Layered Metal Oxide Nanosheets with Enhanced Interlayer Space for Electrochemical Deionization

Advances in anion-intercalated layered double hydroxides for supercapacitors: study of chemical modifications and classifications

Hybrid material-based electrochemical supercapacitors (SCs) possessing improved energy density (ED), enhanced stability, high porosity, and a large accessible surface area have attracted attention as promising energy storage devices. SCs also demonstrate excellent specific capacitance (Cs) across various current densities, increased capacitance, and high cell voltages, all contributing to improved ED. Layered double hydroxides (LDHs), with their anionic exchange capabilities and laminar structures, offer significant potential for boosting charge transfer in SCs. This review provides a comprehensive overview of the recent advances in anion-based LDHs, discussing their storage mechanisms, chemical modifications, and classification based on interlayer anions. The roles of different anions, including monovalent, divalent, and polyoxometalates, in enhancing storage properties are examined. In addition, the challenges, future research directions, and practical perspectives of anion-storing LDHs are presented. Hence, this review provides a concise overview of anion-based LDHs for SCs, highlighting their potential significance in energy storage applications.

High Performance Capacitive Deionization Cathode of Nickel Hexacyanoferrate Doped with Trace Molybdenum: Breaking the Capacity-Stability Trade-Off

Nickel hexacyanoferrate (NiHCF) is considered one of the most promising electrode materials for capacitive deionization (CDI) because of its excellent cycling stability and other advantages. However, the poor desalination ability and low adsorption capacity caused by a single reaction site seriously restrict its practical application. Here, a high-valence transition metal element Mo-doped strategy is proposed to utilize traces of Mo6+ to activate the inert-sites within NiHCF. The Mo-doped NiHCF electrodes (NiMox-HCF) with multiple pairs of redox active sites and long cycling capability were designed, breaking the trade-off between high adsorption capacity and cycling stability. The results show that the preferred NiMo0.3-HCF not only retains the excellent cycling stability (91% after 200 cycles), but also possesses a high adsorption capacity of 90.92 mg g-1 at 1.2 V, which is much better than those of NiHCF under the same conditions. In addition, it has good practical application in simulated brackish water and circulating cooling water. Structural characterization and theoretical calculations indicate that the Mo doping strategy enhanced electronic conductivity while maintaining structural stability. This research proposes a new method to activate inert sites using high-valence elements, thus effectively balancing the adsorption capacity and cycling stability of the electrode.

Selective Trapping of In(III) Ions under σ-π* Bond Synergistic Effects by Modulating Lewis Basicity of Capture Sites on Nanofibers

Effectively selective recovery and separation of indium from alternative resources are of great environmental and economic significance. Although adsorption plays a critical role in this process, the design of highly selective capture sites remains a great challenge. Inspired by molecular orbital theory and hard and soft acids and bases theory (HSAB), we recognize that the nonequivalent orbital hybridization of In(III) ions renders them susceptible to deformation, exhibiting softer Lewis acidity. Herein, the thioacetamide-modified nanofiber (TAANF), with the O═C─NH─C═S as the capture sites, was prepared through an electrospinning technique combined with chemical modification. As expected, the O═C─NH─C═S exhibits softer Lewis basicity via modulated Lewis basicity of C═S by C═O, which better matches the Lewis acidity of In(III) ions to improve affinity. Adsorption studies showed that TAANF exhibited excellent properties for In(III) ions, especially in terms of selectivity; the selectivity coefficients range from 20 to 276 for K(I), Ca(II), Na(I), Mg(II), Mn(II), Zn(II), and Fe(II) ions in a multicomponent system. Furthermore, the capture mechanism indicates that In(III) ions not only can accept electrons from capture sites but also donate rich d2 orbit electrons to the π orbitals of capture sites, as demonstrated by XAFS, XPS, and DFT. This enables selective capture of In(III) ions by forming a stable six-membered ring under the synergistic effect of σ and feedback π bonds (σ-π*). Finally, this work provides a strategy to design highly selective capture sites and holds promise for recovering In(III) ions from alternative sources.

