Hierarchical Co3O4@PPy@MnO2 core–shell–shell nanowire arrays for enhanced electrochemical energy storage

doi:10.1016/j.nanoen.2014.04.014

Nano Energy

Volume 7, July 2014, Pages 42-51

https://doi.org/10.1016/j.nanoen.2014.04.014 Get rights and content

Highlights

•
Co₃O₄@PPy@MnO₂ core–shell–shell nanowire arrays were synthesized as electrode materials.
•
The assembled asymmetric supercapacitor exhibits excellent cycling behavior.
•
The as-prepared device is capable of driving a DC mini-motor for ca. 30 s.

Abstract

Combining hydrothermal synthesis, electrodeposition with soaking process, we synthesized coaxial nanowire arrays consisting of Co₃O₄ nanowire as the core, polypyrrole (PPy) as the inner shell and MnO₂ outer layer as the exodermis. The key to fabricate one-dimensional hierarchical architecture, Co₃O₄@PPy@MnO₂ “core–shell–shell” nanowires, was to introduce a PPy intermediate layer on the surface of Co₃O₄ nanowire, which could enhance the conductivity of nanowire arrays and act as a reactive template to induce a coating of amorphous MnO₂. The device based on the ternary composite Co₃O₄@PPy@MnO₂ nanowire arrays exhibited prominent electrochemical performance with a high energy density of 34.3 Wh kg⁻¹ at a power density of 80.0 W kg⁻¹ and a remarkable long-term cycling stability. In addition, the performance of as-assembled asymmetrical supercapacitor was demonstrated using a DC motor. The results imply that ternary composite based electrode materials have enormous potential for energy storage devices and systems.

Graphical abstract

We report supercapacitor electrode materials composed of ternary composite, i.e. Co₃O₄ nanowires as the core, polypyrrole (PPy) as the inner shell and MnO₂ outer layer as the exodermis, and demonstrate their electrochemical performance for energy storage applications.

Introduction

Heterostructured nanomaterial is drawing a tremendous amount of attention in energy storage devices. To date, intensive efforts have been devoted to the synthesis of self-supported core/shell heterostructures, which could combine the advantages of different materials and exhibit several interesting features [1], [2], [3]. For instance, the core/shell nanowires not only provide large active surface area and short ions diffusion path but also show a potential synergy. Therefore, design and synthesis of core/shell nanoarrays with hierarchically porous structures is promising for the development of high performance electronic and electrochemical energy conversion storage devices.

Metal oxides and hydroxides store electrochemical energy by surface redox reactions, and it is well known that Co₃O₄, MnO₂, Co(OH)₂, CoO, NiO, RuO₂, and Ni(OH)₂ are the most extensively investigated cathode pseudocapacitive materials. In order to meet the requirement of higher specific capacitance and structural stability, one effective strategy is the integration of these oxides/hydroxides or conductive polymer into core/shell nanoarrays [4], [5], [6]. Typically, researchers prepare the core/shell nanowire arrays based on binary heterostructures, which first constructs metal oxide backbone and subsequently coats the shell materials [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. Most recently, there are a few reports on fabricating more complex hierarchical nanoarchitecture – ternary “core–shell–shell” nanowire arrays, which has been considered as a promising approach to further increase the effective utilization of active materials [17], [18], [19], [20], [21]. Wang et al. reported WO_3−x@Au@MnO₂ core/shell nanowires with a specific capacitance of 588 F g⁻¹ at a scan rate of 10 mV s⁻¹ and 1195 F g⁻¹ at a current density of 0.75 A g⁻¹ [19]; Xia et al. described hierarchically structured Co₃O₄@Pt@MnO₂ nanowire arrays for pseudocapacitors with a high capacitance (539 F g⁻¹ at 1 A g⁻¹), an excellent cycle performance and rate capability [20]; Hu et al. synthesized a sandwich configuration of Co₃O₄@Au@MnO₂, with high specific capacitances of 851.4 F g⁻¹ at 10 mV s⁻¹ and 1532.4 F g⁻¹ at 1 A g⁻¹ and good rate performance [21]. Among these ternary hierarchical nanostructures, noble metal nanoparticles (NPs), such as Pt NPs and Au NPs, are employed as intermediate layers owing to their high electrical conductivity. However, considering the intrinsic low capacitance contribution from noble metals and their inherently costly nature, conductive polymers as promising alternatives could be introduced into ternary composites because they have advantages of relatively high capacitance, low cost, excellent conductivity, high chemical stability and mechanical flexibility [7], [8], [9], [22], [23]. Most recently, Fan et al. prepared novel Co₃O₄/PEDOT-MnO₂ core/shell nanowire arrays on 3D graphite foams for supercapacitors. Although the integrated material exhibited superior electrochemical properties, Co₃O₄ nanowires were just used as the core backbone and contributed negligible capacitance to the electrode in a neutral solution [17].

