Metal-organic framework-derived cupric oxide polycrystalline nanowires for selective carbon dioxide electroreduction to C2 valuables

Article abstract of DOI:10.1039/d0ta03565c

Carbon dioxide (CO2) electroreduction is promising for balancing the carbon cycle for a sustainable society. However, an efficient electrocatalyst is the key to selectively converting CO2 and generating valuable products. In this work, metal-organic framework (MOF) derived porous cupric oxide nanowires are prepared by a controllable annealing method for the efficient CO2 reduction. These polycrystalline nanocatalysts demonstrate a high Faradaic efficiency (FE) of ～70percent for C2 products at -1.3 V vs. RHE. A partial current density of ～141 mA cm-2 for ethylene with a FE of ～37percent is achieved in a home-made flow cell at -1.3 V vs. RHE. The in situ/ex situ investigations indicate that the oxide-derived metallic copper with abundant interfaces would be the real active sites for highly selective CO2 electrolysis. This work offers effective copper catalysts to selectively convert CO2 toward valuable products, and more importantly provides insightful understanding of developing efficient catalytic materials for energy conversion. This journal is

Full text of DOI:10.1039/d0ta03565c

View Article Online
View Journal
Journal of
Materials Chemistry A
Materials for energy and sustainability
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: B. Y. Xia, F. Yang,
P. L. Deng, Q. Wang, J. Zhu, Y. Yan, L. Zhou, K. Qi, H. Liu and H. S. Park, J. Mater. Chem. A, 2020, DOI:
10.1039/D0TA03565C.
Volume
Number 12
28 March 2018
Pages 4883-5230
6
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry A
Materials for energy and sustainability
rsc.li/materials-a
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 2050-7488
COMMUNICATION
Zhenhai Wen et al.
An electrochemically neutralized energy-assisted low-cost
acid-alkaline electrolyzer for energy-saving electrolysis
hydrogen generation
rsc.li/materials-a

Page 1 of 16
Journal of Materials Chemistry A
Metal-organic Framework-derived Cupric Oxide Polycrystalline Nanowires for Fast Carbon Dioxide
View Article Online
DOI: 10.1039/D0TA03565C
Electroreduction to C2 Valuables
Fan Yang a, PeiLin Deng a, Qingyong Wang a, Jiexin Zhu b, Ya Yan c, Liang Zhou b, Kai Qi a, Hongfang Liu a,
Ho Seok Park d*, and Bao Yu Xia a*
a
Key Laboratory of Material Chemistry for Energy Conversion and Storage (Ministry of Education), Key
Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering,
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology (HUST),
1037 Luoyu Road, Wuhan 430074, PR China
b State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School
of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, PR China
c
School of Materials Science and Engineering, University of Shanghai for Science and Technology, 516
Jungong Road, Shanghai, 200093, PR China
d
Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and
Technology (SAIHST), SKKU Advanced Institute of NanoTechnology (SAINT), School of Chemical
Engineering Sungkyunkwan University
*Corresponding authors: byxia@hust.edu.cn (B.Y. Xia); phs0727@skku.edu (H. S. Park)
1

Journal of Materials Chemistry A
Page 2 of 16
Abstract: Carbon dioxide (CO2) electroreduction is promising in balancing carbon cycle for sustainable
View Article Online
DOI: 10.1039/D0TA03565C
society. However, efficient electrocatalyst is the key to selectively convert CO2 and generate valuable products.
In this work, metal-organic frameworks (MOFs) derived porous cupric oxide nanowires are prepared by
controllable annealing method for the efficient CO2 reduction. This polycrystalline nanocatalysts demonstrates
a high Faradaic efficiency (FE) of ~70% for C2 products at -1.3 V vs. RHE. A partial current density of ~141
mA cm-2 for ethylene with a FE of ~37% is achieved in a home-made flow cell at -1.3 V vs. RHE. The in-/ex-
situ investigations indicate that the oxide-derived metallic copper with the abundant interfaces would be the
real active sites for highly selective CO2 electrolysis. This work offers effective copper catalysts to selectively
convert CO2 toward valuable products, and more importantly provides insightful understandings in developing
efficient catalytic materials for energy conversion.
Keywords: Carbon dioxide reduction; Electrocatalyst; Oxide-derided Cu; Interface; Hydrocarbons;
2

