Stable supercapacitor electrode based on two-dimensional high nucleus silver nano-clusters as a green energy source

Article abstract of DOI:10.1039/d0dt03608k

Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant features and they have attracted an immense amount of research attention over the last year. There is a lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nanoclusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high dimensional structure could be very interesting and useful for novel applications in particular. In this study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the combination of two synthetic methods. The high nucleus silver cluster units are connected together via tetradecafluoroazelaic acid (CF2) and this leads to the high stability of the polymer. This highly stable conductive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g-1 at 4.5 A g-1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s-1 to 1 V s-1), meaning it could act as a green energy source. This journal is

Full text of DOI:10.1039/d0dt03608k

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Stable supercapacitor electrode based on
two-dimensional high nucleus silver nano-clusters
as a green energy source†
Cite this: Dalton Trans., 2021, 50,
2606
Jing Zhuge, ‡a Farzaneh Rouhani,‡b Fahime Bigdeli,‡b Xue-Mei Gao,‡c
Hamed Kaviani,b Hong-Jing Li,c Wei Wang,c Mao-Lin Hu, *a Kuan-Guan Liu*c and
b
Ali Morsali
*
Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant
features and they have attracted an immense amount of research attention over the last year. There is a
lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nano-
clusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination
of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication
in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high
dimensional structure could be very interesting and useful for novel applications in particular. In this
study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the com-
bination of two synthetic methods. The high nucleus silver cluster units are connected together via tetra-
decafluoroazelaic acid (CF2) and this leads to the high stability of the polymer. This highly stable conduc-
tive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g−1 at
4.5 A g−1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and
long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s−1 to 1 V
Received 18th October 2020,
Accepted 18th January 2021
DOI: 10.1039/d0dt03608k
rsc.li/dalton
s
−1), meaning it could act as a green energy source.
form.7–9 The brilliant properties of the group 11 elements (Cu,
Ag and Au), such as the enhanced metallophilic interactions,
Introduction
The supramolecular assemblies of bridged molecular oxides, have led to their frequent use in the synthesis of novel cluster
organic shells and metal ions lead to the formation of metal complexes to overcome repulsion between cationic metal
clusters.1,2 The connections of the metal ions to the organic centers. Among the nanoclusters of the group 11 elements,
shell, usually formed of organic ligands, determine the dimen- high-nuclearity Ag-NCs with atomically precise properties and
sions of the product and often prevent further diverse structures have attracted a tremendous amount of
polymerization.3,4 The properties of these nano-meter scale research interest.4,10–15 Their atomically precise structures and
materials are different from those of their ingredients.5,6 In well-defined compositions could be helpful in understanding
more precise terms, unlike the nanoparticles, clusters have a the structure–property relationships of the nanoclusters.6,16
well-defined composition and identical structure, size and Their attractive electronic and geometric features lead to prom-
ising physical/chemical performances in various fields of
application, in particular catalysis, bio-sensing, and lumine-
aCollege of Chemistry and Materials Engineering, Wenzhou University,
scence sensing processes.17,18
Wenzhou 325035, China. E-mail: maolin_hu@yahoo.com
bDepartment of Chemistry, Faculty of Sciences, Tarbiat Modares University,
The protecting ligands are highly effective in controlling
the properties of silver NCs, and can control the size and struc-
Tehran 14115-175, Iran. E-mail: Morsali_a@modares.ac.ir
cState Key Laboratory of High-efficiency Coal Utilization and
Green Chemical Engineering, and Ningxia Key Laboratory for Photovoltaic Materials,
Ningxia University, Yin-Chuan, Ningxia, 750021, China.
E-mail: liukuanguan@nxu.edu.cn
ture of the product, and also play a vital role in dominant
aggregation and stabilization of the clusters.19–23 In the struc-
ture of most Ag-NCs, the surface anchors include three kinds
of conventional organic ligands and two types of inorganic
ligands. Coexisting flexible coordination of the silver ions,
argentophilic interactions and also a lack of understanding of
the synthesis mechanism make studying the preparation of
†Electronic supplementary information (ESI) available. CCDC 2020546. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
d0dt03608k
‡These authors contributed equally.
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Ag-NCs with controlled features an attractive area.6,9,24,25 reported by Oje et al.50 A specific capacitance of 431 F g−1 at a
Therefore, establishing an accurate method to synthesize Ag- 2 mV s−1 scan rate was achieved for the Ag thin film electrode
NCs with a controlled size and shape is highly desirable.