Ultrafast, Targeting Fluorion-Capture Electrochemical Nanosystem Assembled with Polymeraldine Salt-Modulated Ti3C2Tx MXene

Fluoride-containing groundwater has become a major concern since it serves as a source of drinking water for over half the world's population. Here, we develop an ion-selective polymeraldine salt (PANI-Clx; PANI = polyaniline) modulated Ti3C2Tx MXene electrode as a mediator for electrochemical capture of fluoride ion (F-) from groundwater. The single-stage configuration equipped with PANI-Clx/Ti3C2Tx electrode as anode and activated carbon as cathode exhibits an ultrafast removal rate of 4.7 mg-F- g-1 min-1 toward F- and high selectivity coefficients. Density-functional theory calculations and characterizations reveal that PANI-Clx/Ti3C2Tx can lower the charge-transfer resistance and activation energy, promoting the synergy of high selectivity of nitrogen-related motifs in PANI-Clx and a fast rate of ion intercalation in Ti3C2Tx. A stack-based multi-stage configuration operated at a staircase descent voltage mode is applied to produce freshwater from practical groundwater with low energy consumption (0.92 kWh kg-1-F-). Our findings pave the way for the electrochemical production of potable water from fluorine-containing groundwater.

Unveiling the neglected role of oxygen doping in nitrogen-doped carbon for enhanced capacitive deionization performance

Nitrogen-doped carbons (NCs) have demonstrated notable advantages for application in capacitive deionization (CDI). However, the potential roles of different nitrogen configurations in the CDI process, especially how the neglected oxygen doping synergistically works, remain unclear. In this work, we systematically addressed these critical issues and revealed the significant role of trace oxygen doping in enhancing the desalination performance of NC electrodes. By introducing oxygen into nitrogen-doped carbon nanosheets (ONC-S), using guanine as the precursor, we obtained abundant pyridinic and pyrrolic nitrogen configurations. This design aims to synergistically enhance the charge distribution, wettability, and ion diffusion of the target electrodes. Compared with commercial activated carbon and other state-of-the-art materials, our ONC-S electrode demonstrates superior specific capacitance, excellent cycling stability, and enhanced desalination efficiency. These findings highlight the synergistic effects of trace oxygen doping and the nitrogen configuration, offering valuable insights into the mechanisms driving the improved CDI performance.

Elaborate Designed Three-Dimensional Hierarchical Conductive MOF/LDH/CF Nanoarchitectures for Superior Capacitive Deionization

Rational exploration of cost-effective, durable, and high-performance electrode materials is imperative for advancing the progress of capacitive deionization (CDI). The integration of multicomponent layered double hydroxides (LDHs) with conjugated conductive metal-organic frameworks (c-MOFs) to fabricate bifunctional heterostructure electrode materials is considered a complex but promising strategy. Herein, the fabrication of elaborately designed three-dimensional hierarchical conductive MOF/LDH/CF nanoarchitectures (M-CAT/LDH/CF) as CDI anodes via a controllable grafted-growth strategy is reported. In this assembly, carbon fiber (CF) provides exceptional electrical conductivity facilitating rapid ion transfer and acts as a sturdy foundation for even distribution of NiCoCu-LDH nanosheets. Moreover, the well-ordered NiCoCu-LDH further acts as interior templates to create an interface by embedding c-MOFs and aligning two crystal lattice systems, facilitating the graft growth of c-MOFs/LDH heterostructures along the LDH nanosheet arrays on CF, leading to accelerated ion diffusion kinetics. Density functional theory (DFT) confirms the unique structure of M-CAT/LDH/CF promotes interfacial charge transfer from NiCoCu-LDH to M-CAT. This enhancement accelerates ion transfer, decreases ion migration energy, and leads to better ion diffusion kinetics and a smoother Cl- shuttle. Accordingly, the asymmetrical M-CAT/LDH/CF cell exhibited superior specific capacitance (315 F g-1), excellent salt adsorption capacity (147.8 mg g-1), rapid rate (21.1 mg g-1 min-1), and impressive cyclic stability (91.4 % retention rate). This work offers valuable insights for designing heterostructure electrode materials based on three-dimensional interconnected networks, contributing to further advancements in CDI technology.

