Search for multi-functional catalysts: The electrooxidation of acetaldehyde on Platinum–Ruthenium–Rhodium electrodeposits

Abstract

a b s t r a c tPreliminary studies on the influence of Platinum-Rhodium electrodeposits upon the rate of acetaldehyde electrooxidation showed that Rhodium plays a dual role during electrooxidation, because it favors the break of C-C bonds whilst prevents the deliverance of oxygen-containing species, thus inhibiting the oxidation steps. Based on these results, in this work Platinum-Ruthenium and Platinum-Ruthenium-Rhodium electrodeposits were prepared and characterized by electrochemical and spectroscopic methods (FTIR in situ). The addition of Ruthenium is justified by its ability to promote a facile oxidation of adsorbed species by activation of water molecules. The results indicate a compromise between the existence of superficial sites able to break carbon chains (provoked by Rhodium) and responsible by the oxidation of adsorbed species (provoked by Ruthenium). Among the atomic compositions investigated, PtRuRh (73:23:04) shows the maximum activity towards acetaldehyde electrooxidation, but the production of acetic acid seems to be the main responsible for this activity.

Ethylene Glycol Electro-Oxidation on Platinum-Free Surfaces: How the Composition of PdRuRh Surfaces Influences the Catalysis

“…These data are in line with those observed for Pt-Ru-Rh catalysts. 23 Furthermore, as the catalyst is enriched by Ru the currents associated to the reduction of oxides (the ill-defined cathodic waves at ca. 0.6 V) become less prominent while the currents in the double layer region grow.…”

“…22 On the other hand, Rh is known to have the ability to break C−C bonds, as already shown for the electro-oxidation of acetaldehyde. 23,24 In this context, several spectroelectrochemical studies address the electrooxidation of EG in the past few years, [25][26][27] but the use of ternary catalysts Pd-Ru-Rh is unprecedented in the literature.…”

Oxidation of isotopically-labeled ethanol on platinum–tin–rhodium surfaces: Enhancing the production of CO2 from methyl groups

“…For the estimation of the surface areas we used the CO-stripping procedure in a 0.1 M HClO 4 solution, as described elsewhere [8]. The charge involved in the oxidation of a monolayer of adsorbed CO was used to estimate the surface areas, assuming a charge density of 420 μC cm −2 .…”

“…It is already well-established that ad-atoms, such as Ru [7,8], Rh [9] and Sn [10] catalyze the electro-oxidation of ethanol (and related species) compared to Pt alone. Ad-atoms can accelerate reactions (i) by supplying oxygen donor species (coming from water molecules) at lower potentials than Pt [11]; (ii) via electronic effects, in which ad-atoms likely induce changes in the energies of the adsorbent sites [12]; (iii) or via blocking of those sites required for the formation of poisoning species, as adsorbed CO and molecular fragments (third-body effect) [13].…”

Electrooxidation of ethanol on Pt and PtRu surfaces investigated by ATR surface-enhanced infrared absorption spectroscopy

“…7,14,15 Unfortunately, using electrodeposited surfaces causes a noticeable reduction of the band intensities referent to adsorbed CO. 16 The reason for this effect probably originates from scattering of part of the infrared radiation provoked by the rough structure of the surface. 16,17 As a consequence, important information concerning the role played by CO during the electrooxidation of organic molecules is often lost when investigating electrodeposits.…”