One-dimensional MoO₂, MoO₃, and Magnéli-phase Mo₄O₁₁ nanorod-based supercapacitors: Impacts of crystal phases and 3d-valences

Ranjit A. Patil^1*, Yuan-Ron Ma¹

¹Department of Physics, National Dong Hwa University, Hualien, Taiwan

* Presenter:Ranjit A. Patil, email:ranajitpatil@outlook.com

One-dimensional nanorods of Magnéli-phase Mo₄O₁₁ were prepared using hot-filament metal oxide vapor deposition technique at 1000, 1050, 1100, 1150, and 1200 °C. The long straight and uniform nanorods grew on indium-tin-oxide (ITO) thin films coated glass substrates. In addition, the 1D Magnéli-phase Mo₄O₁₁ nanorods were used to synthesize the 1D MoO₂ and MoO₃ nanorods by the thermal reduction and oxidation processes, respectively. The 1D Magnéli-phase Mo₄O₁₁ nanorods consist of various combinations of two orthorhombic (α) and monoclinic (η) crystals and varying mixtures of Mo⁴+, Mo⁵+, and Mo⁶+ (3d5/2 and 3d3/2) cations. The 1D MoO₂ nanorods have only monoclinic (η) crystals and various complex mixtures of Mo⁴+, Mo⁵+, and Mo⁶+ (3d5/2 and 3d3/2) cations. The 1D MoO₃ nanorods contain only orthorhombic (α) crystals and varying mixtures of Mo⁵+ and Mo⁶+ (3d5/2 and 3d3/2) cations. In comparison, the MoO₂ nanorods supply more oxidation states than the Mo₄O₁₁ and MoO₃ nanorods. According to the results of the cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance (EI) spectroscopy, the capacitive performances of the MoO₂ nanorod-based supercapacitors are much better than the MoO₃ and Magnéli-phase Mo₄O₁₁ nanorod-based supercapacitors. Therefore, the crystal phases and 3d-valence conversions tremendously affect the supercapacitive behaviors of the MoO₂, MoO₃, and Magnéli-phase Mo₄O₁₁ nanorod-based supercapacitors.

Keywords: Molybdenum oxide nanorod, Magnéli-phase, crystal structures effect, 3d valance, supercapacitor