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Concentration ratio of [OH−]/[BH4 −]: A controlling factor for the fuel efficiency of borohydride electro-oxidation
- Source :
-
International Journal of Hydrogen Energy . Dec2009, Vol. 34 Issue 23, p9436-9443. 8p. - Publication Year :
- 2009
-
Abstract
- Abstract: The fuel efficiency of borohydride electro-oxidation on carbon-supported Au and Ag electrodes was found to be highly dependent on the concentration ratio of [OH−]/[BH4 −] in the solution. Near-8e reactions occurred when [OH−]/[BH4 −]≥5. However when [OH−]/[BH4 −] was smaller than 5, hydrogen gas was evolved and the fuel efficiency was reduced. Only 3e reaction stoichiometry was obtained at [OH−]/[BH4 −]=1. Detailed cyclic voltammetry (CV) studies revealed that both the Au/C and Ag/C showed different anodic waves in varied NaOH–NaBH4 solutions. The CV analysis results suggest that BH3OH−, an intermediate possibly produced by homogeneous hydrolysis, is responsible for the electrochemical reaction at [OH−]/[BH4 −]=1. Comparison of CV voltammograms in borohydride solutions with that in the H2-bubbled NaOH solution suggests that borohydride electro-oxidation on Au or Ag electrode is through direct BH4 − oxidation rather than through a hydrogen ionization mechanism. It is concluded that there exists an inherent competition between two oxidizing species of OH− and H2O during borohydride electro-oxidation, that is, if accessible OH− ions are not sufficient for each BH4 − to accomplish the 8e electro-oxidation, part of BH4 − will react simultaneously with H2O to generate hydrogen. [Copyright &y& Elsevier]
Details
- Language :
- English
- ISSN :
- 03603199
- Volume :
- 34
- Issue :
- 23
- Database :
- Academic Search Index
- Journal :
- International Journal of Hydrogen Energy
- Publication Type :
- Academic Journal
- Accession number :
- 45080208
- Full Text :
- https://doi.org/10.1016/j.ijhydene.2009.09.078