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Article https://doi.org/10.1038/s41467-025-57307-6
Electronic metal-support interaction
modulates Cu electronic structures for CO
2
electroreduction to desired products
Yong Zhang
1
,FeifeiChen
1
,XinyiYang
1
,YiranGuo
1
, Xinghua Zhang
2
,
Hong Dong
1
,WeihuaWang
1
,FengLu
1
,ZunmingLu
2
,HuiLiu
3
,HuiLiu
1
,
Yao Xiao
4
&YahuiCheng
1
In this work, the Cu single-atom catalysts (SACs) supported by metal-oxides
(Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
) are used as theoretical models to
explore the correlations between electronic structures and CO
2
RR perfor-
mances. For these catalysts, the electronic metal-support interaction (EMSI)
induced by charge transfer between Cu sites and supports subtly modulates
the Cu electronic structure to form different highest occupied-orbital. The
highest occupied 3d
yz
orbital of Al
2
O
3
-Cu
SAC
enhances the adsorption strength
of CO and weakens C-O bonds through 3d
yz
-π* electron back-donation. This
reduces the energy barrier for C-C coupling, thereby promoting multicarbon
formationonAl
2
O
3
-Cu
SAC
. The highest occupied 3d
z2
orbital of TiO
2
-Cu
SAC
accelerates the H
2
O activation, and lowers the reaction energy for forming
CH
4
. This over activated H
2
O, in turn, intensifies competing hydrogen evolu-
tion reaction (HER), which hinders the high-selectivity production of CH
4
on
TiO
2
-Cu
SAC
.CeO
2
-Cu
SAC
with highest occupied 3d
x2-y2
orbital promotes CO
2
activation and its localized electronic state inhibits C-C coupling. The mod-
erate water activity of CeO
2
-Cu
SAC
facilitates *CO deep hydrogenation without
excessively activating HER. Hence, CeO
2
-Cu
SAC
exhibits the highest CH
4
Far-
adaic efficiency of 70.3% at 400 mA cm−2.
Renewable energy-driven electrochemical carbon dioxide reduction
reaction (CO
2
RR) is a promising method for achieving carbon cycle
and clean production of chemicals1,2.CO
2
molecules are deeply
reduced on the Cu-based catalyst surface into hydrocarbons and
oxygen-containing compounds such as methane (CH
4
), ethylene
(C
2
H
4
), ethanol (EtOH), etc., through multiple electron-proton coupled
steps of CO
2
RR3. Although these high value chemicals and high energy
density fuels have broad markets, industrial-scale implementation of
CO
2
RR still has a long way to go4. On the one hand, in aqueous media,
water (H
2
O) molecules serve as the proton source for electrochemical
reactions, leading to a conflict between CO
2
RR and hydrogen evolu-
tion reaction (HER)5–8. The proton-electron coupling properties of
CO
2
RR require effective activation of H
2
O and smooth proton transfer
to avoid excessive activation of H
2
O, otherwise HER would competi-
tively overwhelm CO
2
RR. On the other hand, deep hydrogenation of
adsorbed CO (*CO) and C-C coupling often coexist and compete with
each other, resulting in lowproduct selectivity7,9–11. The adsorption and
coverage of key *CO intermediate on the catalyst surface are crucial in
controlling the selectivi ty of C
2
products10,11. Hence, the rational design
and controllable synthesis of catalysts based on the deep under-
standing of reaction mechanism and structure-activity relationship is
crucial for precise regulation of the competitive pathways for CO
2
RR.
Modulating the electronic structure of a catalyst and elucidating
its influence over catalytic activity is an effective approach for studying
Received: 23 August 2024
Accepted: 18 February 2025
Check for updates
1
Department of Electronic Science and Engineering, Nankai University, Tianjin, China.
2
School of Material Science and Engineering, Hebei University of
Technology, Tianjin, China.
3
Institute of New-Energy Materials, Tianjin University, Tianjin, China.
4
College of Chemistry and Materials Engineering, Wenzhou
University, Wenzhou, China. e-mail: hui_liu@tju.edu.cn;liuhui@nankai.edu.cn;xiaoyao@wzu.edu.cn;chengyahui@nankai.edu.cn
Nature Communications | (2025) 16:1956 1
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the structure-activity relationships. To modulate Cu electronic struc-
ture, research interest has concentrated on alloying12,13,doping
engineering14,15, metal-support interaction (MSI) modulation16,17,andso
on. In heterogeneous catalysis, MSI significantly affects the catalytic
performance as it modulates the electronic and geometric structures
of metal as well as coordination environments. The electronic metal-
support interaction (EMSI) was further proposed by Campbell, which
goes beyond MSI and provides a much more detailed explanation of
the enhanced properties of supported catalysts than MSI18–20.EMSIis
associated with the orbital rehybridization and charge transfer across
the metal-support interface, leading to the formation of new chemical
bonds and the realignment of molecular energy levels19–21. By precisely
controlling the d-band structure of metal through EMSI, the adsorp-
tion scaling relation can be disrupted to regulate the adsorption of key
intermediates. Thisis crucial for the precise control of CO
2
RR pathway
because protonating to form key intermediates (such as *COOH and
*CHO) is difficult on weakly adsorption surface, while over-
strengthening of the adsorption energy would favor HER according
to the adsorption scaling relation10,22. However, limited by the intrinsic
bulk effects, accurately identifying the orbital information of metal
particles or clusters still poses challenges inproviding design guidance
or performance enhancement explanations for supported catalysts20.
The EMSI based on single-atom catalysts (SACs) provides a bridge
for theoretical electronic structure studies and the design of hetero-
genous catalysts because their electronic structure can be easily
characterized through experiments and theoretical calculations20,23–25.
Strong EMSI not only stabilizes the single-atom metals due to the
thermodynamicallyfavorable metal-support bond formation, but also
leads to the charge redistribution induced via electron transfer,
affecting the energy level distribution of the 3 d orbitals of single
atoms26–30. For example, Ma et al. reported that the coordination
environment of Fe-N
5
raises the energy level of Fe 3d
z2
orbital com-
pared to that of Fe-N
4
, thereby enhancing COOH adsorption and
promoting *CO desorption26. Therefore, the energy level of Cu 3dstate
may be manipulated by coordination structural perturbations of the
Cu atom30. Although SACs have been widely used for CO
2
RR, general
relationships between electronic structures and the catalytic behaviors
of SAC remain unclear. Hence, a comprehensive atomic-level insights
into the structure-activity relationship of Cu SAC is urgently needed
for guiding the regulation of *CO deep hydrogenation or coupling.
