[en] This paper reports that by using a radioactive labeling method and electrochemistry, results were obtained that show that interactions of bisulfate anion with well-ordered single-crystal electrodes are different from those with the polycrystalline electrodes. In particular, the anion surface concentration on the polycrystalline rhodium electrode increases monotonically with the electrode potential and then decreases when the surface becomes electrooxidized. With Rh(111), the surface stability of bisulfate is observed in a broad electrode potential range. Likewise, the hydrogen adsorption process apparently overcomes a higher energy barrier to nucleate into surface water-bisulfate network on Rh(111) than it does on the polycrystalline surface. These findings, and the corresponding results obtained with platinum electrodes, demonstrate some unique electrochemical properties of electrode materials that have a regular atomic periodicity and a long-range crystallographic order. extension of this work to surfaces covered by underpotential-deposited-metal (UPD) adlayers illustrates the principles of enhanced absorption