VOLTAMMETRIC INVESTIGATION OF A SOLID IN THE ABSENCE OF A SOLUTION PHASE - ELECTROCHEMICAL REDUCTION OF AIR-DRY MOLYBDENUM OXIDE POWDERS

A 1.2 mm layer of air-dry MoO3 between two glassy carbon electrodes is electrochemically reduced to hydrogen molybdenum bronze (HMB). The reduction is accomplished by either cyclic voltammetry or constant applied potential electrolysis in a solid matrix biamperometric cell. Initiation of the reduction requires application of a large enough potential, ca 3.0 V, across the cell to cause oxidation of water vapor adsorbed at the anode. Because the HMB is electrochemically oxidized, the development of subsequent cyclic voltammograms is observed in a lower potential range, +/- 1.5 V. A small amount of water, which is presumably adsorbed from the atmosphere to the MoO3, is required for the following reasons: it is the source of the proton needed to form the H(x)MoO3, it is oxidized in the anodic reaction that initiates the bronze formation; and it provides a charge transport path across the otherwise non-conducting MoO3.