Electrochemical Modeling of Iodide Oxidation in Metal-Halide Molten Salts

The oxidation of iodide in NaI-AlBr3, NaI-AlCl3, and NaI-GaCl3 molten salts was analyzed using simulation software to extract relevant kinetic parameters. The experimental oxidation potentials were ordered AlCl3 < AlBr3 < GaCl3, with higher oxidation potentials correlating with softer Lewis acidity of the metal halide. An iodide oxidation and metal halide speciation model was developed and simulated to fit the electrochemical response, enabling determination of electrochemical charge transfer parameters and chemical equilibrium constants. NaI-AlBr3 displayed the fastest electron transfer rates yet showed the lowest current densities. All salts revealed smaller than expected current densities, explained by equilibrium between various species, where some are not electrochemically active at the studied potentials. These equilibrium reactions are due to the various metal halide species, controlling the reactant concentration of iodide and the resultant current. We hypothesize the electrochemically active iodide species, present as a metal halide monomer (MX3I−), is decreased dramatically from the expected concentration, sequestered as a more stable metal halide dimer species (M2X6I−) with a higher oxidation potential. Traditional Tafel analysis of the experimental data supports the validity of the simulations. These results increase understanding of iodide oxidation in low-temperature Lewis acidic molten salts and inform task-specific molten salt design.

Boosting hydrogen generation by anodic oxidation of iodide over Ni–Co(OH)2 nanosheet arrays

Prominent iodide oxidation performance is achieved over Ni doped Co(OH)2 nanosheet arrays obtained by a substrate oxidation strategy at room temperature.

INFLUENCE OF THE NANOCLUSTER {MOFE} POLYOXOMETALATE ON OXIDATION OF IODIDE-IONS BY PERSULFATE

Изучены каталитические свойства нанокластерного железомолибденового полиоксометаллата {MoFe} в растворах при реализации окисления персульфатом йодид-ионов. Использована автоматизированная установка на базе спектрофотометрического метода анализа, управляемая компьютером. Сравнение литературных данных и кинетических данных окисления иодида персульфатом показывает, что кеплерат является гетерогенным катализатором. Эти данные позволяют предполагать нерадикальный механизм для разложения персульфата на поверхности молекул кластера на первой стадии реакции окисления иодида калия. Значение эффективной энергии активации процесса указывает на каталитическое воздействие {MoFe} на промежуточной стадии разложения пероксида водорода. Catalytic properties of the nanocluster iron-molybdenum polyoxometalate {MoFe} in solutions during the oxidation of iodide ions by persulfate have been studied. Automated installation based on spectrophotometric method of analysis controlled by computer was used. Comparison of literary data and kinetic datа on the oxidation of iodide with persulfate showed that keplerate {MoFe} is a heterogeneous catalyst. These data allowed to assume a non-radical mechanism for persulfate decomposition on the surface of cluster molecules at the first stage of the potassium iodide oxidation reaction. The value of the effective activation energy of the process indicates the catalytic effect of {MoFe} at the intermediate stage of the decomposition of the hydrogen peroxide.

SPECTROPHOTOMETRIC DETERMINATION OF IODATE IN IODIDES OF ALKALINE METALS

Conditions for interaction of the iodate ions with iodide and methylene blue as a chromogenic reagent were studied. The interaction of iodate with an excess of iodide depends on the medium acidity. In dilute acids, the reaction of IO3 with Г is accompanied with a release of iodine which oxidizes the dye. The observed weakening of the color which is proportional to the concentration of iodate ions in the solution, results from the oxidative destruction of methylene blue. Spectra of methylene blue, conditions of the redox interaction, as well as the effect of the solution acidity and reagent concentration on the completeness of the reaction were studied. The light absorption of the solutions was measured at a wavelength of 664 nm. The reaction of the free iodine formation is rapid and quantitative at pH 4 - 5 . The desired acidity of the medium was attained using 1 M solution of acetic acid. The optimal concentration of methylene blue was determined. The results of the study formed a base for developing a technique of iodate ion determination in iodides of alkaline metals. The analyzed solutions were prepared with addition of sodium acetate to prevent iodide oxidation by atmospheric oxygen. To eliminate the interfering effect of Fe (III), sodium pyrophosphate (which should be introduced after acidification of the solution and isolation of iodine) was used. The accuracy of the technique was proved in spike tests on the model solutions and real samples by the method of sample weight variation. The developed technique was tested in determination of the iodate ions in cesium and sodium iodides. The relative standard deviation does not exceed 15%. The sensitivity of the developed technique is 10 times higher compared to the technique based on the formation of an iodine-starch complex.