CuO Nanoplates for High-Performance Potassium-Ion Batteries

Bafi A1 inhibits nano-copper oxide-induced mitochondrial damage by reducing the release of copper from lysosomes

This study demonstrated that both copper oxide nanoparticles (CuO-NPs) and copper nanoparticles (Cu-NPs) can cause swelling, inflammation, and cause damage to the mitochondria of alveolar type II epithelial cells in mice. Cellular examinations indicated that both CuO-NPs and Cu-NPs can reduce cell viability and harm the mitochondria of human bronchial epithelial cells, particularly Beas-2B cells. However, it is clear that CuO-NPs exhibit a more pronounced detrimental effect compared with Cu-NPs. Using bafilomycin A1 (Bafi A1), an inhibitor of lysosomal acidification, was found to enhance cell viability and alleviate mitochondrial damage caused by CuO-NPs. Additionally, Bafi A1 also reduces the accumulation of dihydrolipoamide S-acetyltransferase (DLAT), a marker for mitochondrial protein toxicity, induced by CuO-NPs. This observation suggests that the toxicity of CuO-NPs depends on the distribution of copper particles within cells, a process facilitated by the acidic environment of lysosomes. The release of copper ions is thought to be triggered by the acidic conditions within lysosomes, which aligns with the lysosomal Trojan horse mechanism. However, this association does not seem to be evident with Cu-NPs.

Oxygen vacancy-rich Ag/CuO nanoarray mesh fabricated by laser ablation for efficient bacterial inactivation

The contamination of drinking water by microbes is a critical health concern, underscoring the need for safe, reliable, and efficient methods to treat pathogenic microorganisms. While most sterilization materials are available in powder form, this presents safety risks and challenges in recycling. Herein, this study reports the preparation of an innovative copper oxide supported silver monolithic nanoarray mesh with abundant oxygen vacancies (Ag/CuO-VO) by laser ablation. The instantaneous high temperature caused by laser ablation preserves the material's original structure while generating oxygen vacancies on the CuO surface. The Ag/CuO-VO mesh demonstrated a remarkable ability to inactivate over 99% of Escherichia coli (E. Coli) within 20 min. The oxygen vacancies in the Ag/CuO-VO enhance interactions between oxygen species and the Ag/CuO-VO, leading to the accumulation of large amounts of reactive oxygen species (ROS). The generated ROS effectively disrupt both layers of the bacterial cell wall - the peptidoglycan and the phospholipid - as confirmed by Fourier Transform Infrared (FTIR) spectroscopy, culminating in cell death. This research presents a monolithic material capable of inactivating pathogenic microorganisms efficiently, offering a significant advancement in water sterilization technology.

SAXS unveils porous anodes for potassium-ion batteries: dynamic evolution of pore structures in Fe@Fe2O3/PCNFs composite nanofibers

The porous structure of composite nanofibers plays a key role in improving their electrochemical performance. However, the dynamic evolution of pore structures and their action during ion intercalation/extraction processes for negative electrodes are not clear. Herein, porous carbon composite nanofibers (Fe@Fe2O3/PCNFs) were prepared as negative electrode materials for potassium-ion batteries. Electrochemical test findings revealed that the composites had good electrochemical characteristics, and the porous structure endowed composite electrodes with pseudo-capacitive behaviors. After 1500 discharge/charge cycles at a current density of 1000 mA g-1, the specific capacity of the potassium-ion batteries was 144.8 mAh g-1. We innovatively used synchrotron small-angle X-ray scattering (SAXS) technique to systematically investigate the kinetic process of potassium formation in composites and showed that the kinetic process of potassium reaction in composites can be divided into four stages, and the pores with smaller average diameter distribution are more sensitive to changes in the reaction process. This work paves a new way to study the deposition kinetics of potassium in porous materials, which facilitates the design of porous structures and realizes the development of alkali metal ion-anode materials with high energies.

Mn2+-Triggered Swing-Arm Robot Strategy Using Anemone-Like Thi@AuPd@Cu-MOFs as Signaling Probes for the Detection of T-2 Toxin

Herein, we synthesized anemone-like copper-based metal-organic frameworks (MOFs) loaded with gold-palladium nanoparticles (AuPd@Cu-MOFs) and polyethylenimine-reduced graphene oxide/gold-silver nanosheet composites (PEI-rGO/AuAg NSs) for the first time to construct the sensor and to detect T-2 toxin (T-2) using triple helix molecular switch (THMS) and signal amplification by swing-arm robot. The aptasensor used PEI-rGO/hexagonal AuAg NSs as the electrode modification materials and anemone-like AuPd@Cu-MOFs as the signal materials. The prepared PEI-rGO/hexagonal AuAg NSs had a large specific surface area, excellent electrical conductivity, and good stability, which successfully improved the electrochemical performance of the sensors. The AuPd@Cu-MOFs with high porosity provided a great deal of attachment sites for the signaling molecule thionine (Thi), thereby increasing the signal response. The aptasensor developed in this study demonstrated a remarkable detection limit of 0.054 fg mL-1 under optimized conditions. Furthermore, the successful detection of T-2 in real samples was achieved using the fabricated sensor. The simplicity of the THMS-based method, which entails modifying the aptamer sequence, allows for easy adaptation to different target analytes. Thus, the sensor holds immense potential for applications in quality supervision and food safety.

