Impact of the crystal phase and 3d-valence conversion on the capacitive performance of one-dimensional MoO2, MoO3, and Magnéli-phase Mo4O11 nanorod-based pseudocapacitors. (May 2018)

• Record Type: Journal Article
• Authors: Pham, Duy Van; Patil, Ranjit A.; Yang, Chun-Chuen; Yeh, Wan-Chi; Liou, Yung; Ma, Yuan-Ron
• Is Part Of: Nano energy. Volume 47(2018)
• Page Start: 105
• Page End: 114
• Publication Date: 2018-05
• Subjects: MoO3 -- MoO2 -- Magnéli-phase Mo4O11 -- Nanorods -- Pseudocapacitors; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2018.02.044
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: One-dimensional nanorods of MoO2, MoO3 and Magnéli-phase Mo4 O11 were effortlessly prepared using the hot-filament metal oxide vapor deposition technique. Long straight and uniform nanorods were gr own on indium-tin-oxide (ITO) thin film coated glass substrates. Thermal reduction and oxidation were then used to process 1D Magnéli-phase Mo4 O11 nanorods synthesized at 1000, 1050, 1100, 1150, and 1200 °C into 1D MoO2 and MoO3 nanorods, respectively. The nanorods prepared at higher synthesis temperatures were thinner and longer. The 1D Magnéli-phase Mo4 O11 nanorods consisted of various combinations of two orthorhombic ( α ) and monoclinic ( η ) crystals and varying mixtures of Mo 4+, Mo 5+ and Mo 6+ (3d5/2 and 3d3/2 ) cations. The 1D MoO2 nanorods were comprised of only monoclinic ( η ) crystals and various complex mixtures of Mo 4+, Mo 5+ and Mo 6+ (3d5/2 and 3d3/2 ) cations. The 1D MoO3 nanorods contained only orthorhombic ( α ) crystals and varying mixtures of Mo 5+ and Mo 6+ (3d5/2 and 3d3/2 ) cations. Comparison of the crystal phases and 3d valences showed that the MoO2 nanorods supplied more oxidation states than the Mo4 O11 or MoO3 nanorods. According to the results of cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance (EI) spectroscopy, the capacitive performance of the MoO2 nanorod-based pseudocapacitor was much better than that of the MoO3 and Magnéli-phase Mo4 O11 nanorod-based pseudocapacitors. The crystal phases and 3d-valence conversions clearly had a tremendous impact on the capacitive behaviors of the MoO2, MoO3, and Magnéli-phase Mo4 O11 nanorod-based pseudocapacitors. Graphical abstract: MoOx nanorod-based pseudocapacitive device consisting of two MoOx -nanorods/ITO/glass substrates (as two electrodes) and an electrolyte of 1 M LiClO4 in a propylene carbonate solvent. fx1 Highlights: Synthesis of rare and stable one-dimensional (1D) Magnéli-phase M4 O11 nanorods. Unique compositional transformation from Mo4 O11 nanorods to 1D MoO2 and MoO3 nanorods without any morphological change. Impact of the crystal phase and 3d-valance on the capacitive performances of 1D MoO x nanorod-based pseudocapacitors. Excellent performances of the MoO2 nanorods-based pseudocapacitors using impedance spectroscopy.