Abnormal infrared effects on bismuth thin film-EMImBF4 ionic liquid interface

► Bismuth has an anomalous spectroelectrochemical response for a metal. ► S-polarized spectra are more intensive and have reversed peaks compared to the p-polarized spectra. ► Both s- and p-polarized spectra describe the adsorbed layer, which is against the surface selection rule. ► Bi thin films give infrared spectroelectrochemical response characteristic to a semiconductor or to a semimetal.