In situ STM studies on germanium tetraiodide electroreduction on Au(111) in the room temperature molten salt 1-butyl-3-methylimidazolium hexafluorophosphate

Abstract

The electroreduction of GeI₄ on flame annealed Au(111) films was investigated by in situ STM in the room temperature molten salt 1-butyl-3-methylimidazolium hexafluorophosphate which has an electrochemical window of 4 V on Au(111). The first visible surface changes on Au(111) are seen in the form of 2-dimensional, apparently 230–270 pm high islands which slowly merge followed by a 3-dimensional growth. With further reduction the growth slows down and apparently stops. The surface is composed of terraces with an average height of 330 ± 30 pm. Upon oxidation the deposited layers show a ‘worm-like’ pitting. If the electrode potential is reversed after a short oxidation time, the induced defects slowly heal out on the time scale of 90 min electrochemically and by an Ostwald type ripening. The deposited films have a thickness of roughly 13–16 nm.