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Partial charge transfer in the underpotential deposition of metals

1988; Elsevier BV; Volume: 245; Issue: 1-2 Linguagem: Inglês

10.1016/0022-0728(88)80055-x

2590-2954

G. Salié,

Force Microscopy Techniques and Applications

The kinetics of underpotential deposition of metals are treated according to the general theory of chemisorption reactions including more than one adsorbed state. Attention is called to the formation of completely discharged metal in the underpotential range, forming an alloy with the substrate. An underpotential deposit may consist of partially charged adsorbate as well as completely discharged bulk portions. Miscibility gaps in the bulk should lead to sharp peaks in cyclic voltammograms. The change in the double layer charge due to alloy formation must be introduced into the charge balance. An outline for the determination of partial charge transfer coefficients l of adsorbed states from ring-disk and twin electrode thin layer experiments is given, based on charge-mass relations. The analysis of measuring methods shows that in potentiostatic step experiments the time-dependent course of the quotient of disk/ring currents allows the various processes to be separated, at least the first and the last step. The constancy of measured l with respect to potential excludes that more than one intermediate contributes to an observed adsorbed state. A discussion of non-monotonic current transients in potential step experiments is given.