Carbon-incorporated Fe <sub>3</sub>O <sub>4</sub> nanoflakes: high-performance faradaic materials for hybrid capacitive deionization and supercapacitors

Author(s): Lei Chen ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Xingtao Xu ⁶ ^, ⁷ ^, ⁸ ^, ⁹ , Lijia Wan ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Guang Zhu ¹⁰ ^, ¹¹ ^, ¹² ^, ⁵ , Yanjiang Li ¹⁰ ^, ¹¹ ^, ¹² ^, ⁵ , Ting Lu ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Munirah D. Albaqami ¹³ ^, ¹⁴ ^, ¹⁵ ^, ¹⁶ ^, ¹⁷ , Likun Pan ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Yusuke Yamauchi ⁶ ^, ⁷ ^, ⁸ ^, ⁹ ^, ¹⁸

Publication date (Electronic): 2021

Journal: Materials Chemistry Frontiers

Publisher: Royal Society of Chemistry (RSC)

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Abstract

Here, we introduce a new strategy using urea for the synthesis of carbon-incorporated 2D Fe ₃O ₄ (2D-Fe ₃O ₄/C) nanoflakes which show superior potential for hybrid capacitive deionization and supercapacitors.

Abstract

Here, we introduce a new strategy using urea for the synthesis of carbon-incorporated 2D Fe ₃O ₄ (2D-Fe ₃O ₄/C) nanoflakes under solvothermal conditions with the following pyrolysis process under an inert atmosphere. Thanks to the structural advantages of 2D-Fe ₃O ₄/C, including 2D flakes providing a larger accessible surface area and exposing more active sites, as well as carbon incorporation promoting electrical conductivity for faster charge transfer, the 2D-Fe ₃O ₄/C displays a high specific capacitance of 386 F g ⁻¹ at 1 A g ⁻¹ in a three-electrode system. More importantly, when further assembled into a hybrid supercapacitor with pre-synthesized NiCo-layered double hydroxides as positive electrodes, the assembled supercapacitor device delivers a high-energy density of 32.5 W h kg ⁻¹ at 400 W kg ⁻¹ and little capacitance loss with bending angles ranging from 0° to 180°. As another capacitive application in desalination, 2D-Fe ₃O ₄/C also shows a high desalination capacity of 28.5 mg g ⁻¹ over 7.5 min, which suggests a very high mean desalination rate of 3.8 mg g ⁻¹ min ⁻¹. Our results not only highlight the significance of 2D metal oxide nanosheets/nanoflakes, but also hold great potential for high-performance capacitive applications in supercapacitors and desalination.

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Templated nanocrystal-based porous TiO(2) films for next-generation electrochemical capacitors.

Torsten Brezesinski, John Wang, Julien Polleux … (2009)

The advantages in using nanoscale materials for electrochemical energy storage are generally attributed to short diffusion path lengths for both electronic and lithium ion transport. Here, we consider another contribution, namely the charge storage from faradaic processes occurring at the surface, referred to as pseudocapacitive effect. This paper describes the synthesis and pseudocapacitive characteristics of block copolymer templated anatase TiO(2) thin films synthesized using either sol-gel reagents or preformed nanocrystals as building blocks. Both materials are highly crystalline and have large surface areas; however, the structure of the porosity is not identical. The different titania systems are characterized by a combination of small- and wide-angle X-ray diffraction/scattering, combined with SEM imaging and physisorption measurements. Following our previously reported approach, we are able to use the voltammetric sweep rate dependence to determine quantitatively the capacitive contribution to the current response. Considerable enhancement of the electrochemical properties results when the films are both made from nanocrystals and mesoporous. Such materials show high levels of capacitive charge storage and high insertion capacities. By contrast, when mesoscale porosity is created in a material with dense walls (rather than porous walls derived from the aggregation of nanocrystals), insertion capacities comparable to templated nanocrystal films can be achieved, but the capacitance is much lower. The results presented here illustrate the importance of pseudocapacitive behavior that develops in high surface area mesoporous oxide films. Such systems provide a new class of pseudocapacitive materials, which offer increased charge storage without compromising charge storage kinetics.