Bioinspired Catechol-Grafting PEDOT Cathode for an All-Polymer Aqueous Proton Battery with High Voltage and Outstanding Rate Capacity

Design of high-performance proton batteries by reducing interstitial water molecules in copper-iron Prussian analogues

Prussian blue analogues (PBAs) are considered to be a potentially beneficial cathode material in proton batteries. Among them, Cu,Fe based-Turnbull's blue analogue (CuFe-TBA) stands out in proton batteries because of its unique crystal structure and continuous hydrogen bond lattice network, which promotes the Grotthuss mechanism and enhances the reaction kinetics of proton conduction. However, in the process of preparing CuFe-TBA by co-precipitation method, the crystal water content of the product cannot be controlled, and excessive lattice water will affect the cycle stability. To solve these problems, we employ a chemical inhibition strategy using polyvinylpyrrolidone (PVP) to regulate the nucleation and crystal growth rate of CuFe-TBA. This strategy effectively reduces the crystalline water content, thereby ensuring that the PBAs remain electrically conductive while maintaining their electrochemical stability and safety over the operating voltage range. The appropriate amount of PVP modified CuFe-TBA (CuFe-TBA-PVP-3) has the characteristics of large specific surface area and moderate crystal water and has high discharge specific capacity and long cycle stability. CuFe-TBA-PVP-3 shows the high specific capacity of 80.9mAh g-1 at a current density of 0.1 A g-1, demonstrating exceptional charge/discharge specific capacity. Furthermore, the capacity retention rate is 91.23 % at 5 A g-1 after 50,000 cycles. Therefore, CuFe-TBA-PVP-3 provides new insights and directions for the development of next-generation aqueous proton batteries.

Spatially Coupling Electronic-Ionic Transport in Organic Mixed Conductors as Cathodes for Efficient Zn-V Batteries

In conventional electrodes, concentration polarization by unbalanced charge transport and solid-state diffusion resistance result in sluggish reaction kinetics, hindering the practical application of zinc-ion batteries. Here, we propose an integrated mixed electronic-ionic conductor by spatially coupling charge transport pathways, which could achieve redistribution and fast transport of charge (Zn2+/e-). Operando electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy revealed the charge transport mechanisms and intrinsic conducting characteristics at timescale. Through confinement by vanadium oxide, dual-conductive pathways were self-assembled at the nanoscale and provided effective charge storage. This provided high charge density and accelerated ionic diffusion in the bulk phase, resulting in more active sites and faster reaction kinetics. Moreover, reversible ionic channels from the self-doping/de-doping process reduced the dissolution of active materials by protons and enabled conversion chemistry, improving cycling stability at low current density. Consequently, the modulated cathode (PEDOT-SO3-ZnVO) delivered a high-rate performance of 310/148 mAh g-1 (0.2/10 A g-1) at 10 mg cm-2. Importantly, the conventional electrode at 21 mg cm-2 achieved an ultra-high areal capacity of 6.0 mAh cm-2 and superior cycling stability (79.1% retention over 100 cycles at 0.2 A g-1). This work opens the way for the precise modulation of the electrochemical performance of functional nanomaterials.

Biomass-derived semiconductors for renewable energy technologies

Semiconductor materials play a crucial role in advancing renewable energy technologies, enabling efficient photocatalytic hydrogen production, energy conversion, and energy storage. Compared to traditional non-renewable semiconductors, next-generation semiconductor materials derived from abundant and renewable feedstocks have garnered increasing research interest. Integrating renewable semiconductors into emerging energy technologies provides unprecedented opportunities for achieving sustainability goals. Among renewable resources, biomass-derived materials have recently emerged as particularly promising candidates for semiconductor development, driven by progress in synthetic strategies. This review focuses on key synthetic approaches for producing semiconductors from biomass-derived materials, specifically tailored for sustainable energy systems. We classify various biomass-based molecular precursors and discuss their conversion methods, properties, associated challenges, and potential advantages in practical applications.

