High Charge Density Research Articles

Nucleophilicity at copper(-I) in a compound with a Cu–Mg bond

Copper is ubiquitous as a structural material, and as a reagent in (bio)chemical transformations. A vast number of chemical reactions rely on the near-inevitable preference of copper for positive oxidation states to make useful compounds. Here we show this electronic paradigm can be subverted in a stable compound with a copper-magnesium bond, which conforms to the formal oxidation state of Cu(-I). The Cu-Mg bond is synthesized by the reaction of an N-heterocyclic carbene (NHC) ligated copper alkoxide with a dimeric magnesium(I) compound. Its identity is confirmed by single-crystal X-ray structural analysis and NMR spectroscopy, and computational investigations provide data consistent with a high charge density at copper. The Cu-Mg bond acts as a source of the cupride anion, transferring the NHC-copper fragment to electrophilic s-, p-, and d-block atoms to make known and new copper-containing compounds.

Programmable Electromagnetic Wave Absorption via Tailored Metal Single Atom-Support Interactions.

Metal single atoms (SA)-support interactions inherently exhibit significant electrochemical activity, demonstrating potential in energy catalysis. However, leveraging these interactions to modulate electronic properties and extend application fields is a formidable challenge, demanding in-depth understanding and quantitative control of atomic-scale interactions. Herein, in situ, off-axis electron holography technique is utilized to directly visualize the interactions between SAs and the graphene surface. These interactions facilitate the formation of dispersed nanoscale regions with high charge density and are highly sensitive to external electromagnetic (EM) fields, resulting in controllable dynamic relaxation processes for charge accumulation and restoration. This leads to customized dielectric relaxation, which is difficult to achieve with current band engineering methods. Moreover, these electronic behaviors are insensitive to elevated temperatures, having characteristics distinct from those of typical metallic or semiconducting materials. Based on these results, programmable EM wave absorption properties are achieved by developing a library of SA-graphene materials and precisely controlling SA-support interactions to tailor their responses to EM waves in terms of frequency and intensity. This advancement addresses the customized anti-EM interference requirements of electronic components, greatly enhancing the development of integrated circuits and micro-nano chips. Future efforts will concentrate on manipulating atomic interactions in SA-support, potentially revolutionizing nanoelectronics and optoelectronics.

Mix-Charged Nanofiltration Membrane for Efficient Organic Removal from High-Salinity Wastewater: The Role of Charge Spatial Distribution.

The efficient removal of organic contaminants from high-salinity wastewater is crucial for resource recovery and achieving zero discharge. Nanofiltration (NF) membranes are effective in separating organic compounds and monovalent salts, but they typically exhibit an excessive rejection of divalent salts. Modifying the charge characteristics of NF membranes can improve salt permeation; however, the role of charge spatial distribution in governing salt transport behavior is not fully understood. In this study, we developed a mix-charged NF membrane with a horizontal charge distribution by employing interfacial polymerization combined with a polyester template etching and solvent-induced polyamine intercalation strategy. The ratio of positive to negative charge domains in the membrane can be precisely controlled by adjusting the aqueous monomer ratio and polyamine modifier type. X-ray photoelectron spectroscopy (XPS) depth profiling and separation layer thickness analysis confirmed the complete penetration of polyamines into the separation layer, providing direct evidence of the formation of horizontally distributed charge domains. This unique charge distribution results in a high charge density and a near-electroneutral surface, which facilitates the permeation of the divalent salts. The size-dependent "plug-in" modification and covalent cross-linking further reduce pore size, enhancing rejection of small organic molecules. Additionally, the membrane demonstrated exceptional antifouling performance against both negatively and positively charged pollutants, attributed to its unique charge distribution and smooth surface. Molecular dynamics (MD) simulations further revealed that weak electrostatic interactions and a tightly bound hydration layer contribute to the membrane's superior antifouling properties. This work provides valuable insights into the design of NF membranes with tailored microstructures and charge distributions for improved water treatment performance.

