Controlling the Hydrophilicity of the Electrochemical Interface to Modulate the Oxygen-Atom Transfer in Electrocatalytic Epoxidation Reactions

Abstract

The electrocatalytic epoxidation of alkenes at heterogeneous catalysts using water as the sole oxygen source is a promising safe route toward the sustainable synthesis of epoxides, which are essential building blocks in organic chemistry. However, the physico-chemical parameters governing the oxygen-atom transfer to the alkene and the impact of the electrolyte structure on the epoxidation reaction are yet to be understood. Here, we study the electrocatalytic epoxidation of cyclooctene at the surface of gold in hybrid organic/aqueous mixtures using acetonitrile (ACN) solvent. Gold was selected, as in ACN/water electrolytes gold oxide is formed by reactivity with water at potentials less anodic than the oxygen evolution reaction (OER). This unique property allows us to demonstrate that a sacrificial mechanism is responsible for cyclooctene epoxidation at metallic gold surfaces, proceeding through cyclooctene activation, while epoxidation at gold oxide shares similar reaction intermediates with the OER and proceeds via the activation of water. More importantly, we show that the hydrophilicity of the electrode/electrolyte interface can be tuned by changing the nature of the supporting salt cation, hence affecting the reaction selectivity. At low overpotential, hydrophilic interfaces formed by using strong Lewis acid cations are found to favor gold passivation. Instead, hydrophobic interfaces created by the use of large organic cations favor the oxidation of cyclooctene and the formation of epoxide. Our study directly demonstrates how tuning the hydrophilicity of electrochemical interfaces can improve both the yield and selectivity of anodic reactions at the surface of heterogeneous catalysts.

Disclosing the interfacial electrolyte structure at Na-insertion electrode materials: origins of desolvation phenomenon

“…License: CC BY-NC-ND 4.0 the solvent arrangement. 68,69 Here, as a reference (z = 0), the distance corresponding to the minimum of each PMF is taken, being different from the density profile plots discussed earlier. Since there is no free energy barrier in approaching a Na + ion to the graphite surface in DMC or EC-DMC (Figure 6a), it can easily penetrate the closest solvent layer to the surface.…”

Correlating substrates reactivity at electrified interfaces with electrolyte structure in synthetically relevant organic solvent/water mixtures

“…Nevertheless, the past few years have seen a growing interest being paid to the role of non-covalent interactions in liquid electrolytes and at electrochemical interfaces, with numerous demonstrations of their role in governing the outcome of electrocatalytic and electrosynthetic reactions. [1][2][3] Hence, both the kinetics and selectivity of aqueous electrocatalytic reactions have been tuned by electrolyte engineering approaches, in particular through the use of tailored supporting salt ions. Pivotal results were obtained for the hydrogen evolution reaction (HER), 4,5 the oxygen evolution reaction (OER) 6,7 and the CO2 and N2 reduction reactions.…”

“…22,25 These mixtures constitute a novel class of electrolytes and offer a formidable playground to tune electrocatalytic and electrosynthetic reactions via the modulation of the electrolyte nano/microstructure. 1 Indeed, while binary mixtures https://doi.org/10.26434/chemrxiv-2024-g1jhk ORCID: https://orcid.org/0000-0003-2300-7582 Content not peer-reviewed by ChemRxiv. License: CC BY-NC-ND 4.0 of water and water-soluble organic solvents are macroscopically homogeneous, bulk heterogeneity can occur at different length scales depending on the molar fraction of water and the nature of the organic solvent.…”

Merging Electrocatalytic Alcohol Oxidation with C-N Bond Formation by Electrifying Metal-Ligand Cooperative Catalysts

“…Further increasing the amine loading did not improve yield, nor the pre-activation of the catalyst with excess of strong base (Table 1, entry 1 and 2). Given the important effect of electrolyte cations, 44,45 the electrolyte composition was probed (NaOH, KOH, and CsOH), but resulted in reduced yields and conversions of BnOH (Table 2, entries 2-4). The size of anions (Cs2CO3, Li2CO3) also reduced yields and conversion of BnOH (Table 2, entries 5-6).…”