Structure sensitivity of electrochemical adsorption and reduction of acetol on noble metal electrodes

Abstract

Abstract 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 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 (PdML). 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\xa0V 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\xa0V 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\xa0=\xa03, whereas Pd exhibits the ability to produce both 1,2-propanediol and acetone at pH\xa0=\xa01 and pH\xa0=\xa03, 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.