Adhesion Strategy for Cross-Linking AgNWs/MXene Janus Membrane: Stretchable and Self-Healing Electromagnetic Shielding and Infrared Stealth Capabilities

Developing lightweight polymer shielding membranes with additional physicochemical properties is of great significance for addressing the complex contemporary security demands. However, precise structural design at the molecular level remains a challenge. Herein, a unique Janus composite membrane is assembled from conductive AgNWs/MXene 1D/2D network and polyurethane elastomer (MPHEA), displaying combined superior electromagnetic shielding effectiveness (EMSE) of up to 80 dB and remarkable infrared stealth capability at a wide temperature range of room temperature to 50 °C. Moreover, the endowed chemical crosslinking in the membrane resulted in the exceptional mechanical strength, self-healing, and superior adhesion. The maintained electromagnetic shielding (over 20 dB) even under a strain of 40% and the recovered shielding efficiency of 90% after mechanical damage and self-healing are observed, which is attributed to the synergistic 3D polymer elastic and 1D/2D conductive network in the multi-dimensional crosslinked MPHEA@AgNWs/MXene composite membrane. This work has represented an excellent micro-nano structure design strategy on multifunctional electromagnetic wave manager in complex application scenario.

Confinement-induced Ni-based MOF formed on Ti3C2Tx MXene support for enhanced capacitive deionization of chromium(VI)

MXenes, as a novel two-dimensional lamellar material, has attracted much attention. However, MXenes lamellar are prone to collapse and stacking under hydrogen bonding and interlayer van der Waals forces, which affects their electrochemical and capacitive deionization performance. A three-dimensional Ni-1,3,5-benzenetricarboxylate/Ti3C2Tx (Ni-BTC/Ti3C2Tx) composite electrode material was developed to enhance the electrochemical and capacitive deionization performance. The uniformly decorated Ni-BTC can prevent MXenes from aggregation and provide a large specific surface area and rich pore structure. As a substrate supporting Ni-BTC, MXenes can effectively disperse the growth of Ni-BTC and enhance the ion transport rate. In addition, the unique three-dimensional structure of Ni-BTC/Ti3C2Tx provides horizontal charge transfer paths like two-dimensional nanosheets and has unique vertical charge transfer paths between nanosheets. Therefore, the Ni-BTC/Ti3C2Tx exhibits an exceptional chromium(VI) removal rate of 94.1%. The electrosorption capacity of the Ni-BTC/Ti3C2Tx for chromium(VI) is 124.5 mg g-1, much higher than that of the pure Ti3C2Tx (55.5 mg g-1). The superior CDI efficiency accomplished through the Ni-BTC/Ti3C2Tx electrode is due to the unique three-dimensional network structure and synergistic effect of the pseudocapacitance generated by the unique assembly of Ni-BTC and Ti3C2Tx. Ni-BTC/Ti3C2Tx is a promising CDI electrode material that can be used for capacitive deionization.

Succulent inspired grown g-C3N4@lithium sodium niobate for supercapacitors and piezo-tuned electrochemical potential controlled smart electromagnetic shielding management

A synchronous way of energy generation and storage in a single portable device is in high demand for the development of high-end electromagnetic interference (EMI) free modern electronics. Thus, this study highlights the devising of a piezoelectrically self-chargeable symmetric supercapacitor (PSCS) device using a polyvinyl alcohol (PVA)/succulent inspired grown g-C3N4@lithium sodium niobate (GNLNN)/potassium hydroxide (KOH) based piezo separator with GNLNN electrode. The GNLNN electrode exhibits a surface capacitive controlled specific capacitance of 503 F g-1. The PSCS device exhibits an energy density of 15.3 W h kg-1 and a power density of 4.2 kW kg-1 with an impressive capacitive retention capability of 93.2% after 6000 cycles of charging-discharging. The PSCS device can be charged up to 393 mV within 180 s under 14.2 N of cyclic pressing by human finger imparting. The fabricated PSCS device was also investigated for self-charging potential regulated smart EMI shielding applications. The smart PSCS device achieves an 88.3 dB increment from 40.9 dB of EMI shielding under charging from 0 mV to 300 mV. The increased charging potential of the PSCS device enhances the destructive interference and leads to boosted absorption and decreased reflection of incident EM radiation.