A ladder-type organic molecule with pseudocapacitive properties enabling superior electrochemical desalination

The availability of clean water is fundamental for maintaining sustainable environments and human ecosystems. Capacitive deionization offers a cost-effective, environmentally friendly, and energy-efficient solution to meet the rising demand for clean water. Electrode materials based on pseudocapacitive adsorption have attracted significant attention in capacitive deionization due to their relatively high desalination capacity. In this study, a novel organic compound, PTQN, is introduced, featuring a ladder-type structure enriched with imine-based active sites, specifically designed for capacitive deionization. This advanced molecular design imparts the PTQN compound with exceptional pseudocapacitive properties, enhanced electron delocalization, and superior structural stability, which are supported by both experimental results and theoretical analyses. As an electrode, PTQN exhibits a high pseudocapacitive capacitance of 238.26 F g-1 and demonstrates excellent long-term stability, retaining approximately 100 percent of its capacitance after 5000 cycles in NaCl solution. The involvement of PTQN active sites in the Na+ electrosorption process was further elucidated using theoretical calculations and ex situ characterization. Moreover, a hybrid capacitive deionization (HCDI) device employing the PTQN electrode exhibited an impressive salt removal capacity of 61.55 mg g-1, a rapid average removal rate of 2.05 mg g-1 min-1, and consistent regeneration performance (∼97.04 percent after 50 cycles), demonstrating its potential for capacitive deionization systems. Furthermore, the PTQN electrode displayed superior removal efficiency for tetracycline. This work contributes to the rational design of organic materials for the development of advanced electrochemical desalination systems.

Molecular Micellar Aggregate Electrolytes Enable Durable Electrochemical Proton Storage

Proton electrochemistry holds eminent potential for developing high capacity and rate energy storage devices in the post-lithium era. However, the decomposition of water in acidic aqueous electrolytes causes electrode corrosion, leading to capacity fading. Herein, we report a judicious design of molecular micellar aggregates as non-aqueous electrolytes for stable and high-voltage electrochemical proton storage. The key to our strategy lies in introducing cetyltrimethylammonium bromide (CTAB), forming micelles to improve the miscibility of acetonitrile (ACN) and H3PO4, afford channel for proton transport, and electrostatically interact with phosphate ions of H3PO4 to further promote proton transport. Such aggregates impart rapid and stable electrochemical proton storage with a widened operating voltage (1.8 V vs. 1.5 V in aqueous electrolyte). By optimizing CTAB content, proton transport can be enhanced. Asymmetric full proton battery using the optimal CTAB electrolyte achieves a maximum energy density of 102.8 Wh kg-1 and a maximum power density of 10.1 kW kg-1. Our simple yet robust route to micellar aggregate electrolytes enables stable proton storage, underscoring its potential for grid-scale energy storage, emergency power supplies, and portable electronics.

Challenges and Opportunities for Rechargeable Aqueous Sn Metal Batteries

Rechargeable aqueous batteries based on metallic anodes hold tremendous potential of high energy density enabled by the combination of relatively low working potential and large capacity while retaining the intrinsic safety nature and economical value of aqueous systems; However, the realization of these promised advantages relies on the identification of an ideal metal anode chemistry with all these merits. In this review, the emerging Sn metal anode chemistry is examined as such an anode candidate in both acidic and alkaline media, where the inertness of Sn toward hydrogen evolution, flat low voltage profile, and low polarization make it a unique metal anode for aqueous batteries. From a panoramic viewpoint, the key challenges and detrimental issues of Sn metal batteries are discussed, including dead Sn formation, self-discharge, and electrolyte degradation, as well as strategies for mitigating these issues by constructing robust Sn anodes. New design approaches for more durable and reliable Sn metal batteries are also discussed, with the aim of fully realizing the potential of Sn anode chemistry.

Photoexcited Electro-Driven Reactive Oxygen Species Channeling for Precise Extraction of Biomarker Information from Tumor Interstitial Fluid

Direct electrochemical detection of miRNA biomarkers in tumor tissue interstitial fluid (TIF) holds great promise for adjuvant therapy for tumors in the perioperative period, yet is limited by background interference and weak signal. Herein, a wash-free and separation-free miRNA biosensor based on photoexcited electro-driven reactive oxygen channeling analysis (LEOCA) is developed to solve the high-fidelity detection in physiological samples. In the presence of miRNA, nanoacceptors (ultrasmall-size polydopamine, uPDA) are responsively assembled on the surface of nanodonors (zirconium metal-organic framework, ZrMOF) to form core-satellite aggregates. The produced lifetime-constraint singlet oxygen upon light irradiation is captured by the catechol of constrained uPDA, and the oxidized quinone is immediately electro-reduced to the catechol at transient collision process on the electrode, resulting in a cascade electron transfer and amplified current. Thereby, the nanosensor exhibits a low detection limit (1.1 fM), and high reproducibility (relative standard deviation of 2.0%). Compared with quantitative real-time polymerase chain reaction (qRT-PCR), the clinical accuracy (area under the curve value) is significantly increased from 0.75 to 0.93 in distinguishing breast cancer patients from healthy donors. This study demonstrates an inspiration on the synergy of the reactive oxygen channeling between nanodonor/nanoacceptor and the synchronous electron transfer cascade on the electrode to solve the bottleneck problem of detecting unprocessed clinical samples in a sample-in-answer-out manner.

