One-dimensional structured γ-MnOOH nanorods were prepared by a simple and easy hydrothermal method, and the growth mechanism of γ-MnOOH nanorods in the hydrothermal reaction system was proposed and discussed. The electrochemical test results show that the γ-MnOOH nanorods exhibit high charge storage capacity as well as excellent cycle life.

Abstract

MnOOH has received much attention from researchers as a supercapacitor electrode material. In this article, one-dimensional γ-MnOOH nanorods were prepared by the hydrothermal method using the redox reaction between MnO₄ ⁻ and Mn²⁺, and the effects of temperatures on the crystalline phases and electrochemical properties of the samples were investigated. The materials were characterized using XRD, FT-IR, SEM, TEM, Raman and XPS; electrochemical properties were tested using CV, GCD and EIS. The results show that the reaction temperature plays an important role in the generation of γ-MnOOH. The samples were pure phases of γ-MnOOH (M-140) at the reaction temperature of 140 °C, showing interlaced nanorod morphology, and when the reaction temperature was increased to 180 °C, a mixed phase of MnOOH and Mn₃O₄ appeared. In contrast, the electrochemical performance of γ-MnOOH nanorods (M-140) was superior to the other samples, reaching a specific capacitance of 221 F/g at a current density of 0.2 A/g. The capacitance retention was 93.8 % after charging and discharging the M-140 2000 times at a current density of 6 A/g. Supercapacitors assembled with γ-MnOOHand activated carbon (AC) have excellent energy storage performance, and a high energy density of 40.6 Wh/kg is obtained at a power density of 196.7 W/kg.