Engineering Bismuth–Tin Interface in Bimetallic Aerogel with a 3D Porous Structure for Highly Selective Electrocatalytic CO2 Reduction to HCOOH

Article abstract of DOI:10.1002/anie.202102832

Electrochemical reduction of CO₂ (CO₂RR) into valuable hydrocarbons is appealing in alleviating the excessive CO₂ level. We present the very first utilization of metallic bismuth–tin (Bi-Sn) aerogel for CO₂RR with selective HCOOH production. A non-precious bimetallic aerogel of Bi-Sn is readily prepared at ambient temperature, which exhibits 3D morphology with interconnected channels, abundant interfaces and a hydrophilic surface. Superior to Bi and Sn, the Bi-Sn aerogel exposes more active sites and it has favorable mass transfer properties, which endow it with a high FE_HCOOH of 93.9 %. Moreover, the Bi-Sn aerogel achieves a FE_HCOOH of ca. 90 % that was maintained for 10 h in a flow battery. In situ ATR-FTIR measurements confirmed that the formation of *HCOO is the rate-determining step toward formic acid generation. DFT demonstrated the coexistence of Bi and Sn optimized the energy barrier for the production of HCOOH, thereby improving the catalytic activity.

Full text of DOI:10.1002/anie.202102832

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International Edition: doi.org/10.1002/anie.202102832
German Edition: doi.org/10.1002/ange.202102832
CO2 Electroreduction
Hot Paper
Engineering Bismuth–Tin Interface in Bimetallic Aerogel with a 3D
Porous Structure for Highly Selective Electrocatalytic CO2 Reduction
to HCOOH
Zexing Wu, Hengbo Wu, Weiquan Cai, Zhenhai Wen, Baohua Jia, Lei Wang,* Wei Jin,* and
Tianyi Ma*
Abstract: Electrochemical reduction of CO2 (CO2RR) into
valuable hydrocarbons is appealing in alleviating the excessive
CO2 level. We present the very first utilization of metallic
bismuth–tin (Bi-Sn) aerogel for CO2RR with selective
HCOOH production. A non-precious bimetallic aerogel of
Bi-Sn is readily prepared at ambient temperature, which
exhibits 3D morphology with interconnected channels, abun-
dant interfaces and a hydrophilic surface. Superior to Bi and
Sn, the Bi-Sn aerogel exposes more active sites and it has
favorable mass transfer properties, which endow it with a high
FEHCOOH of 93.9%. Moreover, the Bi-Sn aerogel achieves
a FEHCOOH of ca. 90% that was maintained for 10 h in a flow
battery. In situ ATR-FTIR measurements confirmed that the
formation of *HCOO is the rate-determining step toward
formic acid generation. DFT demonstrated the coexistence of
Bi and Sn optimized the energy barrier for the production of
HCOOH, thereby improving the catalytic activity.
structural durability and plentiful mass/electron transfer
channels, endowing their widely applications in diverse
electrocatalytic reactions.[2c,3] Relative to the monometallic
aerogel, bimetallic aerogels contain more favorable pores and
coupling effects and then benefiting to improve the electro-
catalytic performance further.[2c,4] Until now, most of the
reported bimetallic aerogels are derived from noble metals,
and seldom non-noble bimetallic aerogel electrocatalysts are
investigated.[5] Especially for CO2RR, non-noble metals
derived bimetallic aerogels are not reported yet which could
alleviate the ever-increasing CO2 emission and thereby
closing the anthropogenic carbon cycle.
CO2RR into feedstocks and fuels, powered by intermit-
tent recurring energies (e.g. wind, ocean and solar energies), is
considered as one of the most appealing approaches to
alleviate the ever-increasing greenhouse effect and energy
crisis.[6] Among the various products generated during
CO2RR, nontoxic formic acid, as one kind of liquid product,
is easily to store and carry, and also has been regarded as ideal
candidate for hydrogen storage and fuel cells.[7] However, the
conversion efficiency of CO2RR is low due to the thermody-
namic stable feature of CO2, multi-electron reaction pathway
and the competitive reaction of hydrogen evolution reaction
(HER), then leading to the sluggish reaction kinetics, large
activation overpotential and poor selectivity.[8] Consequently,
it is of immensely significance to exploit highly-efficient,
selective and stable electrocatalysts to lower energy con-
sumption and improve the selectivity to form formic acid.
