Analysis of the electrodeposition process of rhenium and rhenium oxides in alkaline aqueous electrolyte

The electrodeposition of rhenium and rhenium oxides from an alkaline aqueous solution containing 0.125 mol dm−3 NH4ReO4 + 0.01 mol dm−3 NaOH (pH 13.3 ± 0.1) has been studied. Cyclic voltammetry studies were carried out using two electrodes, polycrystalline platinum and polycrystalline gold, and the galvanostatic electrodeposition was conducted on a pure copper electrode (99.9%). Information regarding rhenium electrodeposits has been obtained by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results in an alkaline aqueous electrolyte suggest that the electrocrystallization process follows a multi-step mechanism influenced by hydrogen adsorption. The main conclusion was that rhenium, rhenium (IV) oxide and rhenium (VI) oxide coexist in the electrodeposited material.