produced at a 350 W forward power. However, no significant
Generally, three typical synthesis methods based on temp- information was obtained about silver clusters to be used as
erature conditions are used for the formation of silver clusters: supercapacitors. One of the vital factors that promotes the
(i) low temperature, (ii) ambient temperature (which can be operation of supercapacitors is the electrical conductivity of
divided into stirring and ultra-sonication categories), and (iii) the electrode active material. The extension of high nucleus
the solvothermal method.16,26
coinage metal clusters in several dimensions can provide
Applying a series of changes in the structure of this type of effective ways for electrons to pass through the structure and
material can be a method of engineering at the molecular level form a conductive poly-cluster.50,51
in order to access novel functional materials.27–29 Therefore,
In our previous study, we constructed an Ag8 one-dimen-
engineering and synthesis of the nano-polyclusters engender a sional structure and used it as a supercapacitor electrode.31
wider range of potential applications.30,31 The cluster units of The cyclic stability of the Ag8 one-dimensional structure (SSc)
the polyclusters can be considered as constructing atoms of is about 91% at 16 A g−1 for 5000 charge–discharge cycles. By
the molecules which are connected together by interaction changing the synthesis methods and outer ligands in that
between ligands or metals through metallophilic interactions study, we attempted to achieve a high dimensional poly-cluster
to form high dimensional structures.32 For example, Au–Au that could tolerate acidic or alkaline conditions for supercapa-
interactions with proper orientations lead to the formation of citive tests. Also, in high dimensional poly-clusters, the dis-
a stable linear supracluster Au25(SBu)18 in which the SBu tance between the metallic nodes that were fixed by bridging
ligand is butane thiolate.33 In another example, ligands can affect the structural conductivity. In this study a
Au25(SCH2CH2CH3)18 clusters were formed through Au-SR facile method for the construction of a 14-nucleus two dimen-
motifs.34 On the other hand, the formation of the polycluster sional Ag poly-cluster is presented, by combination of the
structure resulted in metal–organic polyhedra (MOP) with ambient and solvothermal methods. This conductive metallic
widespread applications, which are strongly dependent on the 2D poly-cluster based on fluorinated derivatives of dicarboxylic
coordination bonds, which connect the organic linkers acid is introduced as a supercapacitor electrode. Silver poly-
together.35,36 To date, most of the synthesized networks of clusters without any modification process can act as a high
clusters include dimers or oligomers of the thiolated gold clus- performance stable electrode with a long cycle life over 6000
ters and tetravalent actinides.37,38 Following on from these cycles (about 95%), an excellent power density and a high
studies, we started to construct silver polyclusters by the com- capacitance. The presence of fluorinated groups, the 2D expan-
bination of two synthetic methods (ambient temperature and sion of the high nucleus metallic structure, and conductivity
solvothermal synthetic methods). In this study, a unique lead to form a effective supercapacitor electrode for green
14-nucleus silver poly-cluster based on a 2D polymer was pre- energy source.
pared. In this structure, high nucleus cluster units connect
together via tetradecafluoroazelaic acid (CF2). The CF2 sectors
are rigid linear rods which adopt a helical configuration owing
2. Experimental
to intramolecular steric repulsions along the carbon backbone.
2.1. Materials and methods
Porous carbon based materials are one of the most impor-
The synthesis of the silver polyclusters [Ag14(SPri)6(C9F14O4)4
tant composites for use in supercapacitors owing to their good
(DMF)8]∞ (SPc) was performed by adding 0.132 g of tetradeca-
fluoroazelaic acid (0.3 mmol) in a mixture of AgSPri (0.055 g,
0.3 mmol) in 3 mL of DMF, Agtfa (tfa = trifluoroacetate, 0.066 g,
0.3 mmol) and AgOTF (OTF = trifluoromethanesulfonate,
0.077 g, 0.3 mmol) under 2 min of ultrasound treatment. The
obtained colorless solution was mixed with 1 mL of a 0.1 M
tetramethylammonium hydroxide in methanol. The achieved
solution was sealed in a tube and heated to 70 °C overnight.
After the reaction, the mixed solution was filtered, and the fil-
trate was evaporated at room temperature. Yield: 15.3 mg, 7.1%
(based on AgSPri). The crystal size used for the single crystal
X-ray diffraction studies was 0.22 × 0.18 × 0.15 mm. The CCDC
number of the SPc Structure is 2020546.†
electrical conductivity and large surface area. Porous carbons
in combination with other elements, such as nitrogen, phos-
phorus and sulfur can improve the stability and performances
of the supercapacitors.39,40 Recently, porous carbon materials
obtained from natural materials such as PM2.5, pine needles
and metal–organic frameworks were proposed as electrodes
with a good performance for use in capacitors.41–43 Nano poly-
clusters provide an opportunity for the preparation of electro-
des with a high performance and stability without any doping
process or modification. Today, the significant impact of the
presence of silver nanoparticles on the performance of super-
capacitors is well known by researchers. Numerous groups
have studied the significant effect of increasing the amount of
Ag nanoparticles on the performance of all three types of
supercapacitors.44–46 In the vast majority of reports, silver is
2.2 Electrode preparation
used as an additive to the base structure to improve its pro- A combination of the SPc acetylene black and polytetrafluoro-
perties, of which there are various examples.47–49 Direct use of ethylene with 85 : 10 : 5 mass ratios was used for construction
silver thin film electrodes for supercapacitor applications was of the working electrode. The obtained viscous slurry was de-
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posited on a 1 × 1 cm2 size Ti foam, then pressed under 10
MPa pressure and prior to the electrochemical test it was dried
under vacuum for 10 h at 80 °C. The average weight of the
active electrode material was about 1–1.2 mg.
