Rotating ring-disc electrode (RRDE) investigation of borohydride electro-oxidation

Abstract

Rotating ring-disc electrode (RRDE) voltammetry is applied for the in situ determination of hydroxy borohydride (BH 3(OH) −) formation during borohydride (BH 4 −) electro-oxidation on a gold (Au) electrode in 6.0 M NaOH solution. The BH 3(OH) − is detected at the ring electrode due to its further oxidation to BH 2(OH) 2 − by maintaining its potential in the range of −0.800 to −0.600 V vs. normal hydrogen electrode (NHE) while oxidizing BH 4 − on the disc electrode. The study reveals that the generation of BH 3(OH) − increases if the anodic polarization of the disc electrode is increased. The RRDE ring-shielding experiments show that the electro-oxidation of BH 4 − 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 BH 3(OH) − oxidation in the potential range of −0.800 to −0.600 V with 0.33 M NaBH 4 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 BH 3(OH) − depends on the pH value.