In this paper, we study the electrocatalytic reduction of methyl vinyl ketone on Pt(111) and Pd-modified Pt(111) electrodes, as well as some of its expected hydrogenation derivatives and isolated... Show moreIn this paper, we study the electrocatalytic reduction of methyl vinyl ketone on Pt(111) and Pd-modified Pt(111) electrodes, as well as some of its expected hydrogenation derivatives and isolated functional moieties. The selectivity and Faraday efficiency have been calculated via sampling the catholyte solution after two hours of electrolysis. Furthermore, the adsorbates involved in the deactivation process on both surfaces were studied by means of potential opening experiments and in situ infrared spectroscopy. The Pd-modified Pt(111) electrode is very active (even mass transport limited) for the selective electrochemical hydrogenation of the C=C to 2-butanone, in the hydrogen underpotential deposition potential window (between 0 and 0.2 VRHE), with limited poisoning. Pt(111) is much less active, and poisons rapidly with adsorbed CO. The poison is formed from the C=C bond, not from the C=O moiety, as evidenced by the same poisoning occurring for ethylene. Further hydrogenation to the saturated alcohol happens at more negative potentials, but with 2-butenol as intermediate, not 2butanone, as the latter species interacts too weakly with the (111) surface. Show less
Acetol - a dehydration product of glycerol - can be selectively reduced to 1,2-propanediol and acetone through hydrogenation and dehydroxylation reactions, thereby providing a platform toward an... Show moreAcetol - a dehydration product of glycerol - can be selectively reduced to 1,2-propanediol and acetone through hydrogenation and dehydroxylation reactions, thereby providing a platform toward an efficient upgrading of biomolecules. To shed light on the relationship between the reactivity and the electrode structure, we report the electrochemical reduction of acetol on low-index platinum single crystals and their corresponding epitaxial palladium monolayers (Pd-ML). Combining cyclic voltammetry and in-situ spectroscopy measurements, Pt(110) and Pt(111) are shown to be active surfaces for acetol adsorption and reduction at potentials near 0 V vs.RHE, though accompanied by the dissociative adsorption of acetol to poisoning CO. For the Pt(100) surface, the activities of both acetol reduction and hydrogen evolution are inhibited by the most prominent CO poisoning among the three surfaces. In contrast, no electrochemical acetol reduction is detected on palladium monolayer near 0 V vs.RHE, irrespective of the surface crystallographic orientation. However, acetol decarbonylation still proceeds especially on PdMLPt(110), which suffers from the most severe poisoning from the low-index surfaces. Furthermore, to access practical applications, we extend the study on the effect of the electrode material, the applied potential, and the electrolyte pH on the selectivity of acetol reduction. At sufficiently negative potentials, Au and Pt are appropriate candidates toward hydrogenation reaction to 1,2-propanediol at Ph = 3, whereas Pd exhibits the ability to produce both 1,2-propanediol and acetone at pH = 1 and pH = 3, the selectivity of which is strongly dependent on the potential. Given these mechanistic insights into acetol adsorption and reduction at the specific electrodes and facets, this work provides guidance on how to rationally design electrocatalysts toward efficient electrochemical hydrogenation. (C) 2021 The Authors. Published by Elsevier Ltd. Show less
Among heterogeneous electrocatalysts, gold comes closest to the ideal reversible electrocatalysis of CO2 electrochemical reduction (CO2RR) to CO and, vice versa, of CO electroxidation to CO2 (COOR)... Show moreAmong heterogeneous electrocatalysts, gold comes closest to the ideal reversible electrocatalysis of CO2 electrochemical reduction (CO2RR) to CO and, vice versa, of CO electroxidation to CO2 (COOR). The nature of the electrolyte has proven to crucially affect the electrocatalytic behavior of gold. Herein, we expand the understanding of the effect of the widely employed bicarbonate electrolytes on CO2RR using gold monocrystalline electrodes, detecting the CO evolved during CO2RR by selective anodic oxidation. First, we show that CO2RR to CO is facet dependent and that Au(110) is the most active surface. Additionally, we detect by in situ FTIR measurements the presence of adsorbed COtop only on the Au(110) surface. Second, we highlight the importance of acid-base equilibria for both CO2RR and COOR by varying the electrolyte (partial pressure of CO2 and the concentration of the bicarbonate) and voltammetric parameters. In this way, we identify different regimes of surface pH and bicarbonate speciation, as a function of the current and electrolyte conditions. We reveal the importance of the acid-base bicarbonate/carbonate couple, not only as a buffering equilibrium but also as species involved in the electrochemical reactions under study. Show less