Importance of Morphology of Layered Double Hydroxide in Electrochemical Energy Storage and Catalysis

The development of nanomaterials for energy storage and conversion has always been important. Layered double hydroxide (LDH) is a promising material due to its high capacity, tunable composition and easy synthesis. In this work, the morphology of NiCo-LDH is tuned with surfactants including sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), and investigated the correlation between morphology and electrochemical properties. NiCo-LDH-SDS with a layered structure exhibited a specific capacitance of 1004 C g-1 at 1 A g-1, which is higher than that of the needle-like NiCo-LDH-CTAB (678 C g-1) and the rod-like NiCo-LDH (279 C g-1). Meanwhile, NiCo-LDH-SDS and NiCo-LDH-CTAB showed a reduction of 36 and 19 mV, respectively, in their overpotentials at 10 mA cm-2 compared to NiCo-LDH. Contact angle and adhesive force measurements proved the influence of morphology on the interfacial properties that layered structure is favorable for the timely detachment of the bubbles. Therefore, rational morphology regulation of LDH can effectively alter the gas-liquid-solid interface and thereby accelerate the reaction kinetics. The connections between morphologies, bubbles releasing and electrochemical performance are well established in this work, which can be applied in the investigation of nanomaterials for energy-related activities, especially the ones concerning bubbles releasing processes.

Reversible Zn and Mn deposition in NiFeMn-LDH cathodes for aqueous Zn-Mn batteries

Introducing NiFeMn-Layered Double Hydroxide (LDH) as an innovative cathode material for Zn-Mn batteries, this study focuses on bolstering the electrochemical efficiency and stability of the system. We explored the effect of varying Zn/Mn molar ratio in the electrolyte on the battery's electrochemical performance and investigated the underlying reaction mechanism. Our results show that an electrolyte Zn/Mn molar ratio of 4 : 1 achieves a balance between capacity and stability, with an areal capacity of 0.20 mA h cm-2 at a current of 0.2 mA and a capacity retention rate of 53.35% after 50 cycles. The mechanism study reveals that during the initial charge-discharge cycle, NiFeMn-CO3 LDH transforms into NiFeMn-SO4 LDH, which then absorbs Zn2+, Mn2+, and SO4 2- ions to form a stable composite substrate. This substrate enables the reversible deposition-dissolution of Mn ions, while Zn ions participate in the reaction continuously, with most Mn- and Zn-containing compounds depositing in an amorphous phase. Although further optimization is needed, our findings provide valuable insights for developing Zn-Mn aqueous batteries, highlighting the potential of LDHs as cathode substrates and the pivotal role of amorphous compounds in the reversible deposition-dissolution process.

Scalable Production of 2D Non-Layered Metal Oxides through Metal-Organic Gel Rapid Redox Transformation

Two-dimensional (2D) nonlayered metal compounds with porous structure show broad application prospects in electrochemistry-related fields due to their abundant active sites, open ions/electrons diffusion channels, and faradaic reactions. However, scalable and universal synthesis of 2D porous compounds still remains challenging. Here, inspired by blowing gum, a metal-organic gel (MOG) rapid redox transformation (MRRT) strategy is proposed for the mass production of a wide variety of 2D porous metal oxides. Adequate crosslinking degree of MOG precursor and its rapid redox with NO3 - are critical for generating gas pressure from interior to exterior, thus blowing the MOG into 2D carbon nanosheets, which further act as self-sacrifice template for formation of oxides with porous and ultrathin structure. The versatility of this strategy is demonstrated by the fabrication of 39 metal oxides, including 10 transition metal oxides, one II-main group oxide, two III-main group oxides, 22 perovskite oxides, four high-entropy oxides. As an illustrative verification, the 2D transition metal oxides exhibit excellent capacitive deionization (CDI) performance. Moreover, the assembled CDI cell could act as desalting battery to supply electrical energy during electrode regeneration. This MRRT strategy offers opportunities for achieving universal synthesis of 2D porous oxides with nonlayered structures and studying their electrochemistry-related applications.