In this communication, the Co₃O₄@PPy@MnO₂ “core–shell–shell” nanowire arrays on nickel foam substrate was presented, and their microstructural and electrochemical properties were also investigated. Figure 1 illustrated the three-step synthesis of Co₃O₄@PPy@MnO₂ nanowire arrays using hydrothermal synthesis, electrochemical polymerization and in-situ redox reaction. In the experiment, to ensure efficient electrolyte penetration, three-dimensional nickel foam with uniform macropores and high conductivity was served as the current collector. The synthesis procedure of nanowire arrays was summarized briefly in the following three steps as shown in Figure 1: step (i), Co₃O₄ nanowire core backbone was grown on nickel foam by the hydrothermal and postannealing method [24]; step (ii), a conductive polymer of PPy film was assembled on Co₃O₄ nanowire surface by potentiostatic deposition; step (iii), by soaking Co₃O₄@PPy in aqueous KMnO₄ solution a redox reaction occurred in 3-D ordered nanowire interface, forming the final product, i.e. Co₃O₄@PPy@MnO₂ core–shell–shell hybrid nanowires. In the ternary composite of Co₃O₄@PPy@MnO₂, PPy was chosen as the intermediate layer because it is capable of performing charge storage by a fast redox reaction [25], [26]. Moreover, the electrical conductivity of Co₃O₄ (10⁻²–10⁻⁴ S cm⁻¹) is much lower than that of conducting PPy (10–100 S cm⁻¹) and therefore the presence of PPy layer on Co₃O₄ nanowire core provides the effective pathway for fast electron transport and accelerates the reaction kinetics between electroactive center and current collector. Furthermore, the deposited PPy layer could act as an interfacial template to nucleate and grow MnO₂ coating via a green chemical reaction, in which amorphous MnO₂ could be obtained by in-situ redox reaction between KMnO₄ and conductive polymer at room temperature [17], [27].

Section snippets

Chemicals and materials

All chemicals were purchased from Aldrich and used without further purification unless otherwise indicated. If not specified, all solutions were prepared using deionized water (ca. 18.2 MΩ cm resistivity).

Preparation of Co₃O₄ nanowires arrays

Co₃O₄ nanowire arrays are grown directly on a nickel foam substrate via a modified hydrothermal process [24]. In experiment, 0.155 g Co(NO₃)₂·6H₂O, 0.0425 g NH₄F, 0.1613 g CO(NH₂)₂ and 0.0538 g hexadecyl trimethyl ammonium bromide (CTAB) were dissolved in 30 ml distilled water by magnetic stirring

Results and discussion

The field emission scanning electron microscopy (FESEM) images of as-synthesized Co₃O₄, Co₃O₄@PPy and Co₃O₄@PPy@MnO₂ hybrid nanowire arrays are shown in Figure 2. The experimental results indicate that nickel foam skeletons are uniformly covered with Co₃O₄ nanowires (see Figure 2a). The average diameter of these Co₃O₄ nanowires is approximately 50–80 nm, and their surface is smooth (see Figure 2b). After electrochemical polymerization for 50 s, Co₃O₄ nanowire core is well wrapped by the

Summary and conclusions

In summary, a core–shell–shell heterostructure of Co₃O₄@PPy@MnO₂ nanowire arrays was fabricated on nickel foam through a facile three-step synthesis approach. The ternary architectures consisted of the metal oxides nanowire core and the conductive polymer shell decorated by metal oxide could combine the advantages of three pseudocapacitive materials, exhibiting synergy for the enhancement of electrochemical performance. An asymmetric two-electrode supercapacitor was prepared and could drive a

Supporting Information Available

Supplementary results on SEM micrographs (Figure S1-S2), HRTEM and XRD results (Figure S3), EDS results (Figure S4), EELS results (Figure S5), Raman spectrum (Figure S6), FTIR spectrum (Figure S7), XPS spectrum (Figure S8), CV curves (Figure S9, S12), chart/discharge curves (Figure S10), and Nyquist plot of the EIS (Figure S11). Figure S13 and Video S1 show that a rotating DC motor is driven by an AC//Co₃O₄@PPy@MnO₂ aqueous supercapacitor device in 1.0 M NaOH solution, which was charged for 26

Acknowledgment

The authors thank the Micro and Nano Fabrication Laboratory of The Chinese University of Hong Kong (CUHK) for technical support. This work was financially supported by the Shun Hing Institute of Advanced Engineering with the Project no. RNE-p4-13, and the Staff Start-up Fund for Research at CUHK.

