Nickel undergoes significant deactivation as a cathode during alkaline water electrolysis in 8 mol l KOH at 70 degreesC. Addition of dissolved V2O5 was found to result ill reactivation or the nickel cathode and formation of a vanadium-bearing deposit. Tafel measurements at different electrode states indicated no change in the Tafel parameters for the fresh or initial) and vanadium-modified . Furthermore, vanadium addition did not appear to enhance the electrocatalytic activity beyond that for fresh nickel. A rotating ring-disk electrode Was used for detection Of Solution intermediates of the hydrogen evolution reaction in KOH with and without dissolved V,V2O5,. Based oil cyclic voltammograms for the ring (with a hydrogen-evolving Ni disk), no Solution intermediates were detected before or after vanadium addition. The action of vanadium was through a solid Surface species as opposed to a homogeneous species in solution. A mercury electrode was then used to shift hydrogen evolution cathodically , revealing the potential region masked by large hydrogen currents oil a nickel electrode. Cyclic voltammetry on mercury in KOH with dissolved V2O5, showed a cathodic peak that was absent in voltammograms for blank KOH. Therefore, formation of the deposit occurred at a potential coincident with that of hydrogen evolution Oil nickel.