Herein, the Cu SACs supported by Al
2
O
3
(Al
2
O
3
-Cu
SAC
), CeO
2
(CeO
2
-Cu
SAC
), and TiO
2
(TiO
2
-Cu
SAC
) are constructed by atomic layer
deposition (ALD) technique and the correlations between the char-
acteristics of electronic structures and the CO
2
RR performance are
rationalized through detailed characterization and density functional
theory (DFT) calculations. The switching of supports subtly modulates
the electronic structure of Cu sites to form three SACs with completely
different highest occupied orbitals (3d
yz
orbital for Al
2
O
3
-Cu
SAC
,3d
x2-y2
orbital for CeO
2
-Cu
SAC
,and3d
z2
orbital for TiO
2
-Cu
SAC
). The 3d
yz
of
Al
2
O
3
-Cu
SAC
tends to interact with the π* anti-bonding orbital of CO,
which enhance CO adsorption on Al
2
O
3
-Cu
SAC
and weaken the C-O
bonds through 3d
yz
-π* electron back-donation. Meanwhile, the Cu
electron delocalization increases the CO adjacent-adsorption energies
on Al
2
O
3
-Cu
SAC
. These enhance the C-C coupling on Al
2
O
3
-Cu
SAC
,
resulting in a lowest ratio of CH
4
Faradaic efficiency (FE) to C
2
FE
(FE
CH4
/FE
C2
, 1.08). The3d
z2
of TiO
2
-Cu
SAC
exhibits strong hybridization
with the σbonding and σ* anti-bonding orbitals of H
2
O, which
enhances the adsorption of H
2
O and promotes H
2
O dissociation by
weakening O-H bonds. Therefore, TiO
2
-Cu
SAC
exhibits a highest FE
CH4
/
FE
C2
of 4.14. However, this over activated H
2
O, in turn, intensifies
competing HER, which hinders the high-selectivity production of CH
4
on TiO
2
-Cu
SAC
.The3d
x2-y2
orbital effectively promotes CO
2
activation
and its localized Cu electronic state inhibits C-C coupling. This makes
CeO
2
-Cu
SAC
exhibit a FE
CH4
/FE
C2
of 3.16. Meanwhile, the moderate
water activity of CeO
2
-Cu
SAC
facilitates *CO deep hydrogenation
without excessively activating HER, resulting in the highest CH
4
FE of
70.3% at 400 mA cm−2.
Results
Theoretical analysis of electronic structure
To explore the structure-activity relationship of Cu single-atom elec-
tronic structure in selective *CO deep hydrogenation or coupling,
theoretical analysis based on DFT + U calculations was conducted. By
loading Cu single atoms on Al
2
O
3
,CeO
2
, and TiO
2
supports to mod-
ulate the electronic structure of Cu single-atom (Supplementary Fig. 1
and Supplementary data 1), named as Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,and
TiO
2
-Cu
SAC
. As shown in Supplementary Fig. 2, the partial density of
states (PDOS) of Cu 3 dorbitals of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
, and TiO
2
-
Cu
SAC
surfaces are calculated, and the respective energy levels of 3 d
xy
,
3d
x2-y2
,3d
yz
,3d
xz
,and3d
z2
are plotted based on their d-band center
(Fig. 1a)30. Instead of forming a broad d-band, each 3d state is spatially
highlylocalized with a narrow energy window. On Al
2
O
3
-Cu
SAC
,the3d
yz
is the highest occupied-orbital; on CeO
2
-Cu
SAC
,the3d
x2-y2
is the
highest occupied-orbital; while on TiO
2
-Cu
SAC
,the3d
z2
is the highest
occupied-orbital. Clearly, changing the support can significantly affect
the highest occupied-orbital of the Cu single-atom due to the orbital
rehybridization and charge transfer across the metal-support interface
(Supplementary Fig. 3)21.Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
each present Cu single-atoms with three completely different highest
occupied-orbitals. The highest occupied d-orbitals often play an
important role in regulating the binding modes of intermediates
because the electrons filled on the orbital closer to the Fermilevel (E
f
)
are more active27. From the orbital wave functions, it can be observed
that the 3d
yz
orbital (localize in Zaxis) symmetry and energy-match
with the π* orbital of CO, facilitating the formation of 3d
yz
-π*bonds
(Fig. 1b). The 3d
z2
orbital symmetry and energy-match with the σ
orbital of CO as well as σ/σ* orbital of H
2
O, thereby aiding in the
formation of d
z2
-σ/σ* bonds (Fig. 1b and Supplementary Fig. 4). The
3d
x2-y2
orbital symmetry and energy-match with the π*orbitalsofCO
2
,
promoting the formation of 3d
x2-y2
-π* bonds.
Figure 1c and Supplementary Figs. 5, 6 show the PDOS of CO and
H
2
O molecular frontier orbitals as well as the PDOS of CO and H
2
O
adsorption on Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
surfaces. The
PDOS proves that the strong hybridization between CO and Cu atom
mainly contributes from the 3d
yz
and 3d
z2
orbital, and the hybridiza-
tion between H
2
O and Cu mainly contributes from the 3d
z2
orbital. The
hybridization of the Cu 3dorbital with the CO σis primarily con-
tributed by the 3d
z2
orbital, while the contribution to the CO π*is
mainly from the 3d
yz
orbital. This aligns with the analysis of the orbital
wave functions. On Al
2
O
3
-Cu
SAC
,the3d
z2
orbitalof Cu hybridize with σ
orbitalof CO, while stronger hybridization occurs between the highest
occupied 3d
yz
orbital and π* orbital of CO than that of CeO
2
-Cu
SAC
and
TiO
2
-Cu
SAC
31. The d-band center of 3d
yz
(−0.26 eV) on Al
2
O
3
-Cu
SAC
are
closer to the E
f
than that on CeO
2
-Cu
SAC
(−0.50 eV) and TiO
2
-Cu
SAC
(−0.64 eV), making more active electrons in 3 d
yz
easily back-donate to
the π* of CO as formation of Cu-CO bonds29,32. Moreover, due to anti-
bonding feature of the π* orbital, the 3d
yz
-π* bonding will weaken C-O
bonds in *CO, which can facilitate the subsequent reactions of *CO
(hydrogenation or coupling)29,32. In contrast, the highest occupied 3d
z2
orbital of TiO
2
-Cu
SAC
exhibits strong hybridization with the σorbital of
CO, while the hybridization between 3d
yz
and π* is lower than that of
Al
2
O
3
-Cu
SAC
(Supplementary Fig. 6a). Due to the bonding and anti-
bonding orbitals of H
2
Oisσand σ*, the hybridization between Cu 3d
and H
2
OonTiO
2
-Cu
SAC
are remarkably stronger than that on Al
2
O
3
-
Cu
SAC
and CeO
2
-Cu
SAC
(Fig. 1c and Supplementary Fig. 6b, d), leading
to an enhanced ability for TiO
2
-Cu
SAC
to adsorb H
2
O. In addition, the
interaction between the d
z2
orbital and the anti-bonding σ*orbital
weakens the O-H bonds, thereby promoting the dissociation of H
2
O.
On CeO
2
-Cu
SAC
, the highest occupied 3d
x2-y2
orbital tends to couple
with the lowest π*orbitalofCO
2
(Supplementary Fig. 7), weakening
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 2
Content courtesy of Springer Nature, terms of use apply. Rights reserved
C-O bonds and favoring hydrogenation on the low-coordinate O atom
to form the crucial *COOH intermediate, thereby promoting the acti-
vation of CO
2
to form *COOH27,33.
The CO adsorption energies of Cu single-atom on these three
supports follows the order Al
2
O
3
-Cu
SAC
(−1.22 eV) > CeO
2
-Cu
SAC
(−0.74 eV) > TiO
2
-Cu
SAC
(−0.46 eV), consistent with the energy level
arrangement of the 3d
yz
orbital (Supplementary Fig. 8 and Fig. 1a). The
H
2
O adsorption energies are strongly related to the position of the 3d
z2
orbital energy level, showing the order TiO
2
-Cu
SAC
(−0.89 eV) > Al
2
O
3
-
Cu
SAC
(−0.30 eV) > CeO
2
-Cu
SAC
(−0.16 eV). The crystal orbital Hamilton
population (COHP) was further used to analyze the Cu-C bond
strength in Cu-CO andthe Cu-O bond strength in Cu-H
2
O(Fig.1d, e and
Supplementary Fig. 9)34.OnAl
2
O
3
-Cu
SAC
, the Cu single-atom exhibits
the strongest Cu-C bonding with an integrated COHP (ICOHP) of
−3.88 eV, followed by CeO
2
-Cu
SAC
(−3.71 eV) and TiO
2
-Cu
SAC
(−3.65 eV).