Lijuan Han received her B.Sc. in Chemistry from Northwest Normal University and M.Sc. in Physical Chemistry from Lanzhou University. Afterwards, she joined Dr. Li Zhang's group at the Chinese University of Hong Kong as Shun Hing Research Assistantin 2013. Her current research is focused on the design and synthesis of nanostructured electrode materials for energy storage devicesand electrochemical biosensors.

References (30)

X. Xia et al.
ACS Nano
(2012)
J. Liu et al.
Adv. Mater.
(2011)
X.H. Xia et al.
Nano Lett.
(2014)
M. Toupin et al.
Chem. Mater.
(2004)
R. Liu et al.
J. Am. Chem. Soc.
(2008)
B. Tian et al.
Nature
(2007)
L.Q. Mai et al.
Nat. Commun.
(2011)
G.P. Wang et al.
Chem. Soc. Rev.
(2012)
J. Jiang et al.
Adv. Mater.
(2012)
C.Z. Yuan et al.
Angew. Chem. Int. Ed.
(2014)
C. Zhou et al.
Nano Lett.
(2013)

X. Xia et al.

Nano Lett.

(2013)

Z.L. Wang et al.

Sci. Rep.

(2013)

L. Bao et al.

Nano Lett.

(2011)

L. Huang et al.

Nano Lett.

(2013)

G. Zhang et al.

Nano Energy

(2013)

L. Yu et al.

Chem. Commun.

(2013)

L. Huang et al.

ACS Appl. Mater. Interfaces

(2013)

J. Sun et al.

Nano Energy

(2014)

Cited by (146)

