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A stable film of zinc hexacyanoferrate is deposited on a GC (glassy carbon) substrate following a specific electrochemical protocol. The electrode maintains its characteristic even after dry and wet processes. SEM characterization confirms the cubic morphology of the materials and the IR suggests the presence of the FeII-C-N-ZnII structural unit. The electrochemical characterization indicates a very good stability of the film, thus opening application in ion exchange system. The focus is on monovalent, divalent, and trivalent ions. These results, the zinc low toxicity, and cost make zinc hexacyanoferrate films a promising candidate for many electrochemical applications.

The paper reports a detailed study about the influence of the electrolyte composition in nickel-hexacyanoferrate (NiHCF) electrochemical behavior. Shapes and positions of the CV waves are strongly related to the cation of the supporting electrolyte, which undergoes intercalation/de-intercalation during the redox process. The electrochemical behavior of NiHCF has been characterized in different electrolyte solutions containing either pure monovalent or trivalent metal nitrates. Nickel-hexacyanoferrate permits the reversible insertion of a wide variety of monovalent, divalent and trivalent ions in aqueous solution; the characteristic potential Ep of the cathodic process depends upon the nature of the intercalated cation. Electrochemical measurements demonstrate the unprecedented fast kinetics of trivalent ion insertion associated with this material. The reported findings represent the first systematic step toward understanding the principles of multivalent charge screening and provide a novel cation intercalation mechanism in NiHCF, assisted by both water molecules and ferrocyanide vacancies. The synergistic mechanism can reduce the electrostatic repulsion and provide a preferential path for the rapid cation intercalation.

The treatment of tannery wastewaters is a complex task due to the complexity of the waste: a mixture of several pollutants, both anionic and cationic as well as organic macromolecules which are very hard to treat for disposal all together. Geopolymers are a class of inorganic binders obtained by alkali activation of aluminosilicate powders at room temperature. Such activation process leads to a cement like matrix that drastically decreases mobility of several components via entrapment. This process taking place in the matrix can be hypothesized to be the in-situ formation of zeolite structures. In this work we use a metakaolin based geopolymer to tackle the problem directly in an actual industrial environment. To obtain a geopolymer, the metakaolin was mixed with 10 wt% of wastewater added with sodium hydroxide and sodium silicate as activating solutions. This process allowed a rapid consolidation at room temperature, the average compressive strength was between 14 and 43 MPa. Leaching tests performed at different aging times confirm a high immobilization efficiency close to 100%. In particular, only the 0.008 and 2.31% of Chromium and Chlorides respectively are released in the leaching test after 7 months of aging.

The paper presents an experimental study on mortar samples taken from historic and monumental buildings damaged or collapsed following the seismic events in Central Italy (2016-2017). Sixty-one samples were analysed via a set of diagnostic investigations to characterize the mortar and correlate it with the performance of the masonry. The techniques used were: X-ray diffraction, scanning electron microscopy and microanalysis, differential scanning calorimetry, calcimetry, Fourier-transform infrared spectroscopy, soluble salt analysis by conductimetry and dosage of anionic species by ion chromatography, particle-size analysis, direct shear. Microstructural characterization of the mortars revealed differences in mortar composition depending on their provenance. In particular the samples from Norcia contained large quantities of calcite while in the mortars from Pretare, dolomite was identified. In the case of Amatrice, only a few samples showed crystalline phases and compounds ascribable to binders. These results were largely confirmed by the other chemical and physical analysis performed, and mechanical tests also demonstrated low cohesion. The tests showed that in almost all the samples, poor quality mortars were used, and, in some cases, underachieving binder mortar.

