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首页> 美国政府科技报告 >Atomic structure of active sites in O(sub 2) reduction on Au(111)/Tl(sub ad) electrodes in acid and alkaline solutions
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Atomic structure of active sites in O(sub 2) reduction on Au(111)/Tl(sub ad) electrodes in acid and alkaline solutions

机译：酸性和碱性溶液中au（111）/ Tl（亚ad）电极O（sub 2）还原活性位点的原子结构

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Surface x-ray scattering has been used to determine the structure of Tl adlayers on the Au(111) electrode surface during the course of 0(sub 2) reduction. 0(sub2)reduction is considerably catalyzed by Ti adlayers on Au(111). The half-wave potential is shifted to more positive values in the presence of the Ti adlayer. In both, acid and alkaline solutions Ti causes a change in the reaction mechanism from a 2e-reduction to a 4e-reduction in a limited potential range. The in-plane x-ray diffraction measurements revealed that the close-packed rotated-hexagonal Ti phase, which exists in the potential range between -0.4V and the bulk Ti deposition at (approx.) -0.7 V, has a lower activity for O(sub 2) reduction than the low-coverage phases in both solutions. It supports a 2e-reduction. O(sub 2) reduction does not change the Ti coverage in this phase but causes a significant decrease of the in-plane diffracted intensity. The lower coverage phases which exist at more positive potentials, viz., aligned hexagonal in alkaline solution and patches of the (2 (times) 2) Ti phase in acid solution, are conducive to a 4e-reduction. The diffraction intensity from these two phases, however, vanishes quickly during O(sub 2) reduction. It appears that the Ti coverage remains on the surface unchanged. These observations indicate that the O(sub 2) molecules interact directly with the Ti atoms prior to the charge transfer. This provides the most direct evidence that the outer sphere charge transfer mechanism in O(sub 2) reduction is not operative for some surfaces. H(sub 2) O(sub 2) reduction is facile on the surface covered with the low-coverage Ti phases, while it is almost completely suppressed by the rotated-hexagonal phase.

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