3D hierarchical NiCo<inf>2</inf>O<inf>4</inf>@Co<inf>3</inf>S<inf>4</inf>@MnS@PPy core-sheath nanowire arrays as high-performance electrode for all-solid-state asymmetric supercapacitors
2024, Journal of Energy Storage
To cater to the mushrooming advanced energy storage devices need, designing and preparing novel electrode materials with excellent electrochemical properties (including high capacitance and prominent cycling stability) are urgent but challenging. Here, we successfully synthesized 3D hierarchical NiCo₂O₄@Co₃S₄@MnS@PPy (NC@CS@MS@PPy) core-sheath nanowire arrays grown on highly conductive carbon cloth using a multistage process. Owing to a lot of synergy between the multiple components in the as-obtained composite, the prepared electrode material indicates an excellent specific capacitance of 2.67 F cm⁻² at 1 mA cm⁻² or 2557.58 F g⁻¹ at 1 A g⁻¹ and high cycling stability (83.64 % capacitance retention after 20,000 cycles even at a high current density of 20 mA cm⁻²). When coupled with the activated carbon (AC, as a negative electrode), the assembled all-solid-state NC@CS@MS@PPy//AC asymmetric supercapacitor (ASC) device showed outstanding electrochemical properties with a high area specific capacitance 684.38 mF cm⁻² at 3 mA cm⁻² and better long-term cycling stability (96.76 % retention of the initial capacitance after 20,000 cycles). More importantly, by taking advantaging of the multiple compositional merits and structural features of the positive electrode, the device delivered the highest energy density of 81.1 Wh kg⁻¹ at 800 W kg⁻¹ and retained 26.2 Wh kg⁻¹ at the highest power density of 16 KW kg⁻¹. Furthermore, two ASCs connected in series powered 20 red light-emitting diodes (LEDs) for >10 min. This work manifests that the prepared hierarchical NC@CS@MS@PPy core-sheath nanowire arrays have impressive potential as high-performance electrodes for supercapacitor.
α-MnO<inf>2</inf> composite with gold nanoparticles on carbon cloth modified with MOFs-derived porous carbon for flexible and activity-enhanced sodium-ion supercapacitors
2023, Journal of Alloys and Compounds
Improving the catalytic activity of electrodes in a limited space is crucial to energy storage devices such as supercapacitors. Herein, the surface activity of the flexible electrode (Au-MnO₂/CPCN@CC) is enhanced by combining gold particles (AuNPs) modified α-MnO₂ with conductive porous carbon nanoflakes (CPCN) derived from the metal-organic framework (MOF) on carbon cloth (CC). The Au-MnO₂/CPCN@CC electrode exhibits a higher specific capacity of 503.7 F/g at 0.125 mA/cm² and retains 87.68% capacity after 10,000 cycles in 1 M Na₂SO₄, while the structure without AuNPs achieves 242.6 F/g and 61.07% capacity retention after 10,000 cycles. The high stability of Au-MnO₂/CPCN@CC stems from the good pseudocapacitance ratio of 83.80% at 1 mV/s compared to 78.43% of MnO₂/CPCN@CC and 40.88% of Au/CPCN@CC. The supercapacitor assembled with Au-MnO₂/CPCN@CC as the positive electrode and activated carbon (AC) as the negative electrode in 1 M NaPF₆ shows an excellent power density of 79.96 W/kg at 71.48 Wh/kg as well as 81.93% capacitance retention after 10,000 cycles. Density-functional theory (DFT) calculations of Au-MnO₂/CPCN composite reveal a sodium-ion adsorption energy of 3.744 eV and a large DOS near Fermi level. Hence, Au nanoparticles (AuNPs) and MOFs-derived CPCN lead to enhanced surface electron transport of MnO₂ and ultimately superior performance.
Unidirectional growth of polyaniline on 3D CoO nanowires for aqueous asymmetric supercapacitors
2023, Journal of Energy Storage
Metal oxide-based binary nanohybrids are a new class of binder-free supercapacitor electrodes. This paper reports the enhanced electrochemical performance of polyaniline (PANI)/CoO nanowires grown on Ni foam for use in aqueous asymmetric supercapacitors (SCs). Several synthetic parameters were optimized for the unidirectional growth of PANI on CoO nanowires. The rationally designed core-shell structured electrode exhibited a high specific capacity of 1113C g⁻¹ (specific capacitance of 2473 F g⁻¹) at a current density of 3 A g⁻¹ and good cycling stability of 86.3 % over 10,000 charge/discharge cycles in a 1 M KOH electrolyte through a substantial synergistic contribution from each component. In addition, an aqueous asymmetric supercapacitor based on these PANI/CoO nanowire arrays exhibited a high specific energy of 35.8 Wh kg⁻¹ and high cycling stability (89.1 % after 5000 cycles). Two aqueous asymmetric supercapacitors connected in series could light up 19 red light-emitting diodes (LEDs). Therefore, this electrode can be considered a superior candidate for the next-generation SC electrodes.
Coaxial cable-like dual conductive channel strategy in polypyrrole coated perovskite lanthanum manganite for high-performance asymmetric supercapacitors
2022, Journal of Colloid and Interface Science
Perovskite transition metal oxides are promising materials for supercapacitor electrodes due to their high theoretical capacities. However, these materials still suffer from poor conductivity, low specific capacitance, and moderate cycle stability, restraining their practical applications. In this study, LaMnO₃@CC-PPy materials were prepared by two-step electrodeposition based on the inspiring design of coaxial cables. To this end, electrochemically active LaMnO₃ was first grown on carbon cloth (CC) with good flexibility and conductivity and then followed by further coating with polypyrrole (PPy) layer. The best PPy load was identified by adjusting the deposition time. The resulting LaMnO₃@CC-PPy electrodes showed excellent specific capacitance reaching 862F g⁻¹ at 1 A g⁻¹ with retention rate of 75% at high current density of 10 A g⁻¹, indicative of excellent rate performance. The cycle stability of the electrodes also improved after 3000 cycles at 10 A g⁻¹ with a retention rate reaching 66%. To assemble asymmetric supercapacitor (ASC) devices, NiCo₂O₄@CC cathodes were prepared by electrodeposition. Ultra-high energy density of about 73 Wh kg⁻¹ and good cycle stability were recorded with the devices. The high performance of the as-obtained materials was attributed to the existence of internal and external double electric channels, as well as the abundant internal space. These features ensured good conductivity, rapid charge transfer, and fast ion diffusion, thereby significantly improving the overall material cycle stability. In sum, these findings look promising for future preparation of high-performance perovskite supercapacitors.
Enhanced pseudo-capacitance and rate performance of amorphous MnO<inf>2</inf> for supercapacitor by high Na doping and structural water content
2022, Journal of Power Sources
Owing to the advantages of high theoretical capacitance, low cost, and environmental friendliness, MnO₂ shows a great potential as the electrode material for supercapacitors. However, its low conductivity and sluggish ion migration lead to the unsatisfied electrochemical performance especially at high rates. In this work, amorphous MnO₂ with both high Na doping and structural water content (nw-MnO₂) is synthesized via a simple redox reaction in the saturated sodium chloride solution. On the one hand, high Na doping can effectively improve the conductivity of MnO₂; on the other hand, the charge shielding effect enabled by structural water facilitates the rapid ion migration in MnO₂ lattice. In addition, the amorphous feature also provides more active sites and decreases the ion diffusion length. Benefitting from the above merits, the prepared nw-MnO₂ electrode delivers superior rate performance (324.7 F g⁻¹ at 0.5 A g⁻¹ and 182.6 F g⁻¹ even at an ultrahigh rate of 50 A g⁻¹) and excellent cycle stability with 91% of capacitance retention over 10,000 cycles. Moreover, the assembled nw-MnO₂//activated carbon asymmetric supercapacitor delivers a high energy density of 81.1 Wh kg⁻¹ and superior capacity retention of 101% after 7000 cycles.
Degradation of sulfamethoxazole using peroxymonosulfate activated by cobalt embedded into N, O co-doped carbon nanotubes
2021, Separation and Purification Technology
In this study, cobalt embedded into oxygen and nitrogen co-doped CNTs (Co@N-O-CNTs) was prepared by pyrolysis and used to activate peroxymonosulfate (PMS) for degradation of sulfamethoxazole. The experimental results showed that the content of oxygen precursor had important influence on the catalytic activity of Co@N-O-CNTs. When the content of oxygen precursor was 2 g, Co@N-O-CNTs exhibited better catalytic activity than previously reported Co@N-CNTs. Bulk and surface-bound radicals resulted in sulfamethoxazole (SMX) degradation, in which SMX degradation rate reached 0.247 min⁻¹ with the mineralization of 35.6%. The possible pathway of SMX degradation was proposed based on the identified degradation products. Characterization results indicated that nitrogen, oxygen and cobalt in the structure of Co@N-O-CNTs-2 were active sites for PMS activation. Theoretical calculation suggested that nitrogen and oxygen co-doping created more active sites to activate PMS compared with single nitrogen doping. During the six cycling experiments, Co@N-O-CNTs-2 exhibited good catalytic and structural stability. The influencing factors, including temperature, pH, PMS concentration, chloridion, bicarbonate and humic acids were investigated. This study could provide a way to boost active sites of nitrogen doped carbonaceous materials to effectively activate PMS for degradation of emerging organic pollutants.

