In-situ external reflection FTIR spectroelectrochemical and XPS investigations of cobalt-cyanometallates as inorganic polymeric materials on a platinum electrode.
Cobalt-cyanometallate films electrochemically deposited on a platinum electrode were studied by cyclic voltammetry (CV), in-situ FTIR spectroelectrochemistry (FTIRs) and potential resolved XPS measurements. The experimental results reveal that the CoHCF film on Pt electrode exists in two forms. The major form of the inner layer of the film is (M(+))(2)Co(II)Fe(II)(CN)(6) where M(+)denotes a cationic counter ion, in which both the Fe(2+)and Co(2+)centers can be oxidized to Fe(3+)and Co(3+)in the potential range of 0-1.0 V vs. Ag/AgCl in NaCl solution. The major form of the outer layer is Co(II)(2)Fe(II)(CN)(6), in which electrochemical reactions in this potential range are limited by kinetic sluggishness. The FTIR and XPS spectra indicated that the Co centers change from high-spin state to low-spin state accompanying the Co(2+)/Co(3+)oxidation reaction. In addition, the cations' effect on electrochemical reactions of CoHCF is also discussed.
Structure of Cobalt Hexacyanoferrate Films Synthesized from a Complex Electrolyte
Films of cobalt hexacyanoferrate (CHCF) are produced under potentiodynamic conditions (E= –0.25 to 0.6 V, v= 0.05 V s–1) from a 2 mM K3Fe(CN)6+ 2 mM Na3Co(NO2)6+ 0.5 M Na2SO4solution. According to scanning electron microscopy, the thick CHCF film initially obtained during the synthesis has a heavily porous structure unusual for films of hexacyanoferrates of transition metals, the size of its crystallites is 200–600 nm. A thinner film has a more compact structure and its crystallites are smaller. The X-ray diffraction pattern for a reduced film shows rhombohedral distortion of the fcc lattice with parameters a= 1.035 nm and α = 91.43°. The patterns for partially and completely oxidized films nicely fit an fcc crystalline lattice typical for hexacyanoferrates (ais 1.006 and 0.993 nm, respectively). The assumption that both hexacyanoferrate and cobalt ions are electroactive in this particular case is confirmed by the IR and X-ray photoelectron spectroscopy techniques.
Effect of temperature on the solvated electron in 1-propanol
Abstract The technique of pulse radiolysis has been used to study the effect of temperature on the solvated electron in 1-propanol. The spectrum of the solvated electron has been measured in the range 140–298 K. The wavelength at maximum absorption, λ max , decreases with decreasing temperature (corresponding to an increase in the energy, E max ) but the spectral width at half height, ΔE 1 2 , changes little with temperature. At temperatures above ≈180 K, the formation of the solvated electron is complete at the end of the pulse and its spectrum shows no change in shape with time. Below ≈170 K, the absorption spectrum is time-dependent in both liquid and glassy phases, the changes being attributed to the solvation process. The reaction(s) leading to solvated electron formation following the pulse show an activation energy of 22±2 kJ mol − and the solvated electron decays with an activation energy of 20±2 kJ mol −1 . The yield of solvated electrons decreases continuously with decreasing temperature in the range 298-77 K and, at all temperatures studied, is less than the total ionization yield measured by scavenging techniques.