Nano-Sized Structurally Disordered Metal Oxide Composite Aerogels as High-Power Anodes in Hybrid Supercapacitors

Advances in Mn-Based MOFs and Their Derivatives for High-Performance Supercapacitor

As the most widely used metal material in supercapacitors, manganese (Mn)-based materials possess the merits of high theoretical capacitance, stable structure as well as environmental friendliness. However, due to poor conductivity and easy accumulation, the practical capacitance of Mn-based materials is far lower than that of theoretical value. Therefore, accurate structural adjustment and controllable strategies are urgently needed to optimize the electrochemical properties of Mn-based materials. Metal-organic frameworks (MOFs) are porous materials with high specific surface area (SSA), tunable pore size, and controllable structure. These features make them attractive as precursors or scaffold for the synthesis of metal-based materials and composites, which are important for electrochemical energy storage applications. Therefore, a timely and comprehensive review on the classification, design, preparation and application of Mn-based MOFs and their derivatives for supercapacitors has been given in this paper. The recent advancement of Mn-based MOFs and their derivatives applied in supercapacitor electrodes are particularly highlighted. Finally, the challenges faced by Mn-MOFs and their derivatives for supercapacitors are summarized, and strategies to further improve their performance are proposed. The aspiration is that this review will serve as a beneficial compass, guiding the logical creation of Mn-based MOFs and their derivatives in the future.

Amorphization-induced abundant coordinatively unsaturated Ni active sites in NiCo(OH)2 for boosting catalytic OER and HER activities at high current densities for water-electrolysis

The large overpotential required for oxygen evolution reaction (OER) is one of the major factors limiting the efficiency of electrochemical water-electrolysis for hydrogen production. In this work, to decrease OER energy barrier and obtain low overpotential, amorphous-crystalline NiCo(OH)2 nanoplates are in-situ grown on nickel foam surface to form a catalyst-based electrode (ac-NiCo(OH)2/NF) for water-electrolysis application. As the inner amorphization of NiCo(OH)2 results in increased electron density of the metal sites, leading to the formation of tensile Ni-O bond, the coordinatively unsaturated Ni sites in the down-shift d-band centers toward Fermi level can lower the antibonding states. This can lead to optimized adsorption and desorption energies for oxygen-containing intermediates for OER. As expected, the prepared ac-NiCo(OH)2/NF electrode presents a low overpotential of 364 mV to deliver 1000 mA cm-2 toward OER with impressively high robust stability. When this electrocatalyst electrode serves as both the anode and cathode, the assembled anion exchange membrane (AEM) electrolyser only needs a cell voltage of 1.68 V to drive the overall water-electrolysis process at a current density of 10 mA cm-2.

Heterostructures of MXenes and transition metal oxides for supercapacitors: an overview

MXenes are a large family of two dimensional (2D) materials with high conductivity, redox activity and compositional diversity that have become front-runners in the materials world for a diverse range of energy storage applications. High-performing supercapacitors require electrode materials with high charge storage capabilities, excellent electrical conductivity for fast electron transfer, and the ability of fast charging/discharging with good cyclability. While MXenes show many of these properties, their energy storage capability is limited by a narrow electrochemically stable potential window due to irreversible oxidation under anodic potentials. Although transition metal oxides (TMOs) are often high-capacity materials with high redox activity, their cyclability and poor rate performance are persistent challenges because of their dissolution in aqueous electrolytes and mediocre conductivity. Forming heterostructures of MXenes with TMOs and using hybrid electrodes is a feasible approach to simultaneously increase the charge storage capacity of MXenes and improve the cyclability and rate performance of oxides. MXenes could also act as conductive substrates for the growth of oxides, which could perform as spacers to stop the aggregation of MXene sheets during charging/discharging and help in improving the supercapacitor performance. Moreover, TMOs could increase the interfacial contact between MXene sheets and help in providing short-diffusion ion channels. Hence, MXene/TMO heterostructures are promising for energy storage. This review summarizes the most recent developments in MXene/oxide heterostructures for supercapacitors and highlights the roles of individual components.