Fragmented charged domain wall below the tetragonal-orthorhombic phase transition in BaTiO3

Ferroelectric charged domain walls are known for their high electrical conductivity, making them promising candidates for modern electronics. A remarkably high conductivity and nominal charge density has been found in the head-to-head ferroelastic domain wall of tetragonal barium titanate. Conductivity of this domain wall decreases by several orders of magnitude when the temperature drops down below about 5 °C when the tetragonal phase transforms to the orthorhombic one. We explored the evolution of these ferroelectric charged domain walls in BaTiO3 crystals, while they undergo this phase transition by in situ optical microscopy. Our results reveal that, below the phase transition, the domains adjacent to charge domain walls become twinned, and the head-to-head charged domain wall transforms into a superdomain wall, which is broken into alternating micrometer-scale segments with and without the excess bound charge. Since the macroscopic conductive channel along such fragmented superdomain wall is disrupted, these observations explain the observed loss of the domain wall conductivity below the phase transition.

Ultrafast Synthesis of Oxygen Vacancy-Rich MgFeSiO4 Cathode to Boost Diffusion Kinetics for Rechargeable Magnesium-Ion Batteries.

Rechargeable magnesium ion batteries (RMBs) have drawn extensive attention due to their high theoretical volumetric capacity and low safety hazards. However, divalent Mg ions suffer sluggish mobility in cathodes owing to the high charge density and slow insertion/extraction kinetics. Herein, it is shown that an ultrafast nonequilibrium high-temperature shock (HTS) method with a high heating/quenching rate can instantly introduce oxygen vacancies into the olivine-structured MgFeSiO4 cathode (MgFeSiO4-HTS) in seconds. As a proof of concept, the MgFeSiO4-HTS exhibits a higher electrochemical property and fast insertion/extraction kinetics in comparison to those prepared from the conventional sintering method. The MgFeSiO4-HTS displays remarkable long-term cycling lifespan properties with a reversible capacity of 85.65 and 54.43 mAh g-1 over 500 and 1600 cycles at 2 and 5 C, respectively. Additionally, by combining the electrochemical experiments and density functional theory calculations, oxygen vacancies can weaken the interaction and energy barrier between the Mg2+ ions and the cathode, enhancing the Mg2+ diffusion kinetics.

Construction of a red phosphorus-molybdenum dioxide electron-rich interface for efficient photocatalytic reduction of carbon dioxide.

Developing efficient catalysts to enhance photoreduction carbon dioxide (CO2) into hydrocarbon fuels is a great challenge. As metallic material, molybdenum dioxide (MoO2) has very high conductivity and charge density, which make it a promising candidate as photocatalyst. However, its photocatalytic activity is limited by the serious charge recombination. How to effectively make full use of the metallic MoO2 for photocatalytic CO2 reduction is still a critical issue. The potential effective way to solve this problem is to introduce appropriate auxiliary catalysts to construct electron-rich interfaces. In this study, red phosphorus (P) is dispersed on MoO2 nanoparticles to construct electron-rich interfaces which can serve as the active site for photocatalytic CO2 reduction. The results show that the reduction of CO2 by pure MoO2 only produces carbon monoxide (CO) and methane (CH4). However, with the aid of red P, the P-MoO2 photocatalyst can produce ethylene (C2H4) with the yield of 5.43μmol h-1 g-1, and the CO and CH4 yields are also significantly improved. Experimental results and density functional theory (DFT) calculations indicate that photogenerated carriers can migrate from MoO2 to the interface, and the reduction of CO2 occurs at the interface. This study provides a significant insight for the design of efficient photocatalysts by using metallic photocatalysts.

Fabrication of alginate-based bio-tribopositive films via amine modification and metal ion coordination for high surface charge density

Fabrication of alginate-based bio-tribopositive films via amine modification and metal ion coordination for high surface charge density

Double helix rotating TENGs driven by ultra-low loading for harvesting high-entropy water flow energy

Water flow energy in rivers and lakes is a huge clean energy source and widely distributed in nature. Its low water velocity makes it difficult for electromagnetic generators to effectively harvest this energy. Therefore, harvesting high-entropy water flow energy is of great significance to the development of distributed power supply and sensing. In this study, we present a double helix rotating triboelectric nanogenerator (DHR-TENG) that can effectively convert the ultra-low water flow energy into electrical energy. DHR-TENG is designed to optimize space utilization and has a reciprocating transmission mechanism to ensure the continuous operation, achieving a surprisingly high charge density of 356.69 μC⋅m-3 and peak power density of 11.66 W⋅m-3. Compared with similar structures reported by predecessors, the maximum elevation is about 242 times and 2 times, respectively. A stable electrical output performance was achieved by DHR-TENG at ultra-low water flow velocity of 0.4∼0.8 m/s, the harvested energy can drive self-powered temperature sensor systems and wireless signal transmission systems. This work not only effectively improves the electrical output performance at ultra-low water flow velocity, but also helps to promote environmental monitoring and provides a feasible method for establishing early warning in the environment.

