Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte-Driven Nanostructuring

Article abstract of DOI:10.1002/anie.201910155

Production of multicarbon products (C₂₊) from CO₂ electroreduction reaction (CO₂RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO₂RR catalysts that are highly selective for C₂₊ products via electrolyte-driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO₂ into ethylene and multicarbon alcohols in aqueous 0.1 m KHCO₃ solution, with the iodine-modified catalyst displaying the highest Faradaic efficiency of 80 % and a partial geometric current density of ca. 31.2 mA cm^?2 for C₂₊ products at ?0.9 V vs. RHE. Operando X-ray absorption spectroscopy and quasi in situ X-ray photoelectron spectroscopy measurements revealed that the high C₂₊ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis, presence of subsurface oxygen and Cu⁺ species, and the adsorbed halides.

Full text of DOI:10.1002/anie.201910155

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Chemie
International Edition: DOI: 10.1002/anie.201910155
German Edition: DOI: 10.1002/ange.201910155
Electroreduction
Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols
via Electrolyte-Driven Nanostructuring
Dunfeng Gao, Ilya Sinev, Fabian Scholten, Rosa M. Arꢀn-Ais, Nuria J. Divins,
Kristina Kvashnina, Janis Timoshenko, and Beatriz Roldan Cuenya*
Abstract: Production of multicarbon products (C2+) from CO2
electroreduction reaction (CO2RR) is highly desirable for
storing renewable energy and reducing carbon emission. The
electrochemical synthesis of CO2RR catalysts that are highly
selective for C2+ products via electrolyte-driven nanostructur-
ing is presented. Nanostructured Cu catalysts synthesized in the
presence of specific anions selectively convert CO2 into
ethylene and multicarbon alcohols in aqueous 0.1m KHCO3
solution, with the iodine-modified catalyst displaying the
highest Faradaic efficiency of 80% and a partial geometric
current density of ca. 31.2 mAcmÀ2 for C2+ products at À0.9 V
vs. RHE. Operando X-ray absorption spectroscopy and quasi
in situ X-ray photoelectron spectroscopy measurements re-
vealed that the high C2+ selectivity of these nanostructured Cu
catalysts can be attributed to the highly roughened surface
morphology induced by the synthesis, presence of subsurface
oxygen and Cu+ species, and the adsorbed halides.
to multicarbon hydrocarbons and oxygenates (C2+) with high
energy density is highly desirable, but is severely limited by
the slow kinetics of multiple proton and electron transfer
steps during C C coupling.[1–4] Cu, among the studied metals,
À
is the only one producing hydrocarbons and alcohols in
considerable amounts. However, polycrystalline Cu usually
suffers from high overpotential and low C2+ selectivity.[5] The
formation of C2+ products during CO2RR has been found to
be extremely sensitive to the catalyst structure.[1,6–8] There-
fore, nanostructured electrocatalysts capable of efficient
generation of multicarbon products from CO2RR might be
developed through rational design.
It is well-known that the activity and selectivity of CO2RR
catalysts strongly depend on the precise control of their
structure, such as the content of defects,[9] subsurface oxygen
or Cu+ species,[10–15] the specific shape of the nanocrystals,[16–18]
or the surface composition and atomic ordering in bimetallic
nanostructures.[19,20] Previous experimental and theoretical
studies demonstrated that Cu(100) is the most favorable
Introduction
[21–23]
À
crystal orientation for the C C coupling process.
How-
The electrochemical production of fuels and chemical
feedstocks from CO2 and water using the electricity derived
from renewable energy holds promise as a sustainable process
that might help to mitigate some of our current energy and
climate challenges. CO2 electroreduction reaction (CO2RR)
ever, the surface of Cu electrodes under electrochemical
environments often undergoes reconstructions induced by
applied potentials,[24–26] the intermediates formed during
CO2RR,[27] as well as specifically adsorbed anions.[28–30] On
the other hand, some anions either present in the electro-
lyte[12,31,32] or adsorbed on the electrode surface,[33] have been
shown to play a vital role in the dynamic evolution of the
catalyst structure under reaction conditions as well as the
activity and selectivity of CO2RR. These important findings
might be used in the design and development of new
electrodes via electrochemical modifications.