Page 3 of 16
Journal of Materials Chemistry A
The growing population and developing industrial lead to the sharp increasing of fossil fuel demand and
View Article Online
[1,
DOI: 10.1039/D0TA03565C
carbon dioxide (CO2) emission, which consequently result in the greenhouse effect and ocean acidification.
2] CO2 conversion is promising to reduce CO2 emission and balance carbon cycle for the sustainable society.[3]
Compared to the slow photochemical conversion in nature, the electrochemical CO2 reduction powered by
renewable energy is viable as it can be easily controlled under ambient condition and simultaneously generate
valuable products.[4, 5] However, this process involves the complex multistep electron-coupled-proton reaction,
which leads to multiple products and even the hydrogen by-product from the competitive hydrogen evolution
reaction (HER).[6] Among them, C2 products including ethylene (C2H4) are more desirable for the industrial
economy and energy fuel application.[7] Therefore, exploring efficient electrocatalysts to realize CO2
conversion for generating the target C2 products is highly desirable.
Among various metallic catalysts, copper compounds are the most promising alternatives for converting
12]
14]
CO2 to hydrocarbons.[8-10] Consequently, crystalline engineering,[11,
structure designing[13,
and
[10, 15, 16]
composition tuning approaches
are extensively employed to enhance the activity and selectivity of
Cu-based materials in the CO2 conversion. Nevertheless, their efficiencies in the selective generation of C2
products are still low due to the competitive HER and other products generated simultaneously during the CO2
reduction process.[5] Recently, oxide-derived copper (OD-Cu) polycrystals have been proved to be effective
in CO2 conversion.[12, 17, 18] For example, the thick Cu2O films prepared by annealing Cu foil demonstrates a
capability in generating a wide product distribution of carbon monoxide, methane, ethylene, etc.[17] Moreover,
Kanan’s group reported a high FE of ~50% over the OD-Cu nanoparticles with rich grain boundaries (GBs)
for the reduction of CO to ethanol and acetate.[19] It is believed that the strong binding capability of
intermediates (CO*, COH*, CHO*) on the (sub)surface of OD-Cu catalysts is the key to realize the deep CO2
reduction.[12, 18, 20] These OD-Cu nanomaterials are the interconnected nanocrystalline network, which endow
intrinsically abundant interface, and these metastable sites at the surfaces/interface may be responsible for its
3

Journal of Materials Chemistry A
Page 4 of 16
unusual catalytic properties.[12, 19] Therefore, realizing the controlled synthesis and understanding the
View Article Online
DOI: 10.1039/D0TA03565C
structural elucidation of OD-Cu with abundant surface/interface will enable the design of more efficient CO2
reduction catalysts for the target C2 valuables.[19, 21]
Metal-organic frameworks (MOFs) are emerged as a new class of porous materials, which are constructed
by organic ligands and metal ions with the atomic level periodicity.[22] Their uniform distribution of metal
ions in the MOFs would provide the excellent opportunities to form the polycrystalline with interconnected
network and abundant interface.[23] To this end, we employ the copper-aspartic acid (Cu-ASP) nanofibers to
prepare cupric oxide (CuO) nanowires for the CO2 electrolysis.[24] As expected, the porous CuO nanowires
with abundant crystalline surface/interface are successfully achieved by the controllable annealing treatment.
The resultant CuO nanowires exhibit excellent activity for the selective CO2 reduction with a maximum FE
of 70% for C2 products (C2H4 and CH3CH2OH) at -1.3 V vs. RHE in a H-cell. A smaller onset potential (< -
0.3 V vs. RHE) and partial current density of ~141 mA cm-2 are achieved at -1.3 V vs. RHE for C2H4 with FE
of ~37% in a home-made flow cell. Moreover, the ex-/in-situ results reveal that the oxide-derived metastable
Cu sites at the surface/interface would be active sites for the stabilization of intermediate and the production
of C2 valuables. This work provides effective Cu electrocatalysts and significant understandings for selective
CO2 reduction, we anticipate the MOF-derived concept may provide crucial insights in the surface/interface
engineering for preparing efficient electrocatalyst toward selective CO2 conversion technologies.
o
The porous CuO nanowires are obtained by controllable annealing Cu-ASP nanofibers at 300~600 C in
the air environment. X-ray powder diffraction (XRD) pattern of the initial Cu-ASP materials reveals the well-
define MOFs crystalline structure without any Cu or CuO impurities (Figure S1).[24] The pure CuO phase
(JCPDS: 44-0706) is found after annealing process, which suggests the complete oxidation and transformation
of Cu-ASP precursors to CuO (Figure S2). Moreover, the annealing process also results in the morphology
and structure changes. Scanning electron microscopy (SEM) images show the rougher surface and bigger
4

