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Platinum surfaces in perchloric acid: Pt(111), Pt(100), Pt(110) – perchlorate

  • M. NowickiEmail author
  • K. Wandelt
Part of the Condensed Matter book series (volume 45B)

Abstract

In this chapter the experimental results on adsorption of perchlorate ion on Pt(111), Pt(100) and Pt(110) surfaces are described.

The difference between different anion adsorption behavior and structure is a consequence of two fundamental properties: interaction strength, which on all low-index surfaces increases in the order ClO4 < SO42− < Cl < Br < I, and the symmetry of the anion and the surface, e.g., for the tetrahedral (bi)sulfate anions, the interaction strength increases from Pt(100) ≈ Pt(110) to Pt(111), while the spherical halide anions are more strongly bound on (100) than on (111) sites.

No specific ClO4 adsorption/desorption peaks are found with all three low-index planes of Pt in 0.01 M aqueous perchlorate solution. Instead, on Pt(111) hydrogen upd [under-potential deposition] (at 0.0–0.3 V vs. Pd/H), OH adsorption (at 0.5–0.8 V vs. Pd/H), and finally surface oxidation (at 0.95–1.1 V vs. Pd/H) are observed. Both the OHad and oxide states are perturbed significantly as the perchlorate concentration increases suggesting a competition between OH and ClO4 adsorption. The H-upd region remains unchanged, but ClO4 decomposition to Cl is reported (see Cu-ClO4 in Chap.  192[ https://doi.org/10.1007/978-3-662-53908-8_192]).

On Pt(100) from 0 to 0.1 V (Pd/H), the oxidation (2H → 2H+) of hydrogen gas, previously formed in a more negative going sweep, is recorded. Between 0.1 and 0.4 V, a broad range of hydrogen upd starts to overlap with the adsorption of OH up to 0.6 V. At potentials >0.8 V, the Pt(100) surface is oxidized. So, H upd on Pt(100) differs from the narrower range of H upd on Pt(111). In contrast to Pt(111), no variation of the onset of electrooxidation is found.

On Pt(100) the upd region consists of two states at 0.09 V and 0.22 V. Electrochemical oxide formation happens between 0.7 and 0.9 V with a large oxide peak at 0.96 V (Pd/H). Also on Pt(110) and Pt(311), marginal changes in the onset of electrooxidation are recorded, again suggesting the competitive adsorption of ClO4 anions.

All in all the interaction strength of ClO4 increases in the sequence Pt(111)>Pt(311)>Pt(110)>Pt(100), probably due to the abundance of threefold hollow sites on the respective surface [1, 2, 3].

References

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    Markovic, N.M., Ross, P.N.: Surf. Sci. Rep. 45, 117 (2002)ADSCrossRefGoogle Scholar
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    Sawatari, Y., Inukai, J., Ito, M.: J. Electron Spectrosc. Relat. Phenom. 64(65), 515 (1993)CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany 2018

Authors and Affiliations

  1. 1.Institute of Experimental PhysicsUniversity of WroclawWroclawPoland
  2. 2.Institute of Physical and Theoretical ChemistryUniversity of BonnBonnGermany

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