Exploring the Biological Impact of β-TCP Surface Polarization on Osteoblast and Osteoclast Activity.

β-tricalcium phosphate (β-TCP) is a widely utilized resorbable bone graft material, whose surface charge can be modified by electrical polarization. However, the specific effects of such a charge modification on osteoblast and osteoclast functions remain insufficiently studied. In this work, electrically polarized β-TCP with a high surface charge density was synthesized and evaluated in vitro in terms of its physicochemical properties and biological activity. Polarization was performed to achieve a high surface charge density, which was quantified using a thermally stimulated depolarization current. The proliferation and differentiation of MC3T3-E1 osteoblast-like cells were assessed via WST-8 and alkaline phosphatase assays. Tartrate-resistant acid phosphatase (TRAP) activity and a resorption pit assay were used to evaluate the impact of surface charge on RAW264.7 osteoclast-like cell activity. Polarized β-TCP exhibited a surface charge of 1.3 mC cm-2. Electrically polarized surfaces significantly enhanced osteoblast proliferation and differentiation. TRAP activity assays demonstrated effective osteoclast differentiation of RAW264.7 cells, with enhanced activity observed on charged surfaces. Resorption pit assays further revealed improved osteoclast resorption capacity on β-TCP surfaces with a polarized charge. These findings indicate that β-TCP with a highly dense surface charge promotes osteoblast proliferation and differentiation, as well as osteoclast activity and resorption capacity.

Controlled Heterovalent Vanadium Ion Coordinated Flower-Shaped Supramolecules Cathode for Zinc-Ion Storage.

Vanadium-based materials, which offer multiple oxidation states and rich redox reactions in zinc-ion batteries (ZIBs), have gained substantial attention. However, achieving green and efficient preparation of vanadium oxides-based materials featured with a controlled content of different heterovalent vanadium remains a significant challenge. Herein, a vanadium-supramolecular flower-shaped material (VSF) with heterovalent vanadium was prepared using NH4VO3 as vanadium metal center and hexamethylenetetramine as organic ligand in aqueous solution. The optimal ratio of material (PVSF) after controlling VSF presintering is 2/1 (V5+/V4+). Employing PVSF-2/1 as cathode in ZIBs can achieve a high specific capacity of 398.9 mAh g-1 at 0.2 A g-1, which is increased by 0.2 and 3.5 times as compared with that of pure VO2 and V2O5, respectively. After 2000 cycles, it still delivers a specific capacity of 225 mAh g-1 at 5.0 A g-1. The Zn∥PVSF-2/1 pouch cells were assembled with a satisfactory specific capacity of 339 mAh g-1 at a current of 0.2 A g-1. The excellent performance is ascribed to regulation and coordinated promotion of heterovalent states. The structural pathways corresponding to V5+ act as Zn2+ transport channels to increase Zn2+ transport capability. The V4+ cause high charge density distribution of the V-O lattice layer to provide abundant active sites for the adsorption/desorption process of Zn2+.

Regulation of Electron Cloud Density by Electronic Effects of Substituents to Optimize Photocatalytic H2 Evolution of Carbon Dots.

Carbon dots (CDs) have a wide light absorption range, which are promising candidates for photocatalytic water splitting H2 evolution, but they show low activity for hydrogen evolution reaction (HER) due to the slow transfer efficiencies of photogenerated carriers. The electron cloud density of photocatalyst is essential for the separation and migration of photogenerated carriers. In this study, the effect mechanism of electron cloud density regulated by the substituents with different electronic effects on the photocatalytic HER of glucose-based CDs is clarified. CDs-SO3H and CDs-OH are first obtained by introducing electron-drawing group (─SO3H) and electron-donating group (─OH) using a tailoring post-processing strategy. Experimental results show that the H2 yield catalyzed by CDs-SO3H is 89.95 µmol•g-1 in 4 h, which is about four times that of CDs, and 7.4 times that of CDs-OH. The ─SO3H induces a much negative energy band and high electron cloud density on CDs edges, promoting the separation and transfer of photogenerated carriers; while the CDs-OH exhibits a high positive charge density and an upward energy band, hindering the surface complexation of electron-hole pairs and HER. This study will provide an insight into the design of CDs catalysts with efficient photocatalytic HER at a molecular level.

