Electronic Structure, Morphological Aspects, Optical and Electrochemical Properties of RuO2 Nanocrystals

• Published in: Electronic materials letters 2019, 15(5), , pp.645-653
• Main Authors: Silva, R. C., Gouveia, A. F., Sczancoski, J. C., Santos, R. S., Sá, J. L. S., Longo, E., Cavalcante, L. S.
• Format: Article
• Language: English
• Subjects: Band structure of solids; Characterization and Evaluation of Materials; Characterization and Modeling; Chemistry and Materials Science; Condensed Matter Physics; Conduction bands; Crystal structure; Crystals; Density functional theory; Electrochemical analysis; Electronic structure; Emission analysis; Energy gap; Field emission microscopy; First principles; Heat treatment; Hydrothermal crystal growth; Materials Science; Mathematical analysis; Morphology; Nanocrystals; Nanotechnology; Nanotechnology and Microengineering; Optical and Electronic Materials; Optical properties; Orbitals; Original Article - Theory; Quantum mechanics; Ruthenium oxide; Scanning electron microscopy; Sodium sulfate; Spectrum analysis; Surfactants; Synthesis; Valence band; X-ray diffraction; 전자/정보통신공학
• ISSN: 1738-8090; 2093-6788
• DOI: 10.1007/s13391-019-00160-9

This letter reports the synthesis of RuO 2 nanocrystals by the anionic surfactant-assisted hydrothermal method at 90 °C for 24 h followed by heat treatment at 500 °C for 1 h. These crystals were structurally characterized by means of X-ray diffraction (XRD) and Rietveld refinement analysis. Field emission scanning electron microscopy (FE-SEM) was employed to observe the morphological features these crystals. The optical behavior was investigated by ultraviolet–visible (UV–Vis) spectroscopy. First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level were employed to obtain the electronic band structure and density of states. For electrochemical behavior, the supercapacitor properties of RuO 2 crystals were investigated by cyclic voltammetry. XRD patterns and Rietveld refinement data indicate that RuO 2 crystals have a rutile-type tetragonal structure. FE-SEM images showed the presence of sphere-like RuO 2 crystals with an average crystal sized at around 19.13 nm. The experimental band gap energy ( E gap[exp] ) was estimated at 2.60 eV by using UV–Vis spectroscopy, while the theoretical calculations indicate an E gap[theo] at 1.92 eV. These calculations revealed a band structure predominantly composed of O 2 p orbitals (valence band) and Ru 4 d orbitals (conduction band). The specific capacitance measured for RuO 2 film was 193 F g −1 at 5 mV s −1 in an electrode with 0.5 mg of electroactive material in 1 M Na 2 SO 4 solution. Graphic Abstract For the first time, we report on the electronic structure, optical and electrochemical behavior of RuO 2 nanocrystals/film synthesized by the anionic surfactant-assisted hydrothermal synthesis (90 °C for 24 h) followed by heat treatment (500 °C for 1 h).