Engineering π-Electron Bridge Enables Low-Potential 2D Redox Polymer Anodes for High-Voltage Aqueous All-Organic Batteries

Aqueous all-organic batteries (AAOBs) have emerged as a hot topic but their development was plagued by limited choices of anode materials, generally facing an intractable trade-off between low potential and high stability. Here, we propose a novel π-electron bridge engineering strategy to explore a class of 2D dioxin-bridged redox covalent organic polymer (RCOP) as trade-off-breaking anodes for high-voltage AAOBs. By establishing a tunable RCOP platform, we perform theoretical study to scrutinize how bridge units between active sites affect the electrode potential and redox activity for the first time. We discover that compared to common pyrazine bridge, the weakened conjugation and strong electron donor character of the proposed dioxin bridge can induce elevated LUMO level and enriched π-electron populations in active sites, heralding a low electrode potential and enhanced redox activity. Besides, the nonaromaticity-induced molecular flexibility of dioxin bridge mitigates intermolecular stacking for sufficient active sites exposure. To experimentally corroborate this, a new dioxin-bridged 2D RCOP (D-HATN) and its pyrazine-bridged analogue (P-HATN) are synthesized for proof-of-concept demonstration. D-HATN displays excellent compatibility with Na+/Zn2+/NH4 +/H3O+ and obviously lower redox potentials in various dilute electrolytes compared to P-HATN and most reported organic anodes, while featuring rapid Grotthuss-type proton conduction and unprecedented durability in acid - 91.8 % capacity retention after 20000 cycles. Thus, the D-HATN-involved all-organic proton battery delivers an average output voltage of 0.75 V, which can be further elevated to 1.63 V with alkaline-acidic hybrid electrolyte design, affording markedly-increased specific energy.

A High-capacity Benzoquinone Derivative Anode for All-organic Long-cycle Aqueous Proton Batteries

Quinone compounds, with the ability to uptake protons, are promising electrodes for aqueous batteries. However, their applications are limited by the mediocre working potential range and inferior rate performance. Herein, we examined quinones bearing different substituents, and for the first time introduce tetraamino-1,4-benzoquinone (TABQ) as anode material for proton batteries. The strong electron-donating amino groups can effectively narrow the band gap and lower the redox potentials of quinone materials. The protonation of amino groups and the amorphization of structure result in the formation of an intermolecular hydrogen-bond network, supporting Grotthuss-type proton conduction in the electrode with a low activation energy of 192.7 meV. The energy storage mechanism revealed by operando FT-IR and ex situ XPS features a reversible quinone-hydroquinone conversion during cycling. TABQ demonstrates a remarkable specific capacity of 307 mAh g-1 at 1 A g-1, which is one of the highest among organic proton electrodes. An all-organic proton battery of TABQ//TCBQ has also been developed, achieving exceptional stability of 3500 cycles at room temperature and excellent performance at sub-zero temperature.

Poly(3, 4-Ethylenedioxythiophene) as Promising Energy Storage Materials in Zinc-Ion Batteries

Benefiting from the advantages of high conductivity and good electrochemical stability, the conjugated conducting polymer poly (3, 4-ethylenedioxythiophene) is a promising energy storage material in zinc-ion batteries. Zinc-ion batteries have the advantages of high safety, environmental friendliness, and low cost, but suffer from unstable cathode material structure, poor electrical conductivity, and uncontrollable dendritic growth of zinc anodes. PEDOT, with its fast electrochemical response and wide potential window, is expected to make up for the shortcomings and enhance capacity and cycle life of zinc-ion batteries. Herein, in this review different polymerization methods of poly (3, 4-ethylenedioxythiophene) as well as their structure and properties are summarized; the progress in doping strategies related to the increasing conductivity and dispersivity of poly (3, 4-ethylenedioxythiophene) materials is discussed; specific applications of poly (3, 4-ethylenedioxythiophene)-based materials in anode, cathode, electrolyte, and binder of zinc-ion batteries are explored; and the representative advancements for improving the electrochemical performance of poly (3, 4-ethylenedioxythiophene) in zinc-ion batteries are emphasized. Finally, the current challenges of poly (3, 4-ethylenedioxythiophene) as promising materials in zinc-ion batteries and an insight into their future research directions are pointed out.