Generation of Charges During the Synthesis of Nanopowders of Doped Cerium Dioxide in Combustion Reactions.

The development and characterization of synthesis techniques for oxide materials based on ceria is a subject of extensive study with the objective of their wide-ranging applications in pursuit of sustainable development. The present study demonstrates the feasibility of controlled synthesis of Ce1-xMxO2-δ (M = Fe, Ni, Co, Mn, Cu, Ag, Sm, Cs, x = 0.0-0.3) in combustion reactions from precursors comprising glycine, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and cellulose as organic components. Controlled synthesis is achieved by varying the composition of the precursor, the type of organic component, and the amount of organic component, which allows for the influence of the generation of high-density electrical charges and outgassing during synthesis. The intensity of charge generation is quantified by measuring the value of the precursor-ground potential difference. It has been demonstrated that an increase in the intensity of charge generation results in a more developed morphology, which is essential for the practical implementation of ceria as a catalyst to enhance contact with gases and solid particles. The maximum value of the potential difference, equal to 68 V, is obtained during the synthesis of Ce0.7Ni0.3O2-δ with polyvinyl alcohol in stoichiometric relations, which corresponds to a specific surface area of 21.7 m2 g-1. A correlation is established between the intensity of gas release for systems with different organic components, the intensity of charge generation, morphology, and the value of the specific surface area of the samples.

Fabrication of Porous MXene/Cellulose Nanofibers Composite Membrane for Maximum Osmotic Energy Harvesting.

Two-dimensional (2D) nanofluidic channels are emerging as potential candidates for harnessing osmotic energy from salinity gradients. However, conventional 2D nanofluidic membranes suffer from high transport resistance and low ion selectivity, leading to inefficient transport dynamics and limiting energy conversion performance. In this study, we present a novel composite membrane consisting of porous MXene (PMXene) nanosheets featuring etched nanopores, in conjunction with cellulose nanofibers (CNF), yielding enhancement in ion flux and ion selectivity. A mild H2O2 oxidant is employed to etch and perforate the MXene sheets to create a robust network of cation transportation nanochannels that effectively reduces the energy barrier for cation transport. Additionally, CNF with a unique nanosize and high charge density further enhances the charge density and mechanical stability of the nanofluidic system. Under neutral pH and room temperature, the PMXene/CNF membrane demonstrates a maximum output power density of 0.95 W·m-2 at a 50-fold KCl gradient. Notably, this represents a 43% improvement over the performance of the pristine MXene/CNF membrane. Moreover, 36 nanofluidic devices connected in series are demonstrated to achieve a stable voltage output of 5.27 V and power a calculator successfully. This work holds great promise for achieving sustainable energy harvesting with efficient osmotic energy conversion utilization.

Dual-Emission Afterglow of Carbon Dots Induced by an Inorganic Salt for Anticounterfeiting and Temperature Sensing.

Afterglow carbon dots (CDs) have been extensively studied for sensing and anticounterfeiting because they can effectively block out the interference of background light. In this work, m-APBA CDs are obtained hydrothermally with m-aminophenylboric acid (m-APBA) and different kinds of inorganic salts (IS). When m-APBA CDs are combined with CaCl2 and MgCl2, dual-emission afterglow can be achieved based on CaCl2 and MgCl2 having the strongest aggregation ability, high charge density, structural confinement, and defects with respect to m-APBA CDs. The as-obtained CDs@CaCl2 exhibits a dual mode afterglow with a quantum yield of 4.81% and lifetimes of 352 ms (delayed fluorescence) and 205 ms (phosphorescence). The afterglow of CDs@IS can be excited by both UV and visible light at the same time, which could be recorded for about 8 and 4 s. This unique method of inducing the m-APBA CD afterglow has the advantages of simple synthesis, low cost, and adjustable afterglow emission. Moreover, CDs@IS showed exceptional performance in anticounterfeiting and temperature sensing, further establishing its practical utility.

