Chemical synthesis of mesoporous CoFe2O4 nanoparticles as promising bifunctional electrode materials for supercapacitors

doi:10.1016/j.matlet.2013.08.055

Materials Letters

Volume 111, 15 November 2013, Pages 35-38

https://doi.org/10.1016/j.matlet.2013.08.055 Get rights and content

Highlights

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Binary compound cobalt iron oxide (CoFe₂O₄) with broad potential window was synthesized.
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CoFe₂O₄ exhibited a high specific capacitance (142 F g⁻¹, 2 mV s⁻¹) and a long cycling life (71.8% retention after 1000 cycles).
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A hard template of Al₂O₃ derived from co-precipitating Al(NO₃)₃ precursor solutions created a highly porous morphology.

Abstract

A promising mesoporous cobalt iron oxide (CoFe₂O₄) electrode material for supercapacitors has been synthesized via a chemical co-precipitation method using aluminum nitrate (Al(NO₃)₃) as a precursor of aluminum oxide (Al₂O₃) hard template. The as-prepared CoFe₂O₄ materials were spherical-like nanoparticles with diameter of around 25 nm. Moreover, the as-prepared CoFe₂O₄ materials exhibited a high specific surface area (140.6 m² g⁻¹) and high porosity (0.23 cm³ g⁻¹). The fabricated CoFe₂O₄ electrode showed typical pseudocapacitive behavior with a broad potential window (1.5 V), a high specific capacitance (142 F g⁻¹, 2 mV s⁻¹) and a long cycling life (71.8% retention after 1000 cycles).

Introduction

With worldwide increasing warmth in the energy storage field of supercapacitors, 3d transition metal oxides ranging from noble metal oxides to inexpensive metal oxides, characterized by highly reversible capacities, long cycle performance and high power density, have been extensively studied [1]. Among them, RuO₂ could exhibit prominent performance with pseudocapacitance as high as 720 F g⁻¹ [2], but the expensive cost and high toxicity apparently hinder its commercial application, which made MnO₂, Co₃O₄, Fe₃O₄, V₂O₅ and NiO, especially binary system materials Co–Ni, Fe–Mn, Co–Mn, Mn–Ni oxides environmental and economical alternatives of choice for improved applicability [1].

Ferrosoferric oxide (Fe₃O₄) and cobalt oxide (Co₃O₄) of spinel series are both attractive candidates for the application in supercapacitors owning to their low-cost and environmental friendly nature, as well as excellent electrochemical capacitive behavior [3], [4]. Their binary compound cobalt iron oxide (CoFe₂O₄), as an efficient magnetic material on demand in fields of electronics, photomagnetism, catalysis, has widely been studied [5]. In 2005, Kuo and Wu [6] had a report of CoFe₂O₄ with a specific capacitance of 7.1 F g⁻¹ in neutral NaCl electrolyte, which shed light on its electrochemical properties by improving inherent structure.

Herein, we employ a hard template of Al₂O₃ derived from co-precipitating Al(NO₃)₃ precursor solution to fabricate the porous capacitive CoFe₂O₄. And the artificial porous structures are proved to largely enhance the electrochemical performance of the CoFe₂O₄ materials.

Section snippets

Experimental

In a typical procedure, first, 2.25 g Al(NO₃)₃·9H₂O, 4.85 g Fe(NO₃)₃·9H₂O and 1.75 g Co(NO₃)₂·6H₂O were dissolved in 120 mL deionized water to form a well-mixed solution. Excessive NH₃·H₂O was subsequently added to the solution dropwise until a pH level of 10 was reached. The obtained dark brown precipitation was further vigorously stirred at 50 °C for 4 h with a constant speed in a water-jacketed reaction vessel using circulating thermostatic bath. Then, the as-prepared sample was obtained by

Results and discussion

Fig. 1a displays the XRD patterns of T-CoFe₂O₄ and CoFe₂O₄ materials. All the resultant peaks can be indexed as a face-centered-cubic spinel phase. The identified eight diffraction peaks at 2θ value of 30.21°, 35.70°, 37.13°, 43.16°, 54.13°, 57.36°, 62.96° and 74.32° correspond to the (2 2 0), (3 1 1), (2 2 2), (4 0 0), (4 2 2), (5 1 1), (4 4 0) and (5 3 3) crystal planes, respectively, which is in well agreement with the standard patterns for CoFe₂O₄ (JPCDS No. 22-1086). No signals of Al₂O₃ phase (JCPDS No.

Conclusions

In summary, the mesoporous CoFe₂O₄ materials for supercapacitors have been successfully synthesized with assistance of co-precipitating Al₂O₃ template. High BET specific surface and porosity of 140.6 m² g⁻¹ and 0.23 cm³ g⁻¹ were obtained which facilitate the Faradaic pseudocapacitive performance by virtue of sufficient electroactive sites and easy ions pathways. The unique mesoporous CoFe₂O₄ electrode delivered a wide potential window of 1.5 V and a high specific capacitance of 142 F g⁻¹ at 2 mV s⁻¹,

Acknowledgments

We gratefully acknowledge the financial support of this research by National Basic Research Program of China (2012CB932800), Scientific Research Foundation for the Returned Overseas Chinese Scholars and State Education Ministry (SRF for ROCS, SEM).

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Chemical synthesis of mesoporous CoFe2O4 nanoparticles as promising bifunctional electrode materials for supercapacitors

Highlights

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgments

Electrochimica Acta

Materials Letters

Electrochimica Acta

Electrochimica Acta

Electrochemistry Communications

Chemical synthesis of mesoporous CoFe₂O₄ nanoparticles as promising bifunctional electrode materials for supercapacitors