Page 5 of 16
Journal of Materials Chemistry A
nanoparticles with the increase of annealing temperatures (Figure S3). The CuO nanowires obtained by
View Article Online
o
DOI: 10.1039/D0TA03565C
annealing at 400 C demonstrate the wheat spikes-like morphology with porous structure (Figure 1a), which
is significantly different with the smooth surface of initial Cu-ASP nanofibers (Figure S1b). Transmission
electron microscopy (TEM) image in Figure 1b clearly shows the porous structure of CuO nanowires, the
selected-area electron diffraction (SAED) pattern contains bright rings and spots (Figure 1b inset), indicating
the polycrystal nature for CuO nanowires. Closer observation in Figure 1c reveals that these nanoparticles
(30-50 nm) are linked in the nanowire form. Moreover, high-resolution (HR) TEM image confirms the
interconnected nanocrystal particles (Figure S4). This unique structure contains abundant phase
surface/interface, as there are the distinct grain boundary and lattice distortion regions (Figure 1d). HRTEM
image verifies the CuO (002) and CuO (111) planes with the lattice spacings of 0.25 nm and 0.23 nm,
respectively (Figure 1d inset).
The catalytic activity of CuO nanowires for CO2 reduction is firstly studied in H-cell system, in which the
electrolyte is CO2-saturated 0.1 M potassium bicarbonate (KHCO3), and the catalysts are loaded onto the
glassy carbon electrode. As the CuO nanowires would be reduced by in-situ electrochemical CO2 reduction,
these samples are denoted as OD-Cu-1~5 respectively. The commercial polycrystalline Cu foil is often used
as a reference material for comparison with copper-based materials.[17] As shown in linear sweep voltammetry
(LSV) curves (Figure 2a), the Cu foil and OD-Cu catalysts demonstrate the obvious current density responses
in the CO2-saturated KHCO3 compared with Ar-saturated KHCO3 electrolytes (Figure S5). Moreover, the
current density response of OD-Cu-3 catalyst is significantly higher than that of Cu foil (Figure 2a), suggesting
a possible higher activity of CO2 reduction for OD-Cu-3 nanowires. The gaseous and liquid products are then
analyzed by gas chromatography (GC) and nuclear magnetic resonance (NMR) spectroscopy, respectively.
Except the dominated hydrogen product due to the competitive HER, the major reduction products of Cu foil
include C1 products such as CO, HCOOH and CH4, and few C2 products (Figure S6a, S7a). However, MOF-
5

Journal of Materials Chemistry A
Page 6 of 16
derived Cu catalysts exhibit enhanced generation in the C2 products. According to the product distribution,
View Article Online
DOI: 10.1039/D0TA03565C
the FE of H2 and C1 products gradually decrease over the OD-Cu catalyst, while the FE of C2 products (C2H4
and CH3CH2OH) increase under more-negative potentials (Figure S6). In particular, the OD-Cu-3 shows a
remarkably high FE of ~70% for C2 hydrocarbons (43% C2H4 and 25% CH3CH2OH) at -1.3 V vs. RHE
(Figure 2b). Furthermore, OD-Cu-3 catalyst also shows a much higher current density of ~20 mA cm-2 for
hydrocarbons at -1.4 V vs. RHE, while the Cu foil shows only ~1.5 mA cm-2. The partial current densities and
FE of OD-Cu catalysts for C2 products are well-overpass Cu foil at the same potential range (Figure 2c), as
the C1 and H2 products have occupied for more than half of total FE of the Cu foil (Figure S7). In addition,
the OD-Cu-3 electrode also demonstrates an excellent electrochemical stability. The current density and FE
of major product C2H4 is remained during the 12 h CO2 electrolysis at -1.3 V vs. RHE (Figure 2d). Compared
with other Cu-based catalysts, this OD-Cu nanowires also show a comparable FE and current density for C2
hydrocarbons (Table S1).[13, 23, 25-29] However, the partial current density of C2H4 is still limited due to the poor
solubility of CO2. In order to overcome the CO2 mass transport issues, a home-made flow cell equipped with
gas-diffusion electrodes (GDEs) is employed. As shown in Figure 2e, the current response is significantly
improved, and the onset potential is reduced to < -0.3 V vs. RHE (Figure 2e). The FE of C2H4 is ~ 40% and
the partial current density is ~105 mA cm-2 at -1.1 V vs. RHE (Figure 2f). And the partial current density for
C2H4 can further reach ~141 mA cm-2 at -1.3 V vs. RHE with a comparable FE of ~37%, which demonstrates
the practical potential of this CO2 electrolysis system. The GDE separates the CO2 gas and alkaline electrolyte,
which reduce the CO2 diffusion pathway and directly react with CO2 in gaseous. Thus, compared with the H-
cell results, the higher current density and lower onset potential are achieved in the flow cell. Furthermore,
the electrochemical double layer capacitance (Cdl) determines the electrochemical active area (ECSA) (Figure
S8), which represents the number of active sites to some degree. As a result, the OD-Cu-3 provides the highest
ECSA and it implies a similar trend in the CO2 reduction activity (Figure 2c). Therefore, the high CO2
6