Below the E
f
, there are fewer filling electrons in the anti-bonding
orbitals for Cu-C compared to that of Cu-O on Al
2
O
3
-Cu
SAC
, indicating
that 3d
yz
is more favorable for bonding with CO. In contrast, TiO
2
-
Cu
SAC
exhibits the highest ICOHP of −2.45 eV, suggesting that the
3d
z2
orbital is favor for 3d
z2
-H
2
O bonds. Moreover, TiO
2
-Cu
SAC
exhibits
the lowest H
2
O dissociation energy of −0.52 eV, succeeded by Al
2
O
3
-
Cu
SAC
and CeO
2
-Cu
SAC
(Fig. 1f). This provides sufficient activated
protons for *CO deep hydrogenation to form CH
4
.However,excessive
activation of H
2
O could enhance competitive HER, and the formation
energy of H
2
on TiO
2
-Cu
SAC
is as low as 0.18 eV, which may significantly
suppress CO
2
RR activity (Supplementary Fig. 10). On the pure CeO
2
(111) surface far away from Cu single-atom sites, the dissociation
energy of H
2
O is 1.33eV, which can also provide sufficient protons for
CO adsorbed on Cu single-atom sites hydrogenation.
After coordination between Cu and O, a large amount of charge
accumulates around the O atom, while Cu carries the positive charge
due to the higher electronegativity of O than that of Cu. Bader charge
analysis shows that the Bader charge of Cu is 10.13 |e−
|inAl
2
O
3
-Cu
SAC
,
10.57 |e−
|inCeO
2
-Cu
SAC
,and10.37|e
−
|inTiO
2
-Cu
SAC
(Supplementary
Al2O3-CuSAC TiO2-CuSAC
d
Cu Cu
A
B
C
g
Al2O3-CuSAC CeO2-CuSAC TiO2-CuSAC
Cu Cu
Cu 3dyz
CO π* CO σ
abc
ef
hi
PDOS (a.u.)
dyz-π*
dyz/dz2-σ/π
3dyz-π*
Cu 3dz2
3dz2-σ
y
x
z
Cu 3dz2
3dz2-σ
H2O σ
1
0
dz2-σ*
dz2-σ
π
E-EF (eV)
Fig. 1 | Electronic structure analysis. a The Cu 3 ddiagrams of Al
2
O
3
-Cu
SAC
,CeO
2
-
Cu
SAC
, and TiO
2
-Cu
SAC
, respectively. bThe binding modes of CO and H
2
O inter-
acting withCu site. cThe Cu 3 dPDOS of Al
2
O
3
-CuSAC with adsorbed CO and H
2
O,
as well as PDOSof CO and H
2
O orbitals after adsorbed(The inset is anenlarged view
ofthedashedlineinc). The COHP curves of Cu−C bonds and Cu-O bonds in
dAl
2
O
3
-Cu
SAC
and eTiO
2
-Cu
SAC
.fFree energy diagram for the dissociation of *H
2
O.
gThe ELF of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
, and TiO
2
-Cu
SAC
.hSchematic diagram of CO
adjacent-adsorption on Al
2
O
3
-Cu
SAC
surface. iThe CO adsorption energy of Al
2
O
3
-
Cu
SAC
,CeO
2
-Cu
SAC
, and TiO
2
-Cu
SAC
. Relevant source data are provided as a Source
Data file.
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 3
Content courtesy of Springer Nature, terms of use apply. Rights reserved
Fig. 11). The electron localization function (ELF) obtained from DFT
calculations indicates that Al
2
O
3
attracts more electrons from Cu,
leading to electron delocalization around the Cu single atom (Fig.1g)35.
Further calculations are performed for the top-adsorption energy and
adjacent-adsorption energies of CO on the Cu single-atom, and the
corresponding adsorption modes are shown in Fig. 1h and Supple-
mentary Fig. 12. On Al
2
O
3
-Cu
SAC
, there is only a slight decrease in the
CO adjacent-adsorption energies (−0.35 to −1.44 eV) compared to the
top-adsorption energy (Fig. 1i). This indicates that the delocalized
electronic state of Cu on Al
2
O
3
-Cu
SAC
enables more CO molecules to
adsorb around the Cu atom for C-C coupling36.OnCeO
2
-Cu
SAC
,the
electronegativity of Cu is higher than that of Ce, enabling Cu to attract
electrons from Ce, significantly reducing the electron delocalization
around the Cu single-atom (Fig. 1g). As a result, the adjacent-
adsorption energies of CO (0.35 to −0.65 eV) on the Cu atom sig-
nificantly decreases compared to top-adsorption energy, making *CO
more likely to undergo deep hydrogenation in the form of individual
top-adsorption rather than C-C coupling.
Synthesis and characterization
To verify the results of DFT calculations, Cu atoms were deposited on
α-Al
2
O
3
, rutile TiO
2
,andfluorite CeO
2
supports using ALD technique.
Scanning electron microscopy (SEM) and transmission electron
microscopy (TEM) images indicate that the morphologies of these
three supports consist of irregular nanoparticles (NPs) with particle
sizes larger than 50 nm, thus avoiding size effects of supports (Sup-
plementary Figs. 13 and 14)37. X-ray diffraction (XRD) patterns and high-
resolution TEM (HRTEM) images confirm that the supports are pure
phases of Al
2
O
3
,TiO
2
,andCeO
2
(Supplementary Figs. 14 and 15). Ben-
efiting from the ALD technique relying on sequential molecular-level
self-limiting surface reactions38,39, the Cu atom can anchor on supports
in the form of a single atom (Fig. 2a). The Inductively coupled plasma
optical emission spectrometer (ICP-OES) measurements indicate that
the Cu loading amounts for Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
are 1.28 ± 0.23, 1.43 ± 0.09, and 1.76 ± 0.17 wt%, respectively (Supple-
mentary Table 1). Aberration-corrected high-resolution high-angle
annular dark-field scanning TEM (HAADF-STEM) images show that Cu
atoms are atomically dispersed in Al
2
O
3
,TiO
2
,andCeO
2
supports
(Fig. 2b–d), without the presence of any visible clusters at both low and
high magnifications (Supplementary Fig. 16). XRD patterns and SEM
images of the samples after ALD further confirm that no observable Cu
NPs are deposited on supports (Supplementary Figs. 17 and 18).
HAADF-STEM and energy dispersive X-ray spectroscopy (EDS) element-
mapping images indicate that Cu is evenly distributed throughout the
Al
2
O
3
,TiO
2
,andCeO
2
supports (Fig. 2e, f). By controlling the ALD
process, Cu NPs loaded heterogenous catalysts were also prepared to
serve as an expansion of EMSI catalysts (Supplementary Fig. 19). The
catalysts loaded with Cu NPs on Al
2
O
3
and CeO
2
are named Al
2
O
3
-
CuNPs and CeO
2
-CuNPs, respectively. The Cu loading amounts for
Al
2
O
3
-CuNPs and CeO
2
-CuNPs are 2.91 ± 0.34 and 3.34 ± 0.53 wt%,
respectively (Supplementary Table 2). The statistical particle size dis-
tribution of Cu NPs based on TEM images displays that the average
diameter of Cu NPs loaded onto Al
2
O
3
and CeO
2
are 20.0 ± 0.3 nm and
17.4 ± 0.4 nm, respectively (Supplementary Figs. 20 and 21). HRTEM
images of Al
2
O
3
-CuNPs and CeO
2
-CuNPs both reveal interfaces
between Cu NPs and the supports, with the Cu NPs partly and firmly
socketed onto the support surface (Supplementary Figs. 20e and 21b).
