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Title: Controllable synthesis of leaf-like CuO nanosheets for selectiveCO2 electroreduction to ethylene

Authors: Zhonghao Tan, Tingyue Peng, Xiaojie Tan, Wenhang Wang,Xiaoshan Wang, Zhongxue Yang, Hui Ning, Qingshan Zhao,and Mingbo Wu

This manuscript has been accepted after peer review and appears as anAccepted Article online prior to editing, proofing, and formal publicationof the final Version of Record (VoR). This work is currently citable byusing the Digital Object Identifier (DOI) given below. The VoR will bepublished online in Early View as soon as possible and may be differentto this Accepted Article as a result of editing. Readers should obtainthe VoR from the journal website shown below when it is publishedto ensure accuracy of information. The authors are responsible for thecontent of this Accepted Article.

To be cited as: ChemElectroChem 10.1002/celc.202000235

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Controllable synthesis of leaf-like CuO nanosheets for selective

CO2 electroreduction to ethylene

Zhonghao Tan[a], Tingyue Peng[a], Xiaojie Tan[a], Wenhang Wang[a], Xiaoshan Wang[a], Zhongxue

Yang[a], Hui Ning*[b], Qingshan Zhao[b], Mingbo Wu*[a]

[a] Z.H. Tan, T.Y. Peng, X.J. Tan, W.H. Wang, Dr. X.S. Wang, Dr. Z.X. Yang, Prof. M.B. Wu

College of Chemical Engineering, College of New Energy, Institute of New Energy, State Key Laboratory of Heavy Oil Processing, China University of

Petroleum

No. 66, West Changjiang Road, Huangdao District, Qingdao, China, 266580

E-mail: wumb@upc.edu.cn

[b] Prof. H. Ning, Dr. Q.S. Zhao

College of chemical engineering, China University of Petroleum

No. 66, West Changjiang Road, Huangdao District, Qingdao, China, 266580

Supporting information for this article is given via a link at the end of the document.

Abstract: Carbon dioxide reduction reaction (CO2RR) driven by

renewable electricity is a promising way to tackle the CO2 emission

woes and recycle use of CO2. The synthesis of electrocatalyst with

high activity and selectivity towards CO2RR to ethylene remains a

great challenge. Herein, the leaf-like CuO nanosheets are in-situ

fabricated on nitrogen doped graphene (NG) by a novel reduction-

oxidation-reconstruction process. Used as catalyst for CO2RR in 0.1

M KHCO3, a high Faradaic efficiency of ca. 30% towards ethylene with

an ultra-high ethylene/methane ratio of 190 was achieved at -1.3 V vs.

reversible hydrogen electrode. The SEM and TEM imagines confirm

the leaf-like CuO nanosheets display high-curvature structures while

multiple distinguished grain boundaries constructed by CuO(110) and

CuO(111) planes are verified by HRTEM. For the first time, we

present a facile method to combine the high-curvature structure and

grain boundary together to enhance the selectivity of CO2RR to

ethylene over CuO catalyst.

Introduction

Excessive CO2 emission form combustion of fossil fuels has

caused a series of environmental problems. Electrocatalytic CO2

reduction to value added chemicals by renewable electricity is of

great significance for tackling the carbon emissions and recycle

use of CO2.[1-7]

Due to the inert chemical activity of CO2 molecules, highly efficient

catalysts are essential for the efficient CO2 reduction reaction

(CO2RR) .[8-10] The mechanism of CO2RR are quite complicated

and the products are usually diverse, including C1 (CO, CH4,

CH3OH, HCOOH), C2 (C2H4, C2H6, C2H5OH, CH3COOH) and C3+

molecules.[11-16] Until now, the exploration of highly selective

catalysts is still a great challenge. For the C1 products, screens of

catalysts have been investigated and some excellent works have

been reported. For example, Wang et al.[17] synthesized a Ni-N-C

material with coordinatively unsaturated nickel–nitrogen sites,

achieving a high CO Faradaic efficiency (FE) of 92.0–98.0% over

a wide potential range of -0.53 to -1.03 V vs. reversible hydrogen

electrode (RHE). Li et al.[18] reported an ultrathin bismuth

nanosheets prepared via in situ topotactic transformation of

bismuth oxyiodide (BiOI) nanosheet template, where the single

crystallinity and enlarged surface areas affords this material an

excellent electrocatalytic performance for CRR to formate with

~100% selectivity. Wang et al.[19] investigated three copper

complex materials for CO2RR and found under the working

conditions copper(II) phthalocyanine undergoes reversible

structural and oxidation state changes to form ~2 nm metallic

copper clusters, which catalyzes the carbon dioxide to methane

with a high FE of 66%.

