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Selective electroreduction of CO2 into CO over Ag

and Cu decorated carbon nanoflakes†
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Cite this: Energy Adv., 2024,

3, 2367
Ahmad Faraz,a Waheed Iqbal,a Shayan Gul,a Fehmida K. Kanodarwala,b
Muhammad Nadeem Zafar, cd Guobao Xu *de and
Muhammad Arif Nadeem *ad

The electrocatalytic CO2 reduction reaction (eCO2RR) has the potential to effectively cut carbon emission.
However, the activity and selectivity of eCO2RR catalysts are topical due to the intricacy of the reaction
components and mechanism. Herein, we have decorated silver and copper nanoparticles over carbon
nanoflakes to achieve an Ag–Cu NPs/C system that enables selective reduction of CO2 into CO. The
catalyst is prepared by incorporating Ag nanoparticles into a Cu-BTC MOF (HKUST-1) and subsequent car-
bonization that alters the surface composition, with improved activity and faradaic efficiency (FE) towards
selective CO2 reduction. The evaluation of electrocatalytic performance reveals that the synthesized
Received 19th July 2024, catalyst exhibits enhanced electrocatalytic activity and selectivity with a FECO of B 90% at 0.79 VRHE and
Accepted 26th July 2024 a current density ( j) of 44.15 mA cm2 compared to Ag-NPs and Cu/C. The durability test over 40 h con-
DOI: 10.1039/d4ya00462k firms the outstanding stability of Ag–Cu NPs/C. The lower Tafel slope value of only 75 mV dec1 corre-
sponds to the fast reaction kinetics on the surface of Ag–Cu NPs/C. The synthetic protocol in this work
rsc.li/energy-advances offers an easy approach to the betterment of a cost-effective electrocatalyst with improved FE.

Introduction organic frameworks (MOFs), covalent organic frameworks (COFs),

and metal-free carbon based catalysts, have been utilized for the
Using carbon dioxide (CO2) as an alternative source of fuel is one eCO2RR to CO.20–22 MOF derived carbon serves as an ideal
approach to reduce CO2 emission and to provide a green source of support23 due to its high surface area, porosity, thermal stability,
energy.1–4 The electrochemical CO2 reduction reaction (eCO2RR) and chemical stability.24–26 In MOF derived nanomaterials, the
is considered the most efficient technique5 for the sustainable inbuilt synergism between metallic nanoparticles dispersed over
conversion of carbon dioxide into various valuable compounds6,7 the carbon matrix results in improved catalytic performance.27–29
such as acids,8 carbon monoxide (CO),9 alcohols,10 and Recently, catalysts based on transition metals have been
hydrocarbons.11,12 Carbon monoxide could be used as a starting explored as CO2 reduction catalysts.30,31 Precious metals such
material for the production of various useful chemicals.13 as Au, Ag, and Pd are highly active in the eCO2RR to CO but
The eCO2RR faces a few challenges including thermodynamic their high cost hinders the commercialization.32–35 Thus, non-
stability and kinetically inert nature of CO2.14–16 The conversion of noble metal based catalysts are the topic of interest nowadays.
CO2 into CO also competes with the hydrogen evolution reaction The incorporation of non-noble metals into precious metal
(HER).17 Therefore, development of highly selective and efficient based catalysts reduces the cost and has the ability to enhance
eCO2RR catalysts is a major challenge.18,19 Many electrocatalysts, activity towards CO2 reduction.36,37 The intermediate (*COOH)
such as single-atom catalysts, metallic nanoparticles, metal binding strength during the conversion of CO2 determines the
effectiveness of the catalyst.38 The catalyst with optimum
binding strength can efficiently catalyze the cathodic CO2
a
Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan.
reduction.39 According to the famous volcano plot, silver and
E-mail: manadeem@qau.edu.pk; Tel: +92-51-9064-2062
b
University of Technology Sydney, NSW, 2007, Sydney, Australia
copper possess weaker and stronger binding energies for
c
Department of Chemistry, University of Gujrat, 50700, Gujrat, Pakistan *COOH, respectively.40,41 The combination of copper and silver
d
State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of to obtain cost effective and efficient electrocatalysts with opti-
Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China. mum binding strength can be a good choice.42
E-mail: guobaoxu@ciac.ac.cn
e
For example, Francesco et al. found that silver nanowires
School of Applied Chemistry and Engineering, University of Science and
Technology of China, Hefei 230026, China
show a FE of 80% for CO at 1.4 VRHE.43 Mani et al. employed a
† Electronic supplementary information (ESI) available. See DOI: https://doi.org/ molecular silver complex immobilized on graphitized meso-
10.1039/d4ya00462k porous carbon for the eCO2RR to CO and achieved a FE of 90%