Biomimetic Construction of Ferrite Quantum Dot/Graphene Heterostructure for Enhancing Ion/Charge Transfer in Supercapacitors

Spinel ferrites are regarded as promising electrode materials for supercapacitors (SCs) in virtue of their low cost and high theoretical specific capacitances. However, bulk ferrites suffer from limited electrical conductivity, sluggish ion transport, and inadequate active sites. Therefore, rational structural design and composition regulation of the ferrites are approaches to overcome these limitations. Herein, a general biomimetic mineralization synthetic strategy is proposed to synthesize ferrite (XFe₂ O₄ , X = Ni, Co, Mn) quantum dot/graphene (QD/G) heterostructures. Anchoring ferrite QD on the graphene sheets not only strengthens the structural stability, but also forms the electrical conductivity network needed to boost the ion diffusion and charge transfer. The optimized NiFe₂ O₄ QD/G heterostructure exhibits specific capacitances of 697.5 F g^-1 at 1 A g^-1 , and exceptional cycling performance. Furthermore, the fabricated symmetrical SCs deliver energy densities of 24.4 and 17.4 Wh kg^-1 at power densities of 499.3 and 4304.2 W kg^-1 , respectively. Density functional theory calculations indicate the combination of NiFe₂ O₄ QD and graphene facilitates the adsorption of potassium atoms, ensuring rapid ion/charge transfer. This work enriches the application of the biomimetic mineralization synthesis and provides effective strategies for boosting ion/charge transfer, which may offer a new way to develop advanced electrodes for SCs.

Dispersible SnO2 :Sb and TiO2 Nanocrystals After Calcination at High Temperature

High-temperature treatment of functional nanomaterials, through postsynthesis calcination, often represents an important step to unlock their full potential. However, such calcination steps usually severely limit the preparation of colloidal solutions of the nanoparticles due to the formation of sintered agglomerates. Herein, a simple route is reported to obtain colloidal solutions of calcined n-conductive antimony doped tin oxide (ATO) as well as titanium dioxide (TiO₂ ) nanoparticles without the need for additional sacrificial materials. This is achieved by making use of the reduced contact between individual nanoparticles when they are assembled into aerogels. Following the calcination of the aerogels at 500 °C, redispersion of the nanoparticles into stable colloidal solutions with various solvents can be achieved. Although a slight degree of sintering is inevitable, the size of the resulting aggregates in solution is still remarkably small with values below 30 nm.

Oxygen-Vacancy Abundant Nanoporous Ni/NiMnO3/MnO2@NiMn Electrodes with Ultrahigh Capacitance and Energy Density for Supercapacitors

High-performance energy storage devices (HPEDs) play a critical role in the realization of clean energy and thus enable the overarching pursuit of nonpolluting, green technologies. Supercapacitors are one class of such lucrative HPEDs; however, a serious limiting factor of supercapacitor technology is its sub-par energy density. This report presents hitherto unchartered pathway of physical deformation, chemical dealloying, and microstructure engineering to produce ultrahigh-capacitance, energy-dense NiMn alloy electrodes. The activated electrode delivered an ultrahigh specific-capacitance of 2700 F/cm³ at 0.5 A/cm³. The symmetric device showcased an excellent energy density of 96.94 Wh/L and a remarkable cycle life of 95% retention after 10,000 cycles. Transmission electron microscopy and atom probe tomography studies revealed the evolution of a unique hierarchical microstructure comprising fine Ni/NiMnO₃ nanoligaments within MnO₂-rich nanoflakes. Theoretical analysis using density functional theory showed semimetallic nature of the nanoscaled oxygen-vacancy-rich NiMnO₃ structure, highlighting enhanced carrier concentration and electronic conductivity of the active region. Furthermore, the geometrical model of NiMnO₃ crystals revealed relatively large voids, likely providing channels for the ion intercalation/de-intercalation. The current processing approach is highly adaptable and can be applied to a wide range of material systems for designing highly efficient electrodes for energy-storage devices.

Study on the Deterioration Mechanism of Pb on TiO2 Oxygen Sensor

Previous studies have shown that the pollutants in exhaust gas can cause performance deterioration in air-fuel oxygen sensors. Although the content of Pb in fuel oil is as low as 5 mg/L, the effect of long-term Pb accumulation on TiO2 oxygen sensors is still unclear. In this paper, the influence mechanism of Pb-containing additives in automobile exhaust gas on the response characteristics of TiO2 oxygen sensors was simulated and studied by depositing Pb-containing pollutants on the surface of a TiO2 sensitive film. It was found that the accumulation of Pb changed the surface gas adsorption state and reduced the activation energy of TiO2, thus affecting the steady-state response voltage and response speed of the TiO2-based oxygen sensor.