Compared to the C1 products, only few kinds of catalysts have

been reported to exhibit considerable selectivity to C2 products, of

which the copper-based materials are the most attractive,

especially for ethylene.[20-24] Many pioneer researchers have

studied the crystal structure effects of pristine copper towards

CO2RR, where crystal planes, nanoparticle size and edge/corner

morphologies are mostly discussed.[25-27] Chen et al.[23]

demonstrated that the atomic arrangements on Cu single crystal

surfaces is crucial toward product selectivity of electrocatalytic

CO2 reduction. The Cu(100) facets could facilitate ethylene

generation, while the lower stability of adsorbed *O on the

Cu(110) surface could cause the spilt of the reduction pathway

from ethylene to ethanol. Buonsanti’s study[28] reveals a non-

monotonic size-dependence of the selectivity in cube-shaped

copper nanocrystals and an optimal ratio of edge sites over (100)

plane-sites is crucial to maximize CO2RR to ethylene selectivity.

In addition, oxide-derived copper (ODCu) has shown enhanced

CO2RR activity and increased selectivity towards multi-carbon

products, which is closely related to the high curvature structures

derived from the preparation or pretreatment procedure. Cuenya

et al.[29] developed oxidized copper catalysts with lower

overpotentials for carbon dioxide electroreduction and record

selectivity towards ethylene (60%) through plasma treatments.

They found the roughness structure of oxide-derived copper

catalysts facilitates the stabilization of Cu+ species on the surface

during reactions, which may drive the reaction of negatively

charged CO2 reduction intermediates to C2 products. Sargent et

al.[30] presented an electro-redeposition, dissolution and

redeposition of copper from a sol–gel. By in situ X-ray

spectroscopy and density functional theory simulations, they

revealed the beneficial interplay between the sharp morphologies

of ODCu and Cu+ oxidation state. It was found the sharp features

of ODCu kinetically limit methane formation through local pH

effects while the presence of Cu+ stabilizes ethylene

intermediates. Furthermore, the copper nanowire arrays were

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also reported to promote the CO dimerization by resulting an

increased local pH near the copper active sites for ethylene

generation.[31]

Recently, grain boundaries have been designed to stabilize

unique active surfaces for CO2RR to C1 products on Au,[32-33]

SnO2[34-35] and Bi-Zn,[36] etc. However, novel studies on the grain

boundaries of copper materials towards CO2RR to C2 products

are still limited. Lee et al. [37] prepared Ag-incorporated biphasic

Cu2O-Cu catalysts through a facile electrochemical co-deposition

method. They assume that the host Cu2O was partially substituted

by Ag to form a solid Ag-Cu grain boundary, which relatively

suppresses the H2 evolution reaction and encourages the reaction

of mobile CO generated on Ag to a residual intermediate on a Cu

site. Consequently, by varying the elemental arrangement

(phase-separated and phase-blended) of Ag and Cu, they

realized the selectivity control over ethanol and ethylene. Inspired

by Lee’s work, we believe the grain boundary effects toward

ethylene selectivity may also be applicable for ODCu materials.

To our best knowledge, the combining of high-curvature

morphology and grain boundaries to promote the selectivity of

CO2RR to ethylene over copper oxide has yet to be explored.

Herein, we proposed a facile method to synthesize leaf-like CuO

nanosheets with both high-curvature structure and grain

boundaries. A novel procedure of first reduction and then

oxidation method was invented to synthesize the leaf-like CuO

nanosheets and a thermally spontaneous surface reconstruction

strategy was applied to construct the grain boundaries on the

edge of CuO nanosheets. Moreover, all above process can be

successfully carried out when using nitrogen doped graphene

(NG) as supports to obtain CuO/NG composites, which manifest

high selectivity towards ethylene as catalysts for electroreduction

of carbon dioxide.

Results and Discussion

The synthesis procedure of CuO/NG_AN is shown in Scheme 1.

Firstly, the copper hydroxide nanowire was in situ formed on the

NG to obtain Cu(OH)2/NG composite (Fig. S1a) by adding alkali

to a solution containing Cu2+ and NG. Then, using NaBH4 as

reduction reagent, the Cu(OH)2/NG was reduced to Cu/NG (Fig.