Insights into the multi-functional lithium difluoro(oxalate)borate additive in boosting the Li-ion reaction kinetics for Li3VO4 anodes

The rational design of a solid electrolyte interphase (SEI) with high ionic conductivity and high electrochemical stability is significantly important in improving the electrochemical performance of anode materials. Herein, lithium difluoro(oxalate)borate (LiDFOB) is used as an electrolyte additive to generate protective SEI films on Li3VO4 (LVO) anodes. The addition of LiDFOB is beneficial to form a dense, uniform, stable and LiF-richer SEI, which is helpful to boost the Li-ion storage kinetics. In addition, the generated SEI can inhibit the further decomposition of electrolytes and maintain the morphology of LVO anodes during charge/discharge processes. As a result, LVO-based anodes exhibit a much higher capacity (769.5 mA h g-1 at 0.5 A g-1), enhanced rate performance (243.3 mA h g-1 at 5.0 A g-1) and excellent long-term cycling stability (209.9 mA h g-1 after 5000 cycles) when cycled in 1 wt% LiDFOB addition electrolyte. This work confirms that LiDFOB is a promising multi-functional additive for LiPF6 electrolytes and provides new insights into SEI construction towards high-performance LVO anodes.

Loss-free pulverization by confining copper oxide inside hierarchical nitrogen-doped carbon nanocages toward superb potassium-ion batteries

Taking the advantages of hierarchical nitrogen-doped carbon nanocages (hNCNCs) with nanocavities for encapsulation and multiscale micro-meso-macropores/high conductivity for mass/electron synergistic transportation, a conversion-type CuO anode material is confined inside hNCNCs for potassium storage. The so-obtained yolk-shelled CuO@hNCNC hybrids have tunable CuO contents in the range of 11.7-63.7 wt%. The unique architecture leads to the loss-free pulverization of the active components during charge/discharge, which increases the surface-controlled charge storage, shortens the K+ solid diffusion lengths with an enlarged K+ diffusion coefficient, and meanwhile enhances the rate capability and durability. Consequently, the optimized CuO@hNCNC delivers a high specific capacity of 498 mA h g-1 at 0.1 A g-1 and 194 mA h g-1 at 10.0 A g-1 based on the total mass of CuO@hNCNC, and a long-term stability. The capacity based on the CuO active component reaches a record-high 522 mA h g-1 at 1.0 A g-1 after 2000 cycles, which is ca. 2.5 times the state-of-the-art value in the literature. The evolution of the cycling performance with CuO loading is well understood based on the loss-free pulverization. This study demonstrates a new strategy to turn the generally harmful pulverization of active components into a beneficial factor for K+ storage, which paves the way for exploring high-performance anodes for rechargeable batteries.

Sustainable Polyvinyl Chloride-Derived Soft Carbon Anodes for Potassium-Ion Storage: Electrochemical Behaviors and Mechanism

Soft carbon is a promising anode material for potassium-ion batteries due to its favorable properties such as low cost, high conductivity, stable capacity, and low potential platform. Polyvinyl chloride, as a white pollutant, is a soft carbon precursor that can be carbonized at varying temperatures to produce soft carbons with controllable defect and crystal structures. This work investigates the effect of carbonization temperature on the crystalline structures of the obtained soft carbons. In situ Raman spectroscopy was used to elucidate the adsorption-intercalation charge storage mechanism of potassium ions in soft carbons. Soft carbons prepared at the temperature of 800 °C have a defect-rich, short-range ordered structure, which provides optimal intercalation and adsorption sites for potassium ions, resulting in a satisfactory capacity of 302 mAh g-1 . This work presents new possibilities for designing soft carbon materials from recycling plastics for potassium-ion batteries.

Octahedral/Tetrahedral Vacancies in Fe3 O4 as K-Storage Sites: A Case of Anti-Spinel Structure Material Serving as High-Performance Anodes for PIBs

Potassium-ion batteries (PIBs) have attracted more and more attention as viable alternatives to lithium-ion batteries (LIBs) due to the deficiency and uneven distribution of lithium resources. However, it is shown that potassium storage in some compounds through reaction or intercalation mechanisms cannot effectively improve the capacity and stability of anodes for PIBs. The unique anti-spinel structure of magnetite (Fe3 O4 ) is densely packed with thirty-two O atoms to form a face-centered cubic (fcc) unit cell with tetrahedral/octahedral vacancies in the O-closed packing structure, which can serve as K+ storage sites according to the density functional theory (DFT) calculation results. In this work, carbon-coated Fe3 O4 @C nanoparticles are prepared as high-performance anodes for PIBs, which exhibit high reversible capacity (638 mAh g-1 at 0.05 A g-1 ) and hyper stable cycling performance at ultrahigh current density (150 mAh g-1 after 9000 cycles at 10 A g-1 ). In situ XRD, ex-situ Fe K-edge XAFS, and DFT calculations confirm the storage of K+ in tetrahedral/octahedral vacancies.

