Electroactive Organic Compounds Research Articles

Effects of the nature of donor substituents on the photophysical and electroluminescence properties of derivatives of perfluorobiphenyl: donor–acceptor versus donor–acceptor–donor type AIEE/TADF emitters

The synthesis and properties of a group of organic electroactive compounds based on electron-deficient perfluorobiphenyl (PFBP) are described.

A case study on storage and capacity fading mechanism of poly(perylene diimides) cathode in aqueous zinc ion battery

Organic electroactive compounds can be applied as alternative cathodes in aqueous zinc ion batteries (AZIBs) with high stability and low toxicity. In the present study, the storage and capacity fading mechanism of a poly(perylene diimides) named OAP and its monomer, 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (PTCDA), is studied. As disclosed by the structural and electrochemical characterization, OAP exhibits larger capacity, better cycling stability and rate performance compared with the monomer PTCDA, which is due to the reduced solubility in the electrolyte, rougher surface and better tolerance to volume expansion. Electrochemical measurements and ex-situ characterization show that there are two storage ways in OAP-based AZIBs: (1) the redox reaction of the carbonyl groups. Compared with carbonyls in anhydrite groups, the redox reaction of carbonyls in imide groups exhibited better reversibility. (2) partially reversible intercalation and de-intercalation of zinc ion/proton between perylene structures. This work is meaningful for design novel and stable organic electrode materials for AZIBs.

Proton storage chemistry in aqueous zinc‐organic batteries: A review

AbstractBenefiting from the advantageous features of structural diversity and resource renewability, organic electroactive compounds are considered as attractive cathode materials for aqueous Zn‐ion batteries (ZIBs). In this review, we discuss the recent developments of organic electrode materials for aqueous ZIBs. Although the proton (H+) storage chemistry in aqueous Zn‐organic batteries has triggered an overwhelming literature surge in recent years, this topic remains controversial. Therefore, our review focuses on this significant issue and summarizes the reported electrochemical mechanisms, including pure Zn2+ intercalation, pure H+ storage, and H+/Zn2+ co‐storage. Moreover, the impact of H+ storage on the electrochemical performance of aqueous ZIBs is discussed systematically. Given the significance of H+ storage, we also highlight the relevant characterization methods employed. Finally, perspectives and directions on further understanding the charge storage mechanisms of organic materials are outlined. We hope that this review will stimulate more attention on the H+ storage chemistry of organic electrode materials to advance our understanding and further its application.image

RedDB, a computational database of electroactive molecules for aqueous redox flow batteries

An increasing number of electroactive compounds have recently been explored for their use in high-performance redox flow batteries for grid-scale energy storage. Given the vast and highly diverse chemical space of the candidate compounds, it is alluring to access their physicochemical properties in a speedy way. High-throughput virtual screening approaches, which use powerful combinatorial techniques for systematic enumerations of large virtual chemical libraries and respective property evaluations, are indispensable tools for an agile exploration of the designated chemical space. Herein, RedDB: a computational database that contains 31,618 molecules from two prominent classes of organic electroactive compounds, quinones and aza-aromatics, has been presented. RedDB incorporates miscellaneous physicochemical property information of the compounds that can potentially be employed as battery performance descriptors. RedDB’s development steps, including: (i) chemical library generation, (ii) molecular property prediction based on quantum chemical calculations, (iii) aqueous solubility prediction using machine learning, and (iv) data processing and database creation, have been described.

Recent Advances Towards Sustainable Materials and Processes for Energy Conversion and Storage

Recent Advances Towards Sustainable Materials and Processes for Energy Conversion and Storage

Carboxyl-Functionalized TEMPO Catholyte Enabling High-Cycling-Stability and High-Energy-Density Aqueous Organic Redox Flow Batteries

Aqueous organic redox flow batteries (AORFBs) employing synthetically tailorable organic electroactive compounds have received significant attention for energy storage technologies. There have been many efforts in developing electroactive materials for AORFBs with anion-exchange membranes. On the contrary, electroactive compounds that are compatible with cation-exchange membranes in AORFBs are less studied. Here, we report an electroactive 4-carboxylic-2,2,6,6-tetramethylpiperidin-N-oxyl (4-CO₂Na-TEMPO) molecule for neutral AORFBs. The compound exhibits a good solubility of 1.5 M in an aqueous sodium-based solution, which is 3 times more than that of the pristine 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO). When paired with a 1,10-bis(3-sulfonatopropyl)-4,4′-bipyridinium (SPr)₂V anolyte, the resulting RFB operating through a cation-exchange membrane achieved an open-circuit voltage of 1.19 V and a high energy density of 14.7 W h L–¹. In the long-term cycling study, the RFB features a stable capacity retention of 99.94% per cycle over 400 cycles with nearly 100% Coulombic efficiency.