S1b). After oxidation in air, the Cu/NG was transformed to

CuO/NG_A, which was then transferred to CuO/NG_AN through

annealing in N2 atmosphere. Following the same procedure,

CuO_A and CuO_AN were prepared without NG as supports,

where A represents air and N represents nitrogen gas.

Scheme 1. Schematic illustration for the synthesis of CuO/NG_AN.

The XRD patterns of all the samples were shown in Figure 1. The

diffraction peak at 26° was attributed to NG, which is consistent

with previous reports.[38] In CuO/NG_A and CuO/NG_AN, the

position of the characteristic peak of NG has not changed,

indicating the NG is stable during the synthesis of composites. In

the Raman spectra (Figure S2), we can see two typical peaks

around 1350 cm-1 and 1590 cm-1, corresponding to the disordered

sp3C (D band) and in-plane vibrational sp2C (G band). It is

generally agreed that the intensity ratio of the D to G-band (ID/IG)

reveals the disordered structure and defects of the graphitic

carbon material. [39] Here in this work, the value of ID/IG is almost

the same for NG, CuO/NG_A and CuO/NG_AN, confirming the

stability of NG during the synthesis process.

The peaks at 32°,35°,38°,48°,53°,61° and 65° are accurately

indexed to the (110), (002), (111), (202), (020), (113) and (311)

planes of CuO (JCPDS PDF#80-0076) respectively. It was noting

that CuO/NG_A and CuO/NG_AN has the exactly same

characteristic peaks in the XRD patters, indicating the bulk crystal

structure of CuO has no significant change after the annealing

treatment in N2 atmosphere. As control experiments, the XRD

patterns of CuO_A and CuO_AN were also depicted in Figure 1.

It can be seen that all the CuOs have the exactly same

characteristic peaks, proving the bulk crystal phase of CuO was

not changed by NG supporting or annealing treatment.

Figure 1. XRD patterns of NG, CuO_A, CuO_AN, CuO/NG_A and CuO/NG_AN.

In order to further determine the valence state of copper in the

composite, XPS characterization was performed on CuO_A,

CuO_AN, CuO/NG_A and CuO/NG_AN, as shown in Figure S3.

For CuO (Figure S3a, b), no carbon peak was found while an

obvious C 1s peak exists in CuO/NG_A (Figure S3c) and

CuO/NG_AN (Figure S3d). The high-resolution Cu 2p spectra of

all the materials as made were deconvoluted to several Gaussian

peaks corresponding to Cu 2p 1/2 at 954.3 eV and Cu 2p 3/2 at

933.5 eV, confirming the Cu2+ state in the CuOs as made.[40]

Combining the results of XRD and XPS, it can be concluded that

the CuO is successfully synthesized and in situ fabricated on NG.

10 20 30 40 50 60 70

311113020

202

111

002

110

JCPDS PDF#80-0076

2 Theta (degree)

Inte

ns

ity

(a.u

)

CuO/NG_AN

CuO/NG_A

CuO_AN

CuO_A

NG

NG

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Figure 2. Cu2p spectra of a) CuO_A, b) CuO_AN, c) CuO/NG_A and d)

CuO/NG_AN.

The morphologies of all the samples were shown in Figure 3. It

can be seen that all the CuOs are leaf-like nanosheets with a clear

high-curvature edge. In addition, the CuO/NG_A and CuO/NG

_AN behave a smaller degree of aggregation compared to CuO

_A and CuO_AN, which is attributed the supports effects of NG.

Figure 3. SEM images of a) CuO_A, b) CuO_AN, c) CuO/NG_A and d)

CuO/NG_AN.

The TEM images afford more distinguished morphologies of

CuO/NG_A and CuO/NG_AN, as shown in Figure 4a, b. It can be

seen that the leaf-like morphology of CuO nanosheets are

maintained after the annealing treatment in N2 atmosphere.

However, when we look into the fine structures of CuO edge by

HRTEM, only Cu(110) crystals are displayed in the CuO/NG_A

with a uniformly arranged lattice fringes (Figure 4c). However,

Cu(110) and Cu(111) planes simultaneously present in CuO/NG

_AN, forming multiple disordered grain boundaries (Figure 4d).

