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Electrochemistry Communications 124 (2021) 106944
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Electrochemistry Communications
Au-catalyzed electrochemical oxidation of alcohols using an
electrochemical column flow cell
Tatsuya Suga, Naoki Shida*, Mahito Atobe*
Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords:
A novel green system for the electrochemical oxidation of alcohols is demonstrated using a column flow cell.
Voltammetric analysis revealed that the oxidation of 1-phenylethanol and benzaldehyde are promoted by using
both an Au-electrode and an alkaline medium. To conduct such reaction with a column flow cell, we developed a
method to modify a carbon-fiber thread with Au nanoparticles. The column carbon-fiber thread electrode
modified with Au nanoparticles showed a high surface area, enabling the efficient electrochemical oxidation of
various alcohols.
Electrosynthesis
Electrochemical oxidation
Alcohol oxidation
Au catalyst
Electrochemical column flow cell
1. Introduction
heterogeneous transition-metal electrocatalysts are also being actively
investigated because of their high productivity and durability.
The oxidation of alcohols is a fundamentally important class of re-
action at both the laboratory and commercial scale [1,2]. Classical
alcohol oxidations have been carried out using stoichiometric or excess
amounts of oxidants such as hypochlorite, chromium, manganese,
chlorine gas, and peroxides [3]. These oxidants are hazardous, corro-
sive, and/or toxic and also result in an equimolar amount of chemical
waste. Hence, alternative environmentally benign strategies for the
oxidation of alcohols are desired from the viewpoint of sustainability.
Oxidation with heterogeneous or homogeneous catalysts using O2 as a
terminal oxidant has been developed, with excellent examples reported
in the literature [1,4–6]; however, achieving high levels of productivity,
durability, chemoselectivity, and sustainability is difficult. Another op-
tion for the development of a green oxidation process is electrochem-
istry, where redox reactions occur at the electrode surface, driven by
electric energy instead of by chemical reagents. When the cathodic re-
action is a proton reduction reaction, hydrogen gas is generated as the
sole byproduct. In addition, the use of electricity generated from
renewable sources makes the whole process even greener; thus, the
electrochemical oxidation of alcohols is regarded as an ideal sustainable
system.
Gold (Au) is a representative heterogeneous electrocatalyst for
alcohol oxidation and has been investigated for decades [8,9]. As an
electrocatalyst, Au enables the oxidation of alcohols with a small over-
potential under alkaline conditions via the on-surface formation of
adsorbed hydroxide (Au(OH)ads) [8–10]. Zhu and coworkers observed
Au(OH)ads species using in situ liquid secondary-ion mass spectrometry
and elucidated the critical role of Au(OH)ads in the catalysis of alcohols.
– –
O Au), which is generated at
They also reported that Au oxide (Au
higher potentials, exhibits no catalytic activity toward alcohol oxidation
[11]. Xu and coworkers showed that the peak intensity of Au(OH)ads in
attenuated-total-reflectance surface-enhanced infrared absorption
spectra increased with increasing potential, reached a maximum at a
certain potential, and then gradually decreased at higher potentials
[12].
In the present study, we report a novel green system for the elec-
trochemical oxidation of alcohols. Electrochemical measurements using
an Au electrode and a carbon electrode modified with Au nanoparticles
(NPs) were performed with various alcohols, including benzylic, allylic,
and aliphatic alcohols with primary or secondary hydroxy groups, to
confirm the general catalytic activity of Au. To scale up the system, we
used a continuous-flow column cell (Fig. 1), which was originally
developed for the highly sensitive coulometric analysis of trace chemical
substances. Although the application of a column flow cell for
preparative-scale electrosynthesis is rare [13–16], the extremely large
electrode surface area of the system seems suitable for the large-scale
To enable the efficient electrochemical oxidation of alcohols, re-
searchers have developed numerous systems that use electrocatalysts.
Aminoxyl radicals, as a homogeneous electrocatalyst, have been
extensively used for the production of complex and valuable chemicals
such as pharmaceuticals and natural products [7]. On the other hand,
* Corresponding authors.
Received 21 December 2020; Received in revised form 9 January 2021; Accepted 18 January 2021
Available online 28 January 2021