Solution-processed perylene diimide-ethylene diamine cathodes for aqueous zinc ion batteries

Organic electroactive compounds can be applied as alternative cathodes in rechargeable zinc ion batteries (ZIBs) instead of using inorganic cathode materials with low stability or high toxicity. However, many reported organic ZIB cathodes have some limitations, which are their tedious synthesis processes and low yields. In this work, perylene diimide-ethylenediamine/carbon black (PDI-EDA/CB) composites are prepared with a high yield of over 88% under mild conditions via a solution-based processing method. As the organic cathodes in aqueous ZIBs, the PDI-EDA/CB composites have a high specific capacity of 118.0 mA h g−1 at 0.05 A g−1; this capacity can be maintained as 95.0 mA h g−1 even at a high current density of 5.00 A g−1. Also, PDI-EDA/CB has good cycling stability by reserving 70.5% of its initial capacity after 1500 charge-discharge cycles at 1.00 A g−1, outperforming many recently reported ZIB cathodes. As disclosed by the structural and electrochemical characterization of PDI-EDA/CB, its excellent electrochemical performance is due to the zinc ion storage mechanism of PDI-EDA and the solution-based fabrication method.

A quantitative evaluation of computational methods to accelerate the study of alloxazine-derived electroactive compounds for energy storage

Alloxazines are a promising class of organic electroactive compounds for application in aqueous redox flow batteries (ARFBs), whose redox properties need to be tuned further for higher performance. High-throughput computational screening (HTCS) enables rational and time-efficient study of energy storage compounds. We compared the performance of computational chemistry methods, including the force field based molecular mechanics, semi-empirical quantum mechanics, density functional tight binding, and density functional theory, on the basis of their accuracy and computational cost in predicting the redox potentials of alloxazines. Various energy-based descriptors, including the redox reaction energies and the frontier orbital energies of the reactant and product molecules, were considered. We found that the lowest unoccupied molecular orbital (LUMO) energy of the reactant molecules is the best performing chemical descriptor for alloxazines, which is in contrast to other classes of energy storage compounds, such as quinones that we reported earlier. Notably, we present a flexible in silico approach to accelerate both the singly and the HTCS studies, therewithal considering the level of accuracy versus measured electrochemical data, which is readily applicable for the discovery of alloxazine-derived organic compounds for energy storage in ARFBs.

A Viologen-Based Anolyte with a Very Negative Redox Potential for Neutral Aqueous Redox Flow Batteries

Redox flow batteries have been recognized as a promising option for energy-storage purposes, mitigating the intermittency of renewable sources of energy such as solar, wind, and hydroelectric power. In particular, aqueous redox flow batteries (ARFBs) are very attractive owing to high conductivity, relatively low cost, and safe nature of aqueous electrolytes. Performance of ARFBs can be further improved with developing new electroactive species. Viologens are a group of organic compounds with great tunability, making them appealing for flow battery applications. In this study, a viologen-based electroactive compound called MMV is proposed with the potential of improving performance of aqueous flow batteries.The potential of MMV as an anolyte was investigated for developing a neutral aqueous flow battery. MMV required a simple synthesis procedure with inexpensive starting materials, resulting in a low cost. MMV showed solubility of almost 3 M that is relatively high compared to other organic electroactive compounds, such as quinones, especially in neutral electrolytes. The electrochemical reaction of MMV involved the transfer of one electron at fast kinetics. Additionally, MMV demonstrated a redox potential of -1.05 V vs. SCE that is one of the most negative redox potentials reported for organic electroactive species under neutral conditions. These characteristics indicated that MMV is a promising anolyte candidate. Such a very negative redox potential and high solubility provide MMV the potential to significantly improve performance of a flow battery in terms of capacity, energy density, and cell potential. Despite these interesting properties, MMV exhibited a poor cycling performance. MMV underwent irreversible reactions at elevated concentrations. Signs of dimerization and also precipitation were observed during cycling. The irreversible reactions led to a high capacity fade rate (2.1%/cycle). Approaches to improve the cycling performance include synthesizing MMV-derivatives that possess a higher charge compared to that of MMV to possibly limit the extent of both dimerization and precipitation.