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at 1.05 VRHE.44 Similarly, Yang et al. reported using oxide lined autoclave, which was placed in an oven at 120 1C for 12 h.
derived nanoporous silver for the conversion of CO2 to CO and The reaction mixture was allowed to cool to room temperature.
observed a faradaic efficiency of 87% at 0.8 VRHE.45 According The bluish green product was filtered, washed with water and
to Zhipeng et al., the formation of CO by using Cu/Ag(S) can ethanol, and dried in a vacuum oven for further use. The XRD
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achieve a FE of 90% and 2.9 mA cm2 at 1.0 VRHE.46 Similarly pattern of HKUST-1 and the simulated pattern are shown in
Zekun et al. investigated the Cu0.3Zn9.7 electrocatalyst and Fig. S1 (ESI†) which shows the successful synthesis of pure
revealed a FE of up to 90.69% for CO at 1.2 VRHE.47 Similarly, HKUST-1.
Cheng et al. proposed that the electrochemical reduction of
CO2 on the AgCu alloy facilitates C–C coupling kinetics, which Synthesis of Ag@CuBTC
retains a faradaic efficiency of 94  4% towards multi-carbon The synthesized Cu-BTC MOF was used to synthesize Ag@Cu-
Open Access Article. Published on 06 August 2024. Downloaded on 5/21/2025 7:31:16 AM.

products.48 A. Harsh et al. found that the Ag50Cu50/p-Si catalyst BTC. For this purpose, 600 mg of the thermally evacuated
converts CO2 to CO and CH4 with optimal faradaic efficiencies HKUST-1 MOF was dispersed in ethylene glycol and sonicated
of 26% for CO and 18.2% at 0.72 VRHE for CH4.49 Tao et al. for an hour. 250 mg of polyvinylpyrrolidone (PVP) and 400 mg
reported that the Cu–Ag biphasic catalyst achieved a high of AgNO3 were then added to this suspension and subsequently
FECO of 80.25% with a partial CO current density ( jCO) of refluxed for 2 h at 160 1C. After cooling, the product was
4.88 mA cm2 at 0.9 VRHE.50 These reports further reveal filtered, washed with ethanol and water mixture, and dried in
that catalytic performance and properties can be tuned via a vacuum oven.
alteration of surface components.51
In this work, we report an efficient eCO2RR system using Synthesis of Ag–Cu NPs/C
bimetallic silver and copper nanoparticles supported over
The weighed amount of Ag@CuBTC was placed in a tube
carbon nanoflakes (Ag–Cu NPs/C), which was synthesized
furnace which was heated at various set temperatures under a
through pyrolysis of a composite, i.e. silver incorporated in a
hydrogen atmosphere. Ag–Cu NPs/C was formed during the
Cu-BTC MOF (HKUST-1), under reducing environment (H2) in
carbonization of the composite, which was done for six hours in
the high temperature range. HKUST-1 exhibits high stability,
a reducing environment (H2) at various temperatures, including
large pore size, high surface area, tunable structure, and cost
550 1C, 600 1C, 700 1C, and 850 1C, with a ramping rate of
effectiveness which make it a feasible choice to be used as a
10 1C min1 (Scheme 1). For comparison, Ag-NPs and Cu/C were
precursor for the synthesis of nanomaterials. The as-prepared
also synthesized by following this method.
catalyst performs better than conventional Ag or Cu based
catalysts. Dispersion of silver and copper nanoparticles over
Electrochemical measurements
carbon nanoflakes (Ag–Cu NPs/C) facilitates selective and active
catalytic conversion of CO2 to CO. Electrochemical measurements were used to estimate the pre-
pared material’s capacity to reduce CO2. Using a GAMRY
E-5000, all electrochemical investigations were carried out at ambi-
Experimental ent temperature. The eCO2RR was evaluated in a gas tight H-type
cell configured with a three-electrode system. This system featured
Synthesis of the Cu-BTC MOF (HKUST-1) anodic and cathodic compartments partitioned by a proton
A solvothermal approach, based on the existing procedure,52 exchange membrane (PEM; Nafion 117). The drop-casting method
was used with minor modifications to synthesize the Cu-BTC was used to prepare working electrodes. For uniform mixing, a
MOF (HKUST-1). For this purpose, 400 mg of copper nitrate solution of 5 mg synthesized catalyst, 1 mL ethanol, and 20 mL of
trihydrate was dissolved in 12 mL of a water:ethanol mixture Nafion solution was sonicated for 3 h in a water bath. This
followed by the addition of 246 mg of benzene-1,3,5- homogenized slurry was applied uniformly onto a 1 cm2 fluorine
tricarboxylic acid. The above mixture was placed in a Teflon doped tin oxide (FTO) electrode. The coated electrodes were given