Ultra-Wide Interlayered WxMo2xSy Alloy Electrode Patterning through High-Precision Controllable Photonic-Synthesis

Ultra-thin 2D materials have great potential as electrodes for micro-supercapacitors (MSCs) because of their facile ion transport channels. Here, a high-precision controllable photonic-synthesis strategy that provided 1 inch wafer-scale ultra-thin film arrays of alloyed WxMo2xSy with sulfur vacancies and expanded interlayer (13.2 Å, twice of 2H MoS2) is reported. This strategy regulates the nucleation and growth of transition metal dichalcogenides (TMDs) on the picosecond or even femtosecond scale, which induces Mo-W alloying, interlayer expansion, and sulfur loss. Therefore, the diffusion barrier of WxMo2xSy is reduced, with charge transfer and ion diffusion enhancing. The as-prepared symmetric MSCs with the size of 100 × 100 µm2 achieve ultrahigh specific capacitance (242.57 mF cm-2 and 242567.83 F cm-3), and energy density (21.56 Wh cm-3 with power density of 485.13 W cm3). The established synthesis strategy fits numerous materials, which provides a universal method for the flexible synthesis of electrodes in microenergy devices.

Stabilizing NiFe sites by high-dispersity of nanosized and anionic Cr species toward durable seawater oxidation

Electrocatalytic H2 production from seawater, recognized as a promising technology utilizing offshore renewables, faces challenges from chloride-induced reactions and corrosion. Here, We introduce a catalytic surface where OH- dominates over Cl- in adsorption and activation, which is crucial for O2 production. Our NiFe-based anode, enhanced by nearby Cr sites, achieves low overpotentials and selective alkaline seawater oxidation. It outperforms the RuO2 counterpart in terms of lifespan in scaled-up stacks, maintaining stability for over 2500 h in three-electrode tests. Ex situ/in situ analyses reveal that Cr(III) sites enrich OH-, while Cl- is repelled by Cr(VI) sites, both of which are well-dispersed and close to NiFe, enhancing charge transfer and overall electrode performance. Such multiple effects fundamentally boost the activity, selectively, and chemical stability of the NiFe-based electrode. This development marks a significant advance in creating durable, noble-metal-free electrodes for alkaline seawater electrolysis, highlighting the importance of well-distributed catalytic sites.

Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, a high-density semi-metallic molybdenum disulfide (1T'-MoS2) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieve high capacitance up to ≈277.5 F cm-3 under an ultrahigh scan rate of 1000 mV s-1 with a lower charge-transfer resistance and nearly tenfold higher electrochemical active surface area than the 2H-MoS2 electrode, is reported. Furthermore, 1T'-MoS2 electrode demonstrates exceptional volumetric desalination capacity of 65.1 mgNaCl cm-3 in CDI experiments. Ex situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS2 interlayer to accommodate cations such as Na+, K+, Ca2+, and Mg2+, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact 2D-layered nanolaminates with high-volumetric performance for CDI desalination.

Order-in-disordered ultrathin carbon nanostructure with nitrogen-rich defects bridged by pseudographitic domains for high-performance ion capture

Carbon materials with defect-rich structure are highly demanded for various electrochemical scenes, but encountering a conflict with the deteriorative intrinsic conductivity. Herein, we build a highway-mediated nanoarchitecture that consists of the ordered pseudographitic nanodomains among disordered highly nitrogen-doped segments through a supramolecular self-assembly strategy. The "order-in-disorder" nanosheet-like carbon obtained at 800 °C (O/D NSLC-800) achieves a tradeoff with high defect degree (21.9 at% of doped nitrogen) and compensated electrical conductivity simultaneously. As expected, symmetrical O/D NSLC-800 electrodes exhibit superior capacitive deionization (CDI) performance, including brackish water desalination (≈82 mgNaCl g-1 at a cell voltage of 1.6 V in a 1000 mg L-1 NaCl solution) and reusage of actual refining circulating cooling water, outperforming most of the reported state-of-the-art CDI electrodes. The implanted pseudographitic nanodomains lower the resistance and activation energy of charge transfer, which motivates the synergy of hosting sites of multiple nitrogen configurations. Our findings shed light on electrically conductive nanoarchitecture design of defect-rich materials for advanced electrochemical applications based on molecular-level modulation.

