Electrochemical Properties Of Nanostructured Cobalt Hexacyanoferrate

In recent years, transition metal hexacyanoferrates have raised renewed and growing interest due to their wide applications in the field of ion-exchange properties, electrochromism, charge storage, ionic conductivity through zeolitic type pores, reversible photoinduced magnetization, separation and transfer of Cs+, hydrogen storage, corrosion protection and photoinduced ferromagnetic systems. Among the various applications, electrodes modified with Prussian blue are especially attractive since their profound effect on research in the field of electrochemistry in the past decade, but electrode modified with the cobalt analogue of Prussian blue (PB) is exceptional, though it shows good electrocatalytic activity toward a variety of substrates including ascorbic acid, nitrite, hydrazine, p-chlorophenol, NADH, thiosulfate and hydroxylamine. Therefore, the CoHCF nano-materials were synthesized by the aqueous solution, microemulsion and micelle template method, respectively, and were characterized using various means. Then the electrochemical properties of all synthetic materials modified electrode were conducted by cyclic voltammetry.1. We systematically obtained the nanoparticles with the diameter of a few nanometers to dozens of CoHCF nanometers in aqueous solution, as confirmed by various techniques such as infrared spectroscopy (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The electrochemical behavior of CoHCF nanostructures was measured by cyclic voltammetry in supporting electrolyte of LiCl, NaCl, KC1, RbCl, CsCl and NH4Cl. It was found that samples (A-C) in the electrolyte solution of the six studies have one pair of redox peaks attributed to Fe(CN)62+/Fe(CN)63+redox process. The different diffusion order of cation supporting electode solution in samples may be due to the lattice pore size of different samples, as well as the effective radius of the hydrated ions of the cation. With the same cation (K+), the influence of different anions (sulfate, chloride, nitrate, acetate and carbonate) in electrolyte were studied and the results showed that electrochemical properties of electrolyte CoHCF modified electrode were similar. In addition, the sample A-C are relatively good electrochemical behavior, but the stability of the samples is not satisfactory. 2. Then we synthesized a series of cobalt-iron Prussian blue analogues (PBA) containing K+and Cs+in water-in-oil bis(2-ethylhexyl)sodium sulfosuccinate (AOT) reverse microemulsions. The size, morphology and composition of the as-prepared cobalt hexacyanoferrate (CoHCF) can be fine-tuned by conveniently varying the water-to-surfactant molar ratio (w) of the micro emulsion, as confirmed by various techniques such as infrared spectroscopy (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). These nanostructured PBA analogs were thereafter employed to chemically modify electrodes to thoroughly investigate and their electrochemical properties were fabricated and characterized in the presence of LiCl, NaCl, KCl, RbCl, CsCl and NH4Cl by cyclic voltammetry (CV). We found that samples of A-I in the electrolyte solution of the six studies also have one pair of redox peaks, different samples have different diffusion order in different cation supporting electode solution. Slow diffusion rate of Rb+, Cs+and NH4+in modified electrode in CoHCFs can be attributed to the strong bond formed between Rb+, Cs+, NH4+and CoHCF. Reverse microemulsion samples of A-H in our study of the electrolyte solution are relatively good electrochemical stability, however, repeated cycles in the presence of NH4+is blocked. In comparation, samples prepared by the aqueous solution method are blocked in the study of the electrolyte solution repeated. In addition, the other three samples A, B and C change color during the cyclic voltammetry.3. We also synthesized a series of cobalt-iron Prussian blue analogues (PBA) containing K+and Cs+in cetanyl trimethyl ammonium (CTAB) reverse micelle solution. The size, morphology and composition of the as-prepared cobalt hexacyanoferrate (CoHCF) can be changed by conveniently varying the temperature and content of ethanol, as confirmed by various techniques such as infrared spectroscopy (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). These nanostructured PBA analogs were thereafter employed to chemically modify electrodes to thoroughly investigate and their electrochemical properties were fabricated and characterized in the presence of LiCl, NaCl, KCl, RbCl, CsCl and NH4Cl by cyclic voltammetry (CV). It was noteworthy that samples of A-D in the six kinds of electrolyte solution have two pairs of redox peak, respectively vested in Fe(CN)62+/Fe(CN)63+redox process of M2CoⅡFeⅡ(CN)6and MCo1.5ⅡFeⅡ(CN). The diffusion order in6cation supporting electode solution were also different and better redox peaks could be got in NaCl and KCl electrolytes. All samples have similar redox peak in different anion of the same cation, except the carbonate anion.