Second order Stark effect of adsorbed sulfate ions on polycrystalline platinum

A second order Stark effect was observed for the first time both on the band center frequency and on the integrated band intensity of sulfate ions adsorbed at polycrystalline platinum. It was observed that, as the applied potential grows towards positive values, the band frequency is shifted upwards and the integrated band intensity decreases, suggesting that the applied electric field produces bond constrictions of the uncoordinated SO2 group. Lateral interactions were also observed. The adsorption isotherm that best fit the results is the one of Temkin. An adsorption in the form of islands is suggested in order to explain the lateral interaction and the validity of the Temkin isotherm.