Tadayoshi Ohmori

Electroreduction of nitrate ion to nitrite and ammonia on a gold electrode in acidic and basic sodium and cesium nitrate solutions

Abstract The electroreduction of NO 3 − to NO 2 − and NH 3 has been investigated using a polycrystalline Au electrode in 0.5 M NaNO 3 and CsNO 3 solutions with pH in the ranges 1.1–3.0 and 9.85–12.8. The reduction of NO 3 − does not occur significantly in the strongly acidic solutions with pH lower than 1.4 to 1.6: the current efficiency for the NO 3 − reduction is less than 5%. A further increase in pH significantly facilitates the NO 3 − reduction. In basic solutions the reduction of NO 3 − occurs predominantly: the current efficiency reaches the range 80 to 99%. In the case of NaNO 3 solutions the ratio of the current efficiencies for NH 3 and NO 2 − production, CE NH 3 /CE NO 2 − is nearly unity in the acidic solutions and 2 to 3 in basic solutions. On the other hand, in CsNO 3 solutions, the current efficiency of NO 2 − production becomes much higher and the CE NH 3 /CE NO 2 − is 1 to 0.5 at pH in the range 2.0–3.0 and 0.2 to 0.5 at pH in the range 10.0–12.7. Partially positively-charged Na or Cs adatoms underpotentially deposited (upd) on the Au electrode surface are believed to facilitate the adsorption of NO 3 − ions, resulting in the preferential reduction of NO 3 − .

Hydrogen Evolution by Plasma Electrolysis in Aqueous Solution

Hydrogen has recently attracted attention as a possible solution to environmental and energy problems. If hydrogen should be considered an energy storage medium rather than a natural resource. However, free hydrogen does not exist on earth. Many techniques for obtaining hydrogen have been proposed. It can be reformulated from conventional hydrocarbon fuels, or obtained directly from water by electrolysis or high-temperature pyrolysis with a heat source such as a nuclear reactor. However, the efficiencies of these methods are low. The direct heating of water to sufficiently high temperatures for sustaining pyrolysis is very difficult. Pyrolysis occurs when the temperature exceeds 4000°C. Thus plasma electrolysis may be a better alternative, it is not only easier to achieve than direct heating, but also appears to produce more hydrogen than ordinary electrolysis, as predicted by Faradays laws, which is indirect evidence that it produces very high temperatures. We also observed large amounts of free oxygen generated at the cathode, which is further evidence of direct decomposition, rather than electrolytic decomposition. To achieve the continuous generation of hydrogen with efficiencies exceeding Faraday efficiency, it is necessary to control the surface conditions of the electrode, plasma electrolysis temperature, current density and input voltage. The minimum input voltage required induce the plasma state depends on the density and temperature of the solution, it was estimated as 120 V in this study. The lowest electrolyte temperature at which plasma forms is ~75°C. We have observed as much as 80 times more hydrogen generated by plasma electrolysis than by conventional electrolysis at 300 V.

Production of Heat during Plasma Electrolysis in Liquid

Plasma was formed on the surface of an electrode in a liquid solution when metal cathodes underwent high-voltage electrolysis. A real-time heat calibration system was designed for detecting the amount of heat generated during plasma electrolysis. The measured heat exceeded the input power substantially, and in some cases 200% of the input power. The heat generation process depended on the conditions for electrolysis. There was no excess heat at the beginning of plasma electrolysis. However, after plasma electrolysis for a long time, a large amount of heat was generated. The reproducibility would be 100% if all factors such as temperature, voltage and duration were optimized. Based on the heat and the products, we hypothesize that some unique reaction occurs on the cathode surface. This reaction may not occur at energy levels available during electrochemical electrolysis.

Light Emission from Pt during High‐Voltage Cathodic Polarization

Light emission from cathodically polarized Pt electrodes was investigated at cell voltages up to 200 V in aqueous electrolyte solutions. The emission of light was observed when intense cathodic polarization caused the temperature of the Pt electrodes to exceed the boiling temperature of the electrolyte. A thin vapor layer was formed at the metal‐electrolyte interface in which a high electric field ionized vapor molecules to generate a plasma state. The emission of light was caused by the glow discharge at relatively low cell voltages and by the spark discharge at high cell voltages. The spectra of the emitted light were assigned to the constituents of the electrolyte solution, electrode material, and gaseous hydrogen evolved at the electrode.

Hydrogen evolution reaction on gold electrode in alkaline solutions

Abstract The mechanism of the hydrogen evolution reaction (HER) on an Au electrode in 0.5-2 × 10 −5 M NaOH and KOH solutions was investigated by observing the Tafel relationship, differential pseudo-capacitance and time constant of the electron transfer reaction. The HER kinetics follows the slow discharge mechanism over the whole range of solution concentration. It is demonstrated that at high concentrations, 0.5–0.01 M, the underpotential deposition ( upd ) of alkali metal takes place concomitantly, and it leads to poisoning of active sites of gold and thus strongly depresses the electrocatalytic activity. Anomalous concentration dependence of overpotential was observed at lower concentrations and its possible cause is discussed in relation to the upd of alkali metals.

