An in situ IR reflectance spectroscopic study of the electro-oxidation of D-sorbitol on platinum

An in situ infrared (IR) reflectance spectroscopic study of the electrooxidation of D-sorbitol on polycrystalline platinum in perchloric acid medium was carried out by Fourier transform IR spectroscopy (FTIRS), under the SNIFTIRS and SPAIRS variants. Additional information was obtained by electrochemically modulated IR reflectance spectroscopy (EMIRS). In situ IR spectra show that the electrooxidation of D-sorbitol on platinum proceeds via a dual-path mechanism involving both reactive and poisoning intermediates. Linearly and bridge-bonded CO, resulting from the dissociative adsorption of D-sorbitol, which were identified as the main poisoning species present at the surface, are fully oxidised to CO₂ at higher potentials. The superficial coverage in adsorbed CO was found to be function of the electrode potential. Moreover, the electrooxidation process can occur without breaking the initial molecule skeleton, indicating that molecular adsorption of D-sorbitol is also possible. D-glucono-(δ and γ)-lactones, D-glucose and CO₂ were identified as the main reaction products.