[*] Dr. D. Gao, Dr. I. Sinev, F. Scholten, Dr. R. M. Arꢀn-Ais,
Dr. N. J. Divins, Dr. J. Timoshenko, Prof. Dr. B. Roldan Cuenya
Department of Interface Science
Fritz Haber Institute of the Max Planck Society
14195 Berlin (Germany)
E-mail: roldan@fhi-berlin.mpg.de
The morphology and composition of electrochemically
synthesized catalysts is strongly affected by the applied
potential and electrolyte employed.[34] Herein we report an
electrolyte-driven nanostructuring strategy for the facile
synthesis of highly selective CO2RR catalysts. The nano-
structured Cu catalysts synthesized in the presence of specific
anions can selectively convert CO2 to ethylene and multi-
carbon alcohols in aqueous 0.1m KHCO3 solution, with the
KI-pretreated catalyst displaying the highest FE of about
80% and partial current density of about 31.2 mAcmÀ2 for
C2+ products at À0.9 V vs. RHE. The high C2+ selectivity of
these nanostructured Cu catalysts is attributed to their rough
morphology, the presence of subsurface oxygen, Cu+ species,
and adsorbed halides on the surface.
Dr. I. Sinev, F. Scholten, Dr. N. J. Divins
Department of Physics, Ruhr-University Bochum
44780 Bochum (Germany)
Dr. K. Kvashnina
Rossendorf Beamline at ESRF—The European Synchrotron, CS40220
38043 Grenoble Cedex 9 (France)
and
Helmholtz Zentrum Dresden-Rossendorf (HZDR)
Institute of Resource Ecology
PO Box 510119, 01314 Dresden (Germany)
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.201910155.
ꢁ 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co.
KGaA. This is an open access article under the terms of the Creative
Commons Attribution License, which permits use, distribution and
reproduction in any medium, provided the original work is properly
cited.
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Figure 1. SEM images of Cu_Cl, Cu_Br, Cu_I, and Cu_CO3 samples before and after 1 h of CO2RR at À1.0 V vs. RHE in a CO2-saturated 0.1m
KHCO3 solution. The scale bars in the main images and insets are 1 mm and 200 nm for the Cu_Cl sample (A,E), 5 mm and 500 nm for Cu_Br
(B,F), Cu_I (C,G), and Cu_CO3 samples (D,H).
Results and Discussion
halide-modified Cu samples consist of their copper halide
phases, with the exception of the Cu_Cl sample, which also
includes minor Cu2O peaks owing to the instability of CuCl.
More interestingly, these samples show very different
morphologies after 1 h of CO2RR, although most of the
halides and carbon atoms have been removed during the
reaction (Supporting Information, Table S2). Numerous par-
ticles with average size of 220 Æ 60 nm are formed on the
surface of the Cu_Br sample (Figure 1F), while the Cu_I
sample shows a rough surface (Figure 1G), with a very high
roughness factor determined by measuring the double-layer
capacitance (Supporting Information, Table S3). The particles
on the surface of Cu_CO3 are removed during CO2RR,
leading to a porous Cu surface with average pore size of 430 Æ
130 nm (Figure 1H).