Implanting CuS Quantum Dots into Carbon Nanorods for Efficient Magnesium-Ion Batteries

Magnesium-ion batteries (MIBs) are emerging as potential next-generation energy storage systems due to high security and high theoretical energy density. Nevertheless, the development of MIBs is limited by the lack of cathode materials with high specific capacity and cyclic stability. Currently, transition metal sulfides are considered as a promising class of cathode materials for advanced MIBs. Herein, a template-based strategy is proposed to successfully fabricate metal-organic framework-derived in-situ porous carbon nanorod-encapsulated CuS quantum dots (CuS-QD@C nanorods) via a two-step method of sulfurization and cation exchange. CuS quantum dots have abundant electrochemically active sites, which facilitate the contact between the electrode and the electrolyte. In addition, the tight combination of CuS quantum dots and porous carbon nanorods increases the electronic conductivity while accelerating the transport speed of ions and electrons. With these architectural and compositional advantages, when used as a cathode material for MIBs, the CuS-QD@C nanorods exhibit remarkable performance in magnesium storage, including a high reversible capacity of 323.7 mAh g-1 at 100 mA g-1 after 100 cycles, excellent long-term cycling stability (98.5 mAh g-1 after 1000 cycles at 1.0 A g-1 ), and satisfying rate performance (111.8 mA g-1 at 1.0 A g-1 ).

Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

The phosphate KCoCr(PO₄)₂ and iron-substituted variants KCoCr_1-xFe_x(PO₄)₂ (x = 0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route, while a high substitution level of Fe was achieved. Their structures were refined using powder X-ray diffraction and indexed in a monoclinic system with a P2₁/n space group. A 3D framework with six-sided tunnels parallel to the [101] direction was formed in which the K atoms are located. Mössbauer spectroscopy confirms the exclusive presence of octahedral paramagnetic Fe³⁺ ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopy confirmed the presence of paramagnetic Cr³⁺ ions. The activation energy, determined by dielectric measurements, shows that the iron-containing samples present higher ionic activity. Relative to the electrochemical activity of K, these materials could be good candidates for positive and/or negative electrode materials for energy storage applications.

Elucidating the exceptional halide ion etching of bimetallic Ag-Cu oxides for efficient adsorption and porous nanostructure formation

Elucidating the interactions between halide ions and bimetallic oxides can help understand their influences on the physicochemical properties of bimetallic oxides and ultimately lead to better performance, but this has not yet been explored. We report here the first study of the interaction of halide ions with two phase-pure bimetallic Ag-Cu oxides, Ag₂Cu₂O₃ and Ag₂Cu₂O₄, which have different chemical valences of Ag and Cu atoms. We found that halide ions have an aggressive etching effect on both bimetallic oxides, leading to a dramatic evolution of crystal structures and morphology. Halide ions act like "nano-carving knives", selectively etching out silver atoms to form silver halides and leaving a porous CuO skeleton. We revealed that Ag₂Cu₂O₄ underwent a redox reaction with iodide ions (I^-) to produce additional I₃^- in the solution, which was not observed in Ag₂Cu₂O₃. Interestingly, according to the revealed interactions, both bimetallic oxides are confirmed as superior adsorbents to remove I^- from wastewater in terms of a record-high uptake capacity, fast adsorption kinetics, and excellent selectivity for I^-. Furthermore, such a halide etching can be turned into a powerful synthetic strategy. The out-etched silver halides were dissolved to give robust porous CuO nanostructures, which are proved to be excellent glucose-sensing electrodes with high sensitivity, excellent anti-interference, and stability, showing great application potential. This work contributes to improving the understanding of the mechanisms of halide ion-metal oxide interactions and ultimately to innovative applications.

Emerging 2D Copper-Based Materials for Energy Storage and Conversion: A Review and Perspective

2D materials have shown great potential as electrode materials that determine the performance of a range of electrochemical energy technologies. Among these, 2D copper-based materials, such as Cu-O, Cu-S, Cu-Se, Cu-N, and Cu-P, have attracted tremendous research interest, because of the combination of remarkable properties, such as low cost, excellent chemical stability, facile fabrication, and significant electrochemical properties. Herein, the recent advances in the emerging 2D copper-based materials are summarized. A brief summary of the crystal structures and synthetic methods is started, and innovative strategies for improving electrochemical performances of 2D copper-based materials are described in detail through defect engineering, heterostructure construction, and surface functionalization. Furthermore, their state-of-the-art applications in electrochemical energy storage including supercapacitors (SCs), alkali (Li, Na, and K)-ion batteries, multivalent metal (Mg and Al)-ion batteries, and hybrid Mg/Li-ion batteries are described. In addition, the electrocatalysis applications of 2D copper-based materials in metal-air batteries, water-splitting, and CO₂ reduction reaction (CO₂ RR) are also discussed. This review also discusses the charge storage mechanisms of 2D copper-based materials by various advanced characterization techniques. The review with a perspective of the current challenges and research outlook of such 2D copper-based materials for high-performance energy storage and conversion applications is concluded.

