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Graphite electrodes intercalated with various metals (Ni, Co, Pd, Pt, Rh, and Ru) have been bonded with an inorganic polymer and used as cathodes in the hydrogen evolution reactions (HER) in . Four of the most active electrodes showed very good mechanical and electrochemical stability. The overvoltage of the HER at decreased in the following order: −525 mV, for pure graphite and −254, −137, −103, and −58 mV, for the Pd/C, Rh/C, Pt/C, and Ru/C electrodes, respectively. The kinetics of the HER for two electrodes (Ru/C and Pd/C) were measured with the use of an ac impedance technique. In both cases, the HER proceeds via the Volmer‐Heyrovsky mechanism. The results obtained proved that the Pd/C electrode had a larger active surface area than the Ru/C one did.

Hydroxylamine oxidation in acidic media at the rotating platinum, gold, and glassy carbon electrodes was investigated. It was found that the reaction occurred only at the platinum electrode. A single oxidation peak (instead of a wave) was observed at the rotating platinum electrode. Evidence for a kinetic hindrance of the reaction caused by the platinum oxide layer present at the electrode surface was shown. The reaction proceeds via NHOH, NOH, nitrous acid, and the final products are nitrate ions. The process involves hydroxylamine adsorption, which is the reason for the absence of the electrochemical signal in the case of gold and carbon, materials of lower catalytic activity. Hydroxylamine oxidation was accompanied by various homogeneous chemical reactions. The reaction of hydroxylamine with nitrous acid (intermediate product of hydroxylamine oxidation), yielding N 2 O, had a rate constant, estimated on the basis of the ring-disk experiments, equal to (6.4 ± 0.4) 10 4 mol -1 cm 3 s -1 .

Electroreduction of chloramines (mono-, di-, and trichloramine) in I M NH 4 Cl solutions of different pH was investigated at the rotating platinum and gold electrodes. It was found that all chloramines are present in the solution in nonprotonated forms and give well-formed one-step or two-step current-potential waves. The final products of reduction are ammonium (or ammonia) and chloride ions. Monochloramine is reduced in a single two-electron irreversible wave. Hydrazine is not an intermediate in monochloramine reduction. Dichloramine reduction generally proceeds in two two-electron steps (via monochloramine). Below pH 4.3 a kinetic current due to the protonated dichloramine reduction (single four-electron wave) is in force, appearing as an increase of the height of the first step on lowering pH. Due to this process below pH 2.5 only one four-electron reduction wave is observed. Trichloramine reduction occurs in two steps: two-electron trichloramine to dichloramine reduction and four-electron dichloramine reduction. In strong acidic solutions the kinetic current due to the protonated trichloramine reduction has to be taken into account. A reaction mechanism common for all chloramines was proposed with [NXCl.] as an intermediate (X = H 2 , HCl, and Cl 2 for mono-, di-, and trichloramine, respectively). The rate-determining step does not involve proton transfer.

The nitrite oxidation process was reinvestigated at rotating gold and platinum electrodes covered by an oxide layer. The electrochemical properties of the surface oxides were determined by recording the coverage curves of the gold and platinum electrodes at various pH values and for different experiment durations. The reaction mechanism on the oxidized surface was found to be the same as that on the oxide-free surface. The sole effect of the surface oxide was a drop of the standard rate constant of the electrode reaction which was a function of the surface coverage by the oxide. Nitrite oxidation on the oxide-covered electrodes was found to proceed via the innersphere mechanism with inhibitor adsorption on an energetically uniform surface. The kinetic results obtained for the gold and the platinum electrode were almost the same. The complicated shape of rotating disk voltammograms was explained in terms of the increase of the rate of the electrode reaction with increasing electrode potential and the drop of the standard rate constant of the electrode reaction with increasing electrode potential due to the increase of the oxide coverage with electrode potential, the latter process being dependent on the electrode material, pH, and time (scan rate).

High affinity of thallium(I) ions with respect to a copper hexacyanoferrate (CuHCF) film was found. Interaction between the CuHCF film and thallium(I) ions was investigated using the electrochemical quartz crystal microbalance and cyclic voltammetric techniques. In 0.5 M KNO 3 solution, at submillimolar concentrations of Tl(I) ions, the CuHCF film reversibly transforms, during electrochemical experiments, from the potassium into the thallium form. For slightly higher (several millimoles) Tl(I) concentrations, the electrochemical and gravimetric responses prove that the CuHCF film behaves as the thallium form only. Its formal potential (E f 0 ), calculated from the dependence of the E f 0 on [Tl(I)], is for [Tl(I)] = 1 M, 0.28 V more positive than that found for the potassium form. Experimental results obtained suggest that in both cases, potassium(I) and thallium(I) ions, exchange in interstitial positions takes place. Since the ionic radii and the hydration parameters of both ions are similar, we concluded that this high affinity of thallium(I) ions with respect to the CuHCF film, 250-100 times higher than that of potassium(I) ion, results from chemical interactions. In consequence, the solubility product of a thallium analogue of copper hexacyanoferrate is much smaller than that of the potassium form. For different forms they are equal to (pK values): 37.8 (K 2 Cu 3 [Fe(CN) 6 ] 2 ), 46.3 (Tl 2 Cu 3 [Fe(CN) 6 ] 2 ), and 17.2 (Cu 3 [Fe(CN) 6 ] 2 ).