To monitor the evolution of the chemical state and local
environment of Cu during CO2RR we conducted operando
X-ray absorption spectroscopy (XAS) measurements. While
extended X-ray absorption fine-structure spectroscopy (EX-
AFS) data measured in total fluorescence yield mode did not
show any significant difference from the metallic structure
apart from a highly defective structure (Supporting Informa-
tion, Figures S3–S7, Table S4), high-energy resolution fluo-
rescence detected X-ray near edge structure (HERFD-
XANES) spectra are more sensitive to the chemical state
and coordination environment of Cu under reaction con-
ditions.[35,36] Figure 2 shows the Cu K-edge HERFD-XANES
spectra of the as prepared Cu_X samples as well as data from
the same samples obtained during CO2RR at À1.0 V vs. RHE
along with the reference spectra of bulk Cu, Cu2O, CuI, and
CuBr. The spectra suffer from significant self-absorption
effects, but a normalization was used here to have equal self-
absorption in the reference spectra and halide- and carbon-
ate-modified samples. The spectra of the as-prepared Cu_I
and Cu_Br samples show distinctive features of CuI (Fig-
ure 2A; Supporting Information, Figure S8) and CuBr (Fig-
Nanostructured Cu catalysts were synthesized by cycling
electropolished Cu foils in different 0.1m potassium salt
solutions (between 0.3 and 2.2 V vs. RHE) and were denoted
by Cu_X (X = Cl, Br, I) and Cu_CO3, respectively. Additional
details on the synthesis parameters are shown in the
Supporting Information, Table S1. Figure 1 and the Support-
ing Information, Figure S1 show scanning electron microsco-
py (SEM) images of these samples as-prepared, after
immersion in 0.1m KHCO3 solution, as well as after 1 h of
CO2RR at À1.0 V vs. RHE. Cu nanocubes with an edge size
of 250–300 nm are formed on the surface of the Cu_Cl
(Figure 1A) sample as we discussed previously.[18] In clear
contrast, the Cu_Br and Cu_I samples show a faceted crystal
morphology characterized by flatter larger structures for Cu-
Br (Figure 1B) and needle-like shapes for Cu_I (Figure 1C).
A composition of CuBr and CuI was confirmed by energy-
dispersive X-ray spectroscopy (EDX; Supporting Informa-
tion, Table S2). The Cu_CO3 sample shows particles dispersed
on the underlying Cu surface (Figure 1D). After the former
electrolyte-driven surface nanostructuring, when the different
samples are subsequently immersed in the same 0.1m KHCO3
solution for 30 min before applying any potential, the edges of
CuBr and CuI crystals as well as nanocubes in the Cu_Cl
sample become slightly roughed (Supporting Information,
Figure S1), and an increased oxygen content and decreased
halide content are observed due to the slow decomposition of
the Cu halide (CuX) in the aqueous solution (Supporting
Information, Table S2). The highest halide content of the
three Cu_X samples is consistent with the highest stability of
CuI among the possible CuX compounds that could be
formed.[33] The crystalline structure of the copper halide layer
in the as prepared state was further confirmed by grazing
incidence X-ray diffraction (GI-XRD) measurements, as
shown in the Supporting Information, Figure S2. All three
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Figure 2. HERFD-XANES spectra of the Cu_I (A) and Cu_Br (B) samples in the as-prepared state and measured under operando CO2RR
conditions in 0.1m KHCO3 after 1 h of CO2RR at À1.0 V vs. RHE. Reference spectra of bulk Cu, CuI, CuBr, and Cu2O are also plotted. Linear
combination analysis (LCA) of operando HERFD-XANES spectra of the Cu_I sample measured in the as-prepared state (C) and during CO2RR at
À1.0 V vs. RHE (D) are shown. The corresponding subspectral components needed to fit the data (metallic Cu, CuI, and Cu2O) are scaled
according to their weighting parameters.
ure 2B). A broad pre-edge feature between 8979 and
8981 eV, most likely corresponding to metallic Cu, is also
detected for the Cu_I sample. The more intense pre-edge
feature at 8981 eV in the Cu-Br sample points out a higher
amount of metallic Cu. The as-prepared Cu_Cl and Cu_CO3
samples on the other hand show the presence of a dominant
metallic Cu component (pre-edge feature at 8981 eV; Sup-
porting Information, Figures S9, S10, respectively). A slightly
more intense feature at 8986 eV and lower intensity of the
above mentioned metallic feature in the as-prepared Cu_Cl
indicate the presence of CuCl species. Finally, there is no clear
evidence of cationic Cu in the as-prepared Cu_CO3 sample.