Because no other substances were added during the annealing

process, it can be inferred that some of the CuO(110) planes were

transferred to CuO(111) planes spontaneously. Li et al.[41]

proposed the oxygen in CuO can be replaced by nitrogen to form

N-doped CuO at 300 °C under N2 atmosphere. We believe this

reaction may also happens in our experiments when we anneal

the CuO nanosheets in N2 atmosphere. Besides, due to the ultra-

thin and high-curvature structure, our CuO nanosheets is more

sensitive to oxygen, leading to the re-oxidation of N-doped CuO

to CuO in air circumstance. During there process, due to the

switchable nitridation-oxidation reaction associating with the

thermal stress, the Cu(110) planes with higher surface energy will

spontaneously transfer to CuO(111) planes with lower surface

energy,[42] leading to the generation of grain boundaries

eventually.

Figure 4. TEM images of a) CuO/NG_A, b) CuO/NG_AN; HRTEM images of c)

CuO/NG_A, d) CuO/NG_AN.

The activity of all the catalysts towards CO2RR were evaluated by

linear sweep voltammetry (LSV) in an N2 and CO2 saturated 0.1M

KHCO3 electrolyte (Fig. S5). When the electrolyte is saturated by

CO2, the reduction current of all the catalysts increased compared

to those in N2 saturated electrolyte starting from −0.4 V vs. RHE,

indicating the reduction of CO2 suppress the HER when the

applied potential was more negative than -0.4 V vs. RHE. Among

all the catalysts, the CuO/NG_AN has the lowest onset potential

and the highest current density under the same potentials,

indicating it has a better activity than other catalysts as made.

In order to investigate the selectivity of various materials towards

CO2RR to ethylene, the potentiostatic electrolysis of carbon

dioxide was monitored under various potentials from -1.0 V to -

1.4 V vs RHE. The FE of all the products were shown in Figure 6.

For all the catalysts as made, the highest FE of ethylene was

obtained at -1.3 V vs RHE. The CuO/NG_A and CuO/NG_AN

have higher selectivity of ethylene compared to the pristine CuO

_A and CuO_AN respectively, proving NG as support can

enhance the selectivity of ethylene with respect to its dispersing

effect. As control experiment, the catalytic performance of NG for

CO2RR was tested and the results were shown in Fig. S6. It can

be seen that no C2 molecular was found in the gas or liquid

products. However, a high FE of H2 was detected from 86%-87%

while the FE of CO was less than 3.0% under the whole range of

applied potentials. Obviously, NG presents good activity for the

hydrogen evolution reaction (HER) but a gentle ability for CO2-to-

CO. Even so, NG as supports are also reported to facilitate the

CO2RR to ethylene.[43] The HER reaction on NG is conducive to

increase the local pH near CuO nanostructures and facilitate the

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surface coverage of CO2 and CO on the CuO surface, resulting

the accelerating of CO2-to-C2H4 reaction.[44] Both with NG as

supports, CuO/NG_AN presents higher selectivity towards

ethylene than CuO/NG_A at -1.3 V vs RHE, which is attributed to

the grain boundaries formed after the annealing treatment of CuO

under N2 atmosphere. The copper atoms near the gain boundary

are presumed to expose more unsaturated bonds for the

stabilization of C2 intermediates, resulting in the accelerating

generation of ethylene. Finally, among all the catalyst as made,

CuO/NG_AN gives the best performance for electrocatalytic CO2

reduction to ethylene. The highest FE of ethylene is 29% and the

selectivity of ethylene in the carbon contained products is 78%.

The grain boundary associating with the high-curvature structure

and NG supports are all contributed to the excellent catalytic

performance of CuO/NG_AN.

Figure 5. Faradaic efficiency of a) CuO_A, b) CuO_AN, c) CuO/NG_A and d)

CuO/NG_AN.

At last, the durability of all the catalysis was evaluated at -1.3V vs

RHE and the results are shown in Fig. S7. All the catalysts behave

an increasing current density during a long electrocatalysis of CO2

for 15,000 s, which is related to the reduction of CuO under

negative potentials.[45] The samples with NG as supports have a

better stability than those without NG, confirming that NG is an

useful supports to stabilize copper oxide species under negative

potentials.[43] As the optimal material in this work, the FE of

ethylene over CuO/NG_AN shows a minor attenuation from 29%

to 26% after the longtime electrocatalysis of CO2. Fig. S8 shows

the SEM image of CuO/NG_AN after the longtime CO2RR,

proving that the morphology of CuO was maintained to some

extent. However, The XRD pattern of CuO/NG_AN after

electrocatalysis in figure S9 and the XPS pattern of CuO/NG_AN after electrocatalysis in figure S10 show that CuO is reduced to

Cu2O and Cu in the CO2RR process, leading to the increasing

current density and decreasing selectivity. All in all, the stability of

our materials still needs to be improved in the future works.

