ON THE ELECTROCHEMICAL-BEHAVIOR OF SQUARIC ACID ON PT(HKL) ELECTRODESIN ACID-SOLUTIONS - A VOLTAMMETRIC AND IN-SITU FTIRS STUDY

The adsorption and oxidation reactions of squaric acid (SQA) at platin um single crystal electrodes with basal orientations have been studied by combining voltammetric and in situ FTIR experiments. Squaric acid is adsorbed dissociatively at these platinum surfaces, giving rise to dense CO adlayers in a potential-dependent structure-sensitive process . The resulting CO adlayers have been characterized spectroscopically and found similar to those formed at each electrode surface after dosi ng CO from a saturated solution. The main reaction path in the SQA oxi dation mechanism involves the formation and subsequent oxidation of ad sorbed CO to carbon dioxide, which is the main reaction product at pot entials higher than 1.10 V. Both the adsorption of squarate anion and the formation of cyclobutantetrone as an intermediate product are limi ted by the formation of the CO adlayer. These two species have been de tected in a significant amount only in the case of Pt(111), for which the rate of CO formation from SQA between 0.7 and 1.0V is the lowest a mong the basal orientations.