摘要: Experimental and theoretical studies of oxygen reduction (OR) in novel acid and alkaline electrolytes on smooth and supported Pt have been carried out. Similar kinetically limited rates for OR were measured in the 'super-acid' ele... 展开 Experimental and theoretical studies of oxygen reduction (OR) in novel acid and alkaline electrolytes on smooth and supported Pt have been carried out. Similar kinetically limited rates for OR were measured in the 'super-acid' electrolytes trifluoromethane sulfonic acid (TFMSA) and tetrafluoroethane-1,2-disulfonic acid (TFEDSA), with the rotating disk electrode (RDE) technique at 23 degree C and pH = 1. A first-order dependence on O sub 2 pressure was measured. The mechanism for OR on Pt in alkaline electrolytes is complicated by the concurrent oxidation and reduction of Pt. Rotating ring-disk electrode (RRDE) studies carried out with anodic and cathodic potential sweeps in 0.1 to 6.9 M KOH and 0.1 to 4.0 M K sub 2 CO sub 3 revealed similar currents when corrected for O sub 2 solubility differences. In dilute electrolytes, OR proceeds primarily through the 4-electron pathway to water, independent of pH. In KOH, the mechanism for Pt oxidation changes and the fraction of current yielding a peroxide product increases at 2 to 3 M. These changes were not observed in K sub 2 CO sub 3 . Porous gas diffusion electrodes (GDE) with supported Pt catalyst were studied in a special cell with low uncompensated solution resistance. Cyclic voltammograms yielded measurements of the wetted areas of carbon and Pt and the local electrolyte composition. GDE galvanostatic steady-state performance with 100% O sub 2 was measured in 2 to 11 M KOH and 2 to 5.5 M K sub 2 CO sub 3 . Results suggest that OR on carbon contributes to the high currents in 6.9 M KOH at high overpotentials. In K sub 2 CO sub 3 , lower wetted areas and slow OH sup minus ion transport are responsible for the poor performance when compared with KOH. Models for the steady-state operation of porous GDE's were developed. These models account for the diffusion and reaction of O sub 2 and ionic transport in KOH and K sub 2 CO sub 3 . 120 refs., 71 figs., 11 tabs. 收起