Constructing hollow nanotube-like amorphous vanadium oxide and carbon hybrid via in-situ electrochemical induction for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries receive more and more attentions on account of their low cost, high theoretical density and inherent safety. Nevertheless, the lack of suitable cathode materials with excellent performance still severely impedes the development of aqueous zinc-ion batteries. Herein, an in-situ electrochemical induction strategy is developed to prepare hollow nanotube-like amorphous vanadium oxide and carbon (a-V₂O₅@C) hybrid and its electrochemical performance is investigated comprehensively as cathode materials for aqueous zinc-ion batteries. Benefitting from the unique amorphous structure of V₂O₅ and intimate contact between amorphous V₂O₅ and carbon, the a-V₂O₅@C hybrid possess the abundant ion storage sites, isotropic ion diffusion routes and excellent conductivity. As a result, the a-V₂O₅@C hybrid cathode shows outstanding specific capacity of 448 mAh g^-1 at 0.15 A g^-1. Impressively, the a-V₂O₅@C hybrid cathode exhibits superior cycling stability, even when cycling at high current density of 10 A g^-1, that the 96.5% specific capacity retention can be gained over 1500 cycles, corresponding to an average specific capacity loss of only 0.0023% per cycle. Furthermore, the mechanism involved is illustrated by systematical characterizations. Therefore, this work affords a new way for developing high-performance cathode materials for aqueous zinc-ion batteries.

Scalable Spray Drying Production of Amorphous V2 O5 -EGO 2D Heterostructured Xerogels for High-Rate and High-Capacity Aqueous Zinc Ion Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) are promising in stationary grid energy storage due to their advantages in safety and cost-effectiveness, and the search for competent cathode materials is one core task in the development of ZIBs. Herein, the authors design a 2D heterostructure combining amorphous vanadium pentoxide and electrochemically produced graphene oxide (EGO) using a fast and scalable spray drying technique. The unique 2D heterostructured xerogel is achieved by controlling the concentration of EGO in the precursor solution. Driven by the improved electrochemical kinetics, the resultant xerogel can deliver an excellent rate capability (334 mAh g^-1 at 5 A g^-1 ) as well as a high specific capacity (462 mAh g^-1 at 0.2 A g^-1 ) as the cathode material in ZIB. It is also shown that the coin cell constructed based on spray-dried xerogel can output steady, high energy densities over a broad power density window. This work provides a scalable and cost-effective approach for making high performance electrode materials from cheap sources through existing industrialized materials processing.

Secondary Bonding Channel Design Induces Intercalation Pseudocapacitance toward Ultrahigh-Capacity and High-Rate Organic Electrodes

Organic electrode materials have shown extraordinary promise for green and sustainable electrochemical energy storage devices, but usually suffer from low specific capacity and poor rate capability, which is largely caused by inactive components and diffusion-controlled Li⁺ intercalation. Herein, high-rate Li⁺ intercalation pseudocapacitance in organic molecular crystals is achieved through introducing weak secondary bonding channels, far exceeding their theoretical capacity based on redox chemistry at functional groups. The authors' combined experimentally electrochemical characterization with first-principles calculations show that the heterocyclic organic molecule 2,2'-bipyridine-4,4'-dicarboxylic acid (BPDCA) crystal permits a four-electron redox reaction at conventional CO and CN groups and a six-electron intercalation pseudocapacitance along conjugated alkene hydrogen bonding channels (H₂ NC₅ H⋯OC(OH)) and heterocyclic aromatic stacking channels (C₅ H₃ N⋯NH₃ C₅ ). The BPDCA electrode delivers an ultrahigh reversible capacity of 1206 mAh g^-1 at 0.5 A g^-1 and an exceptional rate capability. A 4.8 V high-energy/power-density BPDCA anode-based hybrid Li-ion capacitor is thus realized. This work opens a new avenue for developing organic intercalation pseudocapacitive materials via secondary bonding structure design.