3. Results and discussion
The reaction between the mixture of tetradecafluoroazelaic
acid, AgSPri, Agtfa, and AgOTF in a DMF solution and metha-
nol solution of tetramethylammonium hydroxide occurred
with the aid of ultrasound waves that formed a 14-nucleus Ag
cluster-based 2D polymer SPc. A combination of an ambient
temperature (ultrasonic assisted) and the solvothermal
method were used for the synthesis of SPc. Ultrasound treat-
ment can help the reactants to quickly dissolve in solution,
and promotes the self-assembly process for the formation of
SPc. Comparative experiments were conducted for studying the
effect of the ultrasound time on the performance of the
material. The ultrasound treatment was performed for 0, 2, 5,
10, and 30 min. We found that only the precipitate was
obtained without ultrasound treatment, and the yield and for-
mation of the final crystals were no different whether the ultra-
sound time was 2, 5, 10, or 30 minutes. Based on this, we
think the main role of the ultrasound treatment is facilitating
the dissolving of the reactants, the ultrasound time has no
effect on the self-assembly process for the formation of the
SPc. According to the results of the single-crystal X-ray diffrac-
Fig. 1 (A) Molecular structure and (B) 2D network structure of SPc,
(14fda = tetradecafluoroazelate). Color code: Ag: magenta; S: yellow; C:
gray; O: red; N: blue; F: green. Hydrogens are omitted for clarity.
ˉ
tion analysis, SPc displays a triclinic crystal system and P1
space group. The silver ions and sulfur atoms of the three SPri
molecules form the central skeleton of the cluster and the
outer layer of the cluster structure is comprised of two tetrade- pattern of the powder samples. As observed in Fig. 3A, there is
cafluoroazelate anions and four DMF molecules bonded to the an acceptable agreement between the two patterns indicating
silver atoms. In the core skeleton, the range of the Ag⋯Ag and the phase purity of the synthetic samples. Fig. 3B shows the
Ag⋯S interaction distances is from 2.8985(8) to 3.3222(7) Å and solid-state infrared spectroscopy (IR) of cluster SPc. In the IR
2.4690(19) to 2.6981(16) Å, respectively. Tetradecafluoroazelate spectrum, the broad bands at 2950 cm−1 are assigned to the
linkers are coordinated to the silver ion centers by four O atoms (C–H) vibration, 1675 cm−1 is related to the (CvO) vibration,
through two types of modes, μ5-η1,η2, η1, η1 and μ4-η1,η1, η1, η1; and the coupled vibrational modes of (COH) and (CO) are
the coordination modes of the SPri ligands organized in μ5- observed at 1393 and 1204 cm−1, the vibrational bands for (C–
η1,η1,η1,η1,η1, μ4-η1,η1,η1,η1, and μ3-η1,η1,η1 show that the sulfur F) and (CC) appear at 1160 and 814 cm−1, respectively; the
atoms are also part of the cluster core skeleton. The coordi- band at 664 cm−1 is ascribed to the δ(C–O) and δ(CvO)
nation mode of one of the DMF molecules is μ2-η1, η1 and each bending modes and the band at 540 cm−1 is related to the
of the other three DMF molecules are connected to only one (COO) and (C–O) vibrations. The thermal stability of the
silver atom.
cluster SPc was investigated using thermogravimetry (Fig. 3C).
Each high nucleus silver cluster is surrounded by eight The decomposition of the cluster occurs in two steps. In the
DMF molecules and eight dicarboxylate groups of eight tetra- first step, the DMF molecules and a small portion of the
decafluoroazelaic acid ligands (Fig. 1). The size of the nano- organic ligands are removed at about 100 °C. In the second
cluster is 0.91 × 0.72 × 0.58 nm (Fig. S1†). The binding of clus- step, at 227 °C, the organic portion is completely decomposed.
ters by these ligands leads to the formation of polyclusters. The final residue is about 39.7% of Ag2O, which is in good
The SPc is expanded as 2D sheets in line with the a × c axis. agreement with the theoretically calculated amount (37.8%).
There is no interpenetration between the sheets and the sheets
The crystal image of SPc is inserted in Fig. 3C, which has a
are placed side by side by tetradecafluoroazelate bridges. The light yellow color and diamond shape. The scanning electron
distance between the two-dimensional sheets is 1.02 nm microscopy (SEM) image reveals that SPc has a wide belt-like
(Fig. 2).
morphology. As shown in Fig. 3D, many flakes with a thickness
The simulated X-ray diffractometry (XRD) pattern obtained of several nanometers are shown randomly stacked together,
from the SPc crystallographic data was compared with the XRD which leads to the large specific area of SPc. It is expected that
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Fig. 2 Expansion of the 2D structure of SPc in the direction of a × c.
Fig. 3 (A) Comparison of the simulated XRD pattern and the experimental one, (B) the solid-state IR spectrum, (C) TGA spectrum (crystal picture
inserted) and (D) SEM image of SPc.
the special morphology leads to better interaction of electrode lity, which led us to conduct supercapacitor studies using this
material with electrolyte in favor of the occurrence of the redox structure.
process. The simultaneous presence of unique properties such
A 2 M aqueous solution of potassium hydroxide was
as the presence of high nucleus silver clusters, expansion in selected as the electrolyte. In order to study the stability of the
two dimensions, special morphology, significant conductivity, structure, the SPc was immersed in the electrolyte (KOH, 2 M)
and strong nature of Ag–S and C–F leads to the structural stabi- for 4 h. The powder was separated by centrifugation and dried
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at room temperature. The XRD pattern of the obtained sample
The electrode charge storage mechanism for the charge
and the simulated sample showed an acceptable match. Also, storage system consists of two parts: the capacitance of the
the inductively coupled plasma spectroscopy on the electrolyte electric double layer and the diffusion-controlled contribution
shows a negligible amount of Ag ions (less than 2%) are of the redox reaction of the electrochemically active material.54
released. This result confirms the stability of SPc in the To determine the charge transfer kinetics of the SPc electrode,
selected electrolyte. The structural features, such as the strong the power law was used to specify the contributions of the
metal–metal and Ag–S bonds, and the presence of the tetrade- charge storage and diffusion-controlled reactions based on the
cafluoroazelaic acid ligand can play an effective key role in the CV results. The Ip shows that the peak current could be related
stability of SPc.