More recently, various metals, such as Pd,[9] Sn,[10] Bi,[11] Pb[12]
and In,[13] have been demonstrated relatively excellent
selectivity for formic acid production. The scarcity and high-
Introduction
Developing functional porous nanomaterials is an ever-
lasting hotspot standing at the leading edge of material
science owing to the abundant pores and versatile composi-
tions guaranteed their excellent electrocatalytic performances
in diverse fields.[1] Among the studied porous materials,
metallic aerogel, a category of 3D materials that can be
composed by various metals, have attracted tremendous
attentions owing to the large specific surface area and
abundant interconnected channels.[2] Benefiting from the
intrinsic physicochemical characteristics, the exploited met-
allic aerogels possess abundant active sites, remarkable
[*] Dr. Z. X. Wu, Prof. L. Wang
Prof. Z. H. Wen
State Key Laboratory Base of Eco-chemical Engineering, College of
Chemistry and Molecular Engineering
Qingdao University of Science & Technology
53 Zhengzhou Road, Qingdao 266042 (P. R. China)
E-mail: inorchemwl@126.com
CAS Key Laboratory of Design and Assembly of Functional Nano-
structures, Fujian Provincial Key Laboratory of Nanomaterials
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Fuzhou, Fujian 350002 (China)
H. B. Wu, Prof. W. Jin
Prof. B. H. Jia, Prof. T. Y. Ma
State Key Laboratory of Pollution Control and Resources Reuse
School of Environmental Science and Engineering, Tongji University
1239 Siping Road, Shanghai 200092 (China)
E-mail: wjin@ipe.ac.cn
Centre for Translational Atomaterials, Faculty of Science, Engineering
and Technology, Swinburne University of Technology
John Street, Hawthorn, VIC 3122 (Australia)
E-mail: tianyima@swin.edu.au
Prof. W. Q. Cai
School of chemistry and chemical engineering
Guangzhou University
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202102832.
230 Guangzhou University City Outer Ring Road, Guangzhou 510006
(China)
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cost hindered the large-scale applications of Pd on CO2RR,
even though the favorable selectivity for formic acid.
Recently, Bi- and Sn-based nanomaterials are extensively
investigated for CO2RR in terms of their low-toxic and earth-
abundant merits. However, the catalytic efficiency and
selectivity of Bi- and Sn-based nanomaterials are still far
from satisfactory for CO2RR. Thus, valid and facile avenues
are urgent to develop to improve the catalytic efficiency and
selectivity. It has been identified that the combination of two
elements in the obtained nanomaterials is an effective and
promising approach to facilitate the efficiency and selectivity,
originating from the fact that the coupling effects can
optimize the reaction kinetics or suppress the competition
reactions.[14] Moreover, the formed interfaces in the designed
bimetallic electrocatalysts also act as pivotal role on optimiz-
ing the catalytic performance by improving the CO2 adsorp-
tion ability, altering the electron transfer, causing geometric
structure changes, and varying the coordination environ-
ment.[15] For instance, Huang et al reported that the abundant
Cu/SnO2 interfaces in the prepared CuO/hollow SnO2 heter-
ostructure (CuSn NPs/C-A) decreased the DG for the
formation of COOH*species and then delivered excellent
electrocatalytic performance for CO2RR into HCOOH at
À1.0 V vs. RHE with 33.2 and 3.4 times higher than Cu
nanoparticles (Cu NPs/C) and SnO2 nanoshell/C (SnO2 NSL/
C).[16] Therefore, controlling the nanostructure and composi-
tion of the bimetallic nanomaterials would be a promising
avenue to optimize the catalytic activity. At present, most of
the bimetallic electrocatalysts are synthesized by electro-
deposition, annealing or solution processing which are tedious
and adverse of designing abundant nanostructures.[17] To this
end, constructing bimetallic compound with specific nano-
structures and facile avenue is a promising orientation to
enhance the electrocatalytic performances for CO2RR.
Herein, we prepared a non-noble-metal-based aerogel,
consisting of bimetallic Bi and Sn, at ambient condition within
six hours which exhibited 3D morphology and abundant
interfaces. As a result, the designed Bi-Sn aerogel presented
excellent electrocatalytic performance for CO2RR toward
formic acid with a FE of 93.9% relative to Bi and Sn
nanomaterials which is comparable with the most existed
catalysts. Moreover, the designed electrocatalyst also pre-
sented negligible deterioration of the FE and current density
under flow cell system, demonstrating the excellent stability
of Bi-Sn aerogel.
Figure 1. a) Illustration of the synthesis of Bi-Sn aerogel. b) TEM image
of Bi-Sn. c) XRD patterns of Bi-Sn. d) High-resolution TEM images and
e) the corresponding elemental mappings.
by branched nanowires with random diameters were ob-
served by both SEM and TEM images (Figure S2; Figure 1b).