Scheme 1 Graphical illustration of the synthesis of Ag–Cu NPs/C.

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their appropriate names after being dried for the whole night at 3d3/2 of the Ag0, respectively (Fig. 1(b)). The high-resolution
70 1C in an oven. The prepared catalyst on FTO acted as a working profile of Cu 2p reveals the presence of two characteristic peaks
electrode where the CO2 reduction occurs. The counter electrode at 932.8 eV and 953.0 eV attributed to Cu 2p3/2 and Cu 2p1/2,
used in this experiment was a graphite rod; the reference electrode respectively (Fig. 1(c)). These peaks represent the formation of
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was Ag/AgCl; and the electrolyte was 0.1 M KHCO3. Before perform- copper nanoparticles. The C 1s XPS spectra of Ag–Cu NPs/C are
ing each electrochemical experiment, the electrolyte was degassed displayed in Fig. 1(d), with the peaks at binding energies of
by purging high-purity argon for at least 30 min and then saturated 284.8 eV and 284.5 given to the C–C bond and CQC, respec-
with carbon dioxide. The Nernst equation used for converting tively. The presence of silver and copper peaks implies the
potential values from Ag/AgCl to a standard RHE is as follows: successful incorporation of bimetallic nanoparticles into car-
bon nanoflakes.
ERHE = EAg/AgCl + 0.0592(pH) + 0.1976
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Transmission electron microscopy (TEM) analysis is a

RT
where 0.0592 is equivalent to a factor ; 0.1976 = E1 (standard promising technique for characterizing the morphology and
nF
electrode potential of Ag/AgCl). structure of materials at the nanoscale. The TEM images of
bimetallic silver nanoparticles incorporated into carbon in the
Quantification of the products form of nanoflakes (C) depict the unique morphology of the
The gaseous products of the eCO2RR including CO and H2 were catalyst material and the distribution of silver and copper NPs
identified by using gas chromatography equipped with a capil- throughout the carbon nanoflake support. In contrast, the
lary column of Stabil wax (30 m  0.32 mm I.D.), a 5 mm thick catalyst material was synthesized through the pyrolysis of the
film, and a TCD detector. The Faraday efficiency for CO is Ag@Cu-BTC MOF, which gives it distinct morphological
calculated by using the following formula, given below. features with fully exposed nanoflakes like structures illu-

