Hierarchical heterostructures of Ag nanoparticles decorated MnO2 nanowires as promising electrodes for supercapacitors

Abstract

Coating the redox-active transition-metal oxides (e.g., MnO₂) with a conductive metal layer is one efficient approach to improve the electrical conductivity of the oxide-based electrodes, which could largely boost the energy density and power density of supercapacitors. Here, we report a facile yet efficient method to uniformly decorate conductive silver (Ag) nanoparticles (∼10 nm) on MnO₂ nanowires (width of ∼10–20 nm), which leads to a remarkable improvement of the electrical conductivity and the supercapacitive performance of MnO₂-based electrodes. For instance, at a low scan rate of 10 mV s⁻¹, the as-designed Ag/MnO₂ hybrid electrode delivers a specific capacitance of 293 F g⁻¹, which is twofold higher than that of the bare MnO₂ electrode (∼130 F g⁻¹). In addition, the highly conductive Ag nanoparticle layer can also improve the rate capability of the Ag/MnO₂ nanowire electrode, delivering a high specific energy density and power density of 17.8 W h kg⁻¹ and 5000 W kg⁻¹, respectively, at a current density of 10 A g⁻¹.