Hierarchical CuS@ZnIn2S4 Hollow Double-Shelled p-n Heterojunction Octahedra Decorated with Fullerene C60 for Remarkable Selectivity and Activity of CO2 Photoreduction into CH4

In this work, a hollow double-shelled architecture, based on n-type ZnIn₂S₄ nanosheet-coated p-type CuS hollow octahedra (CuS@ZnIn₂S₄ HDSOs), is designed and fabricated as a p-n heterojunction photocatalyst for selective CO₂ photoreduction into CH₄. The resulting hybrids provide rich active sites and effective charge migration/separation to drive CO₂ photoreduction, and meanwhile, CO detachment is delayed to increase the possibility of eight-electron reactions for CH₄ production. As expected, the optimized CuS@ZnIn₂S₄ HDSOs manifest a CH₄ yield of 28.0 μmol g^-1 h^-1 and a boosted CH₄ selectivity up to 94.5%. The decorated C₆₀ both possesses high electron affinity and improves catalyst stability and CO₂ adsorption ability. Thus, the C₆₀-decorated CuS@ZnIn₂S₄ HDSOs exhibit the highest CH₄ evolution rate of 43.6 μmol g^-1 h^-1 and 96.5% selectivity. This work provides a rational strategy for designing and fabricating efficient heteroarchitectures for CO₂ photoreduction.

Crystal Facet and Architecture Engineering of Metal Oxide Nanonetwork Anodes for High-Performance Potassium Ion Batteries and Hybrid Capacitors

Metal oxides are considered as prospective dual-functional anode candidates for potassium ion batteries (PIBs) and hybrid capacitors (PIHCs) because of their abundance and high theoretic gravimetric capacity; however, due to the inherent insulating property of wide band gaps and deficient ion-transport kinetics, metal oxide anodes exhibit poor K⁺ electrochemical performance. In this work, we report crystal facet and architecture engineering of metal oxides to achieve significantly enhanced K⁺ storage performance. A bismuth antimonate (BiSbO₄) nanonetwork with an architecture of perpendicularly crossed single crystal nanorods of majorly exposed (001) planes are synthesized via CTAB-mediated growth. (001) is found to be the preferential surface diffusion path for superior adsorption and K⁺ transport, and in addition, the interconnected nanorods gives rise to a robust matrix to enhance electrical conductivity and ion transport, as well as buffering dramatic volume change during insertion/extraction of K⁺. Thanks to the synergistic effect of facet and structural engineering of BiSbO₄ electrodes, a stable dual conversion-alloying mechanism based on reversible six-electron transfer per formula unit of ternary metal oxides is realized, proceeding by reversible coexistence of potassium peroxide conversion reactions (KO₂↔K₂O) and Bi_xSb_y alloying reactions (BiSb ↔ KBiSb ↔ K₃BiSb). As a result, BiSbO₄ nanonetwork anodes show outstanding potassium ion storage in terms of capacity, cycling life, and rate capability. Finally, the implementation of a BiSbO₄ nanonetwork anode in the state-of-the-art full cell configuration of both PIBs and PIHCs shows satisfactory performance in a Ragone plot that sheds light on their practical applications for a wide range of K⁺-based energy storage devices. We believe this study will propose a promising avenue to design advanced hierarchical nanostructures of ternary or binary conversion-type materials for PIBs, PIHCs, or even for extensive energy storage.

Self-induced matrix with Li-ion storage activity in ultrathin CuMnO2 nanosheets electrode

Conversion anode materials such as Mn₃O₄ draw much attention due to their considerable theoretical capacity for lithium-ion batteries (LIBs). However, poor conductivity, slow solid-state Li-ion diffusion, and huge volume expansion of the active materials during charge/discharge lead to unsatisfied electrochemical performance. Despite several strategies like nanocrystallization, fabricating hierarchical nanostructures, and introducing a matrix are valid to address these crucial issues, the achieved electrochemical performance still needs to be further enhanced. What is worse, the matrix with less or no Li-ion storage activity may lower the achieved capacity of the electrodes. Herein, ultra-thin CuMnO₂ nanosheets with the thickness of 5-8 nm were evaluated for LIBs. The ultra-thin sheet-like nanostructure offers sufficient contact areas with electrolyte and shortens the Li-ion diffusion distance. Moreover, the in-situ generated Mn and Cu along with their oxides could play the role of matrix and conductive agent in turn at different stages, relieving the stress brought by volume expansion. Therefore, the as-prepared ultra-thin CuMnO₂ nanosheets electrode displays a remarkable reversible capacity, long cycling stability, and outstanding rate capability (a reversible capacity of 1160.5 mAh g^-1 at 0.1A g^-1 was retained after 100 cycles with a capacity retention of 95.1 %, and 717.8 mAh g^-1 at 2.0 A g^-1 after 400 cycles).