Work function-activated proton intercalation chemistry assists ultra-stable aqueous zinc ion batteries.

Manganese oxide (MnOx) cathodes with a Zn2+/H+ co-intercalation mixing mechanism have exhibited great potential for aqueous zinc-ion batteries (AZIBs) owing to their high energy density and optimal electrolyte suitability. However, the strong electrostatic interactions and slow kinetics between the high charge density zinc ions and the fixed lattice in conventional cathodes have hindered the development of AZIBs. Hence, selecting H+ with a smaller ionic radius and reduced electrostatic repulsion as carriers was a feasible strategy. Herein, we developed a series of M-MnO heterojunctions (M=Cu/Co/Ni/Zn) derived from bimetallic metal-organic frameworks (MOF) as cathodes to enable a controllable work function to regulate the proton absorption energy. Therefore, the CO bond derived from the MOF became a fast channel for proton transfer by the bonding effect. Synergistic activation of proton intercalation chemistry by work function and CO bonding. Combined with Density-Functional Theory, the work function exhibited a negative correlation with the proton adsorption energy, which could effectively regulate proton intercalation chemistry. Among them, Cu-MnO delivered optimal electrochemical performance (431.6/150.7mAh g-1 at 0.2/5.0 A g-1), exhibiting superior cycling stability (98.24% capacity retention after 12,000 cycles at 5.0 A g-1). This study provided insights into the work function versus proton chemistry for the development of high-performance cathode materials for AZIB.

Manipulating overcompensation of poly (allylamine hydrochloride) in layer-by-layer nanofiltration membranes for Mg2+/Li+ separation

Surface modification of the positive charges in the polyamide thin-film composite nanofiltration (NF) membranes has been explored for separation of Mg2+/Li+ via Donnan exclusion. However, manipulation of the surface charges in layer-by-layer (LBL) NF membranes presents significant challenges because the overall charge within the entire separation layer, rather than just the top surface, provides effective Donnan effect. In this work, we reported a facile approach to increase the positive charge within poly (styrene sulfonate) (PSS)/poly (allylamine hydrochloride) (PAH) LBL NF membranes. A significant improvement in the permselectivity of (PSS/PAH)2.5 NF membranes was achieved by varying the PAH concentration from 0.001 M to 0.1 M. The increased PAH concentration led to overcompensation within the separation layer, resulting in a higher charge density and increase in the rejection of MgCl2, MgSO4 and LiCl, but decline in the rejection of Na2SO4. Although the pore size slightly reduced, the overall improvement in the permselectivty was mainly attributed to the Donnan exclusion effect. The optimal membrane, prepared using a PAH concentration of 0.1 M, showed a high pure water permeance of 10.9 L m−2 h−1 bar−1 with a MgCl2 rejection of 96.6 %, and the highest separation factor SMg,Li of 19.6 for mixed salt solutions. The assembly process of LBL membranes typically involved two stages during each coating cycle: polyelectrolyte (PE) adsorption and diffusion. PAH concentration primarily affected the adsorption process, while the diffusion process was influenced by NaCl concentration. Higher concentration of PAH and NaCl led to coiled conformation. This collectively led to the overcompensation of PAH. Among these, PAH concentration was identified as a more important factor for overcompensation. This study highlights the versatility of LBL NF membranes, demonstrating their potential for precise ion separation through tailored surface charge manipulation.

A Novel Parameter Estimation Scheme for Supercapacitors

As reliance on sustainable energy grows, the demand for efficient, high-performance energy storage systems becomes increasingly critical, especially in uninterruptible power supplies (UPS), where reliability and fast transitions are essential. Supercapacitors, with their high power density and rapid charging capabilities, are emerging as strong alternatives to lithium-ion batteries in UPS systems. This paper presents a novel real-time estimation technique for monitoring supercapacitor parameters within a UPS, focusing on the dynamic behavior of these parameters and their evolution over the system’s lifecycle. The proposed estimator demonstrates exceptional accuracy, achieving less than 1% error within 120 ms of startup and nearly zero error thereafter. The estimator’s performance remains robust even as supercapacitor parameters change due to aging effects over the lifespan. The UPS system features a modular design, enabling scalability to accommodate higher power requirements or longer backup durations and adaptability to various supercapacitor types. Experimental results highlight the system’s robustness in both charging and backup modes, emphasizing the potential of supercapacitors as key components in future UPS systems.