To acquire the structural information of Cu/metal-oxides SAC,
synchrotron-based X-ray adsorption spectroscopy and X-ray photo-
electron spectroscopy (XPS) were performed. In the X-ray absorption
near-edge structure (XANES) spectra, the absorption edges for Al
2
O
3
-
Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
shift to higher energy than that of
Cu-foil, indicating that the Cu atoms are in an oxidized state (Supple-
mentary Fig. 22)40.Thefirst peaks of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,and
TiO
2
-Cu
SAC
are similar and close to that of CuO (8986.4 eV) in the first
derivative of XANES spectra (Fig. 3a), indicating that the valence of Cu
species in Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
are close to +241.
Only one apparent peak at 1.50 Å corresponding to the first coordi-
nation shell of Cu-O scattering can be detected in the extended X-ray
absorption fine structure (EXAFS) spectra of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,
and TiO
2
-Cu
SAC
(Fig. 3b). This confirms that Cu atoms are atomically
dispersed because no Cu-O-Cu or Cu–Cu metallic bonds are observed.
The EXAFS fitting data for Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
are shown in Fig. 3c, Supplementary Fig. 23, and Supplementary
Table 3. The average Cu-O coordination numbers of Al
2
O
3
-Cu
SAC
,
CeO
2
-Cu
SAC
, and TiO
2
-Cu
SAC
are 3.37, 3.67, and 3.41, respectively.
Combined with the results of theoretical calculations (Cu
1
-O
3
has the
lowest free energy; Supplementary Fig. 1), these data reveal that the
local structure of Cu/metal-oxides SAC comprised one isolated Cu
atom may coordinate with about three oxygen atoms (Cu
1
-O
3
units) in
the triangular pyramid structure between the Cu and O atoms
(Fig. 3d)41,42.Thefitting of Cu 2pXPS spectra indicate that the pre-
dominant oxidation state on the surfaces of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,
and TiO
2
-Cu
SAC
is Cu2+, with proportions of 86.2%, 85.5%, and 86.4%,
respectively. (Fig. 3e). Compared to CuO, the Cu 2pXPS peaks of Al
2
O
3
-
Cu
SAC
and TiO
2
-Cu
SAC
shift to higher binding energy, while Ti 2pand Al
2pXPS peaks shift to lower binding energy than that of pureAl
2
O
3
and
TiO
2
(Supplementary Fig. 24). It means that the electron transfers from
Cu to the adjacent Al
2
O
3
and TiO
2
supports, which results from the
strong EMSI between Cu and metal-oxide supports. In contrast, the Cu
2pXPS peak shifts to lower binding energy on the surface of CeO
2
-
Cu
SAC
, indicating that Cu attracts electrons from CeO
2
supports, pos-
sibly due to the higher electronegativity of Cu compared to Ce atom.
These results of electron transfer between Cu and the supports are
consistent with DFT calculations.
Using CO as a probe molecule, the atomic dispersion of Cu atoms
and the stability of Cu single-atoms during the CO
2
RR process can be
characterized by in-situ Raman spectroscopy (Fig. 3f)43.Inthe0.1M
CO-saturated KHCO
3
solution, Raman peaks attributed to linear top
adsorption (atop) of CO (C-O stretching vibration) are observed at
2087 and 2058 cm−1for Cu
2
O and Cu, respectively44. Bridged adsorp-
tion of CO (i.e., CO adsorbed on two adjacent Cu atoms) is also
observed on the Cu surface. In contrast, bridged adsorption of CO is
not detected on the Cu SAC surface. Raman spectra collected on the
supports show that there is no peak in the range from 1800 cm−1to
2200 cm−1, suggesting that there is no CO adsorption on the supports
(Supplementary Fig. 25). Therefore, the Raman peaks located at 2110,
2105, and 2123 cm−1can be attributed to CO atop on the Cu single-sites
of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
45. DFT calculations based
on the Blyholder model reveal differences in the frequency of C-O
stretching vibrations between Cu single sites and Cu cluster sites
(Supplementary Fig. 26), providing the basis for spectroscopic mea-
surements to assess the stability of Cu single atoms. The stability of Cu
single-atoms correlates well with the affinity between the Cu sites and
supports, specifically, strong interactions between Cu and O lead to
high stability43. To evaluate the stability of Cu single-atoms during the
electroreduction process, a constant potential of −1.5 V (all potentials
in this work are vs. the reversible hydrogen electrode, RHE) was
applied to Al
2
O
3
-Cu
SAC
electrode for 60 min. After electrolysis at −1.5 V
for 60 min, no corresponding Raman peaks are observed for CO
bridge-adsorption on metal Cu sites (Fig. 3g), indicating that Cu
remains anchored in supports in the form of single-atoms during the
electrolysis process. The reduce in intensity of CO atop Raman peaks
could be attributed to the accumulation of bubbles during long-term
electrolysis. Similarly, the stability of the supports during electrolysis is
maintained due to the high reduction potentials of Al
2
O
3
,CeO
2
,and
TiO
2
.Specifically, after prolonged CO
2
electrolysis, CeO
2
-Cu
SAC
does
not show Raman peaks caused by oxygen defects of CeO
2
(570 cm−1),
and the first-order F
2g
Raman peak characteristic of CeO
2
(463 cm−1)
remains present during the whole CO
2
RR process (Fig. 3h)46.In-situ
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 4
Content courtesy of Springer Nature, terms of use apply. Rights reserved
[0 0 1]
1 nm
Cu
Cu
2 nm
[1 1 1]
Cu
[0 1 0]
1 nm
HAADF
50 nm
Cu Al O
100 nm
100 nm
HAADF Cu Ce O
HAADF Cu Ti O
a
bcd
e
f
g
50 nm
100 nm
100 nm
50 nm
100 nm
100 nm
50 nm
100 nm
100 nm
Fig. 2 | Synthesis and structural characterization. a Schematic of the synthesis
process for Cu SAC support with metal-oxide. High-resolution HAADF-STEM ima-
ges of bAl
2
O
3
-Cu
SAC
,cCeO
2
-Cu
SAC
,anddTiO
2
-Cu
SAC
. Atomic models: Al, gray; Ce,
yellow; Ti, bule; and O, red. HAADF-STEM and EDS element-mapping images of
eAl
2
O
3
-Cu
SAC
,fCeO
2
-Cu
SAC
,andgTiO
2
-Cu
SAC
.
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 5
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Raman spectra of Al
2
O
3
-Cu
SAC
and TiO
2
-Cu
SAC
also confirm their sta-
bility during long-term electrolysis (Supplementary Fig. 27)47.