A Molten Alkali Approach to Tailor Hydroxyl Groups of Hexaazatrinaphthalene Toward High-Capacity and Low-Potential Anode of Aqueous Proton Batteries

Hexaazatrinaphthalene (HATN) has attracted a lot of attention in aqueous proton batteries (APBs). However, its redox potential as an anode is insufficiently negative. The introduction of electron-donating substituent groups, such as hydroxyl groups, is considered as a good approach to reduce the redox potential of HATN. Nevertheless, manufacturing hydroxyl-substituted HATN (HATN-OH) requires either expensive precursors or multi-step process, limiting their research. Herein, a straightforward strategy is proposed to synthesize HATN-OH based on the nucleophilic substitution reaction of halogenated HATN in a molten alkali. The redox potential of 1,2,7,8,13,14-hexahydroxy-5,6,11,12,17,18-hexaazatrinaphthalene (34-HATN-6OH) electrode may be lowered by 0.15 V in comparison to HATN, and exhibits a high specific capacity, low redox potential, remarkable rate capability, and outstanding long-term cycling performance. The electrochemical redox kinetics is significantly enhanced owing to the formation of rapid proton transport channels created by intermolecular hydrogen bond network. The assembled MnO2||34-HATN-6OH full battery delivers a high discharge voltage (1.16 V) and cycling stability (74% capacity retention after 5000 cycles). This study provides a general cost-effective molten alkali approach for the synthesis of hydroxyl-substituted conjugated small molecules from their halogenated counterparts and further enriches the regulation means of electro-chemical performances of organic electrodes for enabling high-capacity and high-voltage APBs.

Mussel-Inspired Polymer Binders for Organic Electrodes

The development of polymer binders is necessary to meet the growing demands of modern energy storage technologies. While catechol-containing materials are proven successful in silicon anodes, their application in organic batteries remains unexplored. In this contribution, the synthesis of four polymers are described with nearly identical side chain composition but varying backbone structures. The materials are used to investigate the effect of polymer backbone structure on the binding abilities of catechol-containing materials. Comparative analysis with the commonly used polyvinylidene fluoride (PVDF) binder aims to address two critical questions: 1) Can catechol-rich polymers replace PVDF for use in organic cathodes? and 2) Does the choice of polymer backbone affect the performance of the battery?. The investigation reveals that supramolecular interactions, such as π-π stacking and coordination bonding, are pivotal features of catechol binders. Among the catechol-rich polymers, the polyacrylate binder stands out, likely attributed to its high flexibility. Additionally, introducing an oxygen atom into a catechol-rich polynorbornene enhances lithium-ion conductivity and rate performance. Overall, the findings highlight the viability of catechol-containing polymers as organic cathode binders, and that the choice of polymer backbone is a crucial factor for their use as lithium-ion battery binder materials.

Ladder-Type Redox-Active Polymer Achieves Ultra-Stable and Fast Proton Storage in Aqueous Proton Batteries

A ladder-type rigid-coplanar polymer with highly ordered molecular arrangement has been designed via a covalent cycloconjugation conformational strategy. Benefitting from the extended π-electron delocalization in the highly aromatic ladder-type polymeric backbone, the prepared polymer exhibits fast intra-chain charge transport along the polymeric chain, realizing extraordinary proton-storage capability in aqueous proton batteries.Affordable and safe aqueous proton batteries (APBs) with unique "Grotthuss mechanism," are very significant for advancing carbon neutrality initiatives. While organic polymers offer a robust and adaptable framework that is well-suited for APB electrodes, the limited proton-storage redox capacity has constrained their broader application. Herein, a ladder-type polymer (PNMZ) has been designed via a covalent cycloconjugation conformational strategy that exhibits optimized electronic structure and fast intra-chain charge transport within the high-aromaticity polymeric skeleton. As a result, the polymer exhibits exceptional proton-storage redox kinetics, which are evidenced by in-operando monitoring techniques and theoretical calculations. It achieves a remarkable proton-storage capacity of 189 mAh g-1 at 2 A g-1 and excellent long-term cycling stability, with approximately 97.8 % capacity retention over 10,000 cycles. Finally, a high-performance all-polymer APB device has been successfully constructed with a desirable capacity retention of 99.7 % after 6,000 cycles and high energy density of 56.3 Wh kg-1.