to the scan rate (υ) based on eqn (1):
The SPc were used as a supercapacitor electrode in a three-
electrode cell system. The CV (cyclic voltammetry) tests were
performed in the 0 to +1 V potential range and at various scan
rates from 50 to 1000 mV s−1. The charge under the CV curve
is due to the double-layer capacitance and the redox process at
the electrode surface. The redox peaks within the 0.25 to 0.6 V
potential range are mainly related to the faradaic silver oxi-
dation states in the alkaline electrolyte (Fig. 4A).52,53 However,
at higher scan rates (50–1000 mV s−1) the faradaic peaks are
buried under the very large double layer currents of the elec-
trode (Fig. 4B). Furthermore, owing to the electrode internal re-
sistance, the oxidation and reduction potentials were displaced
in the positive and negative directions. Fig. 4C shows the CV
curves obtained at a fixed scan rate (600 mV s−1), but different
applied voltages. The semi-rectangular shape of all the CV
curves at different potential windows demonstrates the electric
double layer features of the SPc. The high symmetry in the
applied potential window confirms the significant electro-
chemical reversibility of the SPc.
Ip ¼ aυb:
ð1Þ
In which, a and b are the adjustable parameters. The value
of b is close to 0.5 or 1, if b is close to 0.5, the charge storage is
primarily the result of a diffusion-controlled process, and if
the b value is close to 1, the charge storage is the result of a
capacitive process. The slope of log(i) versus log(υ) plot, gives
the b value (Fig. 5). The value of b obtained for the SPc elec-
trode is 0.85, which indicates the dominance of the capacitive
charge storage process in comparison with the diffusion-con-
trolled process. Based on the various charge storage mecha-
nisms of the CV behaviors at different scan rates, the contri-
bution of the charge storage (capacitive and diffusion-con-
trolled) can be separated. The charge storage contribution
from the capacitive and diffusion-controlled processes can be
separated based on the different charge storage mechanisms
from the cyclic voltammetry behaviors at different scan rates.
The currents from the electric double layer have a linear
Fig. 4 (A) and (B) cyclic voltammetry curves of the SPc at low and high scan rates, respectively (C) CV at 600 mV s−1 and various call voltages, (D)
GCD curves of the SPc at 4.5 to 13.0 A g−1
.
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confirm that the dominant charge storage mechanism for the
SPc electrode is a result of the capacitive process, rather than
the diffusion-controlled process.
The obtained results of the galvanostatic charge/discharge
curves (Fig. 4D) were used to calculate the specific capacitance
(Csp) based on eqn (1). The discharge current “I” (A), discharge
time “Δt” (s), potential window during the time “ΔV” (V) and
the mass of electrode “m” (g), were used for the calculation.
Csp ¼ ðI ꢀ ΔtÞ=ðΔV ꢀ mÞ
ð4Þ
The small kink in all the discharge curves is some kind of
instrumental noise. The SPc provided the highest Csp of 372 F
g−1 at 4.5 A g−1 and the calculated Csp at 6, 8, 11, and 13 A g−1
for SPc are 365, 360, 340, and 325 F g−1, respectively. The first
30 charge/discharge curves for the SPc electrode at 11 A g−1 are
presented in Fig. 6A. In addition, the cyclic stability of the
poly-cluster was studied for 6000 cycles (11 A g−1 in a 0–1 V).
As shown in Fig. 6B, 95% of the initial Csp was maintained
after 6000 cycles of charging and discharging, confirming the
long cyclic stability of SPc as a supercapacitor electrode active
material. In addition, the columbic efficiency of SPc at 4.5 A
g−1 for 6000 cycles is about 97%, as presented in Fig. S3.†
Owing to the small size of the obtained crystals of SPc,
which were unsuitable for direct conductivity measurements,
the conductivity measurement was performed on a pressed
pellet of SPc. The sheet electrical resistance values were
measured using a conventional four probe measurement with
the pellets (1 cm in diameter and 0.2 mm in thickness) at
room temperature. The probes were in a straight line, the
initial and final probes were used as a source of the current
and the others were used to measure the voltage. As shown in
Fig. S2,† a linear I–V curve was obtained. In addition, the con-
Fig. 5 Plot of log(i) versus log(v) for the SPc electrode.
relationship with the scan rates (υ). The faradaic currents
present a linear relationship with υ1/2. Thus, the total current
at a specific potential can be divided into the following two
parts: (eqn 2)
Ip ¼ k1υ þ k2υ1=2
ð2Þ
In which, Ip (A), k1 and k2 show the peak current and coeffi-
cients of the capacitive diffusion-controlled currents, respect-
ively. This equation can also be changed to eqn (3), in which
the amount of k1 and k2 achieved from the slope and intercept
of the Ip/υ1/2 versus υ1/2 plot, respectively, can be represented
as:
Ip=υ1=2 ¼ k1υ1=2 þ k2
ð3Þ
Therefore, the contribution of the capacitance and ductivity of 2.3 S cm−1 was obtained for SPc. This measure-
diffusion-controlled current can be calculated separately, by ment is not only beneficial for obtaining more accurate
inserting the values of k1 and k2 in eqn (3). The contributions results, but also provides evidence of the electrical stability of
at various scan rates are presented in Table S1.† The results the SPc.