Cobalt hexacyanoferrate (CoHCF) was electrodeposited into an organically modified silica (ormosil) film with a nanoarray of parallel, cylindrical channels, which were obtained using 20-nm poly(styrene sulfonate), PSS, beads as a templating agent. The PSS was bound to the electrode surface with 3-aminopropyltriethoxysilane, APTES. Methoxytrimethylsilane was the ormosil precursor. Electrochemically assisted processing at a positive potential where the hydrogen ion catalyst was generated was used to deposit the ormosil film. Subsequently, the PSS and APTES were removed to provide the pores. The CoHCF was deposited in the 20-nm channels by cyclic voltammetry of a freshly prepared K3Fe(CN)6, CoCl2 mixture with 1.0 mol dm−3 KCl as the supporting electrolyte. Limiting the number of electrodeposition cycles to 10–20 resulted in CoHCF nanorods in the pores, whereas with 50 cycles bulk-form CoHCF spilled over the outer ormosil surface. Electrocatalytic oxidation of cysteine was successfully performed on these nanorod arrays, which showed greater catalytic activity than bulk-form CoHCF.

The paper describes the time-dependent evolution of the electrochemical deposition of cobalt hexacyanoferrate (CoHCFe) on graphite foil electrode modified with electrochemically formed sol–gel film doped with β-cyclodextrin to impart porosity. With short-time electrodeposition, cyclic voltammetry (CV) shows a single redox couple typical of nano-sized clusters of CoHCFe, while at longer deposition times the CV’s shape evolves to the classical form of a bulk compound in which there are present two redox couples. The electrode modified with β-cyclodextrin (CD) included in the sol–gel film has an active surface that corresponds to pores created by CD stacks normal to the surface. Hence, the electrochemical formation of CoHCFe starts in these conductive pores; only at long deposition times do the clusters overlap to form moieties with the voltammetric characteristics of bulk CoHCFe.

The preparation of cobalt hexacyanoferrate nanoparticles–poly(methyl methacrylate) (CoHCF–PMMA) composites are described together with their characterization and thermochromic properties. CoHCF nanoparticles – investigated by dynamic light scattering – were prepared by optimizing solvent composition and temperature to obtain nanoparticles with a reduced degree of aggregation. The nanoparticles were embedded in a PMMA matrix to obtain a transparent coloured composite which was studied by transmission electron microscopy. The nanoparticle chromic features, enhanced by their reduced sizes, were investigated by UV–vis and FT-IR spectroscopy.

The solid-state electrochemistry and thermochromism of cobalt hexacyanoferrate (CoHCF) in a composite matrix comprising silica sol–gel and generation-4 poly(amidoamine) dendrimer was investigated and compared to analogous studies of CoHCF powders. The thermochromic behaviour over the range, 25–85 °C, of the reduced form in the sol–gel matrix differed from that of the powder. The results suggested that even in the presence of KCl in this matrix, the dominate form of the reduced CoHCF was Co 2 II Fe II (CN) 6 rather than K 2 Co II Fe II (CN) 6 . In contrast, the thermochromic behaviour of the oxidized form of CoHCF was the same as that reported for the powders. The observed cyclic voltammetric behaviour of CoHCF in the sol–gel composite matrix was the same as that of powders in terms of the electrode processes, but the influence of scan rate on the current was dependent upon the cell configuration. With the CoHCF-doped composite contacted to a solution phase, this behaviour was consistent with anion intercalation/de-intercalation control, but in a solid-state cell, a transition from a surface-controlled to a mass-transport controlled current was observed.

The inclusion of a generation-4 polyamidoamine (G4-PAMAM) dendrimer in a silica sol-gel yielded a solid electrolyte that was used to encapsulate Prussian Blue (PB), iron(III) hexacyanoferrate(II), and cobalt hexacyanoferrate. The PB was synthesized in the doped silica by sequential immersion of a monolith in 0.1 M K4Fe(CN)6, water, and 0.1 M FeCl3. Inclusion of G4-PAMAM resulted in a nanoporous anion-exchange material with a capacity of 10.1 mmol g–1, which is about four times greater than the capacity of silica alone. Relative to its G0 counterpart, the G4-PAMAM doped silica increased the rate of formation of PB by a factor of ca. 20. The solid state voltammetry of PB in the doped silica had the usual features for this compound. At 0.1 V vs. a Ag quasi-reference electrode, a reversible reduction was seen; the relationship between current and scan rate was that for a surface-confined redox couple. The quasi-reversible oxidation of PB was observed at 0.85 V. Inclusion of G4-PAMAM increased the lifetime of silica as a solid electrolyte from a few days to at least three months. Raman microprobe mapping analysis demonstrated that PB was homogeneously distributed across the entire width (ca. 1 mm) of the G4-doped monolith with 20-h immersions.