Cu2O/CeO2 Photoelectrochemical Water Splitting: A Nanocomposite with an Efficient Interfacial Transmission Path under the Co-action of p-n Heterojunction and Micro-mesocrystals

Cu 2 O is an ideal p-type material for photoelectrochemical (PEC) hydrogen evolution, while serious electron-hole recombination and photocorrosion restrict its further improvement of the PEC activity. In this work, CeO 2 nanoparticles (NPs) self-assemble on the Cu 2 O octahedra surface, successfully constructing Cu 2 O/CeO 2 structure in which p-n heterojunction and micro-mesocrystals (m-MCs) structure work together. The optimum Cu 2 O/CeO 2 composite without the use of any cocatalyst exhibits 5 times higher photocurrent density (4.63 mA cm -2 at 0 V versus the reversible hydrogen electrode) than that of Cu 2 O octahedra, which is better than most Cu 2 O-based photocathodes without cocatalyst and even comparable with the advanced Cu 2 O-based photocathodes. The hydrogen production of the optimal Cu 2 O/CeO 2 (Faradaic efficiency of ~100%) is 17.5 times higher than that of pure Cu 2 O octahedra and the photocurrent shows almost no decay under the 12 h stability test. The delicately designed Cu 2 O/CeO 2 structure in this work provides reference and inspiration for the design of cathodes materials.

AgCu@CuO aerogels with peroxidase-like activities and photoelectric responses for sensitive biosensing

Photoelectrochemical (PEC) enzymatic biosensors integrate the excellent selectivity of enzymes and high sensitivity of PEC bioanalysis, but the drawbacks such as high cost, poor stability, and tedious immobilization of natural enzymes on photoelectrodes severely suppress their applications. AgCu@CuO aerogel-based photoelectrode materials with both remarkable enzyme-like activities and outstanding photoelectric properties were innovatively designed and synthesized to evaluate the activity of xanthine oxidase with a wide linear detection range and a low limit of detection.

0D/3D coupling of g-C3N4 QDs/hierarchical macro-mesoporous CuO-SiO2 for high-efficiency norfloxacin removal in photo-Fenton-like processes

Photo-Fenton process is an advanced oxidation technology, which is used to eliminate organic pollutants in environmental pollution. In this paper, g-C₃N₄ quantum dots incorporated hierarchical macro-mesoporous CuO-SiO₂ (MM SC-QDs) composite was successfully fabricated by a dual-template method combined with polystyrene sphere (PS) crystal and copolymer F127. With the presence of H₂O₂, MM SC-QDs exhibited excellent degradation performance against the antibiotic pollutant norfloxacin (NOR) under visible-light assisted heterogeneous Fenton process at neutral condition, which was 27 times higher than that of the Bulk CuO-SiO₂. Interconnected macropores, together with abundant mesopores effectively expand specific surface area and improve mass transfer. In addition, the g-C₃N₄ QDs served as the separation center for photogenerated charges, promoting the separation and migration of the charge carriers. Wherein, the long-lived photogenerated electrons were effectively separated and transferred to the surface of CuO-SiO₂, which accelerated the reduction rate of Cu²⁺ to Cu⁺, enhancing the photo-Fenton-like catalytic activity. This stable, efficient, and environmentally friendly Cu-based heterogeneous photo-Fenton-like catalyst is expected to become an effective implementation in organic pollution removal. Meanwhile, this paper proves that Cu-based materials can activate H₂O₂ to generate singlet oxygen (¹O₂) for the degradation of organic pollutants. The transformation mechanism of ¹O₂ was clarified, which is helpful to better understand the Fenton-like reaction process of Cu-based materials.

In Situ Monitoring the Potassium-Ion Storage Enhancement in Iron Selenide with Ether-Based Electrolyte

As one of the promising anode materials, iron selenide has received much attention for potassium-ion batteries (KIBs). Nevertheless, volume expansion and sluggish kinetics of iron selenide result in the poor reversibility and stability during potassiation-depotassiation process. In this work, we develop iron selenide composite matching ether-based electrolyte for KIBs, which presents a reversible specific capacity of 356 mAh g^-1 at 200 mA g^-1 after 75 cycles. According to the measurement of mechanical properties, it is found that iron selenide composite also exhibits robust and elastic solid electrolyte interphase layer in ether-based electrolyte, contributing to the improvement in reversibility and stability for KIBs. To further investigate the electrochemical enhancement mechanism of ether-based electrolyte in KIBs, we also utilize in situ visualization technique to monitor the potassiation-depotassiation process. For comparison, iron selenide composite matching carbonate-based electrolyte presents vast morphology change during potassiation-depotassiation process. When changing to ether-based electrolyte, a few minor morphology changes can be observed. This phenomenon indicates an occurrence of homogeneous electrochemical reaction in ether-based electrolyte, which results in a stable performance for potassium-ion (K-ion) storage. We believe that our work will provide a new perspective to visually monitor the potassium-ion storage process and guide the improvement in electrode material performance.

