Synthesis of OF<sub>2</sub> by Electrolysis of Wet HF

Donohue, John A.; Nevitt, Thomas D.; Zletz, Alex

doi:10.1021/ba-1966-0054.ch018

Cited by 7 publications

(13 citation statements)

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“…2. In a continuous run started at 0.1 m/o water, the yields of oxygen and oxygen difluoride are both less than 5%; with a dry electrolyte the rest of the current presumably goes to form fluorine or corrosion products (3). When the water concentration is increased at 2 hr to 0.26 m/o but voltage is not interrupted, oxygen yield jumps to 22%, oxygen difluoride increased to only 9-10%, and no ozone is yet detected.…”

Section: Resultsmentioning

confidence: 98%

“…for determination of the gaseous products and infrared for water in the electrolyte) have already been described (3,12). The infrared cells are now made by flattening and polishing Kel-F tubing.…”

Section: Methodsmentioning

confidence: 99%

“…Our studies of the production of oxygen difluoride by electrolysis of wet hydrogen fluoride with a nickel/ nickel fluoride anode likewise showed that periodic interruption of the voltage is advantageous (3). We have now improved our experimental and analytical techniques and have observed how the yields are affected by the water and potassium fluoride concentrations of the electrolyte as well as by the applied voltage.…”

mentioning

confidence: 87%

“…Interruption permits reaction [3] to remove such layers and restore the oxygen difluoride yield. Also such oxyfluoride layers can explain the apparent 45% limit on oxygen difluoride yields if the oxygen atoms in it are not available for oxygen difluoride but can only go to oxygen or ozone.…”

Section: Fig 5 Voltage Effectsmentioning

confidence: 99%

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Pulsed Electrolysis of Wet Hydrogen Fluoride

Donohue¹,

Zletz²

1968

J. Electrochem. Soc.

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Although preparative electrolyses are usually carried out at a constant applied potential, recent work has shown that a pulsed potential can be used to advantage in varying the types of products formed (1) and in improving the operation of fuel cells (2). Our studies of the production of oxygen difluoride by electrolysis of wet hydrogen fluoride with a nickel/ nickel fluoride anode likewise showed that periodic interruption of the voltage is advantageous (3). We have now improved our experimental and analytical techniques and have observed how the yields are affected by the water and potassium fluoride concentrations of the electrolyte as well as by the applied voltage. Our results reemphasize the importance of voltage interruption in maximizing oxygen difluoride and reducing ozone and oxygen, the other major products at the anode. In addition, we have found that continuous electrolysis of wet hydrogen fluoride is a potentially good method for producing ozone.Although much work has been done on the preparation of ozone by electrolysis of aqueous acids (4), it has been reported that only sulfuric and perchloric acids give reasonable yields, and only platinum and its alloys are suitable anode materials (5). With respect to aqueous hydrogen fluoride, some investigators suggest that only small amounts of ozone are produced (6-8), and one claims that none is formed (9).Of necessity, comments on the mechanism of any electrolysis in hydrogen fluoride have been pessimistic (10) or highly speculative (11), mainly because product analyses have been incomplete or the results have not been reproducible. Since our results largely avoid such obstacles, they provide a less speculative basis for predicting mechanism. ExperimentalWith the exception of some recent improvements, the electrolysis cell and analytical equipment (g.c. for determination of the gaseous products and infrared for water in the electrolyte) have already been described (3,12). The infrared cells are now made by flattening and polishing Kel-F tubing. These did not fog in wet hydrogen fluoride so the usual absorbence vs. concentration calibration can now be used. Modifications in the electrolysis cell include the introduction of the helium flush gas through a Kel-F gas dispersion disk below the electrodes to ensure better mixing of the electrolyte and removal of the product gases. Also, the anodes are smaller, ranging from 2.5 to 7.5 cm 2. Both electrodes were untreated 20 gauge nickel sheet with about 1/4 in. spacing between cathodes and the anode. A satisfactory Hg/Hg2F2 reference electrode was not developed until late in this work and was used here only for the study of the anode voltage. Details of its construction will be given later (13).Except during interruption, the applied voltage is constant during an entire run. Changing the voltage during a run will generally result in changing, nonreproducible yields. The applied voltage is adjusted manually at the power supply to maintain a preKey words: oxygen difluoride preparation, ozone preparation, mechanism...

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Section: Resultsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 87%

Section: Fig 5 Voltage Effectsmentioning

confidence: 99%

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Pulsed Electrolysis of Wet Hydrogen Fluoride

Donohue¹,

Zletz²

1968

J. Electrochem. Soc.

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“…Weight loss and electron microscope studies were carried out with preweighed anodes that had been exposed to known conditions of electrolysis during previous experiments (1,7). After these experiments, the anodes were removed from the cell, rinsed with hydrogen fluoride to remove potassium fluoride, dried at reduced pressure, and weighed.…”

Section: Methodsmentioning

confidence: 99%