Subscriber access provided by University of South Dakota
Letter
High-Performance Alkaline Organic Redox Flow Batteries Based on 2-Hydroxy-3-Carboxy-1,4-Naphthoquinone Caixing Wang, Zhen Yang, Yanrong Wang, Peiyang Zhao, Wen Yan, Guoyin Zhu, Lianbo Ma, Bo Yu, Lei Wang, Guigen Li, Jie Liu, and Zhong Jin ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.8b01296 • Publication Date (Web): 13 Sep 2018 Downloaded from http://pubs.acs.org on September 14, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Energy Letters
High-Performance Alkaline Organic Redox Flow Batteries Based on 2-Hydroxy-3-Carboxy-1,4-Naphthoquinone
Caixing Wang,†,⊥ Zhen Yang,‡,⊥ Yanrong Wang,† Peiyang Zhao,† Wen Yan,† Guoyin Zhu,† Lianbo Ma,† Bo Yu,† Lei Wang,† Guigen Li,‡,§,* Jie Liu,†,║ and Zhong Jin†,*
†
Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical
Engineering, Nanjing University, Nanjing, Jiangsu 210093, China ‡
Institute of Chemistry & BioMedical Sciences, Nanjing University, Nanjing, Jiangsu 210023,
China §
Department of Chemistry and Biochemistry, Texas Tech University, Texas 79409-1061, United
States ║
Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
Supporting Information Placeholder
1
ACS Paragon Plus Environment
ACS Energy Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ABSTRACT: Aqueous redox flow batteries (ARFBs) based on the electrolyte solutions of redox-active organic molecules are very attractive for the applications of large-scale electrochemical energy storage. Here we propose a high-performance ARFB system by utilizing 2-hydroxy-3-carboxy-1,4-naphthoquinone (2,3-HCNQ) and K4Fe(CN)6 as the anolyte and catholyte active species, respectively. The 2,3-HCNQ molecule exhibits high solubility and can carry out a reversible two-electron redox process with rapid redox kinetics. The assembled 2,3-HCNQ/K4Fe(CN)6 ARFB delivered a cell voltage of 1.02 V and realized a peak power density of 0.255 W cm-2. The 2,3-HCNQ/K4Fe(CN)6 ARFB can be stably operated at a current density of 100 mA cm-2 for long-term cycles (with a capacity retention of ~94.7% after 100 cycles).
TOC GRAPHICS
Redox flow batteries (RFBs) present a promising prospect in grid-scale energy storage, especially for mitigating the intermittent fluctuation of renewable energy sources, such as 1-4 solar and wind power plants . The operation of RFBs depends on the reversible electrochemical reactions of redox-active species dispersed in liquid-phase anolytes 5-8 and/or catholytes . The modular design of redox pairs should take into consideration of several crucial properties, such as solubility, voltage window, reaction kinetics and cycling stability, etc. Over the past decade, great efforts have been made to develop aqueous redox flow batteries (ARFBs) that adopted water-soluble organic molecules in 9-14 electrolytes . Several classes of organic redox-active species, including quinone, viologen, alloxazine, 2,2,6,6-tetramethylpiperidinooxy (TEMPO) and their derivatives have attracted considerable attention for the application in ARFBs, owing to the rapid redox kinetics, low 11-18 corrosivity, high solubility and low cost . It is also known that organic molecules have excellent structural diversity, therefore the electrochemical properties can be easily 19-29 tailored by the modification of different functional groups . Previous works suggested that the electron-donating groups can lower the redox potential, while the electron-withdrawing groups can elevate the redox potential, endowing the organic ARFBs with more flexible voltage 12,14,19 regulation than traditional ARFBs . Generally, the organic molecules often existed in negatively-charged forms either in acidic or alkaline solutions during the whole charge-discharge process, so the crossover issue of active species through the separator can be overcome by employing a cation separator. It should be noticed that the redox species tending to release protons have higher solubility either in acid or alkaline solution, thus contributing to higher energy
density and power density. For example, anthraquinone-sulfonic acid derived from anthraquinone can 13 be dissolved with 1.0 M concentration in acid condition . In addition, the β-OH groups on the anthraquinone can significantly increase the solubility in the alkaline solution for improved proton dissociation in comparison with the 14,27,29 α-OH groups . Alloxazine derived redox molecules also show improved solubility in the alkaline solution after the 17,19 introduction of carboxyl group or hydrotropic agent . Given the fact that a large number of redox-active organic species have relatively-narrow voltage window and low solubility in water that may result in low volumetric energy density, it is vital to design novel organic molecular structures to fully satisfy the demands of ARFBs. The derivatives of naphthoquinone are often served as electron acceptors in biochemical electron transport 30-32 processes in organism, such as photosynthesis and 33-34 aerobic respiration . Ding et al. reported the use of 35 naphthquinone derivates in organic RFBs . Recently, naphthquinone functionalized with diethylene glycol monomethyl ether groups was reported to exhibit a high -1 energy density (264 W h L ) in solvent-free organic redox 36 flow batteries . However, most quinone derivatives exhibit low solubility in water, which would limit the application in ARFBs. 2-Hydroxy-1,4-naphthoquinone (2-HNQ), also well known as "lawsone", is a nature-abundant and low-cost red-orange dye that can be extracted from the leaves of henna trees and the flowers of water hyacinths. Each 2-HNQ molecule can undergo a reversible two-electron redox conversion between the quinone form and the phenol form, offering a potential of -0.70 V vs. Ag/AgCl, thus can be used 29 as a potential anolyte in ARFBs . However, owing to the low solubility of 2-HNQ (0.48 M in alkaline solution) and the possible side reactions with O2, the previous ARFB based on 2-HNQ anolyte (0.2 M) showed a low volumetric capacity, and suffered from large capacity loss and poor cycling stability (