Amorphous anion-rich titanium polysulfides for aluminum-ion batteries

The strong electrostatic interaction between Al³⁺ and close-packed crystalline structures, and the single-electron transfer ability of traditional cationic redox cathodes, pose challenged for the development of high-performance rechargeable aluminum batteries. Here, to break the confinement of fixed lattice spacing on the diffusion and storage of Al-ion, we developed a previously unexplored family of amorphous anion-rich titanium polysulfides (a-TiS _x , x = 2, 3, and 4) (AATPs) with a high concentration of defects and a large number of anionic redox centers. The AATP cathodes, especially a-TiS₄, achieved a high reversible capacity of 206 mAh/g with a long duration of 1000 cycles. Further, the spectroscopy and molecular dynamics simulations revealed that sulfur anions in the AATP cathodes act as the main redox centers to reach local electroneutrality. Simultaneously, titanium cations serve as the supporting frameworks, undergoing the evolution of coordination numbers in the local structure.

Boosting Electrochemical Performance of Hematite Nanorods via Quenching-Induced Alkaline Earth Metal Ion Doping

Ion doping in transition metal oxides is always considered to be one of the most effective methods to obtain high-performance electrochemical supercapacitors because of the introduction of defective surfaces as well as the enhancement of electrical conductivity. Inspired by the smelting process, an ancient method, quenching is introduced for doping metal ions into transition metal oxides with intriguing physicochemical properties. Herein, as a proof of concept, α-Fe2O3 nanorods grown on carbon cloths (α-Fe2O3@CC) heated at 400 °C are rapidly put into different aqueous solutions of alkaline earth metal salts at 4 °C to obtain electrodes doped with different alkaline earth metal ions (M-Fe2O3@CC). Among them, Sr-Fe2O3@CC shows the best electrochemical capacitance, reaching 77.81 mF cm−2 at the current of 0.5 mA cm−2, which is 2.5 times that of α-Fe2O3@CC. The results demonstrate that quenching is a feasible new idea for improving the electrochemical performances of nanostructured materials.

A long-term stable aqueous aluminum battery electrode based on one-dimensional molybdenum-tantalum oxide nanotube arrays

Aluminum ion aqueous batteries (AIBs) are among the most promising candidates for high energy density devices due to the multivalent redox processes associated with Al³⁺ ion intercalation. However, only a few stable AIB electrode materials have been reported so far. MoO₃ is a very promising electrode material due to its octahedral layered crystal structure which can accommodate multivalent cation by intercalation. However, the poor electrochemical stability of MoO₃ and the sluggish intercalation kinetics of Al³⁺ ion in Mo oxides electrodes limit its practical application. In this work, we propose a strategy to overcome such shortcomings of MoO₃ by fabricating electrodes composed of self-ordered one-dimensional (1D) MoTaO_x nanotubes synthesized via electrochemical anodization of Mo-Ta alloy substrates. We show that this approach allows for direct incorporation of Ta in the Mo oxide nanotubes. The resulting MoTaO_x nanotubes, composed of octahedral MoO₃ and rhombohedral Mo₂Ta₂O₁₁ phases, exhibit remarkable electrochemical stability and Al-ion storage properties in aqueous electrolytes that are superior to that of pristine Mo oxide or other most efficient electrode materials reported to date. Such MoTaO_x nanotube-based electrodes can achieve a specific capacity of 1180 mA h cm^-3 (337 mA h g^-1, 141 μA h cm^-2) at 1.25 A cm^-3 (∼0.35 A g^-1, 0.15 mA cm^-2). More importantly, the capacity retention of such nanotube array electrodes remains above 83% of the initial capacity after 3000 cycles.

S, O dual-doped porous carbon derived from activation of waste papers as electrodes for high performance lithium ion capacitors

To circumvent the imbalances of electrochemical kinetics and charge-storage capacity between Li⁺ ion battery anodes and capacitive cathodes in lithium-ion capacitors (LICs), dual carbon based LICs are constructed and investigated extensively. Herein, S, O dual-doped 3D net-like porous carbon (S-NPC) is prepared using waste paper as the carbon source through a facile solvothermal treatment and chemical activation. Benefiting from the combination effect of the rich S,O-doping (about 2.1 at% for S, and 9.0 at% for O), high surface area (2262 m² g^-1) and interconnected porous network structure, the S-NPC-40 material exhibits excellent electrochemical performance as both cathode material and anode material for LICs. S, O doping not only increases the pseudocapacity but also improves the electronic conductivity, which is beneficial to reduce the mismatch between the two electrodes. The S-NPC-40//S-NPC-40 LIC delivers high energy densities of 176.1 and 77.8 W h kg^-1 at power densities of 400 and 20 kW kg^-1, respectively, as well as superior cycling stability with 82% capacitance retention after 20 000 cycles at 2 A g^-1. This research provides an efficient method to convert waste paper to porous carbon electrode materials for high performance LIC devices.

