Mn species incorporation and electrochemical activation on local coordination environments and supercapacitive performance. Comprehensive characterization, including grazing-incidence X-ray diffraction (GIXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), reveals that activation induces significant valence redistribution and coordination evolution of Mn and Zn species, while the Ni/graphene framework remains structurally stable. This activation-driven electronic modulation enhances redox activity and interfacial charge transfer, particularly in the electrochemical activated sample with lower Mn content (NGZn 1 Mn 1 _E). Among the compositions studied, NGZn 1 Mn 1 _E exhibits the best performance, delivering a specific capacitance of 564 mF cm -2 with dominant pseudocapacitive contribution. The electrode demonstrates excellent rate capability and stable cycling behavior. An asymmetric aqueous supercapacitor (NGZn 1 Mn 1 _E//electrochemically activated flake graphite (EAFG)) operates within a 1.0 V window, achieving high areal capacitance and nearly 100% retention after 2000 cycles. Three devices connected in series successfully power LEDs at 3.0 V, confirming practical applicability. This work highlights electrochemical activation as an effective strategy for tuning coordination environments and optimizing multiple transition metal compound-based supercapacitors.