CO
2
RR performance
Electrochemical experiments on Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
, and TiO
2
-
Cu
SAC
were conducted in a flow cell with constant potential electro-
lysis. The main gas products observed during CO
2
RR are CH
4
,C
2
H
4
,
CO, and H
2
, with minor liquid products (Supplementary Fig. 28). Prior
to assessing the CO
2
RR performance of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,and
TiO
2
-Cu
SAC
, thorough consideration was givento exclude the potential
impacts of surface hydroxide adsorption, charge transfer resistance of
the support, and Cu loading amounts on the CO
2
RR performance of
catalysts through a series of electrochemical, BET, and SEM measure-
ments (Supplementary Figs. 29–31 and Supplementary Note 1). The
linear sweep voltammetry (LSV) curves indicate that the current den-
sities of Al
2
O
3
-Cu
SAC
increase the fastest with potential, followed by
CeO
2
-Cu
SAC
and TiO
2
-Cu
SAC
(Fig. 4a). Meanwhile, the current densities
of the samples measured with CO
2
gas at all applied potentials are
higher than those recorded with Ar gas, indicating the occurrence of
CO
2
RR. The smallest difference in current density values between
measurements of TiO
2
-Cu
SAC
in CO
2
and Ar atmospheres indicates that
TiO
2
-Cu
SAC
exhibits the highest HER activity and H
2
O dissociation
ability, followed by CeO
2
-Cu
SAC
and Al
2
O
3
-Cu
SAC
. The product dis-
tribution from −1.1 V to −1.5 V is displayed in Supplementary Fig. 28. At
−1.1 V, the ratio of CH
4
FE to C
2
FE for Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,and
TiO
2
-Cu
SAC
is 1.08, 3.16, and 4.14 respectively, and it increases as the
potential becomes more negative (Fig. 4b). As predicted by the elec-
tronic structure, Al
2
O
3
exhibits the highest selectivity of C
2
among
these three catalysts, while CeO
2
-Cu
SAC
and TiO
2
-Cu
SAC
show selec-
tivity towards CH
4
.AnanalysisoftheCH
4
kinetic isotopic effect (KIE),
defined as the ratio of CH
4
generation rate in H
2
OandD
2
O-based
electrolytes, was performed to assess the impact of electronic struc-
tures on the proton transfer process for CO
2
RR (Fig. 4candSupple-
mentary Fig. 32). The KIE values of Al
2
O
3
-Cu
SAC
are higher than CeO
2
-
e
ab
c
fgh
d
Top view
Side view
1.96 Å 1.96 Å
1.96 Å
Fig. 3 | Characterization of Cu single-sites. a The first derivatives of XANES
spectra. bThe corresponding k
2
-weighted Fourier transform spectra of EXAFS.
cFitting of k
2
-weighted EXAFS data of Al
2
O
3
-Cu
SAC,
CeO
2
-Cu
SAC
, and TiO
2
-Cu
SAC
in
the region of 1.0–2.5 Å. dThe proposed Cu
1
-O
3
configuration of Cu/metal-oxide
SAC. Atomic models: Metal,yellow, Cu, bule; and O, red. eThe Cu 2pXPS spectra.
fThe Ramanspectra of CO adsorption on Cu/metal-oxide SACs, Cu
2
O, and Cu. gIn-
situ Raman spectra of CO adsorption on Al
2
O
3
-Cu
SAC
for long-term electrolysis at
−1.5 V without iR correction. hIn-situ Raman spectra of CeO
2
-Cu
SAC
for long-term
electrolysis at −1.5 V without iR correction. Relevant source data are provided as a
Source Data file.
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 6
Content courtesy of Springer Nature, terms of use apply. Rights reserved
Cu
SAC
and TiO
2
-Cu
SAC
at all potentials and close to 2, indicating that its
rate-determining step involves H
2
O dissociation6.TiO
2
-Cu
SAC
has the
lowest KIE value, indicating that the 3d
z2
orbital significantly accel-
erates the activation process of H
2
O, while CeO
2
-Cu
SAC
shows mod-
erate dissociation rates of H
2
O. Considering the moderate CO
adsorption energy and the localized electronic state of CeO
2
-Cu
SAC
,
CeO
2
-Cu
SAC
demonstrates the highest CH
4
FE of 70.3%, especially at
high current density of 400 mA cm−2(Fig. 4d). Al
2
O
3
-Cu
SAC
and TiO
2
-
Cu
SAC
have relatively low CH
4
FE values of 46.5% and 53.7%, respec-
tively. CeO
2
-Cu
SAC
exhibits excellent performance in terms of the CH
4
FE and partial current density compared to previously reported
excellent catalysts (Supplementary Fig. 33 and Supplementary
Table 4)48.
Further testing was conducted on the CO
2
RR performance of
Al
2
O
3
-CuNPs and CeO
2
-CuNPs to validate the structure-activity rela-
tionships based on EMSI for guiding the design of supported catalysts.
Due to the promotion of C-C coupling bythe Cu electronic structure in
Al
2
O
3
-Cu
SAC
, it exhibits a higher FE
CH4
/FE
C2
. When extending Cu single-
atoms to Cu nanoparticles, more sites for CO or CHO adsorption and
coupling on the Cu surface can lead to the increased selectivity of C
2
product (Supplementary Fig. 34). The FEs of various C
2
products,
including C
2
H
4
, acetate (AcO–
), and EtOH, over the Al
2
O
3
-CuNPs within
a current density range of 200 to 1000 mA cm –2, are depicted in Fig. 4e.
Specifically, under the condition of constant current electrolysis, the
enhanced C
2
selectivity of Al
2
O
3
-CuNPs is observed, achieving the
highest C
2
FE of 81.3% at 900 mA cm−2. In contrast, the selectivity of C
2
ab
cde
fg
CeO2-CuSAC Al2O3-CuNPs
Fig. 4 | CO
2
RR performance. a The LSV curves of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,and
TiO
2
-Cu
SAC
with CO
2
and Ar as supplygases. bThe FE
CH4
/FE
C2
of Al
2
O
3
-Cu
SAC
,CeO
2
-
Cu
SAC
, and TiO
2
-Cu
SAC
at the potentials form −1.1 V to −1.5 V. cKIE of H/D for CO
2
RR-
to-CH
4
conversion at different potentials. dThe corresponding FEs at high current
densities. eFEs of Al
2
O
3
-CuNPs for CO
2
RR at different current densities. Long-term
stability of fCeO
2
-Cu
SAC
and gAl
2
O
3
-CuNPs at a constant current density of
400 mA cm−2.a–gNo iR correction was applied to calculate the applied potential.
The error bars represent standard deviations from at least three independent
measurements. Relevant source data are provided as a Source Data file.
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved
on CeO
2
-CuNPs do not significancy increase as the sites for C-C cou-
pling increased, with the C
2
FE of 35.8% and CH
4
FE of 40.2% at
500mAcm
−2(Supplementary Fig. 35). The LSV curves also reveal that
Al
2
O
3
-CuNPs displays a larger CO
2
response current density than CeO
2
-
CuNPs (Supplementary Fig. 36). The long-term durability of CeO
2
-
Cu
SAC
and Al
2
O
3
-CuNPs were evaluated by continuous CO
2
RR at
400 mA cm−2, with timely replacement of the electrolyte and clean the
GDE to avoid salt deposit (Fig. 4f, g). The applied potential of CeO
2
-
Cu
SAC
maintains stability for 70 h, with the CH
4
FE consistently
remaining above 55%. Al
2
O
3
-CuNPs also shows stability for 70h with a
FE
C2
stable above 62%. Finally, SEM, XRD, XPS, and TEM measurements
were conducted on CeO
2
-Cu
SAC
and Al
2
O
3
-CuNPs catalysts after sta-
bility tests, along with ICP-MS measurement on the electrolyte (Sup-
plementary Figs. 37, 38 and Supplementary Table 5). These results
collectively confirm the stability of the catalysts during long-term
CO
2
RR tests (Supplementary Note. 2).