Synthesis of Two-Dimensional Sr-Doped LaNiO3 Nanosheets with Improved Electrochemical Performance for Energy Storage

Designing a novel, efficient, and cost-effective nanostructure with the advantage of robust morphology and outstanding conductivity is highly promising for the electrode materials of high-performance electrochemical storage device. In this paper, a series of honeycombed perovskite-type Sr-doped LaNiO₃ nanosheets with abundant porous structure were successfully synthesized by accurately controlling the Sr-doped content. The study showed that the optimal LSNO-0.4 (La_0.6Sr_0.4NiO_3-δ) electrode exhibited excellent electrochemical performance, which showed a high capacity of 115.88 mAh g⁻¹ at 0.6 A g⁻¹. Furthermore, a hybrid supercapacitor device (LSNO//AC) based on LSNO-0.4 composites and activated carbon (AC) showed a high energy density of 17.94 W h kg⁻¹, a high power density of 1600 W kg⁻¹, and an outstanding long-term stability with 104.4% capacity retention after 16,000 cycles, showing an excellent electrochemical performance and a promising application as an electrode for energy storage.

Ultrafine Co0.85Se nanocrystals dispersed in 3D CNT network as a flexible free-standing anode for high-performance lithium-ion battery

A flexible free-standing film electrode with high pseudocapacitive contribution and strengthened cyclic stability was successfully prepared.

MoS2 encapsulated in three-dimensional hollow carbon frameworks for stable anode of sodium ion batteries

MoS₂ wrapped in nitrogen-doped three-dimensional hollow carbon frameworks is designed for improved sodium ion battery anode performance.

Three-Dimensional Topotactic Host Structure-Secured Ultrastable VP-CNO Composite Anodes for Long Lifespan Lithium- and Sodium-Ion Capacitors

Performance degradation of lithium/sodium-ion capacitors (LICs/SICs) mainly originates from anode pulverization, particularly the alloying and conversion types, and has spurred research for alternatives with an insertion mechanism. Three-dimensional (3D) topotactic host materials remain much unexplored compared to two-dimensional (2D) ones (graphite, etc.). Herein, vanadium monophosphide (VP) is designed as a 3D topotactic host anode. Ex situ electrochemical characterizations reveal that there are no phase changes during (de)intercalation, which follows the topotactic intercalation mechanism. Computational simulations also confirm the metallic feature and topotactic structure of VP with a spacious interstitial position for the accommodation of guest species. To boost the electrochemical performance, carbon nano-onions (CNOs) are coupled with 3D VP. Superior specific capacity and rate capability of VP-CNOs vs lithium/sodium can be delivered due to the fast ion diffusion nature. An exceptional capacity retention of above 86% is maintained after 20 000 cycles, benefitting from the topotactic intercalation process. The optimized LICs/SICs exhibit high energy/power densities and an ultrastable lifespan of 20 000 cycles, which outperform most of the state-of-the-art LICs and SICs, demonstrating the potential of VP-CNOs as insertion anodes. This exploration would draw attention with regard to insertion anodes with 3D topotactic host topology and provide new insights into anode selection for LICs/SICs.

Towards fast-charging technologies in Li+/Na+ storage: from the perspectives of pseudocapacitive materials and non-aqueous hybrid capacitors

Since the discovery of the pseudocapacitive behavior in RuO₂ by Sergio Trasatti and Giovanni Buzzanca in 1971, materials with pseudocapacitance have been regarded as promising candidates for high-power energy storage. Pseudocapacitance-involving energy storage is predominantly based on faradaic redox reactions, but at the same time the charge storage is not limited by solid-state ion diffusion. Besides the search for pseudocapacitive materials, their implementation into non-aqueous hybrid capacitors stands for the strategy to increase power density by a rational design of the battery structure. Composed of a battery-type anode and a capacitor-type cathode, such devices show great promise to integrate the merits of both batteries and capacitors. Today, the availability of fast-charging technologies is of fundamental importance for establishing electric vehicles on a mass scale. Therefore, from the perspective of materials and battery design, understanding the basics and the recent developments of pseudocapacitive materials and non-aqueous hybrid capacitors is of great importance. With this goal in mind, we introduce here the fundamentals of pseudocapacitance and non-aqueous hybrid capacitors. In addition, we provide an overview of the latest developments in this fast growing research field.

