Precursor Adsorption of SbBr₃ on Au(111) and Au(100) for Antimony Underpotential Deposition in a BMIBF₄ Ionic Liquid – A Comparison with SbCl₃

Keywords: Ionic Liquids, In-Situ STM, Antimony Tri-Halides, UPD, Adsorption

By employing in-situ STM, we have studied precursor adsorption and initial stage of Sb UPD on Au(111) and Au(100) in a SbBr₃-containing BMIBF₄ ionic liquid. It has been observed that the adsorption of SbBr₃ selectively takes place on Au(100), in contrast to that of SbCl₃, with formation of chains with Binom structure as well as squares with Binom structure. The chains are composed of pairs of SbBr₃ molecules, which are bridged with the adjacent SbBr₃ molecules in the chain to form the anisotropy along either of the two characteristic directions of Au(100). The square configured structure is composed of periodically arranged monomeric and dimeric SbBr₃, which will gradually replace the chain structure. Regardless of the precursor adsorption, however, the initial stage of Sb UPD is characterized by the formation of atomic strips, like in the SbCl₃-containing system, which reveals the consistency of discharging behavior of Sb(III) from the SbCl₃ and SbBr₃ molecules. Together with the findings from the SbCl₃-containing system, the results are discussed in view of matching of structures between the pyramidal antimony tri-halides and the crystalline surfaces. The role of the ionic liquid as well as properties of the electrified interface will also be mentioned.