Preparation and stability study of potassium ferrate (VI) coated with phthalocyanine for alkaline super-iron battery

Abstract

The potassium ferrate (VI) coated with phthalocyanine (H 2 Pc) was successfully prepared via a facile coprecipitation process. Scanning electron microscopy and Fourier transform infrared spectrum revealed that K 2 FeO 4 had been coated with H 2 Pc particles. When evaluated as cathodic material for alkaline super-ion battery, the effects of H 2 Pc coating on the electrochemical stability of K 2 FeO 4 electrodes upon prolonged immersion time were investigated by galvanostatic discharge test, open-circuit potential measurements, and electrochemical impedance spectroscopy. The results show that the decomposition of K 2 FeO 4 in electrolyte is obviously suppressed by H 2 Pc coating with a short immersion time, which could enhance the discharge capacity of electrodes. Furthermore, the open-circuit potential of the H 2 Pccoated K 2 FeO 4 electrode is higher than that of the bare K 2 FeO 4 electrode, which indicates the improvement of anticorrosive ability. In addition, the ability of charge transfer between electrode and electrolyte is enhanced by H 2 Pc coating due to the inhibition on formation of Fe (III) layer, but the improved performance will decline upon prolonged immersion time.

The History and the Current Revival of the Oxo Chemistry of Iron in its Highest Oxidation States: FeVI – FeVIII

“…Stabilization of ferrate(VI) electrodes was also achieved by coatings with phthalocyanines, and porphyrines . K 2 [FeO 4 ] was dispersed in an organic solvent previously loaded with the dye by ultrasonical vibration, and the solvent was removed in a vacuum.…”

The adoption and mechanism of KIO4 for redox-equilibrated stabilization of FeO4 2− as an equalizer in water

“…More work is needed to study the effect of the coexisting ions and the type of buffers used on the stabilization of ferrate compounds in solid state or aqueous solution [16]. Walz et al [17] investigated the stabilization of BaFeO 4 materials by nanoporous silica coatings and showed that these coatings * Baohui Wang wangbh@nepu.edu.cn stabilize BaFeO 4 when stored in air and, to a lesser degree, electrolyte solutions.…”

“…Zhang et al [18] investigated that the Y 2 O 3 -ZrO 2 composite coatings were used to greatly improve the stability and charge transfer properties of K 2 FeO 4 cathodes in an alkaline electrolyte relative to the uncoated cathode. More research [16,19,20] combined the use of organic compounds and inorganic materials to coat K 2 FeO 4 to improve the stabilization of ferrate in recent years. In this study, it was found that FeO 4 2− in water was stabilized by the addition of KIO 4 as coexisting oxidized ions and buffers.…”

Structural modification of isomorphous SO 4 2− -doped K 2 FeO 4 for remediating the stability and enhancing the discharge of super-iron battery

“…The protective coatings enabled the separation of the electrolyte and K 2 FeO 4 for a reduction of destroying the K 2 FeO 4 with a relative lift of the charge transfer ability. However, the mixed compounds still indicated a comparative conduct with a low stability [23,24,27,29–31]. For the improvement, poly(3-hexylthiophene)-coated K 2 FeO 4 was prepared to enhance the capacity and stability of K 2 FeO 4 .…”

“…For the stability of the ferrate solution, more works have been presented to study the effect of the coexisting ions and buffers on the stabilization in the aqueous solution [24]. The decomposition rate of the ferrate solutions depends strongly on the initial ferrate concentration, coexisting ions, pH and temperature of the solution [5,14,25].…”