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 À2 by hydroxide (1 M KOH), while in carbonate electrolytes, the exchange current density was 0.24 mA cm À2 (0.3 M CO 3 À2 ) and 0.32 mA cm À2 (0.5 M CO 3 À2 ). 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.Anion exchange membrane (AEM) fuel cells have received considerable attention due to their potential advantages over the proton exchange membrane (PEM) fuel cell. First, in alkaline environment, the fuel oxidation has been shown to have high activity on both Pt and non-Pt catalysts. 1,2 Also, unlike acid systems, high oxygen reduction reaction (ORR) activity has been demonstrated on non-Pt catalysts, such as silver 3 and gold. 4 This suggests that the catalyst layers in AEM fuel cells can be significantly lower cost than their PEM fuel cell counterparts. Also, alcohol versions of the cell can operate on pure fuel because no water is required for fuel oxidation, contrary to the PEM fuel cell where water takes part in the electrochemical reaction and the fuel must be diluted. In addition, during operation, anion transport is from cathode to anode, and the resulting electro-osmotic drag suppresses fuel crossover. Finally, water is produced at the anode and partially consumed at the cathode, which may simplify water management and prevent electrode flooding. There have been several promising reports of hydroxide exchange membrane fuel cells (HEMFCs) using hydrogen, methanol, and ethanol as the anode fuel. [5][6][7][8][9][10][11][12][13][14] The hydrogen oxidation reaction (HOR) has been the focus of many studies in acidic and alkaline media. The rate of hydrogen oxidation varies at different metal surfaces and has been shown to be a structure sensitive process. [15][16][17] In acid media, differences in the kinetics for various metals have been explained by their different adsorptive and electronic properties. 16 Two different adsorbed hydrogen species have been observed in both acidic and alkaline media, 16,17 one with significantly higher binding energy than the other. Hydroxide species adsorbed at these sites with high positive overpotentials have an inhibiting effect on the HOR, which has been attributed to structure sensitive adsorption on different index faces of platinum. 17 In hydroxide alkaline media, the HOR proceeds through the following two-electron reactionI...

No abstract

A technique is described for the analysis of gaseous mixtures by vapor phase chromatography with simultaneous recovery of a portion of each separated fraction for mass spectrometer analysis. This procedure is valuable for positive identification of fractions and permits the analysis of mixtures having identical emergence times.

No abstract

the bulk would suggest. The same is true for potassium, which was not previously known to be occluded in hard gold electroplates. ACKNOWLEDGMENTThe authors would like to acknowledge Irene Payne for performing all of the densitometry and some of the sectioning of substrates. We would also like to thank A. Tartaglia for substrate sectioning and etching, T. Palumbo for the electroplating, and L. Blitzer for the atomic absorption analyses. The reduction of massive amounts of data was made relatively easy by a computer program prepared by T. Loomis, to whom the authors are also indebted.