Conclusion

In summary, we present a facile method to synthesize a leaf-like

CuO by reduction-oxidation method. With an annealing treatment

in N2 atmosphere, we successfully controlled the reconstruction

of surface copper atoms to form grain boundaries of CuO(110)/

CuO(111) while keeping the leaf-like structure maintained. By in

situ fabricated on the nitrogen doped graphene, a novel CuO/NG

composite is prepared and used as electrocatalyst for carbon

dioxide reduction. A new stretagy by combination of high

curvature and grain boundary is applied to imporve the selectivity

of ethylene by electrocatalytic reduction of carbon dioxide on CuO.

At -1.3 V vs RHE, the selectivity of ethylene in the carbon

contained products reaches 78% with an with an

ethylene/methane ratio of 190. This work offered a facile strategy

to exploit morphological effects for elevating the selectivity of

copper-based catalysts for CO2-to-C2H4, which may be widely

used to prepare other highly selective CO2 reduction catalysts.

Experimental Section

Chemicals and materials

Graphene oxide (GO) was supplied from Nanjing XFNANO Materials Tech

Co., Ltd., P.R. China. Copper chloride dihydrate (purity, 99.0%), sodium

hydroxide (purity 96%), melamine (purity 99.99%), sodium borohydride

(purity, 98.0%), and isopropyl alcohol were purchased from Sinopharm

Chemical Reagent Co., Ltd., P. R. China. All the reagents were used as

received without further purification. The deionized water (15 MΩ) in this

work was made by a Millipore system in our lab.

Synthesis of NG

Typically,100 mg GO and 500 mg melamine were fully mixed and then

heated to 700 °C under nitrogen atmosphere for 3 h with a rate 5 °C/min

in a tube furnace. After cooling to room temperature, the solids were

washed with deionized water and recollected by filtration and dried at 60 °C

overnight for further characterizations.

Synthesis of CuO/NG composites

In a typical synthesis, 60 mg copper chloride dihydrate was firstly scattered

into 20 mL NG aqueous suspension (1.0 mg/mL), then 0.5 M of sodium

hydroxide was slowly added to neutralize the solution. After vigorous

stirring for 10 min, 20 mL of 0.03 M sodium borohydride solution was slowly

added, followed by vigorous stirring for 5 h. The above solution was suction

filtered and washed three times with deionized water, the solid was

collected and heated to 200 °C for 3h under air atmosphere to obtain

CuO/NG_A. Then, the as-obtained CuO/NG_A was heated to 300 °C

under nitrogen atmosphere for 3 h. After cooling down to room temperature,

the obtained solid was named as CuO/NG_AN. As control experiments,

the CuO_A and CuO_AN were also prepared using the same method

respectively without NG.

Characterizations

The crystal structure parameters were characterized by X-ray

diffraction( X'Pert PRO MPD) with Cu Ka radiation at 40 kV. SEM images

were carried on a Hitachi S4800 scanning electron microscope. TEM and

HRTEM images were obtained by a JEOL JEM-2100F field-emission

transmission electron microscope. The XPS spectra was recorded by X-

ray photoelectron spectroscopy (Thermofisher Escalab 250Xi) using Al Kα

radiation and 500 μm X-ray spot. Raman was detected by a Renishaw RM-

2000 laser Raman spectrometer (514 nm).

Electrochemical measurements

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In this work, all electrochemical measurements were carried out in a H-

type cell with a three-electrode system and 0.1 M KHCO3 as electrolyte.