Boosting electrochemical oxygen reduction to hydrogen peroxide coupled with organic oxidation

The electrochemical oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2) is appealing due to its sustainability. However, its efficiency is compromised by the competing 4e- ORR pathway. In this work, we report a hierarchical carbon nanosheet array electrode with a single-atom Ni catalyst synthesized using organic molecule-intercalated layered double hydroxides as precursors. The electrode exhibits excellent 2e- ORR performance under alkaline conditions and achieves H2O2 yield rates of 0.73 mol gcat-1 h-1 in the H-cell and 5.48 mol gcat-1 h-1 in the flow cell, outperforming most reported catalysts. The experimental results show that the Ni atoms selectively adsorb O2, while carbon nanosheets generate reactive hydrogen species, synergistically enhancing H2O2 production. Furthermore, a coupling reaction system integrating the 2e- ORR with ethylene glycol oxidation significantly enhances H2O2 yield rate to 7.30 mol gcat-1 h-1 while producing valuable glycolic acid. Moreover, we convert alkaline electrolyte containing H2O2 directly into the downstream product sodium perborate to reduce the separation cost further. Techno-economic analysis validates the economic viability of this system.

Entropy Engineering Constrain Phase Transitions Enable Ultralong-life Prussian Blue Analogs Cathodes

Prussian blue analogs (PBAs) are considered as one of the most potential electrode materials in capacitive deionization (CDI) due to their unique 3D framework structure. However, their practical applications suffer from low desalination capacity and poor cyclic stability. Here, an entropy engineering strategy is proposed that incorporates high-entropy (HE) concept into PBAs to address the unfavorable multistage phase transitions during CDI desalination. By introducing five or more metals, which share N coordination site, high-entropy hexacyanoferrate (HE-HCF) is constructed, thereby increasing the configurational entropy of the system to above 1.5R and placing it into the high-entropy category. As a result, the developed HE-HCF demonstrates remarkable cycling performance, with a capacity retention rate of over 97% after undergoing 350 ultralong-life cycles of adsorption/desorption. Additionally, it exhibits a high desalination capacity of 77.24 mg g-1 at 1.2 V. Structural characterization and theoretical calculation reveal that high configurational entropy not only helps to restrain phase transition and strengthen structural stability, but also optimizes Na+ ions diffusion path and energy barrier, accelerates reaction kinetics and thus improves performance. This research introduces a new approach for designing electrodes with high performance, low cost, and long-lasting durability for capacitive deionization applications.

Confined Space Dual-Type Quantum Dots for High-Rate Electrochemical Energy Storage

Owing to the quantum size effect and high redox activity, quantum dots (QDs) play very essential roles toward electrochemical energy storage. However, it is very difficult to obtain different types and uniformly dispersed high-active QDs in a stable conductive microenvironment, because QDs prepared by traditional methods are mostly dissolved in solution or loaded on the surface of other semiconductors. Herein, dual-type semiconductor QDs (Co9S8 and CdS) are skillfully constructed within the interlayer of ultrathin-layered double hydroxides. In particular, the expandable interlayer provides a very suitable confined space for the growth and uniform dispersion of QDs, where Co9S8 originates from in situ transformation of cobalt atoms in laminate and CdS is generated from interlayer pre-embedding Cd2+. Meanwhile, XAFS and GGA+U calculations are employed to explore and prove the mechanism of QDs formation and energy storage characteristics as compared to surface loading QDs. Significantly, the hybrid supercapacitors achieve a high energy density of 329.2 µWh cm-2, capacitance retention of 99.1%, and coulomb efficiency of 96.9% after 22 000 cycles, which is superior to the reported QDs-based supercapacitors. These findings provide unique insights for designing and developing stable, ordered, and highly active QDs.

