RRDE Studies of the Electro-Oxidation of Borohydrides

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.

Cyclic voltammogram recorded with 0.020 M NaBH4 on Au electrode, with scan rate of 0.100 V s-1. A well-defined oxidation peak (a1) and a broad hump (a2) are observed during the forward sweep. A sharp anodic spike (c1) and a broad wave (c2) are observed during the reverse sweep.
Krishnan P., Yang T.H., Advani S.G., and Prasad A.K., "Rotating ring-disc electrode (RRDE) investigation of borohydride electro-oxidation," Journal of Power Sources, Vol. 182, pp. 106-111, July 15, 2008. doi:10.1016/j.jpowsour.2008.03.064