Realizing Fast Diffusion Kinetics Based on Three-Dimensional Ordered Macroporous Cu9S5@C for Potassium-Ion Batteries

Recently, potassium-ion batteries (PIBs) have been deemed to be a potential next-generation energy storage system for large-scale application because of the similar metal-ion storage mechanism as lithium-ion batteries and rich potassium resources. However, the large-sized potassium ion will cause sluggish reaction kinetics of K⁺ during charge/discharge processes, hindering the development of high-performance PIBs. In this work, copper sulfide embedded in three-dimensional ordered macroporous carbon framework (3DOM Cu₉S₅@C) was prepared through a sulfidation and subsequent ion exchange strategy with 3D ordered macropore Zn-based metal-organic frameworks as a precursor for an advanced PIBs anode. In particular, the interconnected 3D ordered macroporous structure can provide rapid transport channels for the large potassium ions and create a sufficient contact area for solid electrode materials and the liquid electrolyte, which is conducive to improve the ionic diffusion kinetics of batteries. Consequently, when the prepared 3DOM Cu₉S₅@C composite was used as a PIBs anode material, it shows a remarkable potassium storage rate capacity of 170 mA h g^-1 at 2.0 A g^-1 and an excellent cycling stability of 316 mA h g^-1 at 100 mA g^-1 after 200 cycles.

In-situ growth of Cu(2-methylimidazole imidazole)2 on Cu2O polyhedrons for high-performance potassium-ion batteries

In this work, Cu₂O/Cu(2-MeIm)₂ core-shell structure was designed and used as an anode for potassium-ion batteries. The Cu₂O core not only ensured a high energy density through surface redox reactions, but also served as a copper-ion reservoir to keep the stability of skeleton structure of Cu(2-MeIm)₂ shell during electrochemical process. The Cu(2-MeIm)₂ shell, in turn, not only provided high power through rapid K⁺ adsorption/desorption, but also acted as an artificial solid electrolyte interphase layer and accommodated volumetric change during K⁺ intercalation/de-intercalation. The as-designed composite material was studied by X-ray diffraction, thermo gravimetric, Fourier transform infrared, nitrogen adsorption-desorption, X-ray photoelectron spectroscopic and electron microscopic characterizations. As an anode for potassium-ion batteries, it was galvanostatically discharged and charged to study its electrochemical properties, such as Coulombic efficiency, capacity retention and rate performance, and cyclic voltammetry curves were also tested to reveal its K-storage mechanism.

Face-to-Face Growth of Wafer-Scale 2D Semiconducting MOF Films on Dielectric Substrates

The preparation of large-area 2D conductive metal-organic framework (MOF) films remains highly desirable but challenging. Here, inspired by the capillary phenomenon, a face-to-face confinement growth method to grow conductive 2D Cu₂ (TCPP) (TCPP = meso-tetra(4-carboxyphenyl)porphine) MOF films on dielectric substrates is developed. Trace amounts of solutions containing low-concentration Cu²⁺ and TCPP are pumped cyclically into a micropore interface to produce this growth. The crystal structures are confirmed with various characterization techniques, which include high-resolution atomic force microscopy and cryogenic transmission electron microscopy (Cryo-TEM). The Cu₂ (TCPP) MOF film exhibit an electrical conductivity of ≈0.007 S cm^-1 , which is approximately four orders of magnitude higher than other carboxylic-acid-based MOF materials (10^-6 S cm^-1 ). Other wafer-scale conductive MOF films such as M₃ (HHTP)₂ (M = Cu, Co, and Ni; HHTP = 2,3,6,7,10,11-triphenylenehexol) can be produced utilizing this strategy and suggests this method has widescale applicability potential.

Encapsulating V2O3 Nanoparticles in Hierarchical Porous Carbon Nanosheets via C-O-V Bonds for Fast and Durable Potassium-Ion Storage

Vanadium oxide (V₂O₃) has been considered as a promising anode material for potassium-ion batteries (PIBs), but challenging as well for the low electron/ion conductivity and poor structural stability. To tackle these issues, herein, a novel sheetlike hybrid nanoarchitecture constructed by uniformly encapsulating V₂O₃ nanoparticles in amorphous carbon nanosheets (V₂O₃@C) with the generation of C-O-V bonding is presented. Such a subtle architecture effectively facilitates the infiltration of electrolyte, relieves the mechanical strain, and reduces the potassium-ion diffusion distance during the repetitive charging/discharging processes. The generated C-O-V bonding not only accelerated charge transfer across the carbon-V₂O₃ interface but also strengthened the structural stability. Benefiting from the synergistic effects, the as-prepared V₂O₃@C nanosheets display fast and durable potassium storage behaviors with a reversible capacity of 116.6 mAh g^-1 delivered at 5 A g^-1, and a specific capacity of 147.9 mAh g^-1 retained after 1800 cycles at a high current density of 2 A g^-1. Moreover, the insertion/extraction mechanism of V₂O₃@C nanosheets in potassium-ion storage is systematically demonstrated by electrochemical analysis and ex situ technologies. This study will shed light on the fabricating of other metal oxides anodes for high-performance PIBs and beyond.

