Surface structure and anion effects in the oxidation of ethanol on platinum nanoparticles

Abstract

Ethanol oxidation on platinum nanoparticles with well-characterized surfaces is studied using cyclic voltammetry and FTIR techniques. Their behavior is compared with that obtained for platinum single crystal electrodes, in order to rationalize their performance and to understand the effects of the surface structure and anion adsorption on the reactivity. The results clearly demonstrate that there are strong effects of anion adsorption and surface structure on the measured current and oxidation mechanism.Thus, the main product of ethanol oxidation on (111) preferentially oriented Pt nanoparticles is acetic acid, and the amount of CO 2 produced can be considered negligible. On the other hand, (100) preferentially oriented Pt nanoparticles are effective for the cleavage of the C-C bond yielding adsorbed CO, which eventually is oxidized to CO 2 . This nanoparticles electrode has the highest catalytic activity at high potentials, whereas (111) preferentially oriented Pt nanoparticles are more active at low potentials.In addition, no significant differences in the activity are reported by using different supporting electrolytes, which indicates that adsorbed acetate, which results from the adsorption of acetic acid, hinders ethanol oxidation.

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

“…For this reason, these results have to be extended to nanoparticles, which can be effectively applied such systems. As previously demonstrated, the effect of the particular arrangement of the atoms at the surface on the resulting ethanol oxidation activity is valid also for nanoparticles [8], thus highlighting the importance of gaining control of the surface structure of the nanoparticles to increase their electrocatalytic activity. Similar results on the effect of the surface structure of the nanoparticles for other important reactions such as oxygen reduction or other small organic molecule oxidations have been already reported [9][10][11][12][13][14][15][16].…”

“…Very briefly, the predominant shape was cubic for (100) Pt nanoparticles and octahedral for (111) ones. The particle size of both nanoparticles batches was estimated to be about [8][9][10] nm. The electrodes were prepared by depositing a droplet (4 μL) of the aqueous solution containing the nanoparticles on a hemispherical gold substrate, after which the electrode was protected under an Ar stream until complete solvent evaporation.…”

“…Also, and in comparison with previous works [7,8], the ethanol concentration is lowered to prevent problems with membrane saturation in the DEMS experiments. As mentioned before, experiments were carried out at pH values below 4 to avoid carbonate formation from the reaction of CO2 with water, which can mask the CO2 efficiency.…”

Oxidation of ethanol on platinum nanoparticles: surface structure and aggregation effects in alkaline medium

“…With this aim, nanoparticles with different shapes, that is, with different distribution of well-ordered crystallographic domains, have been synthesized. These different nanoparticles have previously allowed extending the correlations between surface structure and reactivity observed with single crystal electrodes for several reactions such as the oxidations of formic acid, methanol, ethanol or ammonia [10][11][12][13] or the reduction of oxygen [14]. Additionally, in some cases, the behavior of the nanoparticle electrodes differs from that observed with single crystal electrodes [15,16].…”

“…3) to study the surface structure effect and to establish correlations with previous results with single crystal electrodes [35]. In addition, the behavior could be compared with that of the same Pt nanoparticles in acidic solutions [12]. In all the experiments, the upper potential limit was set to 0.95 V to avoid changes on the surface structure of the Pt nanoparticles due to oxide formation.…”