EFFECT OF HALIDE ION ADSORPTION UPON PLASMON-MEDIATED PHOTOELECTRON EMISSION AT THE SILVER SOLUTION INTERFACE/

The effect of the roughening of the silver surface upon photoemission observed in the presence of two different scavengers dissolved in an a queous solution, CO2 and NO3- ions, was re-examined. The quantum yield of the photocurrent exhibits a sharp maximum at 370-380 nm in the fre quency range of surface plasmons on silver. These photoyields were str ongly affected by the extent of the roughening of the AE surface and r eached an unusually large value of 0.05 electron per incident photon. Electrochemical oxidation/reduction roughening performed in the presen ce of Cl-, Br-, and ClO4- ions, similar to that employed in enhanced R aman scattering (SERS) experiments, affected the maximum of the photoc urrent and in some cases also its onset potential, Photocurrents arisi ng al potentials more negative than the potential of zero charge (pzc) of silver were principally influenced by changing morphology of the s urface resulting from more or less deep roughening performed in differ ent solutions. On the other hand, the photoelectrochemical behavior of silver at potentials positive with respect to the pzc was clearly aff ected by the specific adsorption of anions of the supporting electroly te, It was, Ln particular, the Br- anion that caused in this potential region the strongest enhancement of the photocurrent, associated with the reduction of scavengers and led to an apparent positive shift of the onset potential. The role played by the specifically adsorbed anio ns is interpreted in terms of slowing down the reverse reactions of so lvated electrons and of reaction intermediates (such as, for example, the NO32- anion) returning to the electrode.