strated in Fig. 1(e)–(g). It represents metallic particles with an
nCOðgÞ þ nCOðdissolvedÞ  n  F
FECO ¼  100% almost spherical shape, and the calculated lattice fringes
I t
d-spacing is 0.344 nm. The sizes of the metallic particles are
where FECO indicates the Faraday efficiency of CO, n denotes determined by HRTEM and fall within the range of 10 nm to
the number of electrons transferred i.e., for CO, n is equal to 2, 40 nm. The high efficiency and selectivity of synthesized
nCO(g) is the quantity of CO in the headspace, and nCO(dissloved) is electrocatalysts may be attributed to the specific porous, nano-
the quantity of CO dissolved in the electrolyte; it has a value of flakes of carbon and the synergistic effect of smaller sized Ag–
1.774  105 and is calculated based on Henry’s law; F Cu nanoparticles. The individual spherical nanoparticles can
represents the faradaic constant whose value is 96 485 C mol1, be seen for Ag–Cu NPs/C, which confirms the successful
I is the total current in amperes (A), and t is the reaction time in formation of both silver and copper nanoparticles that are
seconds (s). dispersed over carbon nanoflakes. As shown in Fig. 1(e)–(g),
various structures of NPs have been produced; however, the two
Results and discussion discrete spherical dark and black contrasting TEM images
made it challenging to distinguish between Ag and Cu nano-
Powder X-ray diffraction (PXRD) patterns of all the as-prepared components. The confirmation of elements and surface quan-
materials are presented in Fig. 1(a) and it can be observed from tification was also confirmed by EDX analyses (Fig. S6, ESI†).
the graph that the XRD spectra of Ag–Cu NPs/C reflect the The actual ratio of Ag and Cu in the optimized catalyst is 1 : 0.75
characteristic peaks of Ag, at 2y of (38.21, 44.51, 64.71, and as confirmed by edx and ICP techniques.
77.71) and Cu at 2y of (43.391, 50.491, and 74.131) corres-
ponding to the crystalline planes of Ag (111) (200) (220) (311)
and Cu (111) (200) (220), respectively. The diffraction peak at ca. Electrochemical studies of Ag–Cu
251 represents the crystal face of porous carbon, as depicted in NPs/C
Fig. S2(a) and (b) (ESI†). The distinct peaks of Ag and Cu match
with the standard Ag card (JCPDS no. 03-065-2871) and Cu Linear sweep voltammetry (LSV) was used to examine the
(JCPDS no. 00-003-1005). All the diffraction peaks correspond to material’s ability to function as an electrode for the reduction
metallic silver, copper, and carbon, and no other impurities can of CO2. In 0.1 M KHCO3 solution saturated with Ar and CO2,
be detected. Ag–Cu NPs/C (850 1C) was analyzed at a rate of 10 mV s1 within
X-ray photoelectron spectroscopy (XPS) was utilized to exam- a potential window of 0 to (1.5 V) vs. Ag/AgCl. In CO2 saturated
ine the electronic properties and the elemental composition of solution, the LSV results of Ag–Cu NPs/C show better current
the surface of the Ag–Cu NPs/C catalyst. The XPS spectra density ( j) and lower overpotential (Z) than those of the Ar
obtained for Ag–Cu NPs/C are illustrated in Fig. 1(b)–(d). After saturated medium (Fig. 2(a)). To gain a better understanding,
careful analysis of the spectra, peaks associated with the an investigation of the eCO2RR was carried out for Ag-NPs, Cu/
elements Ag, Cu, and C were recognized. The Ag 3d and Cu C, and Ag–Cu NPs/C (Fig. 2(b)). The LSV results of Ag–Cu NPs/C
2p high-resolution scans from Ag–Cu NPs/C are shown in exhibit low Z and significantly improved j response for CO2
Fig. 1(b) and (c), respectively. The two prominent peaks of Ag reduction than those of Ag-NPs and Cu/C, confirming the
3d noticed at 368.2 eV and 374.2 eV are due to Ag 3d5/2 and Ag higher activity of Ag–Cu NPs/C. A comparative LSV profile of

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Fig. 1 Comparative PXRD patterns of Ag-NPs (red), Cu/C (blue), and Ag–Cu NPs/C (black) along with their JCPDS. XPS data of Ag–Cu NPs/C (b), Ag 3d
(c) and Cu 2p (d) C1s. (e)–(g) TEM images of Ag–Cu NPs/C at different resolutions (100 nm, 50 nm, and 10 nm).

