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Synthesis of a novel interconnected 3D pore network algal biochar constituting iron nano particles derived from a harmful marine biomass as high performance asymmetric supercapacitor electrodes S.E.M pourhosseini, Omid Norouzi, Pejman Salimi, and Hamid Reza Naderi ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b03871 • Publication Date (Web): 19 Feb 2018 Downloaded from http://pubs.acs.org on February 20, 2018
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Synthesis of a novel interconnected 3D pore network algal biochar constituting iron nano particles derived from a harmful marine biomass as high performance asymmetric supercapacitor electrodes S. E. M. Pourhosseini, † Omid Norouzi , †*Pejman Salimi,‡ and Hamid Reza Naderi†※* †
School of Chemistry, College of Science, University of Tehran, Tehran, Iran of Physical Chemistry, Faculty of Science, Tarbiat Modares University, PO Box 14115175, Tehran, Iran ※ Novin Ebtekar Company, Exclusive Agent of Metrohm-Autolab and Dropsens Companies, Tehran, Iran Corresponding Authors * * E-mail:
[email protected] (Omid Norouzi). * E-mail:
[email protected] (Hamid Reza Naderi) Mailing address: East Hagh Talab St.-South Allame St. Saadat abad Ave. 1997834991 IR – Tehran. Telephone: +98-21-88680843 +98-21-88680844. Fax: +98-21-88687648. Cell phone: +989115455003 ‡ Department
Abstract Via the activation treatment on Cladophora Glomerata (CG) with FeCl3 and KOH, magnetic biochar (MBC) with olive-shaped pores and functional biochar (FBC) with a novel interconnected 3D pore network structure have been successfully prepared by a facile slow pyrolysis process to be applied as electrodes in supercapacitors. To obtain Fe Composite Biochar (FCBC), FBC was functionalized with HNO3 and H2SO4 for extending formation of iron oxide through the hydrothermal method. These electrodes demonstrate remarkable electrochemical behaviors, in terms of wonderful rate capability, high specific capacitance and excellent cycle stability when first served as electrodes for supercapacitors. In addition, we have successfully fabricated an asymmetric supercapacitor with high energy and power densities using FBC as the anode electrode and iron oxide/carbon composites (MBC and FCBC) as the cathode electrodes in a neutral aqueous 3 M KCl electrolyte. Because of the desirable porous structure, high specific capacitance, rate capability, and complementary potential window of the two electrodes, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0−1.8 V and exhibits energy density 41.5 Wh kg-1 at a power density of 900 W kg-1 for FBC//FCBC. The asymmetric supercapacitor also presents stable cycling performance with 93.1% for FBC//FCBC capacitance retention at 8 A g-1 after 10000 cycles. These encouraging results show great potential in developing energy storage devices with high energy and power densities for practical applications.
Keywords: Cladophora Glomerata; Olive-shaped pores; Magnetic biochar; 3D Iron oxide composite; Asymmetric supercapacitor.