Page 7 of 16
Journal of Materials Chemistry A
reduction catalytic activity of series OD-Cu catalysts would be partially ascribed to the active sites created by
View Article Online
DOI: 10.1039/D0TA03565C
the controllable annealing treatment. And the intrinsic activity of OD-Cu series catalysts is investigated by
ECSA-corrected current density, the similar partial current densities of C2 products indicate the same intrinsic
activity among OD-Cu series catalysts (Figure S9).
Since the metal oxides catalysts would also suffer the reduction simultaneously during the cathodic CO2
electrolysis,[27, 30] XRD technique is then employed to investigate the phase structure change. As shown in
Figure 3a, CuO is totally reduced into metallic Cu (JCPDS: 04-0836) after the CO2 electrolysis. Moreover,
the peak pair of Cu 2p XPS spectrum at 933.5 and 953 eV is attributed to Cu(II), and another couple peaks at
~943 and 962 eV is Cu(II) satellites in CuO nanowires. Whereas, OD-Cu just shows the typical peaks at
~932.5 and 952.3 eV for Cu(0)/Cu(I) species, as the same time, the strong Cu2+ satellite peaks in CuO
nanowires disappear. It is distinctly different from the Cu(II) states in the initial CuO nanowire before the CO2
electrolysis (Figure 3b). The Cu LMM Auger spectra in Figure 3c further indicates the different oxidation
state in the OD-Cu sample, the presence of Cu(I) and Cu(II) species in OD-Cu are mainly resulted from the
inevitable oxidation by exposing to air. Furthermore, the adsorption of OH- on the CuO precursor and OD-Cu
sample are then evaluated in 0.1 M KOH at a scan rate of 10 mV s-1 (Figure 3d), as the adsorption of OH- can
-
be used as a substitution for CO2 *,[31-33] which is a very important intermediate in the CO2 conversion.[12, 17,
34]
The potential for surface OH- adsorption on CuO precursor is close to that of OD-Cu, but OD-Cu
demonstrates a much higher peak intensity than CuO, indicating the similar adsorption affinity yet much more
adsorption quantity of OH- on OD-Cu.
Follow the phase changes in the electrochemical CO2 electrolysis, the morphology evolution of OD-Cu
nanowires is then examined (Figure S11). After the electrolysis, the whole nanowires morphologies of OD-
Cu are maintained (Figure 4a). TEM image shows the surface of nanoparticles become slightly rougher while
the core/shell structure is apparently found (Figure 4b). The SAED pattern of OD-Cu (Figure 4b inset) is
7