Mesoporous Cubic Nanocages Assembled by Coupled Monolayers With 100% Theoretical Capacity and Robust Cycling

High capacity and long cycling often conflict with each other in electrode materials. Despite extensive efforts in structural design, it remains challenging to simultaneously achieve dual high electrochemical properties. In this study, we prepared brand-new completely uniform mesoporous cubic-cages assembled by large d-spacing Ni(OH)2 coupled monolayers intercalated with VO4 3- (NiCMCs) using a biomimetic approach. Such unique mesoporous structural configuration results in an almost full atomic exposure with an amazing specific surface area of 505 m2/g and atomic utilization efficiency close to the theoretical limit, which is the highest value and far surpasses all of the reported Ni(OH)2. Thus, a breakthrough in simultaneously attaining high capacity approaching the 100% theoretical value and robust cycling of 10,000 cycles is achieved, setting a new precedent in achieving double-high attributes. When combined with high-performance Bi2O3 hexagonal nanotubes, the resulting aqueous battery exhibits an ultrahigh energy density of 115 Wh/kg and an outstanding power density of 9.5 kW/kg among the same kind. Characterizations and simulations reveal the important role of large interlayer spacing intercalation units and mesoporous cages for excellent electrochemical thermodynamics and kinetics. This work represents a milestone in developing "double-high" electrode materials, pointing in the direction for related research and paving the way for their practical application.

Reduced Lattice Constant in Al-Doped LiMn2O4 Nanoparticles for Boosted Electrochemical Lithium Extraction

Extracting lithium selectively and efficiently from brine sources is crucial for addressing energy and environmental challenges. The electrochemical system employing LiMn2O4 (LMO) electrodes has been recognized as an effective method for lithium recovery. However, the lithium selectivity and stability of LMO need further enhancement for its practical applications. Herein, the Al-doped LMO with reduced lattice constant is successfully fabricated through a facile one-step solid-state sintering method, leading to enhanced lithium selectivity. The reduced lattice constant in Al-doped LMO is proved through spectroscopic analyses and theoretic calculations. Compared to the original LMO, the Al-doped LMO (LiAl0.05Mn1.95O4, LMO-Al0.05) exhibits highercapacitance, lower resistance, and improved stability. Moreover, the LMO-Al0.05 with reduced lattice constant can offer higher Li+ diffusion coefficient and lower intercalation energy revealed by cyclic voltammetry and multiscale simulations. When employed in hybrid capacitive deionization (CDI), the LMO-Al0.05 obtains a Li+ intercalation capacity of 21.7 mg g-1 and low energy consumption of 2.6 Wh mol-1 Li+. Importantly, the LMO-Al0.05 achieves a high Li+ extraction percentage (≈86%) with Li+/Na+ and Li+/Mg2+ selectivity of 1653.8 and 434.9, respectively, in synthetic brine. The results demonstrate that the Al-doped LMO with reduced lattice constant could be a sustainable solution for electrochemical lithium extraction.

Effect of Cobalt on Lifetime of Sb4 O5 Cl2 -Graphene Anode in Chloride-Ion Batteries

Anode materials based on metal oxychlorides hold promise in addressing electrode dissolution challenges in aqueous-based chloride ion batteries (CIBs). However, their structural instability following chloride ion deintercalation can lead to rapid degradation and capacity fading. This paper investigates a cobalt-doped Sb4 O5 Cl2 -graphene (Co-Sb4 O5 Cl2 @GO) composite anode for aqueous-based CIBs. It exhibits significantly enhanced discharge capacity of 82.3 mAh g-1 after 200 cycles at 0.3 A g-1 ; while, the undoped comparison is only 23.5 mAh g-1 in the same condition. It also demonstrated with a long-term capacity retention of 72.8 % after 1000 cycles (65.5 mAh g-1 ) and a favorable rate performance of 25 mAh g-1 at a high current density of 2 A g-1 . Undertaken comprehensive studies via in-situ experiments and DFT calculations, the cobalt (Co) dopant is demonstrated as the crucial role to enhance the lifetime of Sb4 O5 Cl2 -based anodes. It is found that, the Co dopant improves electronic conductivity and the diffusion of chloride ions beside increases the structural stability of Sb4 O5 Cl2 crystal. Thus, this element doping strategy holds promise for advancing the field of Sb4 O5 Cl2 -based anodes for aqueous-based CIBs, and insights gain from this study also offer valuable knowledge to develop high-performance electrode materials for electrochemical deionization.

