Electrochemical oxidation of carbon monoxide, methanol, formic acid, ethanol, and acetic acid on a platinum electrode under hot aqueous conditions

Using a pressure cell equipped with an Ag ∣ AgCl ∣ 0.1 M KCl external pressure-balanced reference electrode (EPBRE), hydrogen, methanol, formic acid, carbon monoxide, ethanol, acetic acid, and glucose were electrochemically oxidized on a Pt electrode under hot aqueous conditions (365−525 K), and the polarization curves were obtained at a sweep rate of 1 or 10 mV s−1. The potential measured versus EPBRE was corrected to the RHE scale based on the experimentally or theoretically calculated pH of the solution at high temperature. During methanol and carbon monoxide oxidation, a strongly adsorbed intermediate presumably CO, was formed but it was oxidized at a lower potential than under ambient temperature. Formic acid was rapidly oxidized around 0 V versus RHE without formation of this adsorbed intermediate. Using a gas mixture of hydrogen and carbon monoxide, it was confirmed that the surface coverage by CO was decreased dramatically with a temperature increase from 425 to 475 K under hot aqueous conditions. Ethanol and acetic acid were also satisfactorily oxidized, but the trial to measure the electrochemical oxidation behavior of glucose was not successful due to the adhesion of char-like compounds to the electrode.