HERFD-XANES spectra of all four samples measured
under CO2RR conditions after 1 h of activation indicate
nearly complete reduction of Cu, showing a close resem-
blance to the reference spectrum of the Cu foil. An exception
however is the Cu_I sample measured at À1.0 V vs. RHE,
which has the position of the pre-edge feature shifted to the
energy typical for Cu2O. To support the described qualitative
observations, linear combination analysis (LCA) of the
XANES spectra was carried out using various combinations
of reference spectra as basis sets (Figure 2C,D; Supporting
Information, Figures S9–S11). According to the LCA analy-
sis, the as-prepared Cu_X samples contain Cu+ species (CuI,
CuBr, CuCl, and/or Cu2O), the relative content of which
follows the sequence Cu_I > Cu_Br > Cu_Cl (63, 32, and
24 at% correspondingly; Supporting Information, Table S5).
Notably, no CuOx could be detected in the as-prepared Cu_I
and Cu_Br samples, while the Cu_Cl and Cu_CO3 samples
contained correspondingly Cu2O (14 at%) and CuO (3 at%).
As mentioned above, the Cu_CO3 sample is fully reduced
after 1 h under CO2RR, while Cu_I, Cu_Br, and Cu_Cl show
the presence of Cu2O in the amounts of 8, 3 and 1 at%,
respectively, albeit the latter two numbers are within the
experimental error. The reduced Cu_I sample still contained
ca. 7 at% of residual CuI. These results also reveal the higher
sensitivity of HERFD-XANES measurements acquired in
grazing configuration to Cu2O and CuI species as compared
to GI-XRD which only shows metallic Cu peaks after CO2RR
(Supporting Information, Figure S2).[36,37]
Quasi in situ X-ray photoelectron spectroscopy (XPS)
measurements were performed to probe the chemical state
and composition of the surface of the Cu catalysts during
CO2RR. The electrochemical cell was directly attached to the
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Information, Figures S12 and S13. Among the Cu_X samples,
the Cu_I sample shows an almost pure CuI surface in its as
prepared state, while the surface of the Cu_Br is composed of
Cu2O (65 at%) and CuBr (35 at%), and that of Cu_Cl is
composed of Cu2O (31 at%), CuCl (56 at%) and CuCl2
(12 at%). The composition difference is also consistent with
the relative stability of the three Cu halides.[33] However, the
Cu_CO3 sample has a starting Cu oxidation state of Cu2+ in
the form of CuO and CuCO3. After CO2RR, most of the Cu+
and Cu2+ species in the as prepared samples were reduced to
metallic Cu. However, a small amount of CuBr still survived
(Figure 3B). Moreover, considerable amounts of halides
(Figure 3C,D) were observed on the Cu surface before but
also after the reaction and subsequent in situ rinsing in water.
The metallic Cu surface of the Cu_I sample seen by XPS,
together with the Cu2O and CuI species revealed by the more
bulk-sensitive XANES measurements (Figure 2), indicate the
presence of subsurface oxygen and Cu+ species in the halide-
derived CO2RR Cu catalysts.
The catalytic activity and selectivity of the nanostructured
Cu catalysts were obtained by performing chronoamperom-
etry measurements in a CO2-saturated 0.1m KHCO3 solution.
All the nanostructured Cu catalysts show significantly higher
geometric current density than an electropolished Cu foil
(EP_Cu), and Cu_I shows the highest current density in the
measured potential range (Figure 4A). However, when the
current densities were normalized by the electrochemically
active surface area (ECSA), the three halide-modified Cu
catalysts show similar specific activity (Supporting Informa-
tion, Figure S17A). Therefore, the high surface area (thus
high density of surface reactive sites) of the roughened Cu
catalysts plays a very important role in the significantly
improved apparent activity compared to a flat Cu surface.
