Ethanol electro-oxidation on carbon-supported Pt–Ru, Pt–Rh and Pt–Ru–Rh nanoparticles

This work investigates the effects of carbon-supported Pt, Pt–Ru, Pt–Rh and Pt–Ru–Rh alloy electrocatalysts on the yields of CO2 and acetic acid as electro-oxidation products of ethanol. Electronic and structural features of these metal alloys were studied by in situ X-ray absorption spectroscopy (XAS). The electrochemical activity was investigated by polarization experiments and the reaction intermediates and products were analyzed by in situ Fourier Transform Infra-Red Spectroscopy (FTIR). Electrochemical stripping of CO, which is one of the adsorbed intermediates, presented a faster oxidation kinetics on the Pt–Ru electrocatalyst, and similar rates of reaction on Pt–Rh and Pt. The electrochemical current of ethanol oxidation showed a higher value and the onset potential was less positive on Pt–Ru. However, in situ FTIR spectra evidenced that the CO2/acetic acid ratio is higher for the materials with Rh, mainly at lower potentials. These results indicate that the Ru atoms act mainly by providing oxygenated species for the oxidation of ethanol intermediates, and point out an important role of Rh on the CC bond dissociation.