Design Strategies for High-Performance Aqueous Zn/Organic Batteries.

Organic electroactive compounds are attractive to serve as the cathode materials of aqueous zinc-ion batteries (ZIBs) because of their resource renewability, environmentally friendliness and structural diversity. Up to now, various organic electrode materials have been developed and different redox mechanisms are observed in aqueous Zn/organic battery systems. In this Minireview, we present the recent developments in the energy storage mechanisms and design of the organic electrode materials of aqueous ZIBs, including carbonyl compounds, imine compounds, conductive polymers, nitronyl nitroxides, organosulfur polymers and triphenylamine derivatives. Furthermore, we highlight the design strategies to improve their electrochemical performance in the aspects of specific capacity, output voltage, cycle life and rate capability. Finally, we discuss the challenges and future perspectives of aqueous Zn/organic batteries.

Pairing Cross-Linked Polyviologen with Aromatic Amine Host Structure for Anion Shuttle Rechargeable Batteries.

Electroactive organic compounds could bring new chemical opportunities to further improve existing electrochemical energy-storage technologies as they can be prepared from less-limited resources and potentially at low environmental footprint. Among the current explored research fields, the anion-ion cell configuration appears poorly investigated although quite promising to promote the fabrication of molecular (metal-free) rechargeable batteries. Herein, we report the synthesis and the electrochemical behavior of both Mg/Li salts of 2,5-(dianilino)terephthalate (MgDAnT and Li2 DAnT) and cross-linked polyviologen (c-PV2+ ) that can reversibly uptake/extract anions at different working potentials, enabling the assembly of full anionic organic batteries. The reversible anion ingress in MgDAnT is however accompanied by solvent co-insertion from the electrolyte that provokes an overpotential effect during the first charge. Full anionic batteries pairing Li2 DAnT with c-PV2+ were assembled giving rise to 0.7 V as output voltage with a specific capacity of 50 mAh per gram of Li2 DAnT.

Opportunities and Challenges for Organic Electrodes in Electrochemical Energy Storage.

As the world moves toward electromobility and a concomitant decarbonization of its electrical supply, modern society is also entering a so-called fourth industrial revolution marked by a boom of electronic devices and digital technologies. Consequently, battery demand has exploded along with the need for ores and metals to fabricate them. Starting from such a critical analysis and integrating robust structural data, this review aims at pointing out there is room to promote organic-based electrochemical energy storage. Combined with recycling solutions, redox-active organic species could decrease the pressure on inorganic compounds and offer valid options in terms of environmental footprint and possible disruptive chemistries to meet the energy storage needs of both today and tomorrow. We review state-of-the-art developments in organic batteries, current challenges, and prospects, and we discuss the fundamental principles that govern the reversible chemistry of organic structures. We provide a comprehensive overview of all reported cell configurations that involve electroactive organic compounds working either in the solid state or in solution for aqueous or nonaqueous electrolytes. These configurations include alkali (Li/Na/K) and multivalent (Mg, Zn)-based electrolytes for conventional "sealed" batteries and redox-flow systems. We also highlight the most promising systems based on such various chemistries relying on appropriate metrics such as operation voltage, specific capacity, specific energy, or cycle life to assess the performances of electrodes.

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds.

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Fabrication of highly stable silver nanoparticles with shape-dependent electrochemical efficacy

Design of effective and efficient nanoscale sensor for the selective monitoring of hydrogen peroxide (H2O2) in environmental samples is of great requirement to avoid several diseases; not only but also include diabetes, cancer, cardiovascular disorders, aging and Alzheimer. Herein, we report the fabrication of highly stable silver nanoparticles (Ag NPs) with three different phases (i.e spherical (Sp), star (St) and pyramidal (Py)) via simple wet chemical approach. Among all the three phases, St-Ag-NPs with more exposed catalytic active sites, poor dipolar non-radiative plasmons multipoles and large number of surface defects which in turn enhance ion(s) diffusion between electrode-electrolyte interfaces; shows highest performance in terms of linear range, limit of detection and sensitivity. We observe no interference between electro-active organic compounds (ascorbic acid (AA), uric acid (UA), dopamine (DA) and glucose) and inorganic (NaCl, KCl, Na2SO4 and K2SO4) species on the as-fabricated St-Ag-NPs based electrode. Furthermore, We were able to account for the amount of H2O2 generated in the discharged water (effluent) from a poultry firm using the designed St-Ag-NPs based electrode over a wide linear range (∼5 mM) in the presence of co-existing electro-active species. These results show reliability of our designed electrode as useful sensing materials for the detection and monitoring of H2O2 mismanagement in an immediate environment.