Figure 3. Quasi in situ Cu Auger LMM XPS spectra of Cu_CO3, Cu_Br,
and Cu_I before (A) and after (B) 1 h of CO2RR at À1.0 V vs. RHE in
a CO2-saturated 0.1m KHCO3 solution. Br 3p and I 3d XPS spectra of
the Cu_Br (C) and Cu_I (D) measured before and after CO2RR are also
shown.
XPS analysis system and the sample transfer was conducted in
UHV. The Cu_X and Cu_CO3 samples were measured with
XPS in the as-prepared state and after 1 h of CO2RR at
À1.0 V vs. RHE as shown in Figure 3 and the Supporting
Figure 4. Total geometric current density (A), total Faradaic efficiency and geometric partial current density of (B) C2+ products, and partial
geometric current densities of C) C2H4, D) C2H5OH, E) n-C3H7OH, and F) CH4 as a function of the applied potential after 1 h of CO2RR in a CO2-
saturated 0.1m KHCO3 solution.
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Figure 5. Time-dependent geometric current densities and Faradaic efficiencies of gas products for the Cu_I sample at À0.9 V vs. RHE (A, B) and
the Cu_CO3 sample at À0.95 V vs. RHE (C, D) in a CO2-saturated 0.1m KHCO3 solution. The insets in (A) and (C) are SEM images of the Cu_I
and Cu_CO3 samples after 1 h and after 22 h of CO2RR. Scale bars: 5 mm (A) and 500 nm (C). Roughness factors (RF) after 1 h and after 22 h of
CO2RR are also indicated.
Nevertheless, apart from the roughness, the increased activity
over the nanostructured Cu catalysts versus EP_Cu could also
be ascribed to defects, their porous structures, and the
presence of adsorbed halide species, Cu+ or subsurface
oxygen species, as we observed by XPS (Figure 3) and
XANES (Figure 2).
followed by washing in water) avoided the complexity of the
co-existence of structural and chemical electrolyte effects
since all CO2RR measurements were done in KHCO3.
Furthermore, higher activity, lower onset potential and higher
C2+ selectivity were obtained for the present electrolyte pre-
nanostructured catalysts as compared to the case where
iodine was added to the electrolyte during the reaction
(Supporting Information, Figure S18). Although the Cu_CO3
sample showed high partial current density for C2+, its
methane partial current density was also higher, comparable
to that of EP_Cu. The simultaneously favorable production of
ethylene and methane over the porous Cu_CO3 is slightly
different from that reported for Cu foam catalysts, which
simultaneously favored the production of ethylene and
ethane, which is probably due to the smaller pore size
(430 nm) in our Cu_CO3. Overall, the iodine modified Cu
catalyst (Cu_I) synthesized via electrolyte-driven nanostruc-
turing showed a high C2+ geometric current density of about
31.2 mAcmÀ2 at À0.9 V vs. RHE (Supporting Information,
Figure S19), superior to previously reported Cu catalysts
(Supporting Information, Table S6).
The total FEs of C2+ products are shown in Figure 4B and
the Supporting Information, Figure S14, and FEs for each
individual product are shown in the Supporting Information,
Figure S15. The highest C2+ FE of about 80% was achieved at
À0.9 V vs. RHE over Cu_I, while the C2+ FEs of about 66–
73% at À1.0 V vs. RHE were obtained over Cu_Cl, Cu_Br,
and Cu_CO3. The C2+ FEs of all nanostructured Cu catalysts
were 3-fold higher than those of the EP_Cu sample (ca. 20%)
at À0.9 V vs. RHE. At more negative potentials (<-1.0 V vs.