Ag–Cu NPs/C, which was synthesized by calcination under a 44.14 mA cm2. This indicates that with the increase in tempera-
reducing environment at different temperatures of 550 1C, ture, the particle size decreases and per unit active surface area
600 1C, 700 1C and 850 1C, reveals the catalytic activity in a increases. This in turn enhances CO2 adsorption and the kinetics
CO2-saturated medium. The recorded j for the electrocatalysts of the eCO2RR. Fig. 2(d) demonstrates the partial CO current
follows in this order: Ag–Cu NPs/C 550 1C (17.22 mA cm2) o density ( jCO) for all synthesized electrocatalysts, notably Ag–Cu
Ag–Cu NPs/C 600 1C (20.1 mA cm2) o Ag–Cu NPs/C 700 1C NPs/C 850 1C exhibits superior activity in the eCO2RR over all the
(25.02 mA cm2) o Ag–Cu NPs/C 850 1C (44.14 mA cm2) remaining synthesized electrocatalysts.
(as illustrated in Fig. 2(c)). It appears that catalytic activity is found The electrochemical impedance spectroscopy (EIS) experi-
to enhance with an increase in carbonization temperature. The ment depicted in Fig. 2(e) was conducted within the frequency
maximum catalytic activity is achieved for Ag–Cu NPs/C (850 1C), limits of 0.01 Hz to 103 kHz to investigate the overall charge
with a low onset potential of 0.430 VRHE and a maximum j of transfer resistance in the circuit. The spectra obtained by

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Fig. 2 Cathodic LSV results of (a) Ag–Cu NPs/C in Ar and CO2 saturated solutions, (b) Ag-NPs, Cu/C and Ag–Cu NPs/C and (c) Ag–Cu NPs/C
synthesized at different temperatures. (d) Partial CO ( jCO) of all the synthesized electrocatalysts. (e) EIS (Nyquist plot) of Ag–C at different temperatures.
(f) Tafel plot of Ag–Cu NPs/C at different temperatures.

plotting Zreal vs. Zimag components of the circuit are called the transfer kinetics on the catalyst’s surface. The Tafel slope
Nyquist plot. The Rpo value determined by fitting is 93.3 ohm (Z vs. log j) is shown in Fig. 2(f). The catalyst material (Ag–Cu
for Ag–Cu NPs/C which is small and confirms the faster NPs/C 850 1C) shows a lower Tafel value of only 75 mV dec1.
electron transfer at the interface, resulting in enhanced The comparatively low Tafel slope obtained for Ag–Cu NPs/C
reduction performance of the eCO2RR, with a smaller charge (850 1C) compared to all the synthesized electrocatalysts is
transfer resistance (Rct). Comparing the impedance results of attributed to the synergistic effect of Ag and Cu. The presence
all the synthesized catalysts indicates that our optimum elec- of copper modifies the d-band of silver and enhances the CO2
trocatalyst, Ag–Cu NPs/C (8501), has the smallest resistance to reduction reaction’s selectivity and activity.
charge transfer having a smaller semicircular diameter, which Chronoamperometry (CA) is the continuous measurement
is attributed to the synergistic interaction of copper and silver of current over time at a fixed potential and is an essential
(as illustrated in Fig. 2(e)). component of electroanalytical techniques. To evaluate the
Tafel slope analysis was carried out to obtain a mechanistic stability of the catalyst material, long term controlled potential
understanding of the eCO2RR and to evaluate the charge electrolysis (CPE) of the CO2 reduction reaction was performed

