Rotating ring-disc electrode (RRDE) voltammetry is applied for the in situ determination of hydroxy borohydride (BH3(OH)–) formation during borohydride (BH4–) electro-oxidation on a gold (Au) electrode in 6.0 M NaOH solution. The BH3(OH)– is detected at the ring electrode due to its further oxidation to BH2(OH)2- by maintaining its potential in the range of −0.800 to −0.600 V vs. normal hydrogen electrode (NHE) while oxidizing BH4– on the disc electrode. The study reveals that the generation of BH3(OH)– increases if the anodic polarization of the disc electrode is increased. The RRDE ring-shielding experiments show that the electro-oxidation of BH4– occurs over a wide potential range of −0.500 to 0.400 V on the Au electrode under hydrodynamic conditions. Chronoamperometry is also used to study the BH3(OH)– oxidation in the potential range of −0.800 to −0.600 V with 0.33 M NaBH4 in three different buffer solutions of pH 10.2, 11.0 and 11.70, respectively. The chronoamperometric studies indicate that the formation and stability of BH3(OH)– depends on the pH value.