DFT calculations and spectroscopic insights into CO
2
RR
Afterward, the DFT calculations were further carried out to reveal the
effect of the electronic structures on the selectivity of CO
2
RR
products. First, the energy required for converting CO
2
to *CO was
calculated for these three models, followed by the formation energy of
CH
4
through deep hydrogenation of *CO (Fig. 5a and Supplementary
Tables 6, 7). Consistent with the conclusions from electronic structure
analysis, the highest occupied 3d
x2-y2
orbital reduces the reaction
energy for CO
2
activation to form *COOH on CeO
2
-Cu
SAC
(−0.38 eV),
which is significantly lower than that on Al
2
O
3
-Cu
SAC
and TiO
2
-Cu
SAC
surfaces. The *COOH intermediate is reduced to the CO* species by
reacting with a proton and releasing a H
2
O molecule. Subsequently, in
the branch of *CO hydrogenation to *CHO or *COH, the *CHO should
be the major species formed from *CO hydrogenation on these sur-
faces because the reaction energy required for *CHO formation is
lower than that for *COH (Supplementary Fig. 39). The reaction energy
for *CO hydrogenation on TiO
2
-Cu
SAC
is the lowest with 0.02 eV, fol-
lowed by CeO
2
-Cu
SAC
of 0.61 eV and Al
2
O
3
-Cu
SAC
of 0.66 eV. In the
pathway for *CHO to form CH
4
, the reaction of *CHOH with a proton
and release of H
2
O to form *CH is the rate-limiting step for CO
2
RR-to-
CH
4
.Thereactionenergiesfor*CHOHto*CHonAl
2
O
3
-Cu
SAC
and
CeO
2
-Cu
SAC
are as high as 1.31 eV and 0.90 eV, respectively. In contrast,
the reaction energy for *CH is reduced to 0.46 eV due to the active
Fig. 5 | DFT calculations and in-situ ATR-IRAS. a Free energy diagram for CO
2
RR
to form CH
4
.bFree energy diagram for *CO-*CHO coupling. In-situ ATR-IRAS spectra
of CO
2
RR over c,dAl
2
O
3
-Cu
SAC
and eCeO
2
-Cu
SAC
. In-situ ATR-IRAS of O-H stretching
vibration for fAl
2
O
3
-Cu
SAC
,gCeO
2
-Cu
SAC
,andhTiO
2
-Cu
SAC
.iFraction of free H
2
Oin
the electrode-electrolyte interface. c–iNo iR correction was applied to calculate the
applied potential. Relevant source data are provided as a Source Data file.
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 8
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protons on TiO
2
-Cu
SAC
. Subsequently, the energy barriers for C-C
coupling on these three surfaces were calculated, which is crucial
for the formation of C
2
products and competes with *CO deep
hydrogenation. Specifically, the energy barrier for *CO-*CHO coupling
is the lowest with 0.37 eV on Al
2
O
3
-Cu
SAC
, followed by TiO
2
-Cu
SAC
of
0.61 eV and CeO
2
-Cu
SAC
of 0.80 eV (Fig. 5b and Supplementary
Fig. 40). It is noteworthy that on all three surfaces, the reaction ener-
gy for *CO dimerization is higher than that for asymmetric coupling
of *CO-*CHO (Supplementary Fig. 41), suggesting a coupling mechan-
ism on Cu SAC surfaces where *CO is hydrogenated to *CHO
and couples with surrounding CO intermediates. DFT calculations
further indicate that when the active sites on the Al
2
O
3
support switch
from Cu single-atom to Cu cluster, the consecutive Cu sites strongly
inhibit the thermodynamic generation of CH
4
while maintaining high
selectivity towards C
2
products (Supplementary Fig. 42).
The in-situ attenuated total reflectance infrared absorption spec-
troscopy (ATR-IRAS) was further carried out at different potentials to
reveal the intermediate absorption manners in different reaction
pathways. The infrared (IR) bands at Al
2
O
3
-Cu
SAC
and CeO
2
-Cu
SAC
are
assigned to corresponding intermediates based on independently
reported studies (Supplementary Table 8). The IR band at 1301cm−1
can be attributed to O-H deformation of *COOH, a critical intermediate
in the CO
2
to *CO conversion pathway (Fig. 5c, e)49,50. The IR bands at
1242 and 1263 cm−1can be attributed to C-H stretching vibration of
*CHO and *C-H deformation in the pathway for *CO deep hydrogena-
tion to produce CH
4
51–53.OnCeO
2
-Cu
SAC
, IR band (1738 cm−1) attributed
to the C = O stretching vibration of *CHO can also be detected54.TheIR
bands at 1340 and 1415 cm−1can be assigned to the O*CCHO inter-
mediate formed after asymmetric coupling of *CO and *CHO55.The
CHO part of O*CCHO is at 1340 cm−1,andtheCOpartofO*CCHOisat
1415 cm−1. The IR band at 2105 cm−1on Al
2
O
3
-Cu
SAC
can be attributed to
top-adsorption of CO (Fig. 5d), while no *CO intermediate is detected
on CeO
2
-Cu
SAC
(Supplementary Fig. 43), possibly due to low *CO
concentration or rapid consumption through hydrogenation56.The
broad IRband in the range of 1550–1700 cm−1can be attributed to H-O-
HbendofadsorbedH
2
O, with the peak on Al
2
O
3
-Cu
SAC
surface
appearing noticeably larger than that on CeO
2
-Cu
SAC
surface, con-
sistent with DFT calculations. To avoid the influence of the broad IR
band from H
2
O and verify whether the adsorbed species on Al
2
O
3
-
Cu
SAC
surface contain hydrogen, in-situ ATR-IRAS were repeated using
D
2
O insteadof H
2
O(0.1MCO
2
-saturated KDCO
3
in D
2
O). The H
2
Oband
disappearsandisredshiftedto1188cm
−1, which is consistent with the
in-plane bending vibration (D-O-D) of D
2
O (Supplementary Fig. 44)54,57.
The adsorbed carbonate band is blueshifted in the deuterated system
to 1496 cm−1, which is consistent with recent reported work52.Thisis
likely due to the deuteration altering the carbonate-bicarbonate
equilibrium and the carbonate adsorption process55. The asymmetric
C = O stretching vibration of *CO
2
−can be detected at 1601 cm−157.
Notability, the IR bands around 1242 (*CHO), 1263 (*C-H), 1301
(*COOH), and 1340 (O*CCHO) cm−1obviously shifted to 1227 (*CDO),
1257 (*C-D), 1285 (*COOD), and 1317 (O*CCDO) cm−1in D
2
O, suggesting
their relation with hydrogen53.OntheAl
2
O
3
-Cu
SAC
surface, the IR bands
of *CHO and *CO both undergo a redshift with increasing potential,
which is caused by the Stark effect (Fig. 5c, d)57. This indicates that *CO
and *CHO are in-situ generated, and coupling reactions occur between
them58. Moreover, the intensity of O*CCHO is significantly higher than
that of *C-H, indicating that the Al
2
O
3
-Cu
SAC
is more favorable for C-C
coupling reactions. In contrast, on the CeO
2
-Cu
SAC
surface, the inten-
sity of *C-H is significancy higher than that of O*CCHO, suggesting that
*CO on the CeO
2
-Cu
SAC
surface is more conducive to hydrogenation,
leading to the generation of a large amount of CH
4
.
The state of H
2
O molecules near the electrode-electrolyte inter-
faces of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
were then analyzed.
