Normalized differential reflectance spectroscopy at polycrystalline platinum electrodes in aqueous acidic electrolytes: Quantitative aspects

Ping Shi, Iosif Fromondi, Daniel Alberto Scherson

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2 Citations (Scopus)

Abstract

The intensity of monochromatic light (λ = 633 nm) reflected off the surface of a polycrystalline Pt electrode, R, has been measured in situ as a function of potential, E, during continuous voltammetric cycles in the range -0.25 < E < 1.05 V vs. SCE, both in 0.5 M HClO 4 and 0.5 M H 2SO 4 aqueous solutions. Plots of the normalized differential reflectance, ΔR/R = [R(E sam) - R(E ref)] / R(E ref) vs. Q n, where E sam and E ref refer to the sampling and reference potentials, respectively, and Q n is the coulometrically determined relative oxide charge (in terms of e/Pt surface atom), were found to deviate from linearity in the PtOH formation region. Improved proportionality between ΔR/R and Q n was achieved up to Q n = 1, upon correcting ΔR/R for double layer effects using the method originally reported by Conway et al. [3]. In the case of 0.5 M H 2SO 4, however, remaining discrepancies could only be resolved by accounting for the charge due to bisulfate desorption induced by PtOH formation on the surface. On the basis of these results, it has been concluded that for both types of electrolytes, ΔR/R is proportional to the PtOH coverage, θ, and independent of the applied potential for Q n ≤ 1, opening new prospects for monitoring θ quantitatively during the course of faradaic reactions.

Original languageEnglish
Pages (from-to)1307-1318
Number of pages12
JournalZeitschrift fur Physikalische Chemie
Volume221
Issue number9-10
DOIs
Publication statusPublished - 2007 Oct 30
Externally publishedYes

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Keywords

  • Adsorption
  • In situ methods
  • Oxide formation
  • Platinum
  • Reflectance spectroscopy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics

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