A Long-Range Planar Polymer with Efficient π-Electron Delocalization for Superior Proton Storage

Due to the unique "Grotthus mechanism", aqueous proton batteries (APBs) are promising energy devices with intrinsic safety and sustainability. Although polymers with tunable molecular structures are ideal electrode materials, their unsatisfactory proton-storage redox behaviors hinder the practical application in APB devices. Herein, a novel planar phenazine (PPHZ) polymer with a robust and extended imine-rich skeleton is synthesized and used for APB application for the first time. The long-range planar configuration achieves ordered molecular stacking and reduced conformational disorder, while the high conjugation with strong π-electron delocalization optimizes energy bandgap and electronic properties, enabling the polymer with low proton diffusion barriers, high redox activity, and superior electron affinity. As such, the PPHZ polymer as an electrode material exhibits fast, stable, and unrivaled proton-storage redox behaviors with a large capacity of 273.3 mAh g-1 at 0.5 A g-1 (1 C) in 1 M H2SO4 electrolyte, which is the highest value among proton-inserted electrodes in aqueous acidic electrolytes. Dynamic in situ techniques confirm the high redox reversibility upon proton uptake/removal, and the corresponding protonation pathways are elucidated by theoretical calculations. Moreover, a pouch-type APB cell using PPHZ electrode exhibits an ultralong lifespan over 30 000 cycles, further verifying its promising application prospect.

Highly Reversible Tin Film Anode Guided via Interfacial Coordination Effect for High Energy Aqueous Acidic Batteries

Sn metal is a preferable choice as anode material for aqueous acidic batteries due to its acid-tolerance, non-toxicity, and ease of recycling. However, the large size and irregular deposition morphology of polyhedral Sn particles are bad for constructing stable and high-capacity Sn metal anode because of severe hydrogen evolution and metal shedding. To tackle this critical issue, 4-tert-octylphenol pentaethoxylate (POPE) is used as an electrolyte additive to generate a thin-film Sn anode with reversible stripping/plating behavior. POPE can not only induce homogeneous surface chemistry by adsorbing on the Sn surface via coordination bonds but also inhibit hydrogen evolution by modulating the solvation shell of Sn2+. The Sn film anode delivers improved electrochemical stability over 480 h with satisfactory rate performance and low polarization. Moreover, the as-assembled PbO2//Sn battery can also provide outstanding durability at 10 mAh cm-2. This work offers new inspiration for developing a reversible Sn metal film anode.

Recent Advances in Aqueous Non-Metallic Ion Batteries with Organic Electrodes

Aqueous non-metallic ion batteries have attracted much attention in recent years owing to their fast kinetics, long cycle life, and low manufacture cost. Organic compounds with flexible structural designability are promising electrode materials for aqueous non-metallic ion batteries. In this review, the recent progress of organic electrode materials is systematically summarized for aqueous non-metallic ion batteries with the focus on the interaction between non-metallic ion charge carriers and organic electrode host materials. Both the cations (proton, ammonium ion, and methyl viologen ions) and anions (chloridion, sulfate ion, perchlorate ion, trifluoromethanesulfonate and trifluoromethanesulfonimide ion) storage are discussed. Moreover, the design strategies toward improving the comprehensive performance of organic electrode materials in aqueous non-metallic ion batteries will be summarized. More organic electrode materials with new reaction mechanisms need to be explored to meet the diverse demands of aqueous non-metallic ion batteries with different charge carriers in the future. This review provides insights into developing high-performance organic electrodes for aqueous non-metallic ion batteries.