Journal of Materials Chemistry A
Page 8 of 16
obviously different from the initial CuO nanowires (Figure 1b inset). The clear diffraction rings reveal the
View Article Online
DOI: 10.1039/D0TA03565C
emergence of metallic Cu crystalline, which is agreement well with the TEM observations. Closer HRTEM
images in Figure 4c and 4d reveals the inter-planar spaces of 0.20 nm, 0.24 nm and 0.27 nm, which are
respectively correspond to Cu2O (111), Cu (111) and Cu (200) facets. Both HRTEM images show some
cuprous oxide phase located at the surface and the crystalline Cu phase at the subsurface. Nevertheless, the
abundant interface is also remained in the in-situ formed OD-Cu materials (Figure S11). TEM images reveal
the structural phase evolution of CuO precursor to the metallic phase, while the presence of cuprous oxide
phase in OD-Cu surface would be attribute to the inevitable oxidation in contact with air (Figure 3).[35, 36] The
transformation of valence state for element copper are then investigated by in-situ Raman spectra during the
CO2 electrolysis (Figure 4e). Before applying an external potential (0 s), the peaks at ~300 and ~620 cm-1 are
attributed to the CuO phase. While the peaks attributed to CuO disappear within 180 s of applying potential,
which indicates the CuO catalyst would be reduced to the metallic copper quickly. Once the potential is
removed, the peaks at ~150, ~300 and ~625 cm-1 are observed and the peak at 150 cm-1 is assigned to Cu2O.
This phenomenon suggests the very active surface of this OD-Cu, which can be oxidized quickly by the
oxygenates in the electrolyte. The consequent in-situ Raman rounds also evidence the fast in-situ reduction
and oxidation.
In addition, the aspartic acid organic ligand includes the N element, and the N 1s XPS spectra of CuO and
OD-Cu also indicate the existence of N element (Figure S10). In order to exclude the influence of N element
on the catalytic result, the aspartic acid is replaced by the succinic acid, which does not contain amino group
of N element and only retains other parts. The copper-succinic acid (Cu-SUC) MOFs is prepared and the CuO-
o
SUC is achieved by annealing the Cu-SUC MOFs at 400 C with 1 h (Figure S12). Similar to the OD-Cu,
CuO-SUC shows the porous structure formed by the interconnected nanoparticles. And the corresponding
catalytic results are also similar with the OD-Cu catalysts (Figure S13, S6 and S7), which indicates N-doping
8

Page 9 of 16
Journal of Materials Chemistry A
does not contribute to the enhanced CO2 reduction and the controllable annealing treatment on Cu-MOFs is
View Article Online
DOI: 10.1039/D0TA03565C
feasible to enhance the selectivity on C2 products. Moreover, based on the ex-/in-situ results and ECSA
measurement, we can speculate the real active sites of the series OD-Cu materials would be the active
interface/surface at the grain boundary or distortion region. Previous results suggest these abundant metastable
sites at the surfaces/interface under the electrochemical reduction environment may be responsible for its
unusual catalytic properties.[12, 19] These active sites at grain boundary/defective regions can stabilize the key
*CO and *COH intermediates. These oxide-derived Cu catalysts would possess strong CO-binding
capability,[20, 37, 38] this property could suppresses the reduction of CO2 to C1 product and enhances CO2
hydrogenation to C2 species via C-C coupling process (the rate-limiting CO* + CO*→ OCCO* step or *CO
+ H* → *CHO step).[19, 39, 40] Finally, C2 products will be highly selectively generated on the abundant
surfaces/interface of MOF-derived copper oxide catalysts.
In summary, porous CuO nanowires with abundant crystalline surface/interface are successfully achieved
by the controllable annealing treatment for selective CO2 electrolysis. The resultant CuO nanowires exhibit a
maximum FE of ~70% for C2 products (C2H4 and CH3CH2OH) at -1.3 V vs. RHE. A smaller onset potential
(<-0.3 V vs. RHE) and partial current density of ~141 mA cm-2 are achieved at -1.3 V vs. RHE for C2H4
production in a home-made flow cell. The ex-/in-situ results reveal that the abundant surface/interface of the
oxide-derived metastable Cu would be beneficial for the stabilization of intermediate and promote the fast
production of C2 valuables. This work provides effective Cu electrocatalysts and significant understandings
for selective CO2 reduction, we anticipate the MOF-derived concept may provide crucial insights in the
surface/interface engineering for preparing efficient electrocatalyst toward selective CO2 conversion.
Conflicts of interest
There are no conflicts to declare.
9