View all citing articles on Scopus

Pengyi Tang received his B.Sc. in Chemical Engineering and Technology from Hunan Normal University in 2010 and M.Sc. in Physical Chemistry from Lanzhou University in 2013. After that,he joined Dr. Li Zhang's group as a Ph.D. candidate in 2013. He is currently working on the metal oxides and polymer based supercapacitor devices and their applications.

Li Zhang received the Ph.D. degree from the University of Basel, Switzerland, in 2007. Afterward, he joined the Institute of Robotics and Intelligent Systems, Swiss Federal Institute of Technology (ETH) Zurich, Switzerland, as a Postdoctoral Researcher in 2007, and as a Senior Scientist from 2009 to 2012. He is currently an Assistant Professor in the Department of Mechanical and Automation Engineering at The Chinese University of Hong Kong. His main research interests include micro-/nanomachines and systems for biomedical applications, and nanomaterials for energy storage and environmental applications.

View full text

Rapid communicationHierarchical Co3O4@PPy@MnO2 core–shell–shell nanowire arrays for enhanced electrochemical energy storage

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Chemicals and materials

Preparation of Co3O4 nanowires arrays

Results and discussion

Summary and conclusions

Supporting Information Available

Acknowledgment

ACS Nano

Adv. Mater.

Nano Lett.

Chem. Mater.

J. Am. Chem. Soc.

Nature

Nat. Commun.

Chem. Soc. Rev.

Adv. Mater.

Angew. Chem. Int. Ed.

Nano Lett.

Nano Lett.

Sci. Rep.

Nano Lett.

Nano Lett.

Nano Energy

Chem. Commun.

ACS Appl. Mater. Interfaces

Nano Energy

Rapid communication
Hierarchical Co₃O₄@PPy@MnO₂ core–shell–shell nanowire arrays for enhanced electrochemical energy storage

Preparation of Co₃O₄ nanowires arrays