Stable CuO with variable valence states cooperated with active Co2+ as catalyst/co-catalyst for oxygen reduction/methanol oxidation reactions

Catalysts/co-catalysts for cathodic oxygen reduction and anodic methanol oxidation reactions (ORR/MOR) play the major roles in promoting the commercialization of direct methanol fuel cells. Herein, bimetallic zeolite-imidazolate-frameworks (CoZn-ZIFs) is used as precursor to synthesize Co₃O₄@NPC/CuO composites as catalysts for ORR and Pt supports/co-catalysts for MOR. The ORR activity (E_1/2 = 0.83 V) and long-term stability (activity retention of 85.5% after 30,000 s) of Co₃O₄@NPC/CuO-400 (400 °C) dodecahedron are better than those of commercial Pt/C (10 wt%) in alkaline electrolytes. The surface CuO with variable valence states (Cu⁰ and Cu²⁺) can be used as both the active component for ORR and the protective layer for Co₃O₄ to enhance catalytic stability. Partial removal of CoO_x from carbon framework promotes the exposure of highly active sites (Co²⁺) on the Co₃O₄. For MOR, the mass activity of Pt-Co₃O₄@NPC/CuO-400 (5 wt%) (1947 mA mg_Pt^-1) is much higher than that of Pt/C (751 mA mg_Pt^-1), mainly attributing to that the Pt active sites are uniformly dispersed on Co₃O₄@NPC/CuO support. The strong interaction between Pt and CuO can reduce the bond strength of Pt-CO to enhance CO resistance. Co₃O₄ can activate H₂O molecules to provide sufficient OH^- species to promote MOR. This study provides a new idea for preparation of active ORR catalysts and MOR co-catalyst from bimetallic ZIFs.

Ultra-small Fe3O4 nanodots encapsulated in layered carbon nanosheets with fast kinetics for lithium/potassium-ion battery anodes

Iron oxides are regarded as promising anodes for both lithium-ion batteries (LIBs) and potassium-ion batteries (KIBs) due to their high theoretical capacity, abundant reserves, and low cost, but they are also facing great challenges due to the sluggish reaction kinetics, low electronic conductivity, huge volume change, and unstable electrode interphases. Moreover, iron oxides are normally prepared at high temperature, forming large particles because of Ostwald ripening, and exhibiting low electronic/ionic conductivity and unfavorable mechanical stability. To address those issues, herein, we have synthesized ultra-small Fe₃O₄ nanodots encapsulated in layered carbon nanosheets (Fe₃O₄@LCS), using the coordination interaction between catechol and Fe³⁺, demonstrating fast reaction kinetics, high capacity, and typical capacitive-controlled electrochemical behaviors. Such Fe₃O₄@LCS nanocomposites were derived from coordination compounds with layered structures via van der Waals's force. Fe₃O₄@LCS-500 (annealed at 500 °C) nanocomposites have displayed attractive features of ultra-small particle size (∼5 nm), high surface area, mesoporous and layered feature. When used as anodes, Fe₃O₄@LCS-500 nanocomposites delivered exceptional electrochemical performances of high reversible capacity, excellent cycle stability and rate performance for both LIBs and KIBs. Such exceptional performances are highly associated with features of Fe₃O₄@LCS-500 nanocomposites in shortening Li/K ion diffusion length, fast reaction kinetics, high electronic/ionic conductivity, and robust electrode interphase stability.

Ultra-small Fe₃O₄ nanodots encapsulated in layered carbon nanosheet nanocomposites were synthesized, showing fast reaction kinetics, high conductivity, and robust stability.

Facile fabrication of hollow CuO nanocubes for enhanced lithium/sodium storage performance

Facile and low-toxicity fabrication of CuO hollow nanocubes towards high-performance alkali ion batteries.

Regulating the Electronic Structure and Water Adsorption Capability by Constructing Carbon-Doped CuO Hollow Spheres for Efficient Photocatalytic Hydrogen Evolution

Copper(II) oxide featuring a narrow bandgap and low toxicity has been frequently applied in the visible-light-driven photocatalytic hydrogen evolution, but it suffers from large intrinsic overpotential and low water adsorption capacity. Herein, we report a self-templated strategy for the preparation of carbon-doped CuO hollow spheres (C-CuO HSs) through thermal transformation of a hierarchical MOF. The hierarchical Cu-MOFs not only act as a template to form interior voids during the thermal transformation, but also serve as precursors to dope C atoms into the CuO lattice. The as-synthesized C-CuO HSs exhibits remarkable photocatalytic performance with a H₂ evolution rate of 67.3 mmol/g/h and the apparent quantum efficiency of 25.3 % at 520 nm in the present of eosin-Y photosensitizer. The high performance of C-CuO HSs is attributed to the hierarchical porous structure and modulated electronic structure of CuO by C-doping with well exposed reactive sites, high water adsorption capability, and low water reduction reaction barrier. The results presented in this work might shed light on the design of high-performance photocatalysts for various energy-related applications.