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through CA at different potentials from 0.4 VRHE to 0.8 VRHE. efficiency, thereby underscoring the robustness and reliability
In CPE studies, the working electrode is held at a constant of the catalyst under continuous operational conditions.
potential (V), and the current vs. time response is recorded. The Product analysis shows that carbon monoxide (CO) is
result of the durability test over 10 h for all potentials is shown the main gaseous product formed in the eCO2RR. Gas chroma-
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in Fig. 3(a), which indicates no remarkable change in j, con- tography (GC) was performed using helium as a carrier gas
firming that the optimum electrocatalyst Ag–Cu NPs/C 850 1C is and the gas quantification was achieved by generating calibra-
stable enough, making it suitable for long time use in the tion curves from the standard of CO. The chromatogram
reduction of CO2. Moreover, the long term stability test of the shows peaks for CO2 and CO, which were detected at distinct
optimum ratio at 0.79 VRHE for 40 h showing only a 2% loss in time intervals. The retention time (Rt) for CO2 in the column
activity is illustrated in Fig. S7 (ESI†). During the stability test, was 5.3 min, while the Rt for CO was 7.4 min. After 1 h, a short
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various parameters, such as catalytic activity, selectivity, and peak of CO was observed; the intensity of the CO peak was
structural integrity, were monitored to ascertain any potential increased after 2–10 h, while the intensity of the CO2 peak
degradation or deactivation of the catalyst. The results indi- decreased which confirms that some of the CO2 actively
cated a consistent performance with a minimal loss in catalytic participated in the reaction and converted to CO as

Fig. 3 (a) CA of Ag–Cu NPs/C 850 1C at different potentials over 10 h. (b) Gas chromatogram of Ag–Cu NPs/C 850 1C at 0.79 VRHE. (c) FECO% at various
applied potentials from 0.4 VRHE to 0.9 VRHE. (d) Linear Cdl plot of Ag–Cu NPs/C at different temperatures. (e) Comparative FECO% of Cu NPs/C, Ag
NPs and Ag–Cu NPs/C. (f) TOF of Ag–Cu NPs/C at different temperatures.

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Table 1 Comparison of previously reported Ag–Cu bimetallic catalysts with our work for the eCO2RR

Catalyst Electrolyte (KHCO3) M Electrolytic cell setup Applied potential (V vs. RHE) FECO% Ref.
Ag–Cu NPs/C 0.1 H-Cell 0.79 90 This work
1.10
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Ag83Cu17 0.5 H-Cell 74 53

Ag dendrites on Cu foam 0.5 Flow cell 0.80 95.7 54
Ag1.01%/CuO 0.1 H-Cell 0.70 91.2 55
Ag@Cu-7 0.1 H-Cell 1.06 82 56
Cu/Ag layered 0.1 H-Cell 0.80 89.1 57
Ag96Cu4 0.1 Flow cell 1.0 98.7 58
Ag84Cu16 dendrite 0.5 H-Cell 0.645 43.9 59
AgCu-50 0.1 H-Cell 0.60 58.4 60
Ag/Cu NWs 0.5 H-Cell 0.82 39.6 61
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Spongeous Ag91Cu9 0.1 H-Cell 0.70 80.6 62

