Guoliang Yuan

Hierarchically structured Co₃O₄@Pt@MnO₂ nanowire arrays for high-performance supercapacitors.

Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors.

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors.

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

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.

Porous manganese oxide generated from lithiation/delithiation with improved electrochemical oxidation for supercapacitors

For manganese oxides with low manganese oxidation states, such as MnO or Mn3O4, the electrochemical oxidation during potential cycling is critical to achieve high supercapacitor performance. In this work, dense Mn3O4 thin films are prepared by pulsed laser deposition. An electrochemical lithiation/delithiation process is applied to the Mn3O4 thin film, which leads to a nanoporous structure of the film and greatly increases the porosity of the film. The nanoporous MnOx thin film electrode exhibits significantly improved supercapacitive performance compared to the as-prepared Mn3O4 thin film electrode. After 1000 cyclic voltammetric scans in 1 M Na2SO4 electrolyte between 0 and 1 V, only part of the surface of the as-prepared Mn3O4 thin film transforms into a MnO2 porous structure while the complete film of the nanoporous MnOx transforms into a MnO2 porous structure. It is believed that the nanoporous structure, which facilitates the electrolyte penetration, leads to the completion of electrochemical oxidation through the film during the potential cycling, resulting in promising supercapacitive performance of the film.