Post-Lithium-Ion Battery Era: Recent Advances in Rechargeable Potassium-Ion Batteries

Lithium shortage and the growing demand for electricity storage has encouraged researchers to look for new alternative energy-storage materials. Due to abundant potassium resources, similar redox potential to lithium metal, and low cost, potassium-ion batteries (PIBs), as one of the promising alternatives, have been applied in energy-storage research recently. However, PIBs do not have adequate competition in their electrochemical efficiency because the molar volume of potassium ions is higher than those in lithium and sodium ions. Therefore, for better application and development of PIBs, finding suitable anode and cathode materials is currently the most important task. The latest developments in electrode materials for PIBs have been outlined in depth in this review. It focuses on the structural design and synthetic methods for novel electrode materials, ingenious optimization and tuning strategies, and explains the intrinsic reaction mechanism. The effects of organic electrolytes and aqueous electrolytes on battery systems are compared and clarified. Finally, theoretical and viable insights are given to the challenges posed by the creation and practical application of PIBs in the future.

Advanced Anode Materials of Potassium Ion Batteries: from Zero Dimension to Three Dimensions

Potassium ion batteries (PIBs) with the prominent advantages of sufficient reserves and economical cost are attractive candidates of new rechargeable batteries for large-grid electrochemical energy storage systems (EESs). However, there are still some obstacles like large size of K⁺ to commercial PIBs applications. Therefore, rational structural design based on appropriate materials is essential to obtain practical PIBs anode with K⁺ accommodated and fast diffused. Nanostructural design has been considered as one of the effective strategies to solve these issues owing to unique physicochemical properties. Accordingly, quite a few recent anode materials with different dimensions in PIBs have been reported, mainly involving in carbon materials, metal-based chalcogenides (MCs), metal-based oxides (MOs), and alloying materials. Among these anodes, nanostructural carbon materials with shorter ionic transfer path are beneficial for decreasing the resistances of transportation. Besides, MCs, MOs, and alloying materials with nanostructures can effectively alleviate their stress changes. Herein, these materials are classified into 0D, 1D, 2D, and 3D. Particularly, the relationship between different dimensional structures and the corresponding electrochemical performances has been outlined. Meanwhile, some strategies are proposed to deal with the current disadvantages. Hope that the readers are enlightened from this review to carry out further experiments better.

Polymer blend directed anisotropic self-assembly toward mesoporous inorganic bowls and nanosheets

Anisotropic mesoporous inorganic materials have attracted great interest due to their unique and intriguing properties, yet their controllable synthesis still remains a great challenge. Here, we develop a simple synthesis approach toward mesoporous inorganic bowls and two-dimensional (2D) nanosheets by combining block copolymer (BCP)-directed self-assembly with asymmetric phase migration in ternary-phase blends. The homogeneous blend solution spontaneously self-assembles to anisotropically stacked hybrids as the solvent evaporates. Two minor phases-BCP/inorganic precursor and homopolystyrene (hPS)-form closely stacked, Janus domains that are dispersed/confined in the major homopoly(methyl methacrylate) (hPMMA) matrix. hPS phases are partially covered by BCP-rich phases, where ordered mesostructures develop. With increasing the relative amount of hPS, the anisotropic shape evolves from bowls to 2D nanosheets. Benefiting from the unique bowl-like morphology, the resulting transition metal oxides show promise as high-performance anodes in potassium-ion batteries.

Boosting the Potassium-Ion Storage Performance in Soft Carbon Anodes by the Synergistic Effect of Optimized Molten Salt Medium and N/S Dual-Doping

Soft carbon is attracting tremendous attention as a promising anode material for potassium-ion batteries (PIBs) because of its graphitizable structure and adjustable interlayer distance. Herein, nitrogen/sulfur dual-doped porous soft carbon nanosheets (NSC) have been prepared with coal tar pitch as carbon precursors in an appropriate molten salt medium. The molten salt medium and N/S dual-doping are responsible for the formation of nanosheet-like morphology, abundant microporous channels with a high surface area of 436 m² g^-1, expanded interlamellar spacing of 0.378 nm, and enormous defect-induced active sites. These structural features are crucial for boosting potassium-ion storage performance, endowing the NSC to deliver a high potassiation storage capacity of 359 mAh g^-1 at 100 mA g^-1 and 115 mAh g^-1 at 5.0 A g^-1, and retaining 92.4% capacity retention at 1.0 A g^-1 after 1000 cycles. More importantly, the pre-intercalation of K atom from the molten salts helps improve the initial Coulombic efficiency to 50%, which outperforms those of the recently reported carbon anode materials with large surface areas. The density functional theory calculations further illuminate that the N/S dual-doping can facilitate the adsorption of K-ion in carbon materials and decrease the ion diffusion energy barrier during the solid-state charge migration.

Boosting glucose oxidation by constructing Cu–Cu2O heterostructures

An octahedral Cu–Cu₂O heterostructure with loose and porous structure was fabricated and exhibits enhanced electrocatalytic activity towards glucose oxidation.