Those nanowires are interconnected randomly and formed
network morphology with abundant pores which is in favor of
the transportation of electrolyte and exposing rich active sites
during electrocatalytic process. Relatively, Sn and Bi present
typical nanoparticle and nanosheets structure, respectively,
which were synthesized using the identical strategy (Figur-
es S3 and S4). Moreover, Bi-Sn, obtained by vacuum drying,
exhibited bulk morphology rather than porous structure,
indicating that the freeze-drying process also plays pivotal
role on the formation of aerogel (Figure S5). The molar ratio
between Bi and Sn also affect the nanostructure of the
designed nanomaterials (Figures S6 and S7). As shown in
Figure 1c, the peaks of the designed Bi-Sn aerogel matched
with the phases of Bi (PDF#44-1246) and Sn (PDF#04-0673)
well, indicating the coexistence of Bi and Sn in the obtained
aerogel. The reference samples exhibit the typical peaks with
the Bi-Sn aerogel (Figure S8). The high-resolution TEM
(HR-TEM) image (Figure 1d) demonstrated that the inter-
planar spacings were 0.29 nm and 0.33 nm, corresponding to
the (200) and (012) planes of Sn and Bi, respectively.
Impressively, rich interfaces between Sn and Bi existed in
the designed electrocatalyst which could act as reactive sites
during catalytic process.[18] TEM and SEM energy dispersive
X-ray spectroscopy (EDX) images (Figure 1e; Figures S9 and
S10) verified the uniform distributions of Bi and Sn, with
a molar ratio of 1.6, in the prepared Bi-Sn.
Results and Discussion
X-ray photoelectron spectroscopy (XPS) was performed
to further investigate the composition and valence state of the
designed nanomaterials (Figures S11–S13). As illustrated in
Figure 2a,b, the binding energies of Bi and Sn in Bi-Sn shifted
to higher binding energy and lower energy compared with Bi
and Sn, respectively, indicating the electronic interactions
between Bi and Sn which would affect the electrocatalytic
performance for CO2RR. For the detailed Bi 4f spectra
(Figure 2c), the peaks located at 156.5 eV and 161.8 eV are
ascribed to the metallic Bi and other two peaks are
contributed to Bi3+.[18a] In Figure 2d, the two main peaks (at
As illustrated in Figure 1a, the Bi-Sn hydrogel with
different molar ratios were prepared with NH4Cl as initiator,
due to its excellent salting-out capability, and NaBH4 as the
reductant agent. Then, the obtained hydrogel was washed by
deionized water several times and dried by freeze-drying
method (see the detail experimental section in supporting
information). The self-supported Bi-Sn hydrogel was yielded
within 6 hours at ambient condition and then aerogel was
obtained with maintained size (Supporting Information,
Figure S1). Obviously, 3D porous nanostructure composed
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electrocatalysts, the electrolysis
measurement at various potentials
has been conducted and recorded
(Figure S14). Accordingly, the gas-
eous and liquid products are quan-
titatively analyzed via online gas
chromatograph (GC) and 1H nu-
clear
magnetic
resonance
(1H NMR) spectroscopy, respec-
tively (Figures S15 and S16). As
revealed in Figure 3b, the designed
Bi-Sn exhibited the highest
FEHCOOH at all the applied poten-
tials relative to other contrast ma-
terials. Specially, the FEHCOOH of
Bi-Sn achieved the highest value of
93.9% at the potential of À1.0 V
vs. RHE, while the values are
78.6%, 76.2% and 81.6% for Sn,
Figure 2. a) Bi 4f and b) Sn 3d XPS spectra associated with Bi-Sn aerogel. c) High-resolution XPS
spectra of Bi and d) Sn in the prepared Bi-Sn aerogel. e) Contact angles of Bi-Sn and bulk Bi-Sn.
f) Illustration of the catalytic mechanism of the designed Bi-Sn.
486.8 eV and 495.2 eV) corresponded to Sn4+ in SnO2 owning
to the oxidation by exposing the samples in the air.[19]
However, the XRD patterns verified the prepared electro-
catalysts are composed by Bi0 and Sn0 which are opposite to
the XPS results. It is mainly because of XPS measurement is
a kind of surface characterization method and XRD is not
sensitive to the surface property. Moreover, the surface
properties of the prepared electrocatalysts are also key
factors on regulating the catalytic performances and selectiv-
ity for CO2RR.[20] As illustrated in Figure 2e, the designed Bi-
Sn aerogel exhibited a contact angle of 10.28, smaller than
bulk Bi-Sn, demonstrating its inherent hydrophilic character
which are in favor of improving its selectivity for the
formation of formic acid.[21] Then, the electronic interactions
between Bi and Sn and the specific surface property would
endow its remarkable electrocatalytic performance toward
CO2RR (Figure 2 f).
bulk Bi-Sn and Bi, respectively (Figure S17). Evidently, the
prepared Bi-Sn aerogel exhibits the largest FEHCOOH and the
small FECO and FEH at À1.0 V (Figure 3c; Figure S18a,b).