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Introduction
Nomenclature Electrical Double-Layer Capacitance Cladophora Glomerata Raw Biochar Magnetic Biochar Functional Biochar Fe Composite Biochar Polytetrafluoroethylene Electrochemical Impedance Spectroscopy X-ray Photoelectron Spectroscopy
EDLC CG RBC MBC FBC FCBC PTFE EIS XPS
Continuous Cyclic Voltammetry Asymmetric Supercapacitor Cell Fourier Transform Infrared Brunauere-Emmette-Teller X-ray Diffraction Cyclic Voltammetry Galvanostatic Charge/Discharge Field Emission Scanning Electron Microscopy Specific Capacitances
CCV ASC FTIR BET XRD CV GCD FESEM SC
With the increase of environmental pollutants of industrial or agricultural activities, the excessive blooming of macroalgae has become a serious problem in coastal areas worldwide, not only they are harmful to the health of human beings through providing adequate conditions for bacterial growth, but also can adversely affect tourism via destroying the beaches 1,2. Therefore, substantial efforts have been focused on marine macroalgae for use as an energy crop or feedstock for the biorefinery3,4. For instance, Norouzi et al. showed that despite the negativism related to the adverse ecological effects of marine green macroalgae, it could be a valuable source for hydrogen-rich gas and phenol production via conventional thermochemical processes5,6. However, in pyrolysis of macroalgae, in addition to the biofuels and valuable chemicals, a large amount of carbon-rich, porous solid called algal biochar is also obtained 7. The unique physical and chemical properties of algal biochar make it applicable to a variety of research and practical applications8. In particular, it has been found that algal biochars could be a good possible alternative to some Nanocarbons (e.g. carbon nanotubes (CNTs), and graphene) to be used in electrode materials based on their low cost, environmentally friendly and scalable as
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well as their relatively high surface area, oxygen functionalities attached on surfaces, hydrophilic characteristic and abundant micro/meso/macro pores 9’10. Based on the superior properties of algal biochar described earlier, there are only a few reports of electrochemical supercapacitive performance developed based on algal biochar. The great potential of algal biochar as high performance supercapacitor electrode can be found in the Wenhua Yu study11. Over the last couple of years, several studies are carried out to synthesize the hybrid materials, composed of nanocarbon based materials and metal oxides materials in order to take advantage of both EDLC and the pseudocapacitance behavior12–15. Among a variety of metal oxides have been investigated for the supercapacitors electrodes, Fe3O4 has been recognized as the most effective redox-based electrode due to its abundant sources, low cost, minimal environmental impact and also owing to the high theoretical capacity (926 mAh g -1)16–18. There are few examples in the literature of such hybrid carbon materials; Rajesh Kumar et al. synthesized three-dimensional reduced graphene oxide nanosheets containing iron oxide nanoparticles hybrids by one-pot microwave approach. The specific capacitances of 3D hybrid materials were 455 F g-1 at the scan rate of 8 mV s-119. In another study, Huailin Fan et al. proposed a novel Fe3O4/Carbon
Nanosheets
by a
hydrothermal
process.
The
synergistic
effects
of
pseudocapacitance and EDLC between graphene and metal oxides turned their prepared composite into a potential candidate for supercapacitor electrodes 20. Naderi et al. also reported that the use of Fe3O4/nitrogen-doped reduced graphene oxide nanocomposites can be a promising way to take advantage of the high surface area of graphene and the fast and reversible faradic redox reactions of Fe3O421. Although, hybrid carbon materials have been recognized as the most effective electrode materials, there still are significant drawbacks in such hybrid materials with lower operating voltage and energy with sacrificing power delivery and cycle life that limits its
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practical applications in the future22,23. One promising method to solve these problems is to develop ASC, which derives benefits of a battery-type faradaic electrode as an energy source and a capacitor-type electrode as a power source that allows improving working voltage beyond 1.5 V21,23,24,26. Thus, the type of electrodes in well-separated potential windows in the same electrolyte plays a vital role to reach high energy density and power density of ASCs. Herein, we discuss the promising modified-biochars derived from a kind of abundant waste coastal macroalgae in the field of ASCs with the main focus on the synthesis, properties, and electrochemical performances of the state-of-the-art materials for anodes and cathodes. FBC was used as an anode electrode owing to their high surface area and appropriate electrostatic chargestorage mechanisms at electrode/electrolyte interfaces. Being pseudocapacitive in nature, a novel interconnected 3D pore network iron oxide/composite (FCBC) and MBC were synthesized and utilized as cathode materials. Scheme 1 illustrates the principle of ASCs, where two dissimilar materials are assembled together as anode and cathode electrodes.
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Scheme 1. Schematic illustration of the fabricated asymmetric supercapacitor device based on FBC as positive electrode and FCBC and MBC negative electrodes.
Experimental section Preparation of RBC, MBC, FBC and FCBC The CG green macroalgae have been considered as a harmful aquatic strain in coastal areas worldwide. In this study, they were collected from Sisangan area, Iran, where a stable coverage was found7. They were dried overnight at room temperature and ground to the particle size