RHE), all the catalysts show decreased C2+ FE and increased
H2 FE, which is due to CO2 mass-transport limitations. The
potential-dependent partial current densities of the various
CO2RR products are shown in Figure 4C–F and the Support-
ing Information, Figures S16, S17. Cu_I showed the highest
partial current densities for ethylene, ethanol, and n-prop-
anol. Compared to the previously reported systems, where
EP_Cu was studied in an electrolyte mixture containing KX
(X = Cl, Br, I) and KHCO3,[17] our new nanostructured
catalytic systems (synthesized by cycling the Cu foil in KX
Stability tests were carried out for the Cu_I and Cu_CO3
samples at potentials for which the highest C2+ FEs were
detected (Figure 5). The current density of Cu_I remained
almost stable within our 22 h test, while a 20% decrease was
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observed for the Cu_CO3 sample. Furthermore, a decrease in Conclusion
the C2H4 FE was observed for both samples, although in the
case of the Cu_I this took place only during the first 5 h,
becoming stable subsequently. The decrease in the C2H4 FE
was accompanied by an increase in methane FE for the Cu_I
sample (a fast decrease in C2H4/CH4 FE ratio; Supporting
Information, Figure S20) and of CO and H2 FE for Cu_CO3.
However, the morphology (inserts in Figure 5A) and rough-
ness (Supporting Information, Table S3) of Cu_I after the
stability test were similar to those after 1 h of CO2RR,
suggesting that the increased production of CH4 (or CO) at
the expense of C2H4 was not caused by morphological
changes, but most likely by the gradual depletion of subsur-
face oxygen species[38–40] and Cu+ species as well as the loss of
adsorbed iodine ions in the Cu_I sample. In clear contrast,
a large number of NPs were formed during CO2RR on the
surface of the Cu_CO3 sample (inserts in Figure 5C) and the
roughness increased accordingly (Supporting Information,
Table S3). The presence of these new low-coordinated sites in
the form of NPs is expected to favor the formation of CO and
We have presented an electrolyte-driven nanostructuring
strategy for the facile synthesis of CO2RR electrocatalysts
highly selective to C2+ products. The proposed synthesis not
only leads to strong morphological modifications of the
sample surface, but also to the presence of residual halides
and cationic Cu species. These Cu electrocatalysts can
selectively convert CO2 into ethylene and multicarbon
alcohols in a KHCO3 solution, with the iodine-modified
catalysts showing the highest FE for C2+ of about 80% and
partial geometrical current density of about 31.2 mAcmÀ2 at
À0.9 V vs. RHE. The superior C2+ selectivity of the halide-
modified Cu catalysts was attributed to their rough surface
morphology combined with electronic and chemical effects
arising from the stabilization of subsurface oxygen as well as
Cu+ species and adsorbed halides on the surface. Cu_CO3
shows both high C2+ and methane selectivity, which is
attributed to its particular nanoporous structure. Stability
tests suggested that the gradual depletion of subsurface
oxygen/Cu+ species and the increased number of low-
coordinated sites formed under reaction conditions are
behind the distinct catalytic performance of the halide- and
carbonate-modified Cu catalysts, respectively. This work
provides new insights required for the design of highly active
C2+-selective CO2RR catalysts.
[41]
H2 and could also lead to the deactivation of the Cu_CO3
sample.