Fig. 6 (A) and (B) cycling stability and columbic efficiency of the SPc at 11 A g−1 for the first 30 and 6000 cycles.
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Fig. 7 (A) Nyquist plot (inset shows the corresponding electrical equivalent circuit), and (B) Bode-phase plot of the SPc.
On the other hand, the Nyquist and Bode plots, using quency are displayed by the Bode-phase plot (Fig. 7B). The
electrochemical impedance spectroscopy (EIS) techniques approximation of the phase angle to 80° indicates the ideal be-
(Fig. 7) were used to study the transport kinetics for the havior of the SPc electrode as an appropriate active material
electrochemical behaviors of the SPc. The two interfacial for use as a supercapacitor electrode. Generally, the brilliant
charge transport processes occurred in the EIS-Nyquist plots of supercapacitive efficiency of SPc could be attributed to its
SPc which were confirmed by two semicircle trends (fitted in appropriate morphology and good conductivity, which helps
50 kHz–50 mHz). The first one could be ascribed to the total the electrons pass through the structure.
charge transport resistance at the electrode/electrolyte inter-
Furthermore, eqn (5) and (6) were used for calculation of
face (Rct ), which is seen in the high-frequency region and the the energy density, and power density, respectively:
1
second semicircle (Rct ) is ascribed to the total resistance of
the charge transport at the interior interface of the SPc flakes.
2
E ¼ ðC ꢀ V 2Þ=ð2 ꢀ 3:6Þ
ð5Þ
ð6Þ
Also, the tiny semicircles confirm the high speed ion
P ¼ ð3600 ꢀ EÞ=Δt:
diffusion to the electrode from the electrolyte.55 In addition,
the Warburg impedance (W) in the Nyquist plot of SPc is
attributed to the diffusion of ions.56 On the other hand, the
changes in the phase angle with respect to the applied fre-
The operating voltage window and discharge time is shown
by the V (V) and Δt (s) symbols. The fabricated supercapacitor
based on SPc in KOH (2 M) reveals values of 51.6 W h kg−1
Fig. 8 (A) XRD pattern of SPc after 6000 charge/discharge cycles, (B) SEM images of SPc after use.
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(energy density) and 2.32 kW kg−1 (power density). After use,
the electrode materials were examined using SEM and powder
XRD analysis. As shown in Fig. 8, the stability of the structure
was confirmed by the intact XRD pattern. The stability of the
structure could be related to the arrangement of the CF2
groups on the superficial surface of SPc. The simultaneous
operation of the double-layer and pseudo-capacitance perform-
ance of the silver nano-polymer and special features, such as
the favorable morphology and low resistance of the structure,
led to the remarkable supercapacitive efficiency of SPc. The
simultaneous presence of these properties is very rare in non-
hybrid materials.
using Phyllanthus amarus and Tinospora cordifolia medic-
inal plants, J. Nanomed. Nanotechnol., 2014, 5, 1.
3 S. F. Yuan, C. Q. Xu, J. Li and Q. M. Wang, A Ligand–
Protected Golden Fullerene: The Dipyridylamido
Au328+Nanocluster, Angew. Chem., 2019, 131, 5967–5970.
4 S.-S. Zhang, F. Alkan, H.-F. Su, C. M. Aikens, C.-H. Tung
and D. Sun, [Ag48(C≡ CtBu) 20 (CrO4)7]: An Atomically
Precise Silver Nanocluster Co-protected by Inorganic and
Organic Ligands, J. Am. Chem. Soc., 2019, 141, 4460–4467.
5 D. Sun, Z.-H. Yan, V. A. Blatov, L. Wang and D.-F. Sun,
Syntheses, topological structures, and photoluminescences
of six new Zn(II) coordination polymers based on mixed tri-
podal imidazole ligand and varied polycarboxylates, Cryst.
Growth Des., 2013, 13, 1277–1289.
6 Y.-P. Xie, J.-L. Jin, G.-X. Duan, X. Lu and T. C. Mak, High-
nuclearity silver(I) chalcogenide clusters: a novel class of
supramolecular assembly, Coord. Chem. Rev., 2017, 331,
54–72.
7 J. F. Corrigan, O. Fuhr and D. Fenske, Metal chalcogenide
clusters on the border between molecules and materials,
Adv. Mater., 2009, 21, 1867–1871.
8 C. P. Joshi, M. S. Bootharaju, M. J. Alhilaly and O. M. Bakr,
[Ag25(SR)18]−: The “golden” silver nanoparticle, J. Am.
Chem. Soc., 2015, 137, 11578–11581.
9 Z. Wang, H.-F. Su, Y.-Z. Tan, S. Schein, S.-C. Lin, W. Liu,
S.-A. Wang, W.-G. Wang, C.-H. Tung and D. Sun, Assembly
of silver Trigons into a buckyball-like Ag180 nanocage,
Proc. Natl. Acad. Sci. U. S. A., 2017, 114, 12132–12137.
10 L. He, Z. Gan, N. Xia, L. Liao and Z. Wu, Alternating Array
Stacking of Ag26Au and Ag24Au Nanoclusters, Angew.
Chem., Int. Ed., 2019, 58, 9897–9901.