The broad band in 3000–3800 cm−1represents the stretching vibra-
tion mode of the O-H bond (Fig. 5f–h), and the broad band can be
divided into three peaks near 3610, 3450, and 3250 cm−1through
Gaussian fitting according to the distinct hydrogen bonding environ-
ments of water (Supplementary Fig. 45)6,59. They belong to water
without hydrogen-bonds (free H
2
O), with weak hydrogen-bonds
(liquid-like H
2
O), and strong hydrogen-bonds (ice-like H
2
O), respec-
tively. In general, an increased degree of hydrogen-bonds lowers the
energy of the O-H stretch, and thus the dissociation energies of H
2
O
increased in the order: free H
2
O <liquid-like H
2
O <ice-like H
2
O59,60.On
TiO
2
-Cu
SAC
, the initial proportion of free H
2
O is 98%, much higher than
CeO
2
-Cu
SAC
of 30% and Al
2
O
3
-Cu
SAC
of 20%. This suggests that the
TiO
2
-Cu
SAC
surface is enriched with free H
2
O, providing more active
protons for *CO deep hydrogenation and the HER reaction. As the
potential becomes more negative, the proportion of free H
2
Oonthe
three electrode surfaces gradually decreases, indicating the con-
sumption of free H
2
O involved in surface reactions (Fig. 5i). The con-
sumption rate of free H
2
OontheTiO
2
-Cu
SAC
surface is the fastest
(30% V−1) due to the strong hydrolytic ability of TiO
2
-Cu
SAC
. However,
an excess of active hydrogen enhances competing HER, increasing the
H
2
FE of TiO
2
-Cu
SAC
. In contrast, the low abundance of free H
2
Oand
weak hydrolytic ability of Al
2
O
3
-Cu
SAC
(10.8% V−1)make*COmore
prone to coupling rather than deep hydrogenation. CeO
2
-Cu
SAC
,
positioned in between Al
2
O
3
-Cu
SAC
and TiO
2
-Cu
SAC
,balances*COdeep
hydrogenation and the HER well, resulting in a CH
4
FE as high as 70.3%.
Discussion
In summary, Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
are successfully
constructed by ALD technique, and based on these catalysts, the cor-
relations between the characteristics of electronic structures and the
CO
2
RR performance are proposed through detailed characterization
and DFT calculations. The EMSI between Cu sites and Al
2
O
3
support
ranks the 3d
yz
orbital as the highest occupied orbital, which enhances
theadsorptionstrengthofCOandweakensC-Obondsthrough3d
yz
-π*
electron back-donation. This reduces the energy barrier for C-C cou-
pling, thereby promoting the formation of C
2
products on Al
2
O
3
-
Cu
SAC
. The EMSI between Cu sites and TiO
2
support ranks the 3d
z2
orbital as the highest occupied orbital, which enhances the adsorption
of H
2
OandpromotesH
2
O dissociation, thus lowering the energy
barrier for forming CH
4
. However, this over activated H
2
O, in turn,
intensifies competing HER, which hinders the high-selectivity pro-
duction of CH
4
on TiO
2
-Cu
SAC
.TheEMSIbetweenCusitesandCeO
2
support ranks the 3d
x2-y2
orbital as the highest occupied orbital, which
promotes CO
2
activation and protonation. CeO
2
-Cu
SAC
effectively
balances the CO adsorption strength with the activation of H
2
O,
resulting in the highest CH
4
FE of 70.3% among the three SACs at
400 mA cm−2. This structure-activity relationship based on EMSI can
provide inspiration for the design of supported catalysts. Under this
guidance, it is predicted that Cu nanoparticles loaded on Al
2
O
3
exhibit
higher C
2
selectivity than those on CeO
2
,andaC
2
FE of 81.3% at
900mAcm
−2is achieved. This work not only provides an efficient
catalyst for potential industrial application, but also gives an in-depth
understanding of the CO
2
RR mechanisms that may inspire the rational
design of other catalysts for the controlled CO
2
RR.
Methods
Preparation of Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
The pure α-Al
2
O
3
,fluorite CeO
2
, and rutile TiO
2
were purchased from
Shanghai Yaoyi Alloy Material Co.,Ltd. To deposit Cu single-atoms on
Al
2
O
3
,CeO
2
,andTiO
2
supports, the atomic layer deposition (ALD)
method was used. Firstly, 0.1 g of supports was evenly dispersed in a
crucible, and then the crucible was placed inside the vacuum chamber,
where the ALD took place. The vacuum chamber temperature was
maintained at 280 °C during the ALD process. Bis(hexa-fluor-
oacetylacetonato) copper(II) (Cu(hfac)
2
, 99.99%, Nanjing Ai Mou Yuan
Scientific Equipment Co. Ltd.) was used as Cu precursors, and H
2
Owas
used as reducing agent. Cu(hfac)
2
was kept at 150 °C and the N
2
carrier
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 9
Content courtesy of Springer Nature, terms of use apply. Rights reserved
gas was kept at 170 °C. The ALD cycle followed a precise sequence:
introducing Cu(hfac)
2
through a solenoid valve for 50 ms and purging
the chamber with N
2
for 12 s. Atthis point, the pressure response inthe
vacuum chamber was 0.5 Pa. Thereafter, H
2
O was injected for 100 ms
and another round of N
2
cleaning was executed for 30 s. This deposi-
tion cycle was repeated 150 times. After ending the ALD cycles, the
vacuum chamber was immediately heated to 480 °C with 5 °C min−1
and kept at 480 °C for 3 h to firmly anchor Cu single atoms on
supports.
Preparation of Al
2
O
3
-CuNPs and CeO
2
-CuNPs
The preparation of Al
2
O
3
-CuNPs and CeO
2
-CuNPs was generally similar
to the method used for SAC. The difference was: introducing Cu(hfac)
2
through a solenoid valve for 3 s and purging the chamber with N
2
for
12 s. At this point, the pressure response in the vacuum chamber was
10 Pa. Thereafter, H
2
O was injected for 200ms and another round of
N
2
cleaning was executed for 15 s. This deposition cycle was repeated
100 times.
Electrochemical CO
2
RR measurements
The obtained catalysts were made into electrode ink for CO
2
RR mea-
surements. 2 mg of catalystwas ultrasonically dispersed into a solution
containing 200 μL of isopropanol (99.9%, MERYER Co. Ltd.), 300 μLof
deionized water, and 20 μLofNafion (5 wt%, Alfa Aesar Co. Ltd.) to
form electrode ink. For CO
2
RR test, drop 80 μL of electrode ink onto
the gas diffusion electrode (GDE, 1.0 cm2active area) and then GDE
were heated at 60 °C for 0.5 h to remove residual isopropanol. The
activity and selectivity of the obtained catalysts were tested in a flow
cell comprising the GDE cathode (YLS-30T, Sinoro Energy Mall), anion-
exchange membrane (Fumasep FAB-PK-130, 130 μm, Sinoro Energy
Mall), Ag/AgCl electrode (3.0M KCl), and the IrO
2
@Ti mesh (0.5 mm
thickness) anode. Supply 20 standard cubic centimeter per minutes
(sccm) of CO
2
to the cathode side and 1.0M KOH (20.0mL) anolyte
stream that flowed through the anode at a rate of 10.0 mL min−1.A
solution of 1.0 M KOH (20.0 mL) was used as cathode electrolyte. The
CO
2
RR performance for the obtained catalysts was evaluated by
applying different currents with a current amplifier in the three-
electrode system at the electrochemical workstation (CHI660E,
Chenhua) with a current amplifier. The LSV curves test was conducted
at potentials from 0 V to −1.5Vvs.RHEwiththescanrateof50mVs
−1.