Ag/AgCl electrode (KCl saturated) and Pt plate (1×1 cm-2) were used as

the reference electrode and counter electrode, respectively. All

electrochemical tests were performed on an electrochemical workstation

(CHI 760, Shanghai CH Instruments Co., China). All working potentials

referred to Ag/AgCl electrode (KCl saturated) were converted to reversible

hydrogen electrode (RHE) using the following equation: E (vs. RHE) = E

(vs Ag/AgCl) + 0.21 V+ 0.0591×pH.[46]

The working electrode was prepared as follows: 1.0 mg sample as made

and 5 μL 5% Nafion solution were dispersed into 200 μL isopropyl alcohol

to form a uniform catalyst ink. Then the catalyst ink was dropped on a L-

type glassy-carbon (GC, ø =10 mm) as a working electrode. Before each

test, high purity carbon dioxide gas (99.999%) was purged into the reaction

cell to saturate the electrolyte for at least 30 min. During the CO2

electrocatalysis tests, the CO2 flow rate was kept at 20 mL/min by a mass

flowmeter till the end of the experiment.

Analysis of products

The gas phase products were detected by an on-line gas chromatography

(BFRL-3420A, China), which was equipped with a thermal conductivity

detector (TCD) for hydrogen detection and a hydrogen flame detector

(FID) for the detection of carbon monoxide and other hydrocarbons. The

liquid phase products were detected by liquid chromatography (LC-2030

Plus, SHIMADZU, Japan).

Acknowledgements

This work is financially supported by the National Natural Science

Foundation of China (21808242); the Shandong Provincial

Natural Science Foundation (ZR2018BB070, ZR2018ZC1458);

the Fundamental Research Funds for the Central Universities of

China (19CX02042A).

Keywords: copper oxide • carbon dioxide • ethylene •

electroreduction • nitrogen doped graphene

[1] X.F. Hou, Y.X. Cai, D. Zhang, L. Li, X. Zhang, Z.D. Zhu, L.W. Peng, Y.Y.

Liu, J.L. Qiao, J. Mater. Chem. A. 2019, 7, 3197-3205.

[2] S.B. Liu, X. F. Lu, J. Xiao, X. Wang, X. W. D. Lou, Angew Chem Int Ed

Engl. 2019, 58, 13828-13833.

[3] Z.R. Zhang, F. Ahmad, W.H. Zhao, W.S. Yan, W.H Zhang, H.W. Huang,

C. Ma, J. Zeng, Nano Lett. 2019, 19, 4029-4034.

[4] J.Q. Tuo, Y.H. Zhu, L. Cheng, Y.H. Li, X.L. Yang, J.H. Shen, C.Z. Li,

ChemSusChem. 2019, 12, 2644-2650.

[5] F.W. Li, A. Thevenon, A. Rosas-Hernandez, Z.Y. Wang, Y.L. Li, C. M.

Gabardo, A. Ozden, C. T. Dinh, J. Li, Y.H. Wang, J. P. Edwards, Y. Xu,

C. McCallum, L. Tao, Z. Q. Liang, M. Luo, X. Wang, H. Li, C. P. O'Brien,

C. S. Tan, D. H. Nam, R. Quintero-Bermudez, T. T. Zhuang, Y. C. Li, Z.

Han, R. D. Britt, D. Sinton, T. Agapie, J. C. Peters, E. H. Sargent, Nature.

2019, 577, 509–513.

[6] K. W. Kimura, K. E. Fritz, J. Kim, J. Suntivich, H. D. Abruna, T. Hanrath,

ChemSusChem. 2018, 11, 1781-1786.

[7] P. Kenis, U. O. Nwabara, E. R. Cofell, S. Verma, E. Negro,

ChemSusChem. 201910,1002，

[8] E.H. Zhang, T. Wang, K. Yu, J. Liu, W.X. Chen, A. Li, H.P. Rong, R. Lin,

S.F. Ji, X.S. Zheng, Y. Wang, L.R. Zheng, C. Chen, D.S. Wang, J.T.

Zhang, Y.D. Li, J Am Chem Soc. 2019, 141, 16569-16573.

[9] D. Ren, J. Gao, L.F. Pan, Z.W. Wang, J.S. Luo, S. M. Zakeeruddin, A.

Hagfeldt, M. Gratzel, Angew Chem Int Ed Engl. 2019, 58, 15036-15040.

[10] Q.G. Zhu, X.F. Sun, D.X. Yang, J. Ma, X.C. Kang, L.R. Zheng, J. Zhang,

Z.H. Wu, B.X. Han, Nat Commun. 2019, 10, 3851.

[11] E. Boutin, M. Wang, J. C. Lin, M. Mesnage, D. Mendoza, B. Lassalle-

Kaiser, C. Hahn, T. F. Jaramillo, M. Robert, Angew Chem Int Ed Engl.