2
However, the FEHCOOH decreased with the applied potentials
increased but the FEH increased which can be attributed to
2
the limited mass transport of CO2 with low concentration in
aqueous solution and cannot supply the fast CO2 consumption
timely.[23] In order to clearly prove the specific catalytic
performances toward HCOOH during CO2RR, the HCOOH
partial current densities of the prepared electrocatalysts were
calculated at various potentials (Figure 3d). It is clearly
revealed that the designed Bi-Sn exhibited the highest JHCOOH
at all the applied potential range, and Bi-Sn reached a partial
current density of 9.3 mAcmÀ2@ À1.0 V, which was nearly 2.4
and 1.8 times higher than Sn (3.84 mAcmÀ2), bulk Bi-Sn
(3.84 mAcmÀ2) and Bi (5.12 mAcmÀ2), respectively, which
are comparable with the reported values (Supporting Infor-
mation, Table S1).
The electrocatalytic CO2RR performances of the pre-
pared Sn, Bi-Sn, bulk Bi-Sn and Bi were conducted within
a gas-tight two-compartment H-cell
with three-electrode system in CO2-
saturated 0.1 M KHCO3. As illus-
trated in Figure 3a, the largest cur-
rent density was achieved at 1.25 V
for
Bi-Sn (18.4 mAcmÀ2) compare with
Sn
(7.9 mAcmÀ2),
bulk
Bi-Sn (12.4 mAcmÀ2) and Bi
(10.3 mAcmÀ2) which is also exceed
most of the state-of-the-art materi-
als for HCOOH generation. Never-
theless, the current density record-
ed by LSV cannot be completely
ascribed to the electrocatalytic
CO2RR, due to the inevitable com-
peting HER, especially in aqueous
electrolyte.[22] To definitely confirm
the total current density derived
CO2RR rather than HER and esti-
Figure 3. a) LSVs of Sn, Bi, Bi-Sn and bulk Bi-Sn in CO2-saturated 0.1 M KHCO3. b) Faradaic
efficiencies of different products of the prepared Bi-Sn aerogel. c) Comparison of formic acid Faradaic
efficiencies of the prepared Bi, Sn, Bi-Sn and bulk Bi-Sn at various applied potentials. d) Partial
current densities for HCOOH of the designed various electrocatalysts. e) Durability test of Bi-Sn in
mate the selectivity of the designed the flow cell configuration for 10 h.
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As a significant parameter to
evaluate the active sites numbers,
electrochemical active surface area
(ECSA) was evaluated by calcu-
lated the double layer capacitance
(Cdl). The value of Cdl was deter-
mined by CV which was performed
at various rates in CO2-saturated
electrolyte (Figure S19). The val-
ues of Cdl for Bi-Sn, Sn, Bi and
bulk Bi-Sn are 2.14 mFcmÀ2,
0.63 mFcmÀ2, 1.05 mFcmÀ2 and
0.54 mFcmÀ2, respectively. Such
results demonstrate that, Bi-Sn
owns the largest ECSA and rich
active sites which is in line with the
above electron microscope results
and then endowed the designed
Bi-Sn aerogel exhibits excellent
electrocatalytic activity. Therefore,
the coupling effects between Sn
and Bi, and the porous nanostruc-
Figure 4. a) ATR-FTIR spectra of Bi-Sn with various applied potentials. b) Illustration of the reaction
mechanism for the generation of HCOOH. Calculated free energy change diagram for CO2 reduction
to c) HCOOH, d) HER, and e) CO on Sn(200), Bi(012), and Sn supported on a Bi(012) surface
(Sn@Bi(012)). f) Calculated limiting potentials for HCOOH, CO and H2 production on Bi(012),
Sn(200) and Sn@Bi(012).
ture act as pivotal role on promoting the electrocatalytic
performance. Moreover, we also investigated the effects of
molar ratios between Bi and Sn on tuning the electrocatalytic
performance for CO2RR and chronoamperometry was con-
ducted under different potentials (Figure S20). It is demon-
strated that the prepared Bi-Sn with the molar ratio of 1:1
exhibits the largest FE (93.9%) relative to 1–2 (83.5%) and
2–1 (74.6%) at the potential of À1.0 V (Figures S21 and S22).
