Cy. Rong et Fc. Anson, UNUSUALLY STRONG ADSORPTION OF HIGHLY-CHARGED HETEROPOLYTUNGSTATE ANIONS ON MERCURY-ELECTRODE SURFACES, Analytical chemistry, 66(19), 1994, pp. 3124-3130
The adsorption of multiply charged, heteropolytungstate anions on merc
ury electrodes is extraordinarily strong. For the chromium(III)-substi
tuted anion, alpha(2)-[P2W17O61Cr(OH2)](7-), the mercury surface is ha
lf-saturated at concentration of the heteropolyanion of only 5 X 10(-9
) M. In the presence of the adsorbed anions, the rate of reduction of
the unadsorbed heteropolytungstates in solution is greatly diminished.
The decreased reduction rates appear to result from increases in the
negative diffuse layer potentials produced by the anion adsorption. Th
e spontaneous adsorption of heteropolytungstates on mercury may prove
useful in their electroanalysis at very low levels and in electrocatal
ytic applications.