Electrooxidation of C₄ Polyols on Platinum Single-Crystals: A Computational and Electrochemical Study

Abstract

Many polyols are abundant and cheap molecules highly spread in the biomass. These molecules have an enormous potential to be used in electrochemical devices to generate energy and/or value-added molecules. The electrooxidation of polyols can produce different substances of interest in the chemical industry concomitantly to high purity hydrogen in electrolyzers. The cost in the production of all these chemicals depends, among other factors, on the develop of more active and selective catalysts. However, in order to search for these materials using computational experiments, it is mandatory to have a better understanding of the fundamental aspect of the reactions, which permit to base the search on the adsorption energies of one or more key reaction intermediates. To contribute to this task, we performed (spectro)electrochemical and computational experiments to study the electrooxidation of C 4 polyols. We show that the electrooxidation of polyols does not depend on the relative orientation of their OH groups. Besides, using Pt single crystals, we demonstrate that the trend for the oxidation of the primary carbon (relative to the secondary) increases in the order Pt(111) < Pt(100) < Pt(110) and that this result can be extended to polyols with longer carbon chains. Finally, computational experiments permit us to rationalize these trends looking at the relative stability of double dehydrogenated intermediates on the Pt basal planes.

An Overview of Glycerol Electrooxidation Mechanisms on Pt, Pd and Au

“…Besides, as found by Koper et al. and Greeley et al., another intermediate that is adsorbed onto Pt(111) by two terminal carbon atoms can be a poisoning species, as the following deprotonation is hard to proceed [33,41, 42] . For those two intermediates to proceed to further deprotonation, two sub‐pathways exist and take effect based on whether there is Pt‐OH(ads).…”

“…Recent GEOR studies have proposed many reaction pathways and mechanisms, contributed by, among others, the groups of Koper, [30,33,34] Coutanceau, [55,74,137] Fernández [37,38,42,134] and Martins [17,84,138] . Soluble intermediates and products are well established by experiment, but evidence for surface‐adsorbed intermediates comes mainly from DFT studies.…”

Highly active Ag/C nanoparticles containing ultra-low quantities of sub-surface Pt for the electrooxidation of glycerol in alkaline media

“…Something similar is likely occurring in Pt(1%)Ag/C, where the Pt atoms are highly dispersed and, consequently, the probability of finding neighboring Pt atoms in this catalyst is much lower than in Pt/C, thus justifying the diminution in the production of CO3 -2 . This fact can also explain the higher tolerance to poisoning of the Pt(1%)Ag/C, once that multiple bonded intermediate are the precursors of CO and/or other still non-identified poisoning intermediates [34].…”

Using the site-knockout strategy to understand the low activity of the nitrate electro-reduction reaction on Pt(111)

“…21 To gain insight into the mechanism complexity and aid in investigating the electrochemical steps and different reaction pathways, density functional theory (DFT) calculations appear as an essential tool to reveal critical information at the atomic level. 15,[23][24][25][26] In the present study, we studied the effect of available continuous sites in the first NO 3 RR step. Therefore, we modified Pt(111) with cyanide ions (Pt(111)-CN), forming hexagonal patterns, 27,28 where the CN groups are adsorbed on top of the platinum atoms through the carbon atom.…”

“…21 To gain insight into the mechanism complexity and aid in investigating the electrochemical steps and different reaction pathways, density functional theory (DFT) calculations appear as an essential tool to reveal critical information at the atomic level. 15,23–26…”