Reactivity of the Gold/Water Interface During Selective Oxidation Catalysis

Abstract

The selective oxidation of alcohols in aqueous phase over supported metal catalysts is facilitated by high-pH conditions. We have studied the mechanism of ethanol and glycerol oxidation to acids over various supported gold and platinum catalysts. Labeling experiments with (18)O(2) and H(2)(18)O demonstrate that oxygen atoms originating from hydroxide ions instead of molecular oxygen are incorporated into the alcohol during the oxidation reaction. Density functional theory calculations suggest that the reaction path involves both solution-mediated and metal-catalyzed elementary steps. Molecular oxygen is proposed to participate in the catalytic cycle not by dissociation to atomic oxygen but by regenerating hydroxide ions formed via the catalytic decomposition of a peroxide intermediate.

Reaction mechanism for methanol oxidation on Au(111): A density functional theory study

“…Consistent with the previous experimental [21][22][23] and theoretical results [31][32][33], the computed E ad value of −0.09 eV indicates very weak binding between the molecular methanol and the Au surface. This unfavorable interaction may account for observed low activity of clean Au surface for methanol oxidation.…”

“…To the best of our knowledge, so far few theoretical efforts have been made with the exact purpose of disclosing the crucial reaction mechanisms of alcohol oxidation on Au(1 1 1) surface [31][32][33]. Previously, Xu et al studied the reaction mechanism for methanol oxidation on a oxygen-covered Au(1 1 1) surface by using density functional theory (DFT) method and pointed out that both methanol and methoxy were activated by oxygen adatoms [33].…”

Glycerol Oxidation in the Liquid Phase over a Gold-Supported Catalyst: Kinetic Analysis and Modelling

“…Indeed, Shang et al calculated the adsorption energy of OH − ions, as 30 kJ/mol, which has the same magnitude order as that obtained in this work, although the values were different. Zope et al [29] also reported that GLY oxidation by adsorbed OH − species was more energetically favourable than by dissolved ones. Moreover, they asserted that the role of O 2 during alcohol oxidation is an indirect one that does not involve a reaction to form the acid products, but a reduction to form the hydroperoxide adduct OOH − , this is in agreement with the kinetic model proposed in the present work.…”

Solvent-free aerobic oxidation of hydrocarbons and alcohols with Pd@N-doped carbon from glucose

“…For benzyl alcohol oxidation, the 4% Pd@C-Glu A -550 was found to be indeed more active than 4% Pd@C-Glu-550 (Supplementary Table S5), partly supporting the proposed assumption. In addition, it was reported that the basic support can improve the formation of alcoholate by means of O-H scission in the liquidphase alcohol oxidation reaction 52 . As a typical basic support, C-Glu A -550 may contribute to O-H scission in the alcohol oxidation, thus promoting the oxidation to some degree.…”