Hydrothermal Synthesis, Characterization, and Electrochemical Properties of MnO2-Titanate Nanotubes (MnO2-TNTs)

MnO2-TNTs were synthesized via a hydrothermal method at temperatures of 60°C, 80°C, 100°C, 125°C, and 150°C. The effect of synthesis temperature on the morphology and electrochemical properties of the MnO2-TNT (labeled as MT) electrode materials was investigated. The phase formation, morphology, and layered structure were characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, respectively. MnO2 was included in the titanate nanotube structure having a combination phase of birnessite-type MnO2 and H2Ti2O5·H2O. Fourier transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy were performed to study the surface functional groups and the surface chemical oxidation state, respectively. Gas adsorption analysis was conducted in order to study the specific surface area and the porosity. The capacitance was controlled by the surface capacitive and diffusion-controlled contributions. The sample synthesized at 80°C exhibited the highest specific capacitance of 155.06 F/g at a current density of 0.5 A/g, with cycling performance of 93.10% after 2000 cycles. It was found that the synthesis temperature affected the morphology, phase composition, specific surface area, and porosity of the prepared materials, in turn affecting in the electrochemical performance of the MnO2-TNT electrode materials.Graphic abstract