Ag88Cu12 aerogel 0.1 M NaHCO3 H-Cell 0.89 89.40 63

illustrated in Fig. 3(b). The change in FECO% by using all the performance of Ag and Cu active sites. The optimum electro-
synthesized Ag–Cu NPs/C electrocatalysts at various potentials catalyst Ag–Cu NPs/C 850 1C gives a high TOF value of B19 
(from 0.4 VRHE to 0.9 VRHE) shows that the maximum FECO% 103 h1 at 0.8 VRHE, much higher (14.6 times) than that of Ag–
is obtained at a potential of 0.79 VRHE, which indicates that Cu NPs/C 550 1C (B1.30  103 h1 at 0.8 VRHE). The higher
the selectivity of CO depends on the applied potential and is TOF value of Ag–Cu NPs/C 850 1C indicates a faster rate of the
summarized in Fig. 3(c). eCO2RR to CO (as illustrated in Fig. 3(f)). Table 1 presents the
The change in FECO% of the optimum ratio of the synthe- comparative analysis of Ag–Cu based electrocatalysts with the
sized electrocatalyst (Ag–Cu NPs/C 850 1C) was analyzed by recent literature.
performing the eCO2RR at a fixed potential of 0.79 VRHE with
the continued bubbling of CO2 for 10 h as shown in Fig. S3
(ESI†). As illustrated in Fig. 3(e), the electrocatalytic perfor- Conclusions
mance of Cu/C, Ag-NPs, and Ag–Cu NPs/C, the comparative
In summary, we presented an Ag–Cu based bimetallic nano-
FECO% graph shows that Ag–Cu NPs/C exhibits superior far-
material, Ag–Cu NPs/C, and evaluated its performance in the
adaic efficiency with a value of 90% than those of pure silver
eCO2RR to CO. Ag–Cu NPs/C was synthesized by the incorpora-
(75%) and copper (20%) metal. This indicates that the selectiv-
tion of silver nanoparticles into Cu-BTC metal organic frame-
ity of the eCO2RR to CO has been improved by combining Ag
works and subsequent carbonization at higher temperature
with MOF-derived Cu/C and can be controlled by adjusting the
under a hydrogen environment. The as-prepared catalyst has
applied potential.
shown high performance for the eCO2RR, with a FECO value
The electrochemically active surface area (ECSA) of the
of B 90% at 0.79 VRHE and a j-value of 44.15 mA cm2 at a
electrodes was measured using an electrical double-layer capa-
low onset potential of 0.430 VRHE. The stability test over 10 h
citance (Cdl) as an indicator to further explore how the electrode
also confirms the excellent performance of Ag–Cu NPs/C. The
material influences electrocatalytic performance. Cyclic voltam-
nanostructure, dispersion, and synergistic combination of sil-
metry (CV) was carried out in the non-faradaic region at various
ver and copper nanoparticles are responsible for accelerating
scan rates ranging from 5 to 50 mV s1 as presented in
the activity and selectivity for the conversion of CO2 to CO. The
Fig. S4(a)–(d) (ESI†). The straight line is obtained by plotting
results demonstrate the potential of this material for the
scanning rates against the corresponding current and the slope
development of sustainable CO2 reduction technologies.
of the straight-line yields the Cdl value. The calculated Cdl
values of 5.075 mF cm2, 5.945 mF cm2, 6.48 mF cm2, and
8.497 mF cm2 for Ag–Cu NPs/C 550 1C, Ag–Cu NPs/C 600 1C, Data availability statement
Ag–Cu NPs/C 700 1C, and Ag–Cu NPs/C 850 1C, respectively, are
Cdl The data underlying this study will be available upon request.
demonstrated in Fig. 3(d). By using the formula ECSA ¼
Cs
the ECSA was calculated, where Cs is the specific capacitance,
and its value is 0.029 mF cm2. The maximum ECSA value Conflicts of interest
obtained for Ag–Cu NPs/C 850 1C was 293 cm2 as illustrated in
There are no conflicts to declare.
Fig. S5 (ESI†). A catalyst with a larger value of the ESCA will
possess more active sites thereby improving its performance for
the eCO2RR (high j and low Z). Note added after first publication
The turnover frequency (TOF) for CO2 reduction was eval-
uated at various potentials between 0.4 V and 0.8 V (vs. RHE) This article replaces the version published on 6th August 2024,
in a CO2-saturated medium to estimate the intrinsic which contained errors in Scheme 1.

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Acknowledgements 13 J. Shan, Y. Shi, H. Li, Z. Chen, Y. Shuai and Z. Wang,

Effective CO2 electroreduction toward C2H4 boosted by Ce-
This work is supported by the Chinese Academy of Sciences doped Cu nanoparticles, Chem. Eng. J., 2022, 433, 133769.
(CAS) (2024PVA0016). MAN acknowledges the CAS for the 14 S. Zhang, Q. Fan, R. Xia and T. J. Meyer, CO2 reduction from
This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.

grant of ‘‘President’s International Fellowship Initiative’’ homogeneous to heterogeneous electrocatalysis, Acc. Chem.
(PIFI) award. Res., 2020, 53(1), 255–264.
15 J. Wang, X. Huang, S. Xi, J. M. Lee, C. Wang, Y. Du and
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