Facile hydrothermal synthesis of Fe 3 O 4 nanoparticle and effect of crystallinity on performances for supercapacitor

Fe 3 O 4 nanoparticles were synthesized by a facile hydrothermal method using triethanolamine. Effects of reaction times (2–8[Formula: see text]h) on crystallinity and electrochemical performances of Fe 3 O 4 were investigated. Samples were analyzed by X-ray diffraction, infrared spectroscopy, N 2 adsorption–desorption, scanning electron microscope, galvanostatic charge/discharge, and cyclic voltammetry. Results showed that the crystallinity of Fe 3 O 4 was increased with hydrothermal time, and the sample prepared at 2[Formula: see text]h displayed amorphous structure with small grain size and large surface area of 165.0[Formula: see text]m 2 [Formula: see text]g[Formula: see text]. The sample exhibited typical pseudocapacitive behavior with capacitance of 383.2[Formula: see text]F[Formula: see text]g[Formula: see text] at 0.5 Ag[Formula: see text] in Na 2 SO 3 electrolyte. After 2000 cycles, the capacitance retention of Fe 3 O 4 at 2[Formula: see text]h was recorded as 83.6%, much higher than 26.3% for sample at 8[Formula: see text]h. It indicated that hydrothermal method was an effective approach to obtain amorphous Fe 3 O 4 , implying the potential application for preparing metal oxide electrode for supercapacitors.