A Self‐Recovery Triboelectric Nanogenerator with High Breakdown Resistance for Water Wave Energy Harvesting

AbstractTriboelectric nanogenerator (TENG) harvesting ocean wave energy is an effective method to alleviate the energy crisis. However, the breakdown phenomenon is ubiquitous for the TENG with a large area of dielectric layer, which not only limits the output and reliability but also highly risks the device failure. Here, a self‐recovery TENG (SR‐TENG) featuring high breakdown resistance is designed, which achieves a high output charge density of 4.24 mC m−2 with the assistance of the charge excitation technique, as well as maintains 87% of the initial output even after six times fierce electric breakdown, minimizing the negative impacts of the breakdown phenomenon. Besides, based on the SR‐TENG, a symmetric anaconda‐shaped self‐charge excited TENG is designed for effective water wave energy harvesting. This work not only sheds light on the self‐recovery phenomenon in TENGs, but also represents a significant step toward the high performance TENG featuring high breakdown resistance and ultimate stability, accelerating the practical applications of TENG for blue energy harvesting.

Electrolyte optimization for enhanced electrode performance in aqueous Zn//WO3 mixed-ion battery

Aqueous electrochemical energy storage has emerged as a low-cost and sustainable technology. Among the diverse array of electrode materials, tungsten trioxide (WO3) holds promise due to its unique electrochemical properties and environmental compatibility. In this study, we investigate the potential of WO3 for aqueous energy storage applications, focusing on its performance in different electrolytes, namely, 0.5 M Na2SO4, 1.0 M ZnSO4, and 0.5 M Al2(SO4)3. Electrochemical measurements and density functional theory (DFT) calculations indicate that the charge density of electrolyte cation influences the WO3 electrode performance. A superior performance is observed in the Al2(SO4)3 electrolyte due to the high charge density of Al3+ ions. We further investigate WO3 as a cathode in the full-cell configuration using Zn metal as an anode and a mixed solution of 1.0 M ZnSO4 and 0.5 M Al2(SO4)3 as an electrolyte. The mixed-ion Zn//WO3 battery exhibits high specific energy and good cycling stability, highlighting the feasibility of WO3 as an electrode for practical aqueous energy storage. Overall, this study provides insights into the electrochemical behavior of WO3 in aqueous environments and underscores its potential for advancing sustainable energy solutions.

Understanding Benzophenone Degradation Pathways to Improve Non-Aqueous Redox Flow Battery Performance

The growing energy demand forces us to look for alternative sources of energy such as wind or solar. However, this type of intermittent energy must be stored for later use. In this sense, redox flow batteries (RFBs) are presented as an interesting tool for energy storage. Non-aqueous RFBs allow a wide electrochemical window for organic solvents such as acetonitrile, propylene carbonate or dimethylformamide. These solvents allow us to reach very positive and negative potentials, opening an electrochemical window greater than 5 V before observing degradation of the solvents.In the design of electrolytes for RFBs it is essential to address aspects such as charge density, stability, price, and the voltage that the redox couple allows us to achieve. In this sense, organic molecules have been widely used as anolytes due to their high charge density, great solubility and the possibility of reaching very negative and positive potentials that would provide RFBs with efficient performance. In our search for organic molecules with E1/2 potentials equal or more negative than -2.0 V, we begun investigating benzophenone and derivatives. The BP family of derivatives have attracted the attention of the anolyte development community due to their extremely negative reduction potentials. In these molecules it is possible to achieve the first reduction at E1/2 -2.25 V vs Ag/Ag+ and the second reduction process at E1/2 -2.8 V vs Ag/Ag+. Although this molecule presents very negative reduction potentials, our initial evaluations show that they are not stable for sufficient time to be used in RFBs. Herein, we detail the degradation mechanism of benzophenones, using product characterization obtained after cycling the anolytes in redox flow batteries. We observed the generation of benzocarbinol and benzopinacol after water and support electrolyte (TBAPF6) addition respectively to a dianion (BP-●●) chemically reduced. Based on the degradation mechanism, we propose a mitigation pathway to improve the performance of these carriers, including modification of ortho position with bulky groups to protect the carbonyl group.