Partial current density results also verified that the obtained
Bi-Sn with 1:1 delivered the largest JHCOOH of 9.3 mAcmÀ2@-
1.0 V, which was higher than 1–2 (7.67 mAcmÀ2) and 2–
1 (7.03 mAcmÀ2) (Figure S23). The calculate results verified
that the prepared Bi-Sn (1–1) possesses the largest value
relative to 1–2 (1.9 mFcmÀ2) and 2–1 (0.31 mFcmÀ2; Fig-
ure S24). Moreover, the SEM and TEM results also proved
that Bi-Sn (1–1) exhibits porous structure. Then, the molar
ratio between Bi and Sn also act as pivotal role on tuning the
electrocatalytic activity. Apart from the electrocatalytic
performance, stability is also a significant parameter of the
synthesized electrocatalyst for practical applications. It can be
seen in Figure 3e that no evident decay of current density and
FEHCOOH is stable during the long-term stability for 10 h,
demonstrating the remarkable stability of the prepared Bi-Sn.
The SEM images verified that the porous nanostructure
maintained well after stability test, confirmed its robust
property (Figure S25). Moreover, the XPS spectra proved
that the chemical composition and valence keep almost
unchanged after stability measurement further verified the
rock-steady character (Figure S26).
the applied potentials varied from À0.6 V to À1.2 V which are
ascribed to the vibration of O-C-O in the two-oxygen bridged
formic acid species (*HCOO), indicating the formation of
*HCOO is the rate-determining step (Figure 4b).[6c,24] In line
with the experimental result (Figure 3b), no typical peaks
located at 1900–2100 cmÀ1, corresponding to the CO*, are
detected during the electrocatalytic process, demonstrating
the negligible generation of CO on the synthesized Bi-Sn
aerogel.[25] Nevertheless, the origin of the outstanding cata-
lytic activities is unobvious. Generally, theoretical calculation
is considered as a valid avenue to elucidate the insight into the
catalytic mechanism based on the models in Figures S27–S29.
As illustrated in Figure 4c, Sn(200) and Bi(012) possess the
strongest and weakest binding energy for *HCOO, respec-
tively, which are unfavorable on the electrocatalytic process.
However, the interaction with *HCOO can be strengthened
by introducing Sn clusters with a calculated limiting potential
of 0.42 V which are lower than the counterparts, which endow
the designed Bi-Sn presents excellent electrocatalytic perfor-
mance for CO2RR. Moreover, the developed Bi-Sn aerogel
owns the moderate adsorption energy for the intermediate
during HER which is the competing reaction for CO2RR
(Figure 4d). We also calculated the Gibbs free energy for the
transformation of CO2 into CO on the prepared Sn, Bi and
Bi-Sn aerogel. As illustrated in Figure 4e, the generation of
*COOH is the limiting step of all the electrocatalysts with
higher value than the formation of *HCOO, indicating the
tendency for the formation of formic acid. The limiting
potentials (Plimit) for the generation of H2, CO and HCOOH
on Bi, Sn and Bi-Sn are presented in Figure 4 f. It can be
clearly observed that the Bi-Sn aerogel owned the lowest Plimit
for the transformation into HCOOH and moderate Plimit for
CO and H2. Then, the synthesized nanomaterial exhibits
electrocatalytic performance for CO2RR with surpassed HER
and CO generation. Projected density of states (DOS) was
also calculated on the prepared catalysts (Figure S30a,b).
As revealed by the experimental results, the developed
Bi-Sn aerogel presents excellent electrocatalytic perform-
ances for CO2RR with superior selectivity for HCOOH
production. In situ attenuated total reflectance-Fourier trans-
form infrared (ATR-FTIR) measurement was conducted to
study the reaction pathway of the prepared Bi-Sn aerogel. As
illustrated in Figure 4a, a characteristic peak located at
1390 cmÀ1 appeared at À0.6 V and increased gradually with
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[4] L. Lu, X. Sun, J. Ma, D. Yang, H. Wu, B. Zhang, J. Zhang, B. Han,
Angew. Chem. Int. Ed. 2018, 57, 14149 – 14153; Angew. Chem.
2018, 130, 14345 – 14349.
[5] R. Du, X. Fan, X. Jin, R. Hꢀbner, Y. Hu, A. Eychmꢀller, Matter
2019, 1, 39 – 56.
Conclusion
In summary, we have successfully synthesized Bi-Sn-based
metallic aerogel with abundant pores and channels, and rich
interfaces. The designed nanomaterial exhibited excellent
selectivity and stability for CO2RR toward the production of
HCOOH under normal pressure at room temperature.
Moreover, the developed Bi-Sn aerogel also exhibited high
FEHCOOH and stability in a flow cell system. This study opens
up an appealing approach to design non-precious-metal-
derived aerogels with rich active sites and channels for
enhancing the electrocatalytic performance and selectivity
toward CO2RR.
