The preparations of Bi film modified working electrode by ex situ
mode were performed according to Serrano et al. [19] with minor
modification. In brief, the working electrode (ILGPE or GCE), the SCE
reference electrode, and the Pt auxiliary electrodes were immersed in
10 mL of 0.1 M acetate buffer solution (pH 4.5) containing 600 μg/L
Bi3+. Deposition E of −0.80 V was applied for 300 s with solution
stirring (without deoxygenating operation), followed by an extended
period (without stirring) of 20 s. Once the Bi film was deposited, the
three electrodes were rinsed thoroughly with water.