Electrooxidation of acetaldehyde on carbon-supported Pt, PtRu and Pt3Sn and unsupported PtRu0.2 catalysts: A quantitative DEMS study

Abstract

The oxidation of acetaldehyde on carbon supported Pt/Vulcan, PtRu/Vulcan and Pt 3 Sn/Vulcan nanoparticle catalysts and, for comparison, on polycrystalline Pt and on an unsupported PtRu 0.2 catalyst, was investigated under continuous reaction and continuous electrolyte flow conditions, employing electrochemical and quantitative differential electrochemical mass spectroscopy (DEMS) measurements. Product distribution and the effects of reaction potential and reactant concentration were investigated by potentiodynamic and potentiostatic measurements. Reaction transients, following both the Faradaic current as well as the CO 2 related mass spectrometric intensity, revealed a very small current efficiency for CO 2 formation of a few percent for 0.1 M acetaldehyde bulk oxidation under steady-state conditions on all three catalysts, the dominant oxidation product being acetic acid. Pt alloy catalysts showed a higher activity than Pt/Vulcan at lower potential (0.51 V), but do not lead to a better selectivity for complete oxidation to CO 2 . C-C bond breaking is rate limiting for complete oxidation at potentials with significant oxidation rates for all three catalysts. The data agree with a parallel pathway reaction mechanism, with formation and subsequent oxidation of CO ad and CH x, ad species in the one pathway and partial oxidation to acetic acid in the other pathway, with the latter pathway being, by far, dominant under present reaction conditions.

Adsorption and electrooxidation of ethylene glycol and its C2 oxidation products on a carbon-supported Pt catalyst: A quantitative DEMS study

“…the adsorption kinetics of these C 2 molecules and the composition of the adlayer [18]. This behavior closely resembles our previous observation of pronounced differences in the adsorption/oxidation behavior of ethanol [27][28][29] and acetaldehyde [27,30] on a Pt/C catalyst. Also from a practical point of view, C-C bond splitting plays an important role in the oxidation of C 2 molecules.…”

“…In contrast, oxidation of the adsorbate formed at potentials ≤0.11 V (Fig. 4c) results in a peak which is shifted to slightly higher potentials, followed by a weak signal extending up to 1.1 V. The oxidation current at high potentials observed after adsorption at low potentials closely resembles findings for ethanol and acetaldehyde adsorbate stripping after adsorption at potentials below 0.36 V [27,30]. In those cases, the Faradaic current/CO 2 ion current in the potential rage of 0.9-1.16 V was attributed to the oxidation of adsorbed hydrocarbon species.…”

“…For adsorption potentials above 0.11 V, only positive (oxidative) currents are observed. The reductive current is attributed to GA reduction to ethane and acetaldehyde (see also below), similar to the adsorption of acetaldehyde (ethane formation) under these conditions [30], while the oxidative current is associated with the oxidative adsorption of GA. Although for adsorption at 0.06 V we do not resolve an oxidative current, adsorption of GA also takes place under these conditions.…”

“…4b). Due to the significant CO 2 formation rate at potentials where OH ad formation on Pt is essentially inhibited, we tentatively relate this signal to oxidative CO 2 formation from a hydrated form of GA (two OH groups attached to the carbon atom) [42], similar to formaldehyde or acetaldehyde oxidation on Pt [24,30]. This way, CO 2 can be formed even at potentials where H 2 O splitting to OH ad is not yet possible on Pt.…”

Influence of the Particle Size Distribution on the Activity and Selectivity of Carbon‐Supported Platinum Nanoparticle Catalysts for Ethanol Electrooxidation

“…This increase is attributed to the oxidation of the Pt surface, which inhibits the CÀC bond splitting. [30] …”