[6] a) P. Deng, F. Yang, Z. Wang, S. Chen, Y. Zhou, S. Zaman, B. Y.
Xia, Angew. Chem. Int. Ed. 2020, 59, 10807 – 10813; Angew.
Chem. 2020, 132, 10899 – 10905; b) Z. X. Wu, Y. Zhao, W. Jin,
B. H. Jia, J. Wang, T. Y. Ma, Adv. Funct. Mater. 2021, 31,
2009070; c) C. Cao, D.-D. Ma, J.-F. Gu, X. Xie, G. Zeng, X. Li, S.-
G. Han, Q.-L. Zhu, X.-T. Wu, Q. Xu, Angew. Chem. Int. Ed.
2020, 59, 15014 – 15020; Angew. Chem. 2020, 132, 15124 – 15130;
d) K. Lv, W. Suo, M. Shao, Y. Zhu, X. Wang, J. Feng, M. Fang, Y.
Zhu, Nano Energy 2019, 63, 103834; e) N. Meng, W. Zhou, Y. Yu,
Y. Liu, B. Zhang, ACS Catal. 2019, 9, 10983 – 10989; f) Z. Gu, N.
Yang, P. Han, M. Kuang, B. Mei, Z. Jiang, J. Zhong, L. Li, G.
Zheng, Small Methods 2019, 3, 1800449; g) X. Lv, L. Shang, S.
Zhou, S. Li, Y. Wang, Z. Wang, T.-K. Sham, C. Peng, G. Zheng,
Adv. Energy Mater. 2020, 10, 2001987; h) G. Li, Y. Qin, Y. Wu, L.
Pei, Q. Hu, H. Yang, Q. Zhang, J. Liu, C. He, Chin. J. Catal. 2020,
41, 830 – 838.
[7] a) X. An, S. Li, A. Yoshida, Z. Wang, X. Hao, A. Abudula, G.
Guan, ACS Sustainable Chem. Eng. 2019, 7, 9360 – 9368; b) Y.
Xing, X. Kong, X. Guo, Y. Liu, Q. Li, Y. Zhang, Y. Sheng, X.
Yang, Z. Geng, J. Zeng, Adv. Sci. 2020, 7, 1902989; c) J. Yang, X.
Wang, Y. Qu, X. Wang, H. Huo, Q. Fan, J. Wang, L.-M. Yang, Y.
Wu, Adv. Energy Mater. 2020, 10, 2001709; d) H. Shang, T. Wang,
J. Pei, Z. Jiang, D. Zhou, Y. Wang, H. Li, J. Dong, Z. Zhuang, W.
Chen, D. Wang, J. Zhang, Y. Li, Angew. Chem. Int. Ed. 2020, 59,
22465—22469; Angew. Chem. 2020, 132, 22651—22655; e) J.
Shao, D. Gao, K. Ye, Q. Wang, G. Wang, Chin. J. Catal. 2020, 41,
1393 – 1400.
Acknowledgements
The authors acknowledge funding from the National Natural
Science Foundation of China (22002068, 51772162, and
52072197), Youth Innovation and Technology Foundation of
Shandong
Higher
Education
Institutions,
China
(2019KJC004), Outstanding Youth Foundation of Shandong
Province, China (ZR2019JQ14), Taishan Scholar Young
Talent Program (tsqn201909114), Major Scientific and Tech-
nological Innovation Project (2019JZZY020405), and Major
Basic Research Program of Natural Science Foundation of
Shandong Province under Grant No. ZR2020ZD09. The
Natural Science Foundation of Shandong Province of China
(ZR2019BB002; ZR2018BB031), Tongji Hundred Talents
Program, and the Fundamental Research Funds for the
Central Universities are thanked for their support.
[8] a) L. Shang, X. Lv, H. Shen, Z. Shao, G. Zheng, J. Colloid
Interface Sci. 2019, 552, 426 – 431; b) K. Wang, D. Liu, P. Deng, L.
Liu, S. Lu, Z. Sun, Y. Ma, Y. Wang, M. Li, B. Y. Xia, C. Xiao, S.
Ding, Nano Energy 2019, 64, 103954.
[9] a) B. Jiang, X.-G. Zhang, K. Jiang, D.-Y. Wu, W.-B. Cai, J. Am.
Chem. Soc. 2018, 140, 2880 – 2889; b) A. Klinkova, P. De Luna,
C.-T. Dinh, O. Voznyy, E. M. Larin, E. Kumacheva, E. H.
Sargent, ACS Catal. 2016, 6, 8115 – 8120.