2019, 58, 16172-16176.

[12] J.Z. Huang, X.R. Guo, G. Yue,Q. Q. Hu, L.S. Wang, ACS Appl Mater

Interfaces. 2018, 10, 44403-44414.

[13] W. Luo, W. Xie, R. Mutschler, E. Oveisi, G. L. De Gregorio, R. Buonsanti,

A. Züttel, ACS Catal. 2018, 8, 6571-6581.

[14] B.X. Zhang, J.L. Zhang, J.B. Shi, D.X. Tan, L.F. Liu, F.Y. Zhang, C. Lu,

Z.Z. Su, X.N. Tan, X. Cheng, B.X. Han, L.R. Zheng, J. Zhang, Nat

Commun. 2019, 10, 2980.

[15] T.T. Zhuang, Y. Pang, Z.Q. Liang, Z. Wang, Y. Li, C.S. Tan, J. Li, C. T.

Dinh, P. De Luna, P.L. Hsieh, T. Burdyny, H.H. Li, M. Liu, Y. Wang, F. Li,

A. Proppe, A. Johnston, D.H. Nam, Z.Y. Wu, Y.R. Zheng, A. H. Ip, H.

Tan, L.J. Chen, S.H. Yu, S. O. Kelley, D. Sinton, E. H. Sargent, Nat. Catal.

2018, 1, 946-951.

[16] Y. C. Li, Z.Y. Wang, T.G. Yuan, D. H. Nam, M. Luo, J. Wicks, B. Chen,

J. Li, F. Li, F. P. G. de Arquer, Y. Wang, C. T. Dinh, O. Voznyy, D. Sinton,

E. H. Sargent, J Am Chem Soc. 2019, 141, 8584-8591.

[17] C.C. Yan, H.B. Li, Y.F. Ye, H.H. Wu, F. Cai, R. Si, J.P. Xiao, S. Miao,

S.H. Xie, F. Yang, Y.S. Li, G.X. Wang, X.H. Bao, Energy Environ.

Sci .2018, 11, 1204-1210.

[18] N. Han, Y. Wang, H. Yang, J. Deng, J.H. Wu, Y.F. Li, Y.G. Li, Nat

Commun. 2018, 9, 1320.

[19] Z. Weng, Y. S. Wu, M. Y. Wang, J. B. Jiang, K. Yang, S. J. Huo, X. F.

Wang, Q. Ma, G. W. Brudvig, V. S. Batista, Y. Y. Liang, Z. X. Feng, H. L.

Wang, Nat Commun. 2018, 9, 415.

[20] H. Xie, T.Y. Wang, J.S. Liang, Q. Li, S.H. Sun, Nano Today 2018, 21,

41-54.

[21] Y. Zheng, A. Vasileff, X.L. Zhou, Y. Jiao, M. Jaroniec, S. Z. Qiao, J Am

Chem Soc. 2019, 141, 7646-7659.

[22] F. Scholten, I. Sinev, M. Bernal, B. Roldan Cuenya, ACS Catal. 2019, 9,

5496-5502.

[23] N.T. Suen, Z.R. Kong, C.S. Hsu, H.C. Chen, C.W. Tung, Y.R. Lu, C.L.

Dong, C.C. Shen, J.C. Chung, H. M. Chen, ACS Catal. 2019, 9, 5217-

5222.

[24] N. Martić, C. Reller, C. Macauley, M. Löffler, B. Schmid, D. Reinisch, E.

Volkova, A. Maltenberger, A. Rucki, K. J. J. Mayrhofer, G. Schmid, Adv.

Energy Mater. 2019, 9. 1901228

[25] H. S. Jeon, S. Kunze, F. Scholten, B. Roldan Cuenya, ACS Catal .2017,

8, 531-535.

[26] C. Choi, T. Cheng, M. Flores Espinosa, H. Fei, X. Duan, W. A. Goddard,

Y. Huang, Adv. Mater. 2018,1805405.

[27] S. Nitopi, E. Bertheussen, S. B. Scott, X. Liu, A. K. Engstfeld, S. Horch,

B. Seger, I. E. L. Stephens, K. Chan, C. Hahn, J. K. Norskov, T. F.

Jaramillo, I. Chorkendorff, Chem Rev. 2019,119,7610-7627.

[28] A. Loiudice, P. Lobaccaro, E. A. Kamali, T. Thao, B. H. Huang, J. W.

