Characterization of mercaptobenzimidazole adsorption on an Au(111) electrode

The adsorption of 2-mercaptobenzimidazole (2-MBI) on Au(111) has been studied with cyclic voltammetry (CV), in-situ subtractively normalised interfacial FT-IR spectroscopy (SNIFTIRS) and scanning tunnelling microscopy (STM). Although adsorbed 2-MBI reduces the interfacial capacity and quenches the characteristic features of the cyclic voltammogram for sulfate adsorption, heterogeneous electron transfer to both the [Fe(CN)(6)](4-/3-) and [Ru(NH3)(6)](3+/2+) redox: systems is only partially impeded. Cyclic voltammetry has also been used to examine the reductive desorption of the thiolate in KOH electrolytes and its subsequent re-adsorption. From the reductive desorption charge, cm(-2) coverage of 2-MBI of 2.6 x 10(-10) molecule is estimated and this points to a flat-lying configuration of the monolayer, in agreement with a previous XPS study. The SNIFTIRS and electrochemical results show that adsorbed 2-MBI is displaced from the surface at positive potentials. STM imaging of adsorbed 2-MBI is also consistent with flat-lying molecules aligned in parallel rows.