Theory of Work-Function Change on Adsorption of Polarizable Ions

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Abstract
We first point out and correct an error which occurred in an earlier, more approximate theory of the work‐function change accompanying ion adsorption. Next, certain of the approximations of this earlier work are lifted to produce a more accurate theory. In particular, the adsorbed ions and their images in the adsorbent are no longer approximated as ideal dipoles. We employ results of recent exact calculations to obtain quite accurate expressions for the electric fields due to these nonideal dipoles and thus for the induced polarization associated with these fields. Furthermore, the images of induced dipoles are explicitly taken into account in their effect upon the self‐consistent depolarizing field. This approach leads to a new expression for the effective dielectric constant of the adsorbed phase which takes cognizance of discreteness effects. Theoretical predictions are found to be in agreement with data for Cs+ and K+ on tungsten for small θ and may apply well up to θ≲0.6. Finally we discuss possible explanations for the discrepancies near θ=1.

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