Transmutation in the Electrolysis of Light Water—Excess Energy and Iron Production in a Gold Electrode

The identification of some reaction products possibly produced during the generation of excess energy is attempted. Electrolysis is performed for 7 days with a constant current intensity of 1 A. The electrolytes used are Na{sub 2}SO{sub 4}, K{sub 2}SO{sub 4}, K{sub 2}CO{sub 3}, and KOH. After the electrolysis, the elements in the electrode near the surface are analyzed by Auger electron spectroscopy and electron probe microanalysis. In every case, a notable amount of iron atoms in the range of 1.0 x 10{sup 16} to 1.8 x 10{sup 17} atom/cm{sup 2} (true area) are detected together with the generation of a certain amount of excess energy evolution. The isotopic abundance of iron atoms, which are 6.5, 77.5, and 14.5% for {sup 54}Fe, {sup 56}Fe, and {sup 57}Fe, respectively, and are obviously different from the natural isotopic abundance, are measured at the top surface of a gold electrode by secondary ion mass spectrometry. The content of {sup 57}Fe tends to increase up to 25% in the more inner layers of the electrode. 8 refs., 11 figs., 3 tabs.

Adsorption of CO and CO2 on polycrystalline Pt at a potential in the hydrogen adsorption region in phosphate buffer solution: An in situ Fourier transform IR study

Adsorption features of CO(ads) and reduced CO2 on a polycrystalline platinum electrode in phosphate buffer solution were investigated by anodic stripping voltammetry (ASV) and in-situ Fourier transform IR (FTIR) measurement. The ASV peak of CO(ads) at 0.45 V (with respect to a reversible hydrogen electrode did not appear in the anodic stripping voltammogram of reduced CO2. However, sequential CO2/CO dosing at 0.05 V added the ASV peak at 0.41 V to the anodic stripping voltammogram of reduced CO2. The ASV peaks at 0.45 and 0.41 V were assigned to bridged CO by IR bands around 1850 cm−1, similar to IR bands in acidic solution. The sequential CO2/CO dosing gave an IR band of bridged CO of 1842 cm−1 at 0.05 V. However, the adsorption of reduced CO2 did not give a strong IR band of bridged CO. The potential dependence of the IR band feature of linear CO from CO gas was different from that from reduced CO2. The electron numbers per site for CO(ads) and reduced CO2 oxidation processes were discussed in comparison with the results of ASV and FTIR.

Excess heat evolution during electrolysis of H2O with nickel, gold, silver, and tin cathodes

Excess heat evolution was measured on nickel, gold, silver, and tin in aqueous K[sub 2]CO[sub 3], Na[sub 2]CO[sub 3], Na[sub 2]SO[sub 4], and Li[sub 2]SO[sub 4] solutions under galvanostatic electrolysis conditions. Steady evolution of excess heat in various electrode-electrolyte systems, but not in Ni/Na[sub 2]CO[sub 3], Ni/Na[sub 2]SO[sub 4], and Ni/Li[sub 2]SO[sub 4], was observed for at least several days of observation. The largest excess heat observed was 907 mW on tin in K[sub 2]SO[sub 4]. 9 refs., 2 figs., 4 tabs.

Neutron Evolution from a Palladium Electrode by Alternate Absorption Treatment of Deuterium and Hydrogen.

We observed neutron emissions from palladium after it absorbed deuterium from heavy water followed by hydrogen from light water. The neutron count, the duration of the release and the time of the release after electrolysis was initiated all fluctuated considerably. Neutron emissions were observed in five out of ten test cases. In all previous experiments reported, only heavy water was used, and light water was absorbed only in accidental contamination. Compared to these deuterium results, the neutron count is orders of magnitude higher, and reproducibility is much improved.

Transmutation in a Gold-Light Water Electrolysis System

AbstractMercury, krypton, nickel, and iron with anomalous isotopic compositions were found to be produced on or in gold electrons during light water electrolysis. In addition, silicon and magnesium with anomalous isotopic compositions were also detected in the precipitates separated from the gold electrode electrolyzed at extremely high current densities. After the electrolysis, the surface of the electrode exhibited an extraordinary structure, i.e., a number of microcraters like volcanoes were developed. The structure of the outside wall of the craters was very much like that of the precipitates, and hexagonal crystallite layers in the inside wall of the craters suggested a partial recrystallization of the electrode material due to some intense heat evolution. The craters developed along the rim of the microcracks, microholes, and scraped edges of the electrode. These results suggest that some nuclear transmutation reactions occur during the electrolysis to produce these effects.