The electro-oxidation of D-and L-glucose has been investigated using the chiral electrode Pt{643} R and its enantiomorph Pt{643} S . Both electrodes are demonstrated to be enantioselective. We ascribe this behavior to the inherent (left or right) "handedness" of kink sites present at the surface. In contrast, no difference in D-and L-glucose oxidation could be detected using stepped Pt{211} and Pt{332} electrodes. Stepped surfaces are achiral, since they lack the prerequisite necessary for the observation of chirality, namely kink sites. For Pt{531}, a surface which contains only kink sites, a diastereomeric product excess of ∼80% is estimated for D-and L-glucose oxidation. This compares with a value of ∼60% for Pt{643}. Hence, the chiral discrimination appears to scale with the surface density of kink sites. These findings constitute the first experimental proof that chiral discrimination is an intrinsic property of kinked single-crystal surfaces.

The adsorption of CO and the electrochemical oxidation of a CO adlayer on stepped Pt electrodes, Pt(443), Pt(332), and Pt(322), has been studied using in situ infrared reflection−absorption spectroscopy (IRAS). Coverage-dependent and potential-dependent spectra of CO adlayers on stepped Pt surfaces are reported. Infrared spectra acquired during oxidation of the CO adlayer provide information on the mechanism of the reaction and the structure of the operational catalytic active site. CO adsorbed on the (111) terraces is found to be more reactive compared to that adsorbed on either (110) or (100) steps. The step trough of either (110) or (100) step is concluded to be the active site for the electrocatalytic oxidation of the CO adlayer, the most reactive combination involving CO from the terrace and an oxygen-containing species in the step trough.

We have combined in situ photoelectrochemical and spectroscopic techniques (Attenuated Total Reflection Infrared, ATR-IR, and Resonance Raman Spectroscopy) for the study of the charge-transfer complex formed upon adsorption of catechol on anatase nanoparticles in contact with aqueous acidic solutions. Vibrational spectroscopies reveal the existence of at least two adsorbate configurations: catecholate in a chelate configuration and molecularly adsorbed catechol, with apparent values of -12.3 and -10.5 kJ mol(-1), respectively. These values are significantly less negative than the values reported for anatase colloidal dispersions. The adsorption of both catechol species on the nanoparticulate anatase thin films follows the Freundlich isotherm. As revealed by resonance Raman spectroscopy, only the adsorbed chelating catecholate forms the charge-transfer complex. The electron transfer from the adsorbate to the anatase nanoparticles has been evidenced by the development of a negative photopotential upon 514.5 or 632.8 nm laser illumination of an anatase nanostructured thin film electrode in contact with a catechol solution. The time evolution of the Raman spectra shows an increasing fluorescence indicating that, upon electron injection, catechol polymerization occurs on the TiO2 surfaces. This conclusion is confirmed by in situ ATR-IR measurements, which show a progressive broadening of the catecholate bands together with the appearance of new signals. This study illustrates the benefits of combining electrochemical, infrared, and Raman techniques for the elucidation of processes occurring at the semiconductor/solution interface. Finally, evidence is given on the different adsorption and reactivity behavior found for suspensions and nanoporous thin films under equivalent experimental conditions.

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