Ethanol oxidation on shape-controlled platinum nanoparticles at different pHs: A combined in situ IR spectroscopy and online mass spectrometry study

• Ethanol electrooxidation on shaped Pt nanoparticles is investigated.
• Solutions with different pHs (< 4) are studied.
• A combined ATR and DEMS approach is employed.
• The rate for CC bond breaking diminishes as pH increases.
• (100) domains are more active for CC bond breaking than (111) ones.

Ethanol oxidation on different shape-controlled platinum nanoparticles at different pHs was studied using electrochemical, Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and, especially, Differential Electrochemical Mass Spectrometry (DEMS) techniques, the latter giving interesting quantitative information about the products of ethanol oxidation. Two Pt nanoparticle samples were used for this purpose: (100) and (111) preferentially oriented Pt nanoparticles. The results are in agreement with previous findings that the preferred decomposition product depends on surface structure, with COads formation on (100) domains and acetaldehyde/acetic acid formation on (111) domains. However, new information has been obtained about the changes in CHx and CO formation at lower potentials when the pH is changed, showing that CHx formation is favored against the decrease in CO adsorption on (100) domains. At higher potentials, complete oxidation to CO2 occurs from both CHx and CO fragments. In (111) Pt nanoparticles, the splitting of CC bond is hindered, favoring acetaldehyde and acetate formation even in 0.5 M H2SO4. C1 fragments become even less when the pH increases, being nearly negligible in the highest pH studied.