A carbonyl-rich conjugated organic compound for aqueous rechargeable Na+ storage with wide voltage window workability

Organic compounds have become an important electrode material for aqueous electrochemical energy storage. However, organic electrodes still face poor performance in aqueous batteries due to insufficient electrochemical activity. In this work, a novel conjugated quinone compound containing a rich carbonyl group was designed. The quinone compound was synthesized by a simple dehydration reaction of pyrene-4,5,9,10-tetrone (PTO) and 1,2-diaminoanthraquinone (1,2-AQ); it contains 4 pyrazines (CN) from AQ and 4 carbonyl groups (CO), as well as a large number of active sites and the excellent conductivity brought by its conjugated structure ensures the high theoretical capacity of PTO-AQ. In the context of aqueous sodium ion batteries (ASIBs), the electrode material known as PTO-AQ exhibits a notable reversible discharge capacity of 117.9 mAh/g when subjected to a current density of 1 A/g; impressively, it maintained a capacity retention rate of 74.3 % even after undergoing 500 charge and discharge cycles, a performance significantly surpassing that of pristine PTO and AQ. Notably, PTO-AQ exhibits a wide operating voltage range (-1.0-0.5 V) and a cycle life of up to 10,000 cycles. In situ Raman and ex situ measurements were used to analyze the structural changes of PTO-AQ during charge and discharge and the energy storage mechanism in NaAC. The effective promotion of Na+ storage brought by a rich carbonyl group was obtained. The structural energy level and electrostatic potential of PTO-AQ were calculated, and the active center distribution of PTO-AQ was obtained. This work serves as a guide for designing high-performance aqueous organic electrode materials that operate across a wide voltage range while also explaining their energy storage mechanism.

Synchronous Redox Reactions in Copper Oxalate Enable High-Capacity Anode for Proton Battery

Proton batteries are competitive due to their merits such as high safety, low cost, and fast kinetics. However, it is generally difficult for current studies of proton batteries to combine high capacity and high stability, while the research on proton storage mechanism and redox behavior is still in its infancy. Herein, the polyanionic layered copper oxalate is proposed as the anode for a high-capacity proton battery for the first time. The copper oxalate allows for reversible proton insertion/extraction through the layered space but also achieves high capacity through synchronous redox reactions of Cu2+ and C2O42-. During the discharge process, the bivalent Cu-ion is reduced, whereas the C═O of the oxalate group is partially converted to C-O. This synchronous behavior presents two units of charge transfer, enabling the embedding of two units of protons in the (110) crystal face. As a result, the copper oxalate anode demonstrates a high specific capacity of 226 mAh g-1 and maintains stable operation over 1000 cycles with a retention of 98%. This work offers new insights into the development of dual-redox electrode materials for high-capacity proton batteries.

High throughput selection of organic cathode materials

Efficient and affordable batteries require the design of novel organic electrode materials to overcome the drawbacks of the traditionally used inorganic materials, and the computational screening of potential candidates is a very efficient way to identify prospective solutions and minimize experimental testing. Here we present a DFT high-throughput computational screening where 86 million molecules contained in the PUBCHEM database have been analyzed and classified according to their estimated electrochemical features. The 5445 top-performing candidates were identified, and among them, 2306 are expected to have a one-electron reduction potential higher than 4 V versus (Li/Li+ ). Analogously, one-electron energy densities higher than 800 Whkg-1 have been predicted for 626 molecules. Explicit calculations performed for certain materials show that at least 69 candidates with a two-electron energy density higher than 1300 Whkg-1 . Successful molecules were sorted into several families, some of them already commonly used electrode materials, and others still experimentally untested. Most of them are small systems containing conjugated CO, NN, or NC functional groups. Our selected molecules form a valuable starting point for experimentalists exploring new materials for organic electrodes.

Searching High-Potential Dihydroxynaphthalene Cathode for Rocking-Chair All-Organic Aqueous Proton Batteries

The lack of acid-proof high-potential cathode largely limits the development and competitiveness of proton batteries. Herein, the authors systematically investigated six dihydroxynaphthalenes (DHNs) and found that 2,6-DHN delivered the best cathode performance in proton battery with the highest redox potential (0.84 V, vs SHE) and a specific capacity of 91.6 mAh g-1 at 1 A g-1 . In situ solid-state electropolymerization of DHNs is responsible for the voltage and capacity fading of DHNs, and 2,6-DHN's excellent electrochemical performance is derived from its high polymerization energy barrier. By compounding with rGO, the 2,6-DHN/rGO electrode can maintain a specific capacity of 89 mAh g-1 even after 12 000 cycles at 5 A g-1 . When it is paired with the 2,6-dihydroxyanthraquinone (DHAQ) anode, the assembled rocking-chair all-organic proton battery exhibited a high cell voltage of 0.85 V, and excellent energy/power densities (70.8 Wh kg-1 /850 W kg-1 ). This study showcases a new-type high-potential proton-containing organic cathode and paves the way for constructing a high-voltage rocking-chair proton battery. Also, in situ solid-state electropolymerization will inspire the further study of phenol-based small-molecule electrodes.