4. Conclusion
In conclusion, for the first time, we synthesized silver polyclus-
ters using a solvothermal method with the assistance of an
ultrasonic technique. The tetradecafluoroazelaic acid acts as a
bridging ligand to connect the cluster units to each other in
the longitudinal and transverse directions. The function of
these types of ligands is important in terms of both the struc-
tural architecture and the creation of potential applications,
such as their use in supercapacitors. This conductive silver
poly-cluster displays a faradaic capacitor behavior, 95% stabi-
lity over 6000 cycles and higher specific capacitance in com-
parison with similar structures. The brilliant efficiency of
these SPcs can be ascribed to the electronic conductivity and
specific morphology of the active material. These features
obliterate common obstacles such as low conductivity, multi-
step synthesis, and agglomeration of the material. These
results provide new horizons to expand the use of conductive
metallic poly-clusters as a green energy source.
11 R. Jin, C. Zeng, M. Zhou and Y. Chen, Atomically precise
colloidal metal nanoclusters and nanoparticles: fundamen-
tals and opportunities, Chem. Rev., 2016, 116, 10346–
10413.
Conflicts of interest
12 E. Khatun, M. Bodiuzzaman, K. S. Sugi, P. Chakraborty,
G. Paramasivam, W. A. Dar, T. Ahuja, S. Antharjanam and
T. Pradeep, Confining an Ag10 Core in an Ag12 Shell: A
There are no conflicts to declare.
Four-Electron
Superatom
with
Enhanced
Photoluminescence upon Crystallization, ACS Nano, 2019,
13, 5753–5759.
Acknowledgements
13 J. W. Liu, Z. Wang, Y. M. Chai, M. Kurmoo, Q. Q. Zhao,
X. P. Wang, C. H. Tung and D. Sun, Core Modulation of
70−Nuclei Core–Shell Silver Nanoclusters, Angew. Chem.,
2019, 131, 6342–6345.
14 Z.-H. Pan, C.-L. Deng, Z. Wang, J.-Q. Lin, G.-G. Luo and
D. Sun, Silver clusters templated by homo-and hetero-
anions, CrystEngComm, 2020, 22, 3736–3748.
This work was supported by the Natural Science Foundation of
China (21571143 and 21601097), the Science & Technology
Project for Young and Middle-aged Talents (Grant. No.
TJGC2018036), the Foundation of State Key Laboratory of
High-efficiency Utilization of Coal and Green Chemical
Engineering (Grant No. 2019-KF-01) and Tarbiat Modares
University.
15 Z. Wang, Y.-M. Sun, Q.-P. Qu, Y.-X. Liang, X.-P. Wang,
Q.-Y. Liu, M. Kurmoo, H.-F. Su, C.-H. Tung and D. Sun,
Enclosing classical polyoxometallates in silver nano-
clusters, Nanoscale, 2019, 11, 10927–10931.
References
1 F. A. Cotton, Molybdenum compounds, in Multiple Bonds 16 Z. Wang, R. K. Gupta, G. G. Luo and D. Sun, Recent pro-
Between Metal Atoms, Springer, 2005, pp. 69–182.
2 K. Singh, M. Panghal, S. Kadyan and J. P. Yadav, Evaluation
of antimicrobial activity of synthesized silver nanoparticles
gress in inorganic anions templated silver nanoclusters:
synthesis, structures and properties, Chem. Rec., 2020, 20,
389–402.
This journal is © The Royal Society of Chemistry 2021
Dalton Trans., 2021, 50, 2606–2615 | 2613

View Article Online
Paper
Dalton Transactions
17 L.-P. Cheng, Z. Wang, Q.-Y. Wu, H.-F. Su, T. Peng, 31 K.-G. Liu, F. Rouhani, H. Moghanni-Bavil-Olyaei, X.-W. Wei,
G.-G. Luo, Y.-A. Li, D. Sun and L.-S. Zheng, Small size yet
big action: a simple sulfate anion templated a discrete
78-nuclearity silver sulfur nanocluster with a multishell
structure, Chem. Commun., 2018, 54, 2361–2364.
X.-M. Gao, J.-Z. Li, X. Yan, M. L. Hu and A. Morsali,
Conductive 1D High-nucleus Silver polymer as a Brilliant
Non-hybrid Supercapacitor Electrode, J. Mater. Chem. A,
2020, 8, 12975–12983.
18 Z. Wang, J.-W. Liu, H.-F. Su, Q.-Q. Zhao, M. Kurmoo, 32 R. Ho-Wu, K. Sun and T. Goodson III, Synthesis and
X.-P. Wang, C.-H. Tung, D. Sun and L.-S. Zheng,
Chalcogens-Induced Ag6Z4@ Ag36 (Z=S or Se) Core–Shell
Nanoclusters: Enlarged Tetrahedral Core and Homochiral
Crystallization, J. Am. Chem. Soc., 2019, 141, 17884–17890.
19 A. Schnepf and H. Schnöckel, Nanoscale Molecular Silver
Cluster Compounds in Gram Quantities, Angew. Chem., Int.
Ed., 2014, 53, 3064–3066.
enhanced linear and nonlinear optical properties of
chromophore–au metal cluster oligomers, J. Phys. Chem. C,
2018, 122, 2315–2329.
