Abstract
The electrochemical oxidation of molybdenum rod electrodes has been investigated in a range of dilute sodium hydroxide solutions. The experimental technique involved potentiokinetic, potentiostatic, and open circuit potential decay measurements of oxidised and cleaned electrode surfaces. In the concentration range O·Ol–lM NaOH, the cyclic voltammogram exhibited three anodic peaks on the anodic half cycle. On reversing the scan direction, two anodic peaks in addition to a reduction peak were again obtained. Splitting of the initial peak is observed. The oxidation states of molybdenum corresponding to the anodic peaks were identified in the light of previous studies employing XPS analysis. It is proposed that the initial oxidation results in reversible formation of highly hydrated, surface bound Mo(III) oxy or hydroxy species. Theformation of Mo(IV) and Mo(VI) is thought to result principally from oxidation of metal, rather than from that of the initially formed Mo(III). It is proposed that the electrochemical formation of M 0 (IV) occurs by a diffusion controlled mechanism. None of the products of oxidation produced effective protection of the metal surface against corrosion.
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