[10] a) F. Wei, T. Wang, X. Jiang, Y. Ai, A. Cui, J. Cui, J. Fu, J. Cheng,
L. Lei, Y. Hou, S. Liu, Adv. Funct. Mater. 2020, 30, 2002092; b) L.
Lu, X. Sun, J. Ma, Q. Zhu, C. Wu, D. Yang, B. Han, Sci. China
Chem. 2018, 61, 228 – 235.
Conflict of interest
The authors declare no conflict of interest.
Keywords: aerogels · bismuth · formic acid · tin
[11] a) 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 – 750; b) Z. Chen,
K. Mou, X. Wang, L. Liu, Angew. Chem. Int. Ed. 2018, 57,
12790 – 12794; Angew. Chem. 2018, 130, 12972 – 12976.
[12] a) N. Zouaoui, B. D. Ossonon, M. Fan, D. Mayilukila, S.
Garbarino, G. de Silveira, G. A. Botton, D. Guay, A. C. Tavares,
J. Mater. Chem. A 2019, 7, 11272 – 11281; b) C. H. Lee, M. W.
Kanan, ACS Catal. 2015, 5, 465 – 469.
[13] a) W. Luo, W. Xie, M. Li, J. Zhang, A. Zꢀttel, J. Mater. Chem. A
2019, 7, 4505 – 4515; b) A. Zhang, Y. Liang, H. Li, X. Zhao, Y.
Chen, B. Zhang, W. Zhu, J. Zeng, Nano Lett. 2019, 19, 6547 –
6553.
[14] a) B. Wei, Y. Xiong, Z. Zhang, J. Hao, L. Li, W. Shi, Appl. Catal.
B 2021, 283, 119646; b) G. O. Larrazꢁbal, A. J. Martꢂn, S.
Mitchell, R. Hauert, J. Pꢃrez-Ramꢂrez, J. Catal. 2016, 343, 266 –
277.
[15] a) D. Gao, Y. Zhang, Z. Zhou, F. Cai, X. Zhao, W. Huang, Y. Li,
J. Zhu, P. Liu, F. Yang, G. Wang, X. Bao, J. Am. Chem. Soc. 2017,
139, 5652 – 5655; b) Y. Wang, P. Han, X. Lv, L. Zhang, G. Zheng,
Joule 2018, 2, 2551 – 2582; c) X. Shen, X. Liu, S. Wang, T. Chen,
W. Zhang, L. Cao, T. Ding, Y. Lin, D. Liu, L. Wang, W. Zhang, T.
Yao, Nano Lett. 2021, 21, 686 – 692; d) X. Chen, D. A. Henckel,
[1] A. G. Slater, A. I. Cooper, Science 2015, 348, aaa8075.
[2] a) R. Du, J. Wang, Y. Wang, R. Hꢀbner, X. Fan, I. Senkovska, Y.
Hu, S. Kaskel, A. Eychmꢀller, Nat. Commun. 2020, 11, 1590;
b) R. Du, W. Jin, R. Hꢀbner, L. Zhou, Y. Hu, A. Eychmꢀller,
Adv. Energy Mater. 2020, 10, 1903857; c) W. Liu, P. Rodriguez, L.
Borchardt, A. Foelske, J. Yuan, A.-K. Herrmann, D. Geiger, Z.
Zheng, S. Kaskel, N. Gaponik, R. Kçtz, T. J. Schmidt, A.
Eychmꢀller, Angew. Chem. Int. Ed. 2013, 52, 9849 – 9852;
Angew. Chem. 2013, 125, 10033 – 10037.
[3] a) Q. Shi, C. Zhu, D. Du, C. Bi, H. Xia, S. Feng, M. H. Engelhard,
Y. Lin, J. Mater. Chem. A 2017, 5, 19626 – 19631; b) Q. Shi, C.
Zhu, H. Zhong, D. Su, N. Li, M. H. Engelhard, H. Xia, Q. Zhang,
S. Feng, S. P. Beckman, D. Du, Y. Lin, ACS Energy Lett. 2018, 3,
2038 – 2044; c) W. Liu, D. Haubold, B. Rutkowski, M. Oschatz,
R. Hꢀbner, M. Werheid, C. Ziegler, L. Sonntag, S. Liu, Z. Zheng,
A.-K. Herrmann, D. Geiger, B. Terlan, T. Gemming, L.
Borchardt, S. Kaskel, A. Czyrska-Filemonowicz, A. Eychmꢀller,
Chem. Mater. 2016, 28, 6477 – 6483; d) R. Du, X. Jin, R. Hꢀbner,
X. Fan, Y. Hu, A. Eychmꢀller, Adv. Energy Mater. 2020, 10,
1901945.
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These are not the final page numbers!