Journal of Materials Chemistry A
Page 10 of 16
Acknowledgements
View Article Online
DOI: 10.1039/D0TA03565C
This work is funded by the National Natural Science Foundation of China (21802048, 21805103, 21805104),
the Fundamental Research Funds for the Central Universities (2018KFYXKJC044, 2018KFYYXJJ121,
2017KFXKJC002) and the National 1000 Young Talents Program of China. The authors also acknowledge
the support of the Analytical and Testing Center of Huazhong University of Science and Technology for XRD,
SEM, TEM, NMR and XPS measurements.
Reference
[1] J. G. Canadell, C. Le Quéré, M. R. Raupach, C. B. Field, E. T. Buitenhuis, P. Ciais, T. J. Conway, N. P.
Gillett, R. Houghton, G. Marland, Proc. Natl. Acad. Sci. 2007, 104, 18866.
[2] M. R. Raupach, G. Marland, P. Ciais, C. Le Quéré, J. G. Canadell, G. Klepper, C. B. Field, Proc. Natl.
Acad. Sci. 2007, 104, 10288.
[3] J. B. Greenblatt, D. J. Miller, J. W. Ager, F. A. Houle, I. D. Sharp, Joule 2018, 2, 381.
[4] D. T. Whipple, P. J. Kenis, J. Phys. Chem. Lett. 2010, 1, 3451.
[5] D. D. Zhu, J. L. Liu, S. Z. Qiao, Adv.ꢀMater. 2016, 28, 3423.
[6] Q. Lu, F. Jiao, Nano Energy 2016, 29, 439.
[7] D. Gao, R. M. Arán-Ais, H. S. Jeon, B. R. Cuenya, Nat. Catal. 2019, 2, 198.
[8] D. Gao, F. Cai, G. Wang, X. Bao, Curr. Opin. Green Sus. Chem. 2017, 3, 39.
[9] S. Nitopi, E. Bertheussen, S. B. Scott, X. Liu, A. K. Engstfeld, S. Horch, B. Seger, I. E. Stephens, K.
Chan, C. Hahn, Chem. Rev. 2019, 119, 7610.
[10]A. Vasileff, C. Xu, Y. Jiao, Y. Zheng, S.-Z. Qiao, Chem 2018, 4, 1809.
[11]A. Loiudice, P. Lobaccaro, E. A. Kamali, T. Thao, B. H. Huang, J. W. Ager, R. Buonsanti, Angew.ꢀChem.ꢀ
Int.ꢀEd. 2016, 55, 5789.
[12]C. W. Li, J. Ciston, M. W. Kanan, Nature 2014, 508, 504.
[13]M. Ma, K. Djanashvili, W. A. Smith, Angew.ꢀChem.ꢀInt.ꢀEd. 2016, 55, 6680.
[14]R. Reske, H. Mistry, F. Behafarid, B. Roldan Cuenya, P. Strasser, J. Am. Chem. Soc. 2014, 136, 6978.
[15]S. Ma, M. Sadakiyo, M. Heima, R. Luo, R. T. Haasch, J. I. Gold, M. Yamauchi, P. J. Kenis, J. Am. Chem.
Soc. 2016, 139, 47.
[16]D. Kim, J. Resasco, Y. Yu, A. M. Asiri, P. Yang, Nat. Commun. 2014, 5, 4948.
[17]C. W. Li, M. W. Kanan, J. Am. Chem. Soc. 2012, 134, 7231.
[18]D. Ren, Y. Deng, A. D. Handoko, C. S. Chen, S. Malkhandi, B. S. Yeo, ACS Catal. 2015, 5, 2814.
[19]X. Feng, K. Jiang, S. Fan, M. W. Kanan, ACS Cent. Sci. 2016, 2, 169.
[20]Y. Zhou, F. Che, M. Liu, C. Zou, Z. Liang, P. De Luna, H. Yuan, J. Li, Z. Wang, H. Xie, Nat. Chem.
2018, 10, 974.
[21]A. Verdaguer-Casadevall, C. W. Li, T. P. Johansson, S. B. Scott, J. T. McKeown, M. Kumar, I. E.
Stephens, M. W. Kanan, I. Chorkendorff, J. Am. Chem. Soc. 2015, 137, 9808.
[22]S. L. James, Chem. Soc. Rev. 2003, 32, 276.
[23]D.-H. Nam, O. S. Bushuyev, J. Li, P. De Luna, A. Seifitokaldani, C.-T. Dinh, F. P. García de Arquer, Y.
Wang, Z. Liang, A. H. Proppe, J. Am. Chem. Soc. 2018, 140, 11378.
10

