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O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.80: Poster

Mittwoch, 29. März 2006, 14:30–17:30, P2

Reactivity studies of formic acid oxidation on the bare and the Cu modified Pd(111) surface — •Klaus Wandelt, Katrin Brandt, and Marco Steinhausen — Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, D-53115 Bonn, Germany

FTIRS, CV and AES have been used to investigate the reactivity of formic acid oxidation on the bare and the Cu modified Pd(111) surface as a function of potential, electrolyte and surface composition. This reaction has thus been studied in pure formic acid as well as in 10 M and 5 mM aqueous formic acid solution. Carbon dioxide evolution which was characterised by the asymmetric O=C=O stretching vibration at 2345 cm⁻¹ has been employed as "probe" for the surface reactivity.
The spectroscopic characterisation of HCOOH/Pd(111) points to an extraordinary acceleration of CO₂ evolution at the electrode as the potential is increased above 0.45 V. Analysis of IR-measurements at constant potentials lead to the assumption that the electronic state of the solid/liquid interface in the open-circuit HCOOH/Pd(111)-H₂SO₄-system corresponds to that at about 0.4 V vs. RHE. Water as solvent plays an important role in formic acid oxidation as a decrease in formic acid concentration in the electrolyte results in an augmentation of the relative reactivity normalized to the number of formic acid molecules in solution. Depending on the direction of the potential scan the rate of formic acid oxidation is inhibited or accelerated by electrochemically deposited Cu on the Pd(111)-surface.