Hydrogen and Methanol Oxidation Reaction in Hydroxide and Carbonate Alkaline Media

The oxidation of hydrogen and methanol by hydroxide and carbonate anions in low temperature alkaline electrolytes was investigated on a polycrystalline platinum rotating disk electrode. The electron equivalence was experimentally determined as 2.0 and 1.9 for oxidation of hydrogen with hydroxide and carbonate anions, respectively. The exchange current density for hydrogen oxidation was measured as 0.14 mA cm(-2) by hydroxide (1 M KOH), while in carbonate electrolytes, the exchange current density was 0.24 mA cm(-2) (0.3 M CO3-2) and 0.32 mA cm(-2) (0.5 M CO3-2). The increased exchange current density through the carbonate pathway was attributed to the ease of bond reorganization between hydrogen and carbonate compared to hydrogen and hydroxide, which results in a more thermodynamically favored process. Also, a more complete methanol oxidation was observed in the presence of hydroxide, though the difference compared to carbonate was not significant. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3543918]