One-step Electrochemical Preparation of Fe3O4 Particles/PVA Composite as High Performance Electrode Materials for Supercapacitors

Supercapacitors or ultracapacitors, have recently attracted considerable attention owing to their high energy density, high charge/discharge rates, and long cycle life performance [1]. Based on the types of energy storage, supercapacitors are also classified into electric double layer capacitors (EDLCs) and pseudocapacitors [2]. In particular, pseudocapacitors, typically including transition metal oxides (MnO2, RuO2, NiO, Co3O4, Fe3O4, etc) or hydroxides (Ni(OH)2,Co(OH)2, etc), as well as electrically conductive polymers (polyaniline, polypyrroles, and polythiophenes), use a reversible faradaic redox reaction at the electrode surface [3]. They generally show higher specific capacitance than EDLCs, made of carbonaceous materials fordouble-layer charge storage [4]. Among various metal oxides, Fe3O4 has attracted great attention due to its low cost and environmentally benign nature [5]. Fe3O4 has been reported to exhibit a high theoretical Li storage capacity, suggesting that it can offer potentially highpseudocapacitance through redox reaction. However, when directly used as a supercapacitor electrode, Fe3O4 alone exhibits a low rate capability owing to its inadequate conductivity, which limits the fast electron transport required by high rate applications [5]. To circumvent thishindrance, an effective method is to fabricate hybrid electrodes by integrating Fe3O4 with a carbon host, such as graphene (CNTs) [3], carbon nanofibers (CNFs) [4] or carbon nanoparticles(CNPs) [5], which can work as conductive channel for ion diffusion. In this work, PVA-coated Fe3O4 and pure Fe3O4 nanoparticles were synthesized via electrochemical deposition method. The as-prepared products characterized by XRD and SEMindicate that PVA coating does not affect the structure and morphology of Fe3O4. The electrochemical properties measured by cyclic voltammetry, galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy tests showed that PVA coated Fe3O4 nanoparticles present improved electrochemical performance (as seen in Fig. 1). A specific capacitance of 115.9 F g−1 is achieved at a scan rate of 5 mV s−1 in 1 M Na2SO3 aqueous solution for the Fe3O4/PVA composite in comparison to that of 88.6 F g−1 for pure Fe3O4. As a result, the composite exhibit enhanced capacitances in comparison with pure iron oxides.

Keywords:

Magnetite , PVA , Nanoparticles , Supercapacitors