Structure of the electrical double layer on Ag(100): Promotive effect of cationic species on Br adlayer formation

Abstract

We revealed the promotive effect of alkali metal cations on Br adlayer formation on an Ag(100) electrode by in-situ measurement of the x-ray specular rod. Alkali metal cations in the electrical double layer affect the onset potential of Br adsorption and the order-disorder transition. We determined the Cs structure in the electrical double layer during Br adlayer formation and found that (1) the Cs structure depends on the coverage of adsorbed Br, and (2) the amount of Cs increases at the initial stage of Br adlayer formation. Structural analysis suggests that hydrated Cs is localized in the area around adsorbed Br via noncovalent interactions. Formation of a Cs-Br complex promotes Br adsorption.