Angewandte
Research Articles
Chemie
U. O. Nwabara, Y. Li, A. I. Frenkel, T. T. Fister, P. J. A. Kenis,
[21] A. K. Buckley, M. Lee, T. Cheng, R. V. Kazantsev, D. M. Larson,
A. A. Gewirth, ACS Catal. 2020, 10, 672 – 682.
[16] P. Wang, M. Qiao, Q. Shao, Y. Pi, X. Zhu, Y. Li, X. Huang, Nat.
Commun. 2018, 9, 4933.
W. A. Goddard III, F. D. Toste, F. M. Toma, J. Am. Chem. Soc.
2019, 141, 7355 – 7364.
[22] S. Liu, X. F. Lu, J. Xiao, X. Wang, X. W. Lou, Angew. Chem. Int.
Ed. 2019, 58, 13828 – 13833; Angew. Chem. 2019, 131, 13966 –
13971.
[17] D. Ren, J. Gao, L. Pan, Z. Wang, J. Luo, S. M. Zakeeruddin, A.
Hagfeldt, M. Grꢄtzel, Angew. Chem. Int. Ed. 2019, 58, 15036 –
15040; Angew. Chem. 2019, 131, 15178 – 15182.
[18] a) G. Wen, D. U. Lee, B. Ren, F. M. Hassan, G. Jiang, Z. P. Cano,
J. Gostick, E. Croiset, Z. Bai, L. Yang, Z. Chen, Adv. Energy
Mater. 2018, 8, 1802427; b) J. Wang, Z. Li, C. Dong, Y. Feng, J.
Yang, H. Liu, X. Du, ACS Appl. Mater. Interfaces 2019, 11, 2763 –
2767; c) R. Ge, J. Huo, M. Sun, M. Zhu, Y. Li, S. Chou, W. Li,
Small 2021, 17, 1903380.
[19] a) X. Zhang, J. Liu, Y. Qiao, A. Kong, R. Li, Y. Shan,
Electrochim. Acta 2019, 320, 134593; b) H. Park, H. Choi, N.
Lee, C. Jung, Y. Choi, S. Song, Y. Choi, K. Kim, J. Kim, J. Lee, H.
Jeon, Ceram. Int. 2020, 46, 12782 – 12787.
[23] J. L. DiMeglio, J. Rosenthal, J. Am. Chem. Soc. 2013, 135, 8798 –
8801.
[24] a) Y. Shi, Y. Ji, J. Long, Y. Liang, Y. Liu, Y. Yu, J. Xiao, B. Zhang,
Nat. Commun. 2020, 11, 3415; b) K. Jiang, J.-Y. Wang, T.-T.
Zhao, W.-B. Cai, J. Electroanal. Chem. 2017, 800, 77 – 81.
[25] a) M. F. Baruch, J. E. Pander, J. L. White, A. B. Bocarsly, ACS
Catal. 2015, 5, 3148 – 3156; b) S. Zhu, Q. Wang, X. Qin, M. Gu,
R. Tao, B. P. Lee, L. Zhang, Y. Yao, T. Li, M. Shao, Adv. Energy
Mater. 2018, 8, 1802238.
[20] a) H.-Q. Liang, S. Zhao, X.-M. Hu, M. Ceccato, T. Skrydstrup, K.
Daasbjerg, ACS Catal. 2021, 11, 958 – 966; b) J. Li, G. Chen, Y.
Zhu, Z. Liang, A. Pei, C.-L. Wu, H. Wang, H. R. Lee, K. Liu, S.
Chu, Y. Cui, Nat. Catal. 2018, 1, 592 – 600.
Manuscript received: February 24, 2021
Accepted manuscript online: March 15, 2021
Version of record online: && &&
,
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Angew. Chem. Int. Ed. 2021, 60, 2 – 8
ꢀ 2021 Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Research Articles
CO2 Electroreduction
Bismuth–Tin aerogel was prepared at
ambient temperature, resulting in a three-
dimensional porous nanostructure with
abundant pores. The material presents
excellent electrocatalytic activity and sta-
bility for formic acid generation with
a high Faradaic efficiency (93.9%) and
partial current density of 9.3 mAcmÀ2 at
À1.0 V vs. RHE.
Z. X. Wu, H. B. Wu, W. Q. Cai, Z. H. Wen,
B. H. Jia, L. Wang,* W. Jin,*
T. Y. Ma*
&&&& — &&&&
Engineering Bismuth–Tin Interface in
Bimetallic Aerogel with a 3D Porous
Structure for Highly Selective
Electrocatalytic CO2 Reduction to
HCOOH
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www.angewandte.org
ꢀ 2021 Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 8
These are not the final page numbers!