33 P. Chakraborty, A. Baksi, S. K. Mudedla, A. Nag,
G. Paramasivam, V. Subramanian and T. Pradeep,
Understanding proton capture and cation-induced dimeriza-
tion of [Ag 29 (BDT) 12] 3− clusters by ion mobility mass
spectrometry, Phys. Chem. Chem. Phys., 2018, 20, 7593–7603.
20 G. G. Luo, H. F. Su, A. Xiao, Z. Wang, Y. Zhao, Q. Y. Wu,
J. H. Wu, D. Sun and L. S. Zheng, Silver–Sulfur Hybrid 34 M. Suyama, S. Takano, T. Nakamura and T. Tsukuda,
Supertetrahedral Clusters: The Hitherto Missing Members
in the Metal–Chalcogenide Tetrahedral Clusters, Chem. –
Eur. J., 2017, 23, 14420–14424.
Stoichiometric Formation of Open-Shell [PtAu24 (SC2H4Ph)
18]− via Spontaneous Electron Proportionation between
[PtAu24 (SC2H4Ph) 18] 2−and [PtAu24 (SC2H4Ph)18] 0, J. Am.
Chem. Soc., 2019, 141, 14048–14051.
21 R. W. Huang, X. Y. Dong, B. J. Yan, X. S. Du, D. H. Wei,
S. Q. Zang and T. C. Mak, Tandem silver cluster isomerism 35 X.-Y. Xie, F. Wu, X. Liu, W.-Q. Tao, Y. Jiang, X.-Q. Liu and
and mixed linkers to modulate the photoluminescence of
cluster–assembled materials, Angew. Chem., Int. Ed., 2018,
57, 8560–8566.
L.-B. Sun, Photopolymerization of metal–organic polyhe-
dra: an efficient approach to improve the hydrostability,
dispersity, and processability, Chem. Commun., 2019, 55,
6177–6180.
22 S. Zhang and L. Zhao, Macrocycle-encircled polynuclear
metal clusters: controllable synthesis, reactivity studies, 36 M. Paul, N. Adarsh and P. Dastidar, Secondary Building
and applications, Acc. Chem. Res., 2018, 51, 2535–2545.
23 Z.-Y. Wang, M.-Q. Wang, Y.-L. Li, P. Luo, T.-T. Jia,
R.-W. Huang, S.-Q. Zang and T. C. Mak, Atomically precise
site-specific tailoring and directional assembly of supera-
Unit (SBU) Controlled Formation of a Catalytically Active
Metal–Organic Polyhedron (MOP) Derived from
Flexible Tripodal Ligand, Cryst. Growth Des., 2014, 14,
1331–1337.
a
tomic silver nanoclusters, J. Am. Chem. Soc., 2018, 140, 37 V. R. Jupally, R. Kota, E. V. Dornshuld, D. L. Mattern,
1069–1076.
G. S. Tschumper, D.-E. Jiang and A. Dass, Interstaple
dithiol cross-linking in Au25 (SR) 18 nanomolecules:
a combined mass spectrometric and computational study,
J. Am. Chem. Soc., 2011, 133, 20258–20266.
24 H. Yu, B. Rao, W. Jiang, S. Yang and M. Zhu, The photolu-
minescent metal nanoclusters with atomic precision,
Coord. Chem. Rev., 2019, 378, 595–617.
25 H. Schmidbaur and A. Schier, Argentophilic interactions, 38 C. Falaise, C. Volkringer, J.-F. O. Vigier, A. Beaurain,
Angew. Chem., Int. Ed., 2015, 54, 746–784.
P. Roussel, P. Rabu and T. Loiseau, Isolation of the Large
{Actinide} 38 Poly-oxo Cluster with Uranium, J. Am. Chem.
Soc., 2013, 135, 15678–15681.
26 G.-G. Luo, Q.-L. Guo, Z. Wang, C.-F. Sun, J.-Q. Lin and
D. Sun, New protective ligands for atomically precise silver
nanoclusters, Dalton Trans., 2020, 49, 5406–5415.
27 S. Mukherjee and P. S. Mukherjee, Versatility of azide in
serendipitous assembly of copper(II) magnetic polyclusters,
Acc. Chem. Res., 2013, 46, 2556–2566.
39 G. Zhu, L. Ma, H. Lv, Y. Hu, T. Chen, R. Chen, J. Liang,
X. Wang, Y. Wang, C. Yan, Z. Tie, Z. Jin and J. Liu, Pine
needle-derived microporous nitrogen-doped carbon frame-
works exhibit high performances in electrocatalytic hydro-
gen evolution reaction and supercapacitors, Nanoscale,
2017, 9(3), 1237–1243.
28 F. Rouhani, F. Rafizadeh-Masuleh and A. Morsali, Highly
Electroconductive Metal–Organic Framework: Tunable by
Metal Ion Sorption Quantity, J. Am. Chem. Soc., 2019, 141, 40 G. Zhu, L. Ma, H. Lin, P. Zhao, L. Wang, Y. Hu, R. Chen,
11173–11182.
T. Chen, Y. Wang, Z. Tie and Z. Jin, High-performance Li-
ion capacitor based on black-TiO2−x/graphene aerogel
anode and biomass-derived microporous carbon cathode,
Nano Res., 2019, 12(7), 1713–1719.
29 F. Rouhani, F. Rafizadeh-Masuleh and A. Morsali, Selective
sacrificial metal–organic frameworks: a highly quantitative
colorimetric naked-eye detector for aluminum ions
in aqueous solutions, J. Mater. Chem. A, 2019, 7, 18634– 41 G. Zhu, T. Chen, Y. Hu, L. Ma, R. Chen, H. Lv, Y. Wang,
18641.
