In Situ Infrared Spectroscopic Studies of Adsorption of Lactic Acid and Related Compounds on the TiO2 and CdS Semiconductor Photocatalyst Surfaces from Aqueous Solutions

In situ attenuated total reflectance infrared (ATR-IR) spectroscopy has been used to determine the structure of adsorbed lactic acid (LA) compounds on the surfaces of titanium dioxide (TiO2) and cadmium sulfide (CdS) photocatalysts. LA was found to chelate onto the TiO2 in a b identate fashion, while in the CdS case, LA was adsorbed electrostatically as the lactate ion. These differing surface interactions are likely to determine the selectivity in the photo-products of LA.