Potentials vs. Ag/AgCl reference electrode were converted to RHE
reference scale using the following equation without iRcompensation:
ERHE =EAg=Ag Cl +0:197 + 0:0591 × pH ,ð1Þ
The gas products were quantified by gas chromatography (GC,
FULI INSTRUMENTS GC9790 Plus) equipped with thermal con-
ductivity detector(TCD) and flame ionization detector (FID) detectors.
The GC was calibrated by five standard gases (H
2
,CO,CH
4
,C
2
H
4
and
C
2
H
6
in CO
2
) before use. The FEs of liquid products were calculated
using the total amount of the products collected at anodes and cath-
odes. The liquid product was detected by liquid 1H nuclear magnetic
resonance (NMR) spectroscopy (Bruker, AVANCE III 400 MHz Nano-
BAY), and 500 μL of electrolyzed electrolyte, 100 μLofD
2
O (99.9%,
MERYER Co. Ltd.) and 10 μLofDMSO(0.4μLmL
−1, MERYER Co. Ltd.)
were mixed uniformly in the NMR tube. FE of the CO
2
RR products were
computed from:
FEð%Þ=Fne
Q×100%,ð2Þ
where F is the Faraday constant (96485 C mol−1), nis the total
product (in mole), eis the number of transferred electrons for each
product, and Qis the current time integral the amount of charge
obtained.
Characterizations
The powder XRD patterns were obtained on a powder diffractometer
(Rigaku Smart Lab 3 kW) using Cu K
α
X-ray source. The SEM images of
the samples were obtained using a JSM-7800F SEM. The TEM images
were obtained with a Talos 200X G2 transmission scanning microscopy
at 200 kV. High-angle annular dark-field-scanning transmission elec-
tron microscopy (HAADF-STEM) characterizations were carried out on
aFEITitan
3G2 60–300 equipped with double aberration correctors,
which was operated at 200 kV. The X-ray absorption spectroscopy a t
the Cu K-edge was obtained at the BL14W beamlines at the Shanghai
Synchrotron Radiation Facility (SSRF) (Shanghai, China), using a Si (111)
crystal monochromator operated in transmission mode. The spectra
were processed and analyzed by the software codes Athena and Arte-
mis. XPS was performed on a Thermo Scientific ESCALAB 250Xi
instrument using Al K
α
X-ray source. The binding energy of the col-
lected spectra was calibrated by the C 1 s binding energy of 284.8 eV.
The inductively coupled plasma mass spectrometry (ICP-MS) datas
were determined using an Aglient 7850 (Ms) system. Nitrogen sorption
isotherms at 77 K were obtained on Micromeritics ASAP 2460.
In-situ Raman spectroscopy measurements
In-situ Raman spectra was recorded on laser Raman spectrometer
(LabRAM HR Evolution) with 785 nm laser (25% intensity). The in-situ
Raman spectroscopy measurements wereperformed in the Raman cell
(Tianjin Gaoss Union Technology Co. Ltd.) with a quartz optical win-
dow, an Ag/AgCl (3.0 M KCl) reference electrode and a Pt counter
electrode. Each Raman spectra was recorded for three accumulations
with an acquisition time of 20 s. The Raman cell was filled with 0.1 M
CO-saturated KHCO
3
electrolyte, and the CO flow rate was maintained
at 2 sccm during the CO adsorption measurements. The structural
evolution of the supports on Al
2
O
3
-Cu
SAC
,CeO
2
-Cu
SAC
,andTiO
2
-Cu
SAC
during the CO
2
RR process was conducted in 0.1 M CO
2
-saturated
KHCO
3
electrolyte, and the flow rate of electrolyte was sat as 2 sccm to
remove bubbles.
In-situ ATR-IRAS measurements
In situ ATR-IRAS was performed on a Nicolet iS50 spectrometer
equipped with an HgCdTe (MCT) detector and a VeeMax III (PIKE
Technologies) accessory. The measurement was conducted in an
electrochemical single-cell furnished with Pt and Ag/AgCl as counter
and reference electrodes. The cell was filled with 0.1 M CO
2
-saturated
KHCO
3
electrolyte. A fixed-angle Si prism (60°) coated with catalysts
embed into the bottom of the cell served as the working electrode.
Chronoamperometry was used for CO
2
RR test and was accompanied
by the spectrum collection (32 scans, 4 cm−1resolution). All spectra
were subtracted with the background.
DFT calculations
All DFT calculations were performed using Vienna ab initio simulation
package (VASP)61. The ion-electron interactions are represented by the
projector augmented wave (PAW) method and the electron exchange-
correlation by the generalized gradient approximation (GGA) with the
Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional62,63.The
Kohn-Shamvalencestateswereexpandedinaplane-wavebasissetwith
a cut-off energy of 450 eV and Brillouin-zone integrations were per-
formed using a (3 × 3 × 1) Monkhorst-Pack mesh during the optimiza-
tion. The bottom three atomic layers were fixed and the vacuum space
was 15 Å to avoid interactions with their periodic images in all calcula-
tions. The structure converges until all the forces on the free atoms were
less than 0.05 eV Å–1. The electronic self-consistent field cycles were set
at 10−5eV. The calculation was performed using generalized gradient
approximation with DFT + U and U - J = 3.0 eV for Cu 3 d;U-J=3.0eVfor
Ti 3 d;U-J=5.0eVforCe4f. The DFT + U method was employed to
calculate final structures and energies without entropy. The chemical
potential of the proton-electron pair (H++e
−
) was equated with the
Article https://doi.org/10.1038/s41467-025-57307-6
Nature Communications | (2025) 16:1956 10
Content courtesy of Springer Nature, terms of use apply. Rights reserved
chemical potential of a hydrogen molecule (H
2
) at the standard hydro-
gen electrode (SHE) potential reference64. The climbing-image-nudged-
elastic-band (CI-NEB) method was applied to locate transition structures
and the profile of the potential-energy surface (PES) was constructed
accordingly65. Frequency calculations were applied to verify the adsor-
bed intermediates and the transition states (with only one imaginary
frequency). The detailed DFT calculation process and descriptions can
be found in Supplementary Figs. 46, 47 and Supplementary Note 3.
Data availability
Source data are provided with this paper and are available from the
corresponding authors upon request. Source data are provided as a
Source Data file. Source data are provided with this paper.
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Acknowledgements
This work was supported by the following grants: National Natural Sci-
ence Foundation of China (No. 52071183, 51871122). The authors would
like to thank Meiyu Li from Shiyanjia Lab (www.shiyanjia.com)fortestsof
the XANES and EXAFS.
Author contributions
Y.C., H.L., (Nankai University), and H.L. (Tianjin University) supervised this
project. Y.Z. designed and performed most of the experiments and
analyzed the experimental data. F. C. performed the SEM measurements
and analyzed the results. Y. Z., X.Y., and Y. G. conducted the catalytic
tests. X.Z. and Z.L. performed the Raman measurements. Y. Z. and H. L.
(Tianjin University) performed the ATR-IRAS measurements. W.W., F.L.,
D.H., Y.X., and Y. Z. carried out the theoretical calculations. Y.Z., Y.C.,
and F.L. performed the TEM measurements and analyzed the results.
Y.X. and Y.Z. performed the BET and XAFS measurements. All authors
participated in the discussion of the research.
Competing interests
The authors declare no competing interests.
Additional information
Supplementary information The online version contains
supplementary material available at
https://doi.org/10.1038/s41467-025-57307-6.
Correspondence and requests for materials should be addressed to
Hui Liu, Hui Liu, Yao Xiao or Yahui Cheng.
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