Elsevier

Materials Letters

Volume 265, 15 April 2020, 127300
Materials Letters

Nanospherical Cu2O/NiO synthesized by electrochemical dealloying as efficient electrode materials for supercapacitors

https://doi.org/10.1016/j.matlet.2020.127300Get rights and content

Highlights

  • Cu2O/NiO/copper foil has been successfully synthesized by dealloying a copper foil coated with Zn-Cu-Ni alloy films.

  • The resultant Cu2O/NiO possesses scalable nanosphere structure.

  • The Cu2O/NiO with nanosphere structure shows high specific capacitance (2255.5 mF/cm2) and excellent cycling stability (94.5% after 5000 cycles).

Abstract

In this study, Cu2O/NiO with nanosphere structure has been successfully synthesized by dealloying a copper foil coated with Zn-Cu-Ni alloy films. First, Zn-Ni films were electrodeposited on copper foil. Next, the Zn-Cu-Ni films were produced by annealing and the Cu2O/NiO was obtained after Zn-dealloying and oxidation. Due to the advantage of the tunable nanosphere structure and dealloying synthesis method, Cu2O/NiO has excellent supercapacitor properties, such as excellent cycling stability (94.5% after 5000 cycles) and high specific capacitance (2255.5 mF/cm2 in 1 mA/cm2). These data suggested that this low-cost oxide Cu2O/NiO with nanosphere morphology synthesized by dealloying method could be a promising electrode material for supercapacitors.

Introduction

In the last two decades, as a result of the extensive growth of the electronics devices and hybrid electrical vehicles, energy demand has been increasing [1]. Supercapacitors, one of the dominant energy-storage devices for portable and grid-level applications, which have attracted considerable attention owning to higher power density, shorter charge transfer time and low-cost [2]. In general, the performance of supercapacitor usually depends on the electrode material [1], [3]. As a result, a lot of new electrode materials have been designed to improve the performance of supercapacitor [4], [5], [6].

Transition metal oxides (TMOs) are important materials for supercapacitor and photoelectrical devices [3], [7], [8], [9], which exhibit multiple advantages, such as low cost, high theoretical capacity, and environmental friendliness [4]. However, its low rate and fast capacity fading during charging-discharging process hinders large-scale practical application [5]. To overcome these limitations, a tremendous amount of effort has been made in structural design and synthesis methods to improve structural stability and conductivity, such as tremella-like NiO [5], Cu2O with various micromorphology [2], [7], [8], [9]. Among these strategies, dealloying is an approach to obtain nanoporous metal with well-interconnected structures, which is helpful to release the stress during the electrochemical cycling, thus providing high performance and long cycle lifespan to the device [10], [11]. There are some studies report the fabrication of NPM (films or wires) by dealloying into current collector for Li-ion battery anodes [10], catalysis [12] and functional nanometer components [13], but only few reports on supercapacitor by dealloying [14].

Herein, we have successfully synthesized the Cu2O/NiO with nanosphere structure by dealloying, and copper foil coated with Zn-Ni-Cu alloy film by electrodepositing and annealing was used as a precursor. The Cu2O/NiO with nanosphere structure shows high specific capacitance (2255.5 mF/cm2) and excellent cycling stability (94.5% after 5000 cycles).

Section snippets

Synthesis of Cu2O/NiO/copper foil (CF)

All materials and reagents employed were of analytical grade and used without further purification. 0.74 g Zn (NO3)2·6H2O, 7.27 g of Ni (NO3)2·6H2O and 1.55 g H3BO3 were dissolved in 50 mL of deionized water, and the copper foil (20 mm × 10 mm × 0.1 mm, purity 99.99%) was washed by HCl, NaOH, deionised water and ethanol respectively. Electrodeposition was carried out on a CHI660E electrochemical workstation by using a three-electrode system containing the above electrolyte, copper foil, Hg/HgO

Results and discussion

The stepwise preparation of the Cu2O/NiO/CF electrode is presented in Fig. 1a. Fig. 1b shows the XRD patterns of the Cu2O/NiO/CF electrode sample, apart from the diffraction peaks of Cu substrate (JCPDS no. 04-0836), the XRD pattern of the sample exhibits diffraction peaks at 2θ angles of 29.6, 36.4, 42.3, 61.3 and 73.5°, corresponding to the (1 1 0), (1 1 1), (2 0 0), (2 2 0), (3 1 1) crystalline planes of Cu2O (JCPDS no. 05-0667), and the peaks at 2θ angles of 37.2, 43.2, 62.8,75.4°,

Conclusions

In summary, we have developed a dealloying method to synthesize Cu2O/NiO on the copper foil, the resultant materials possessed nanosphere structure. The Cu2O/NiO with nanosphere structure shows high specific capacitance (2255.5 mF/cm2) and excellent cycling stability (94.5% after 5000 cycles). This work may shed some light on the viable synthesis of low-cost oxides with scalable morphology for supercapacitors.

CRediT authorship contribution statement

Yidong Miao: Conceptualization, Methodology, Writing - original draft, Investigation. Xuping Zhang: Writing - review & editing, Resources. Yanwei Sui: Supervision, Writing - review & editing. Enyuan Hu: Data curation. Jiqiu Qi: Investigation. Fuxiang Wei: Conceptualization. Qingkun Meng: Visualization. Yezeng He: Visualization. Zhi Sun: Project administration. Yaojian Ren: Visualization. Zhenzhen Zhan: Visualization.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This research was financially supported by the National Natural Science Foundation of China (Grant Nos. 51671214 and 51871238); Xuzhou Science and Technology Project (Grant No. KC18075).

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