J. Liang, X. Li, C. Yan and H. Zhu, Recycling PM2.5 carbon
nanoparticles generated by diesel vehicles for super-
capacitors and oxygen reduction reaction, Nano Energy,
2017, 33, 229–237.
30 K.-G. Liu, F. Rouhani, Q.-D. Shan, R. Wang, J. Li, M.-L. Hu,
X. Cheng and A. Morsali, Ultrasonic-assisted fabrication of
thin-film electrochemical detector of H2O2 based on ferro-
cene-functionalized silver cluster, Ultrason. Sonochem., 42 H. Wang, Q. Yi, L. Gao, Y. Gao, T. Liu, Y. B. Jiang, Y. Sun
2019, 56, 305–312.
and G. Zou, Hierarchically interconnected nitrogen-doped
2614 | Dalton Trans., 2021, 50, 2606–2615
This journal is © The Royal Society of Chemistry 2021

View Article Online
Dalton Transactions
Paper
carbon nanosheets for an efficient hydrogen evolution reac- 51 Q. Miao, F. Rouhani, H. Moghanni-Bavil-Olyaei, K.-G. Liu,
tion, Nanoscale, 2017, 9(42), 16342–16348.
X.-M. Gao, J.-Z. Li, X.-D. Hu, Z.-M. Jin, M.-L. Hu and
A. Morsali, Comparative Study of the Supercapacitive
Performance of three new Ferrocene–based Structures;
Target Designed of a Conductive Ferrocene–Functionalized
Coordination Polymer as supercapacitor electrode, Chem.
– Eur. J., 2020, 26, 9518–9526.
43 T. Liang, H. Wang, R. Fei, R. Wang, B. He, Y. Gong and
C. Yan, A high-power lithium-ion hybrid capacitor based
on a hollow N-doped carbon nanobox anode and its porous
analogue cathode, Nanoscale, 2019, 11(43), 20715–20724.
44 J. Stejskal and M. Trchová, Conducting polypyrrole nano-
tubes: a review, Chem. Pap., 2018, 72, 1563–1595.
45 X. Zhang, Q. Fu, H. Huang, L. Wei and X. Guo, Silver–
quantum–dot–modified MoO3 and MnO2 paper–like free-
standing films for flexible solid–state asymmetric super-
capacitors, Small, 2019, 15, 1805235.
52 P. Liu, J. Liu, S. Cheng, W. Cai, F. Yu, Y. Zhang, P. Wu and
M. Liu, A high-performance electrode for supercapacitors:
Silver nanoparticles grown on a porous perovskite-type
material La0. 7Sr0. 3CoO3− δ substrate, Chem. Eng. J., 2017,
328, 1–10.
46 T. Yeo, J. Lee, D. Shin, S. Park, H. Hwang and W. Choi, 53 S. Nagamuthu and K.-S. Ryu, Synthesis of Ag/NiO honey-
One-step fabrication of silver nanosphere-wetted carbon
nanotube electrodes via electric-field-driven combustion
waves for high-performance flexible supercapacitors,
J. Mater. Chem. A, 2019, 7, 9004–9018.
comb structured nanoarrays as the electrode material for
high performance asymmetric supercapacitor devices, Sci.
Rep., 2019, 9, 1–11.
54 S. Liu, S. Sarwar, H. Zhang, Q. Guo, J. Luo and X. Zhang,
One-step microwave-controlled synthesis of CoV2O6.2H2O
nanosheet for super long cycle-life battery-type super-
capacitor, Electrochim. Acta, 2010, 364, 137320.
47 B. S. Singu and K. R. Yoon, Highly exfoliated GO-PPy-Ag
ternary nanocomposite for electrochemical supercapacitor,
Electrochim. Acta, 2018, 268, 304–315.
48 L. Manjakkal, C. G. Núñez, W. Dang and R. Dahiya, Flexible 55 J. Ji, X. Zhang, Z. Huang, X. Yu, H. Huang, Y. Huang and
self-charging supercapacitor based on graphene-Ag-3D gra-
phene foam electrodes, Nano Energy, 2018, 51, 604–612.
49 B. Pandit, V. S. Devika and B. R. Sankapal, Electroless-de-
posited Ag nanoparticles for highly stable energy-efficient
L. Li, One-step synthesis of graphene oxide/polypyrrole/
MnO2 ternary nanocomposites with an improved electro-
chemical capacitance, J. Nanosci. Nanotechnol., 2017, 17,
4356–4361.
electrochemical supercapacitor, J. Alloys Compd., 2017, 726, 56 J. Arjomandi, J. Y. Lee, R. Movafagh, H. Moghanni-Bavil-
1295–1303.
Olyaei and M. H. Parvin, Polyaniline/aluminum and iron
oxide nanocomposites supercapacitor electrodes with high
specific capacitance and surface area, J. Electroanal. Chem.,
2018, 810, 100–108.
50 A. I. Oje, A. A. Ogwu, M. Mirzaeian, A. M. Oje and
N. Tsendzughul, Silver thin film electrodes for super-
capacitor application, Appl. Surf. Sci., 2019, 488, 142–150.
This journal is © The Royal Society of Chemistry 2021
Dalton Trans., 2021, 50, 2606–2615 | 2615