Communication—A Mechanistic Study on Electrodeposition of Rhenium from Acidic Solution of Ammonium Perrhenate

Abstract

The electroreduction mechanism of ReO4− in acidic solution is investigated intensively via experiments and thermodynamic analysis. High acidity and low ReO4− concentration are the advantageous conditions to fabricate metallic rhenium, while under other conditions only small amount of rhenium oxides can be obtained. The reduction of ReO4− to metallic Re is a multi-step process involving the successive reduction of intermediates. When there is no enough hydrion or the rhenium concentration exceeds a certain value, it is apt to produce a detrimental intermediate ReO2, which will benefit the hydrogen evolution reaction and seriously impede the further reduction of low-valent intermediates.

Water in Sugar Electrolytes and Application to Electrodeposition of Superconducting Rhenium

“…Furthermore, as discussed in Table II, the presence of fructose lowers the electrolyte acidity. Cao et al 38 reported a systematic study on the effect of electrolyte acidity on Re deposition, where a lower acidity was concluded to facilitate the formation of ReO 2 oxides and prevent further reduction to Re metal. This appears to be consistent with the observations here, where the low current efficiency and incorporation of oxide are more pronounced when fructose are present at high concentration.…”

Rhenium-Based Electrocatalysts for Water Splitting

“…It has been described that the use of high concentrations of the precursor ion ReO 4 – promotes the formation of rhenium oxide. , Cao et al reported obtaining Re 0 without rhenium oxides using low concentrations of ReO 4 – and high concentrations of H 2 SO 4 . To deposit metallic rhenium from solutions with high concentrations of ReO 4 – it is necessary to add high concentrations of salts, like sodium sulfate, in addition to H 2 SO 4 .…”

“…Nowadays, most of the studies regarding rhenium are related to bulk surfaces of solid commercial electrodes ,− or rhenium surfaces obtained electrochemically on different substrates, such as Pt, − Au, Cu, ITO, and Si. , The first result of the application of a rhenium electrode for HER was reported in 1975 by Miles and co-workers , that described higher catalytic activity than Os, Ru, and Ni and lower activity than Pd, Pt, Rh, and Ir in 0.1 M H 2 SO 4 with an HER overpotential (η HER ) value of 544 mV at η 2 , respectively. It was not until 2016 that Garcia–Garcia et al reported an onset potential for H 2 of 350 mV, with an overpotential of 470 mV at η 2 , being the first promising data on the catalytic activity of Re in an acidic medium (0.5 M H 2 SO 4 ).…”

“…The electrosynthesis of metallic rhenium on a working electrode has been very complex, mainly because there are several reduction processes to obtain Re 0 from the most common precursor ReO 4 – , generating a mixture of rhenium oxides, mainly ReO 2 and ReO 3 . − , These oxides have also displayed interesting catalytic properties. However, it has been suggested that they act mainly as proton exchange coatings; thus, the registered catalytic properties correspond to the working electrode, Pt .…”

Electrodeposition of Superconducting Rhenium with Water-in-Salt Electrolyte

“…7 Electrodeposition of rhenium was typically carried out from a highly acidic electrolyte 7,8 to avoid the formation of Re oxide, which was found to prevent the deposition of metallic Re. 9,10 While metallic Re has been successfully deposited from such electrolytes, hydrogen evolution reaction dominates the cathodic polarization, not only resulting in low current efficiency but also limiting the potential at which Re deposition occurs. Hydrogen can also be incorporated into the film and changes the morphology and property of films.…”