Page 11 of 16
Journal of Materials Chemistry A
[24]I. Imaz, M. Rubio-Martínez, W. J. Saletra, D. B. Amabilino, D. Maspoch, J. Am. Chem. Soc. 2009, 131,
18222.
View Article Online
[25]H. Zhang, Y. Zhang, Y. Li, S. Ahn, G. T. R. Palmore, J. Fu, A. Peterson, S. Sun, Nanoscale 2019, 11,
DOI: 10.1039/D0TA03565C
12075.
[26]D. Raciti, K. J. Livi, C. Wang, Nano lett. 2015, 15, 6829.
[27]F. Yang, A. Chen, P. L. Deng, Y. Zhou, Z. Shahid, H. Liu, B. Y. Xia, Chem. Sci. 2019, 10, 7975.
[28]X. Tan, C. Yu, C. Zhao, H. Huang, X. Yao, X. Han, W. Guo, S. Cui, H. Huang, J. Qiu, ACS Appl. Mater.
Inter. 2019, 11, 9904.
[29]C.-W. Kung, C. O. Audu, A. W. Peters, H. Noh, O. K. Farha, J. T. Hupp, ACS Energy Lett. 2017, 2, 2394.
[30]P. Deng, H. Wang, R. Qi, J. Zhu, S. Chen, F. Yang, L. Zhou, K. Qi, H. Liu, B. Y. Xia, ACS Catal. 2020,
10, 743.
[31]A. Salehi-Khojin, H.-R. M. Jhong, B. A. Rosen, W. Zhu, S. Ma, P. J. Kenis, R. I. Masel, J. Phys. Chem.
C 2013, 117, 1627.
[32]S. Zhang, P. Kang, T. J. Meyer, J. Am. Chem. Soc. 2014, 136, 1734.
[33]F. Lei, W. Liu, Y. Sun, J. Xu, K. Liu, L. Liang, T. Yao, B. Pan, S. Wei, Y. Xie, Nat. Commun. 2016, 7,
12697.
[34]S. Gao, Y. Lin, X. Jiao, Y. Sun, Q. Luo, W. Zhang, D. Li, J. Yang, Y. Xie, Nature 2016, 529, 68.
[35]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.
[36]Y. Lum, J. W. Ager, Angew.ꢀChem.ꢀInt.ꢀEd. 2018, 57, 551.
[37]K. P. Kuhl, E. R. Cave, D. N. Abram, T. F. Jaramillo, Energ. Environ. Sci. 2012, 5, 7050.
[38]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, Nat. Commun. 2016, 7, 12123.
[39]J. H. Montoya, C. Shi, K. Chan, J. K. Nørskov, J. Phys. Chem. Lett. 2015, 6, 2032.
[40]F. Calle-Vallejo, M. T. M. Koper, Angew.ꢀChem.ꢀInt.ꢀEd. 2013, 52, 7282.
11

Journal of Materials Chemistry A
Page 12 of 16
Figure and caption
View Article Online
DOI: 10.1039/D0TA03565C
Figure 1. (a) SEM, (b, c) TEM, (d) HRTEM images of CuO nanowires. Inset (b) SAED pattern, inset (d)
HRTEM image of lattice fringe.
12

Page 13 of 16
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA03565C
Figure 2. (a) LSV curves of Cu foil and OD-Cu-3 catalyst in Ar-/CO2-statuarted 0.1 M KHCO3 solution, (b)
products FE of OD-Cu-3 at each potential, (c) FE of C1 (CH4, HCOOH, CO), C2 (C2H4 and CH3CH2OH)
products of different catalysts at -1.3 V vs. RHE, (d) Stability test of OD-Cu-3 at -1.3 V vs. RHE during the
12 h electrolysis, (e) LSV curves of OD-Cu-3 in the H-cell and flow cell. (f) FE and partial current density of
C2H4 (red dots) in the flow cell.
13

Journal of Materials Chemistry A
Page 14 of 16
View Article Online
DOI: 10.1039/D0TA03565C
Figure 3. (a) XRD pattern, (b) Cu 2p XPS spectra, (c) Cu LMM Auger spectra, (d) single oxidative scans in
0.1 M KOH at a scan rate of 10 mV s-1 on CuO and OD-Cu catalysts.
14

Page 15 of 16
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA03565C
Figure 4. (a) SEM, (b) TEM, (c, d) HRTEM images and (e) in-situ Raman spectra at -1.0 V vs. RHE for
OD-Cu-3 catalyst. Inset of (b) is the corresponding SAED pattern.
15

Journal of Materials Chemistry A
Page 16 of 16
View Article Online
DOI: 10.1039/D0TA03565C
Enriching Interface: Metal-organic Framework-derived copper oxide nanowires with abundant crystalline
interface contribute to the efficient electrochemical CO2 reduction towards the fast hydrocarbon generation.