Cobalt hexacyanoferrate (CoHCF) nanoparticles have been synthesized by mixing aqueous solutions of K3Fe(CN)6 and CoCl2 under vigorous stirring at different temperatures and following two different procedures, drop-by-drop or immediate mixing. The resulting CoHCF nanoparticles, with dimensions of several tens of nanometers, were characterized using TEM, SEM-EDX, IR, and XRD. Their electrochemical behavior was investigated in comparison with the CoHCF powder bulk compound. The CoHCF nanoparticles exhibit an electrochemically driven conversion to the bulk one that has been investigated by a chemometric approach in order to establish the best synthetic parameters. The rate and the degree of conversion depend on the synthesis temperature.

A new `quasi-solid state' spectroelectrochemical cell for in situ XAS measurements is described and tested using microperoxidase as reference material. The cell substantially improves conventional thin layer cells used for solution XAS spectroelectrochemistry in terms of assembling time and, more important, equilibration of the redox system under study with the applied potential. Spectra can be, in fact, recorded simultaneously during a slow scan rate cyclic voltammetric scan thus permitting correlation of the spectra and the electrochemical curve. Other advantages are the possibility to use very small quantities of material also with second-generation rings. With high intensity sources having focussed beams a further decrease of the specimen weight can be easily obtained and the acquisition time of spectra further reduced.

Hybrid organic/inorganic films, composed of polyaniline (PANI) matrix and Prussian blue-like nickel hexacyanoferrate redox centers, showed reversible electrochromic behavior in acidic potassium salt electrolytes. The system's coloration properties were assessed from various spectroelectrochemical measurements including voltabsorptometry that involved monitoring of the time-derivative signal of absorbance at 700 and 410 nm as a function of linearly scanned potential. Gold-covered foil was used as a conductive, optically transparent, substrate onto which the composite film was electrodeposited by potential cycling in the mixture for modification consisting of aniline monomer, Ni2+, Fe(CN)63− and electrolyte containing K+ and H+ ions. An important feature of hybrid (composite) material was that its electrochromic properties were dominated by color changes occurring in the PANI component. Coloration originating from nickel hexacyanoferrate barely affected the system's electrochromic characteristics. But the cyanometallate redox centers distributed in the PANI matrix behaved reversibly as expected for a system capable of fast charge transport.

The basic thermodynamics of galvanic cells and the fundamentals of electrode kinetics are briefly reviewed with reference to batteries. The advantages of molten salts as electrolytes or as active components in practical batteries are discussed. The molten salt cells currently under development are described.

Electrochemically assisted deposition of an ormosil film at a potential where hydrogen ion is generated as the catalyst yields insulating films on electrodes. When the base electrode is modified with 20-nm poly (styrene sulfonate), PSS, beads bound to the surface with 3-aminopropyltriethoxysilane (APTES), and using (CH3) 3SiOCH3 as the precursor, the resulting film of organically modified silica (ormosil) has cylindrical channels that reflect both the diameter of the PSS and the distribution of the APTES-PSS on the electrode. At an electrode modified by a 20-min immersion in 0.5 mmol dm−3 APTES followed by a 30-s immersion in PSS, a 20-min electrolysis at 1.5 V in acidified (CH3) 3SiOCH3 resulted in an ormosil film with 20-nm pores separated by 100 nm. Cyclic voltammetry of Ru (CN) 6 4− at scan rates above 5 mV s−1 yielded currents controlled primarily by linear diffusion. Below 5 mV s−1, convection rather than the expected factor, radial diffusion, apparently limited the current. © 2014, Springer-Verlag Berlin Heidelberg.