Quinone-amine polymer nanospheres with enhanced redox activity for aqueous proton storage

One of the biggest obstacles to the development of aqueous proton batteries (APBs), despite numerous optimization techniques, is the preparation and use of high-performance electrode materials. In this work, to improve the high solubility, limited capacity and poor cycle life of small organic molecules in APBs, homogeneous dispersed quinone-amine polymer nanospheres (PQANS) (average diameter: 220 nm) were synthesized by a polymerization reaction based on 3,3'-diaminobenzidine (DAB) and benzoquinone (BQ), making them suitable for proton storage in aqueous systems. As an anode for APBs, the obtained PQANS exhibits an improved reversible capacity of 126.2 mAh/g at 1 A/g after 300 cycles. The durable stable measurement of PQANS at 10 A/g was also conducted with a specific capacity of 66.8 mAh/g after 12,000 cycles. A series of in situ or ex situ measurements were used to establish the superior H+ storage mechanism of PQANS. A novel reaction mechanism of redox enhancement was revealed due to the existence of more carbonyl groups after the first cycle. Theoretical calculations were conducted to help illustrate the principle of binding protons with functional groups in PQANS. Finally, a PQANS anode-based aqueous proton full battery was constructed to demonstrate its potential application, which exhibits a specific capacity of 50.6 mAh/g at 1 A/g (600 cycles). This work provides a reference for preparing high-performance polymer-based electrode materials in aqueous batteries.

A High-Density Raman Photometry for Tracking and Quantifying of AchE Activity in The Brain of Freely Moving Animals with Network

A high-density Raman photometry based on a dual-recognition strategy is created for accurately quantifying acetylcholinesterase (AchE) activity in 24 brain regions of free-moving animals with network. A series of 5-ethynyl-1,2,3,3-tetramethyl-based molecules with different conjugated structures and substitute groups are designed and synthesized for specific recognition of AchE by Raman spectroscopy. After systematically evaluating the recognition ability toward AchE, 2-(4-((4-(dimethylamino)benzoyl)oxy)styryl)-5-ethynyl-1,3,3-trimethyl-3H-indol-1-ium (ET-5) is finally optimized for AchE determination, which shows the highest selectivity, the greatest sensitivity, and the fastest response time among the investigated seven molecules. More interestingly, using the developed probe for AchE with high accuracy and sensitivity, the optimized AchE regulated by nitric oxide (NO) is discovered for promoting the neurogenesis of neural stem cells (NSCs). Benefiting from the high-density photometry, it is found that the activity and distribution of AchE varied in 24 brain regions, and the levels of AchE activity in 24 brain regions of Alzheimer's mice (AD) are lower than those of normal mice. It is the first time that a functional network of AchE in 24 brain regions is established. It is also found that the loss of AchE functional network in AD mice is restored and reconstructed by the controlled release of AchE regulated by NO.

2D Conjugated Metal-Organic Frameworks Embedded with Iodine for High-Performance Ammonium-Ion Hybrid Supercapacitors

Ammonium ions (NH4 + ) are emerging non-metallic charge carriers for advanced electrochemical energy storage devices, due to their low cost, elemental abundance, and environmental benignity. However, finding suitable electrode materials to achieve rapid diffusion kinetics for NH4 + storage remains a great challenge. Herein, a 2D conjugated metal-organic framework (2D c-MOF) for immobilizing iodine, as a high-performance cathode material for NH4 + hybrid supercapacitors, is reported. Cu-HHB (HHB = hexahydroxybenzene) MOF embedded with iodine (Cu-HHB/I2 ) features excellent electrical conductivity, highly porous structure, and rich accessible active sites of copper-bis(dihydroxy) (Cu─O4 ) and iodide species, resulting in a remarkable areal capacitance of 111.7 mF cm-2 at 0.4 mA cm-2 . Experimental results and theoretical calculations indicate that the Cu─O4 species in Cu-HHB play a critical role in binding polyiodide and suppressing its dissolution, as well as contributing to a large pseudocapacitance with adsorbed iodide. In combination with a porous MXene anode, the full NH4 + hybrid supercapacitors deliver an excellent energy density of 31.5 mWh cm-2 and long-term cycling stability with 89.5% capacitance retention after 10 000 cycles, superior to those of the state-of-the-art NH4 + hybrid supercapacitors. This study sheds light on the material design for NH4 + storage, enabling the development of novel high-performance energy storage devices.

