The electrochemical reduction of Mo 2O4 (EDTA)^2- is studied at a mercury electrode in pH 7-10 borate and phosphate buffers utilizing the techniques
of cyclic voltammetry, chronoamperometry, and controlled potential coulometry.
The electrochemical reduction of Mo 204(EDTA)^2- is a four-electron, diffusion
controlled process in which the initial step is an irreversible two-electron
transfer. The product is a binuclear dioxo-bridged complex of Mo (III)
with EDTA. Dependence of the electrode reaction mechanism on pH, buffer
composition, and sodium ion concentration is studied . These results indicate
that a chemical protonation step occurs prior to electrochemical reduction.
A treatment of the effect of changes in double layer structure
on the protonation reaction is presented.