Ager, R. Buonsanti, Angew Chem Int Ed. 2016, 128, 5883-5886.

[29] H. Mistry, A. S. Varela, C. S. Bonifacio, I. Zegkinoglou, I. Sinev, Y. W.

Choi, K. Kisslinger, E. A. Stach, J. C. Yang, P. Strasser, B. R. Cuenya,

Nat Commun. 2016, 7, 12123.

[30] P. De Luna, R. Quintero-Bermudez, C.T. Dinh, M. B. Ross, O. S.

Bushuyev, P. Todorović, T. Regier, S. O. Kelley, P. Yang, E. H. Sargent,

Nat.Catal .2018, 1, 103-110.

[31] M. Ma, K. Djanashvili, W. A. Smith, Angew Chem Int Ed .2016, 55, 6680-

6684.

[32] X.F. Feng, K.L. Jiang, S.S. Fan, M. W. Kanan, J Am Chem Soc. 2015,

137, 4606-4609.

[33] R. G. Mariano, K. McKelvey, H. S. White, M. W. Kanan, Science. 2017,

358, 1187-1191.

[34] B. Kumar, V. Atla, J. P. Brian, S. Kumari, N. Tu Quang, M. Sunkara, J.

M. Spurgeon, Angew Chem Int Ed Engl. 2017, 56, 3645-3649.

[35] K. Bejtka, J.Q. Zeng, A. Sacco, M. Castellino, S. Hernández, M. A.

Farkhondehfal, U. Savino, S. Ansaloni, C. F. Pirri, A. Chiodoni, ACS Appl.

Energy Mater .2019, 2, 3081-3091.

[36] T.T. Zhang, Y.L. Qiu, P.F. Yao, X.F. Li, H.M. Zhang, ACS Sustainable

Chem. Eng.

2019, 7, 15190-15196.

[37] S. Lee, G. Park, J. Lee, ACS Catal.2017, 7, 8594-8604.

10.1002/celc.202000235

Acc

epte

d M

anus

crip

t

ChemElectroChem

This article is protected by copyright. All rights reserved.

FULL PAPER

6

[38] S. Zhang, L.N. Sui, H.Q. Kang, H.Z. Dong, L.F. Dong, L.Y. Yu,

Small.2018, 14,1702570.

[39] P. Pachfule, D. Shinde, M. Majumder, Q. Xu, Nat Chem. 2016, 8, 718-

724.

[40] G.H. He, L. Wang, Ionics. 2018, 24, 3167-3175.

[41] P.Q. Li, J.F. Xu, H. Jing, C.X. Wu, H. Peng, J. Lu, H.Z. Yin, Appl. Catal.

B Environ. 2014, 156-157, 134-140.

[42] Z. Chen, J. M. P. Martirez, P. Zahl, E. A. Carter, B. E. Koel, J Chem Phys.

2019, 150, 041720.

[43] H. Ning, Q.H. Mao, W.H. Wang, Z.X. Yang, X.S. Wang, Q.S. Zhao, Y.

Song, M.B. Wu, J. Alloys Compd. 2019, 785, 7-12.

[44] Q. Li, W.L. Zhu, J.J. Fu, H.Y. Zhang, G. Wu, S.H. Sun, Nano Energy.

2016, 24, 1-9.

[45] D. Ren, Y. Deng, A. D. Handoko, C. S. Chen, S. Malkhandi, B. S. Yeo,

ACS Catal. 2015, 5, 2814-2821.

[46] T.T. Zhuang, Z.Q. Liang, A. Seifitokaldani, Y. Li, P. De Luna, T. Burdyny,

F. Che, F. Meng, Y. Min, R. Quintero-Bermudez, C. T. Dinh, Y. Pang, M.

Zhong, B. Zhang, J. Li, P.N. Chen, X.L. Zheng, H. Liang, W.N. Ge, B.J.

Ye, D. Sinton, S.H. Yu, E. H. Sargent, Nat. Catal. 2018, 1, 421-428.

10.1002/celc.202000235

Acc

epte

d M

anus

crip

t

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This article is protected by copyright. All rights reserved.

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Entry for the Table of Contents

The leaf-like CuO nanosheets were synthesized by a facile method and show a high selectivity towards ethylene as catalysts for

electroreduction of carbon dioxide in aqueous solution due to it high-curvature structures and rich grain boundaries.

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