Aqueous Organic Batteries Using the Proton as a Charge Carrier

Benefiting from the merits of low cost, nonflammability, and high operational safety, aqueous rechargeable batteries have emerged as promising candidates for large-scale energy-storage applications. Among various metal-ion/non-metallic charge carriers, the proton (H+ ) as a charge carrier possesses numerous unique properties such as fast proton diffusion dynamics, a low molar mass, and a small hydrated ion radius, which endow aqueous proton batteries (APBs) with a salient rate capability, a long-term life span, and an excellent low-temperature electrochemical performance. In addition, redox-active organic molecules, with the advantages of structural diversity, rich proton-storage sites, and abundant resources, are considered attractive electrode materials for APBs. However, the charge-storage and transport mechanisms of organic electrodes in APBs are still in their infancy. Therefore, finding suitable electrode materials and uncovering the H+ -storage mechanisms are significant for the application of organic materials in APBs. Herein, the latest research progress on organic materials, such as small molecules and polymers for APBs, is reviewed. Furthermore, a comprehensive summary and evaluation of APBs employing organic electrodes as anode and/or cathode is provided, especially regarding their low-temperature and high-power performances, along with systematic discussions for guiding the rational design and the construction of APBs based on organic electrodes.

Integrated Uniformly Microporous C4 N/Multi-Walled Carbon Nanotubes Composite Toward Ultra-Stable and Ultralow-Temperature Proton Batteries

Benefiting from the proton's small size and ultrahigh mobility in water, aqueous proton batteries are regarded as an attractive candidate for high-power and ultralow-temperature energy storage devices. Herein, a new-type C₄ N polymer with uniform micropores and a large specific surface area is prepared by sulfuric acid-catalyzed ketone amine condensation reaction and employed as the electrode of proton batteries. Multi-walled carbon nanotubes (MWCNT) are introduced to induce the in situ growth of C₄ N, and reaped significantly enhanced porosity and conductivity, and thus better both room- and low-temperature performance. When coupled with MnO₂ @Carbon fiber (MnO₂ @CF) cathode, MnO₂ @CF//C₄ N-50% MWCNT full battery shows unprecedented cycle stability with a capacity retention of 98% after 11 000 cycles at 10 A g^-1 and even 100% after 70 000 cycles at 20 A g^-1 . Additionally, a novel anti-freezing electrolyte (5 m H₂ SO₄  + 0.5 m MnSO₄ ) is developed and showed a high ionic conductivity of 123.2 mS cm^-1 at -70 °C. The resultant MnO₂ @CF//C₄ N-50% MWCNT battery delivers a specific capacity of 110.5 mAh g^-1 even at -70 °C at 1 A g^-1 , the highest in all reported proton batteries under the same conditions. This work is expected to offer a package solution for constructing high-performance ultralow-temperature aqueous proton batteries.

Electrochemical Proton Storage: From Fundamental Understanding to Materials to Devices

Simultaneously improving the energy density and power density of electrochemical energy storage systems is the ultimate goal of electrochemical energy storage technology. An effective strategy to achieve this goal is to take advantage of the high capacity and rapid kinetics of electrochemical proton storage to break through the power limit of batteries and the energy limit of capacitors. This article aims to review the research progress on the physicochemical properties, electrochemical performance, and reaction mechanisms of electrode materials for electrochemical proton storage. According to the different charge storage mechanisms, the surface redox, intercalation, and conversion materials are classified and introduced in detail, where the influence of crystal water and other nanostructures on the migration kinetics of protons is clarified. Several reported advanced full cell devices are summarized to promote the commercialization of electrochemical proton storage. Finally, this review provides a framework for research directions of charge storage mechanism, basic principles of material structure design, construction strategies of full cell device, and goals of practical application for electrochemical proton storage.