Although the activity, selectivity, and stability of CO2RR
catalysts are determined by multiple complex factors such as
roughness, defects, shape, and oxidation state, the present
À
data feature that the C C coupling process over the Cu_X
samples, especially Cu_I, is strongly related to the presence
and stabilization of Cu+ species as well as of the adsorbed
halides, as confirmed by operando HERFD-XANES (bulk- Experimental Section
sensitive) and quasi in situ XPS measurements (surface
Cu_Cl, Cu_Br, Cu_I, and Cu_CO3 catalysts were prepared by
sensitive). We found a positive correlation between the
production of C2+ and the amount of Cu+ species in the
halide-modified Cu catalysts in the following order: Cu_I >
Cu_Br > Cu_Cl. Previous theoretical studies predicted that
subsurface oxygen as well as the presence of a Cu+/Cu0
interface plays a crucial role in CO2 activation and CO
dimerization, ultimately resulting in higher C2+ selectivi-
ty.[11,42] Interestingly, the adsorbed halides are known to bind
more strongly to the oxidized Cu surface[12,31] and to facilitate
the formation and stabilization of the intermediates during
CO2RR required to obtain C2+ products. On the other hand,
the Cu_CO3 sample with only metallic Cu species under
reaction conditions, showed higher CH4 selectivity than all
Cu_X samples. The latter is probably attributed to its
nanoporous structure.[43] At the end, we should also highlight
the role of the high ECSA of the present nanostructured Cu
catalysts.[44] Apart from having a higher surface area, a drastic
increase in the ECSA during nanostructuring a flat Cu surface
is usually coupled with the creation of highly reactive surface
sites such as defects and low-coordinated sites. These surface
electrochemically cycling an electropolished Cu foil in 0.1m KCl, KBr,
KI, and K2CO3 solutions with triangular potential scans at a rate of
500 mVsÀ1, respectively. During each cycle, the potential was held at
the negative (E1) and positive (E2) limits for 5 and 10 s, respectively.
The cycled Cu catalysts were prepared with the indicated potential
ranges and number of cycles as shown in the Supporting Information,
Table S1. For other experimental details, including operando and
ex situ characterizations and electrochemical measurements, see the
Supporting Information.
Acknowledgements
We thank Tim Mçller (TU Berlin) for the XRD measure-
ments. This work was supported by the European Research
Council under grant ERC-OPERANDOCAT (ERC-
725915), the German Federal Ministry of Education and
Research (BMBF) under grants #03SF0523C-’CO2EKAT’
and #033RCOO4D-’e-Ethylene’ as well as the Unifying
Systems in Catalysis (UniSysCat, EXC 2008/1- 390540038)
funded by the German Research Foundation (DFG) under
Germanyꢀs Excellence Strategy. The authors also would like
to thank the staff of the beamlines ROBL (ESRF, Grenoble)
and P65 (DESY, Hamburg) for their technical assistance
during the operando XAS measurements.
À
sites might be more favorable for C C coupling during
CO2RR,[1,45] not only improving the apparent activity but also
helping to tune the selectivity towards multicarbon products.
In this work we were able to modify the surface morphology
and its composition and chemical state (Cu+) via an electro-
lyte-driven nanostructuring pre-treatment strategy, which was
found to lead to enhanced C2+ selectivity.
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Conflict of interest
The authors declare no conflict of interest.
Keywords: adsorbed halides · CO2 electroreduction · copper(I) ·
electrolyte-driven nanostructuring · multicarbon products
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Manuscript received: August 9, 2019
Revised manuscript received: August 31, 2019
Accepted manuscript online: September 2, 2019
Version of record online: && &&
,
&&&&
&&&&
www.angewandte.org
ꢀ 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2019, 58, 2 – 9
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Research Articles
Electroreduction
Electrolyte-driven nanostructuring can be
used to synthesize highly selective Cu
catalysts for CO2 electroreduction to
multicarbon products (80% Faradaic
efficiency). Operando spectroscopy
measurements showed that apart from
enhanced roughness from the pre-treat-
ment, the subsurface oxygen and Cu+
species and the adsorbed halides favor
D. Gao, I. Sinev, F. Scholten,
R. M. Arꢁn-Ais, N. J. Divins, K. Kvashnina,
J. Timoshenko,
B. Roldan Cuenya*
&&&& — &&&&
Selective CO2 Electroreduction to
Ethylene and Multicarbon Alcohols via
Electrolyte-Driven Nanostructuring
À
C C coupling, leading to high selectivity
for ethylene, ethanol, and n-propanol.
Angew. Chem. Int. Ed. 2019, 58, 2 – 9
ꢀ 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
&&&&
These are not the final page numbers!