Spectroscopic and non-electrochemical studies

Both these concerns were addressed by the development of modified IR techniques. In the technique of Subtractively Normalised Fourier Transform IR Spectroscopy (SNIFTIRS) or Potential Difference IR (SPAIRS or PDIR) [37], the increased stability and sensitivity of Fourier Transform IR is exploited, allowing usable spectra to be obtained by simple subtraction and ratioing of spectra obtained at two potentials without the need for potential modulation or repeated stepping. A second technique which does not call for potential modulation, but actually modulates the polarisation direction of the incoming IR beam is termed Photo-elastically Modulated Infra-Red Reflectance Absorption Spectroscopy (PM-IRRAS) this was applied to the methanol chemisorption problem by Russell and co-workers [44], and Beden s assignments verified, including the potential-induced shift model for COads. 

Normal SNIFTIRS or FTIR Potential Step experiments also show a steady increase in coverage of COads with increasing potential and time (Fig. 18.7) [48-51]. Simple potential step experiments on polycrystalline Pt surfaces show clear peaks at 2050cm-1 and 1836cm-1, which can be 

The Potential Step FTIR method has now become the preferred approach for exploring the nature of chemisorbates at the surface, and an intensive attack has been carried out using this and related techniques on 

More recent combined STM/IRRAS studies [62] of CO adsorption on Pt(lll) from HCIO4 solution have shown that for saturation coverage, and for E 0.25 V, a (2 x 2)-3CO adlayer forms possessing both terminal and 

If the electrode potential is now swept sufficiently positive for the COads to disappear completely, and then reversed, a clear (V3 x V3)R30° LEED pattern is observed. By contrast, in HC104, there is little evidence of adsorbed anion structure. For methanol oxidation in sulphuric acid on Pt(lll), no structure is seen until E 0.3 V, when LEED showed a disordered (V7 x /7)R19.10 pattern, with bands at 1249 and 1343 cm-1 associated with HSO4. At more positive potentials ( 0.5 V), the 1250 cm-1 band disappears and the 1343 cm-1 band becomes very sharp, as does the V7 structure. Above 0.9 V, however, the current begins to decrease (v.s.) and the V7 structure also begins to deteriorate. There does appear to be some correlation between this structure and activity to methanol oxidation on Pt(lll) in addition, the ratio 0hso4/0co is always higher for methanol oxidation than CO oxidation. 

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