Terephthalic Acid Intercalated CoNi-LDH Materials for Improved Li-O2 Battery

CoNi-LDH (layered CoNi double hydroxides) hollow nanocages with specific morphology are obtained by Ni ion etching of ZIF-67 (Zeolitic imidazolate framework-67). The structure of the layered materials is further modified by molecular intercalation. The original interlayer anions are replaced by the ion exchange effect of terephthalic acid, which helps to increase the interlayer distance of the material. The intercalated cage-like structures not only benefit for the storage of oxygen, and the discharge product reaction, but also have more support between the material layers. The experimental results show that the excessive use of intercalation agent will affect structural stability of the intercalated CoNi-LDH. By adjusting the amount of terephthalic acid, the intercalated CoNi-LDH-2 (with 0.02 mmol terephthalic acid intercalated) is not easy to collapse after 209 cycles and shows the best electrochemical performance in Li-O2 battery.

Activating lattice oxygen in high-entropy LDH for robust and durable water oxidation

The oxygen evolution reaction is known to be a kinetic bottleneck for water splitting. Triggering the lattice oxygen oxidation mechanism (LOM) can break the theoretical limit of the conventional adsorbate evolution mechanism and enhance the oxygen evolution reaction kinetics, yet the unsatisfied stability remains a grand challenge. Here, we report a high-entropy MnFeCoNiCu layered double hydroxide decorated with Au single atoms and O vacancies (AuSA-MnFeCoNiCu LDH), which not only displays a low overpotential of 213 mV at 10 mA cm-2 and high mass activity of 732.925 A g-1 at 250 mV overpotential in 1.0 M KOH, but also delivers good stability with 700 h of continuous operation at ~100 mA cm-2. Combining the advanced spectroscopic techniques and density functional theory calculations, it is demonstrated that the synergistic interaction between the incorporated Au single atoms and O vacancies leads to an upshift in the O 2p band and weakens the metal-O bond, thus triggering the LOM, reducing the energy barrier, and boosting the intrinsic activity.

Enhanced Pseudo-Capacitance Process in Nanoarchitectural Layered Double Hydroxide Nanoarrays Hollow Nanocages for Improved Capacitive Deionization Performance

Layered double hydroxides (LDHs) are perceived as a hopeful capacitive deionization (CDI) faradic electrode for Cl^- insertion due to its tunable composition, excellent anion exchange capacity, and fast redox activity. Nevertheless, the self-stacking and inferior electrical conductivity of the two-dimensional structure of LDH lead to unsatisfactory CDI performance. Herein, the three-dimensional (3D) hollow nanocage structure of CoNi-layered double hydroxide/carbon composites is well designed as a CDI anode by cation etching of the pre-carbonized ZIF-67 template. C/CoNi-LDH has a unique 3D hollow nanocage structure and abundant pore features, which can effectively suppress the self-stacking of LDH sheets and facilitate the transport of ions. Moreover, the introduced amorphous carbon layer can act as a conductive network. When employed as the CDI anode, C/CoNi-LDH exhibited a high Cl^- removal capacity of 60.88 mg g^-1 and a fast Cl^- removal rate of 18.09 mg g^-1 min^-1 at 1.4 V in 1000 mg L^-1 NaCl solution. The mechanism of the Cl^- intercalation pseudo-capacitance reaction of C/CoNi-LDH is revealed by electrochemical kinetic analysis and ex situ characterization. This study provides vital guidance for the design of high-performance electrodes for CDI.