THE HYDROGEN PRESSURE EQUIVALENT TO THE OVERPOTENTIAL - OBSERVATION ON PD HYDROGEN ELECTRODE AND INTERPRETATION ON THE BASIS OF A MIXED-CONTROLLED MECHANISM

A quantitative analysis is presented of the hydrogen pressure that is in equilibrium with adsorbed hydrogen at a Pd cathode and discussed on the basis of a mixed-controlled Volmer-Tafel mechanism of the hydroge n electrode reaction. Experimental evidence which supports this, but n ot the Volmer-Heyrovsky mechanism on a smooth Pd electrode, are discus sed. The effective pressure can be evaluated from the slowly decaying overpotential component appearing in overpotential decay transients. E vidence is given which indicates that the overpotential component is i ndeed caused by adsorbed hydrogen on the electrode surface. The effect s of some catalytic poisons, which augment the equivalent pressure und er otherwise the same conditions, are investigated.