Quinone Electrode Materials for Rechargeable Lithium/Sodium Ion Batteries

AbstractOrganic electrode materials bring about new possibilities for the next generation green and sustainable lithium/sodium ion batteries (LIBs/SIBs) owing to their low cost, environmental benignity, renewability, flexibility, redox stability and structural diversity. However, electroactive organic compounds face many challenges in practical applications for LIBs/SIBs, such as high solubility in organic electrolytes, poor electronic conductivity, and low discharge potential as postive materials. Quinone organic materials are the most promising candidates as electrodes in LIBs/SIBs because of their high theoretical capacity, good reaction reversibility and high resource availability. While quinone electrode materials (QEMs) have so far received less attention in comparison with other organic electrode materials in secondary batteries. In this paper, an overview of the recent developments in the field of QEMs for LIBs/SIBs is provided, emphasizing on the modifications of the quinone compounds in solubility, electronic conductivity, and discharge plateaus. Finally, multifaceted modification approaches are analyzed, which can stimulate the practical applications of QEMs for LIBs/SIBs.

Anthraquinone Functionalized Reduced Graphene Oxide As Electrode Material for Aqueous and Non-Aqueous Rechargeable Batteries

The use of electro-active organic compounds as electrode materials in rechargeable batteries has been a very active research topic due to their high theoretical capacity, availability of various redox potentials depending on the electro-active group, ease of modification of properties, and improved safety. However, the issue of solubility in electrolytes limits their applications in batteries. The most common solutions for this problem involve incorporation of these organic molecules into the insoluble polymeric structures and trapping of these inside porous carbon materials. Here, we have demonstrated the covalent attachment of anthraquinone (AQ) derivatives via nitrene chemistry onto reduced graphene oxide (RGO) as another alternative. The successful synthesis of the RGO functionalized with anthraquinone groups (RGO-AQ) and its utilization as cathode materials in Li-batteries have also been demonstrated. The cells with RGO-AQ used as cathode materials initially discharged 126 mAh/g when cycled between 1.8-3.2V at the rate of 5.35mA/g in LiPF6/ EC:DEC (1:1) electrolyte, and discharged 185.7 mAh/g when cycled between 1.3-3.6V against Li metal at the rate of 6.0 mA/g in LiClO4/ PC electrolyte. The AQ-RGO has been used also as an anode material against in an aqueous battery against NiOOH (AQ-rGO | 30% NaOH | NiOOH). This battery provided a capacity of 140 mA/h at 0.83V and displayed a very good rate capability. Figure 1

An anthraquinone-functionalized reduced graphene oxide as electrode material for rechargeable batteries

The use of electro-active organic compounds as electrode materials in rechargeable batteries has been a very active research topic due to their high theoretical capacity, availability of various redox potentials depending on the electro-active group, ease of modification of properties, and improved safety. However, the issue of solubility in electrolytes limits their applications in batteries. The most common solutions for this problem involve incorporation of these organic molecules into the insoluble polymeric structures and trapping of these inside porous carbon materials. Here, we have demonstrated the covalent attachment of anthraquinone (AQ) derivatives via nitrene chemistry onto reduced graphene oxide (RGO) as another alternative. The successful synthesis of the RGO functionalized with anthraquinone groups (RGO-AQ), and its utilization as cathode materials in Li-batteries have also been demonstrated. The cells with RGO-AQ used as cathode materials initially discharged 126 mA h/g when cycled between 1.8 and 3.2 V at the rate of 5.35 mA/g in LiPF6/EC:DEC (1:1) electrolyte, and discharged 185.7 mA h/g when cycled between 1.3 and 3.6 V against Li metal at the rate of 6.0 mA/g in LiClO4/PC electrolyte.