Niobium-Based Oxides Toward Advanced Electrochemical Energy Storage: Recent Advances and Challenges

Niobium-based oxides including Nb₂ O₅ , TiNb_x O_2+2.5x compounds, M-Nb-O (M = Cr, Ga, Fe, Zr, Mg, etc.) family, etc., as the unique structural merit (e.g., quasi-2D network for Li-ion incorporation, open and stable Wadsley- Roth shear crystal structure), are of great interest for applications in energy storage systems such as Li/Na-ion batteries and hybrid supercapacitors. Most of these Nb-based oxides show high operating voltage (>1.0 V vs Li⁺ /Li) that can suppress the formation of solid electrolyte interface film and lithium dendrites, ensuring the safety of working batteries. Outstanding rate capability is impressive, which can be derived from their fast intercalation pseudocapacitive kinetics. However, the intrinsic poor electrical conductivity hinders their energy storage applications. Various strategies including structure optimization, surface engineering, and carbon modification are effectively used to overcome the issues. This review provides a comprehensive summary on the latest progress of Nb-based oxides for advanced electrochemical energy storage applications. Major impactful work is outlined, promising research directions, and various performance-optimizing strategies, as well as the energy storage mechanisms investigated by combining theoretical calculations and various electrochemical characterization techniques. In addition, challenges and perspectives for future research and commercial applications are also presented.

Encapsulation of Fe3O4 between Copper Nanorod and Thin TiO2 Film by ALD for Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are considered to be promising power sources due to their combination of high-rate capacitors and high-capacity batteries. However, development of a high-performance LIC is still restricted by the sluggish intercalation reaction and unsatisfied specific capacities in battery-type bulk anodes. To overcome these issues, herein, we utilize two-step atomic layer deposition (ALD) to realize a uniform coating of FeO _x and TiO₂ on CuO nanorods, which results in the formation of ternary CuO@FeO _x@TiO₂ composite. After further treatment in H₂/Ar atmosphere, the as-derived Fe₃O₄ is encapsulated between conductive Cu nanorod and hollow TiO₂ shell (denoted as Cu@Fe₃O₄@TiO₂). Owing to the rational design, the binder-free Cu@Fe₃O₄@TiO₂ electrode exhibits an ultrahigh Li-ion storage capacity (1585 mA h g^-1 at 0.2 A g^-1), superior rate capability, and excellent cycle performance (no decay after 1000 cycles), which could efficiently boost the energy-storage capability of LICs. By employing an anode of Cu@Fe₃O₄@TiO₂ and a cathode of activated carbon, the as-constructed full LIC device provides high energy//powder densities (154.8 Wh kg^-1 at 200 W kg^-1; 66.2 Wh kg^-1 at 30 kW kg^-1). These superior results demonstrate that ALD-enabled architectures hold great promise for synthesizing high-capacity anodes for LICs.

Bioinspired aerogel based on konjac glucomannan and functionalized carbon nanotube for controlled drug release

In this study, a facile marine bioinspired surface modification approach for carboxyl-functionalized multiwalled carbon nanotube (CCNT) and enhanced interfacial adhesion with the konjac glucomannan (KGM) matrix were illustrated to develop aerogels. Combined with FT-IR, XRD, Raman, TGA, XPS and SEM results, it was indicated that functionalized CCNT (PCCNT) is a reinforcer through hydrogen bond interactions in the aerogel formation process, which could be the main reason for the enhancement. The swelling and vitro release behavior of KGM/PCCNT aerogels were studied under two conditions using the drug 5-fluorouracil (5-FU). The release amount of 5-FU incorporated into KGM/PCCNT4 aerogel was about 48% at pH 1.2 and 62% at pH 6.8 after11 h, respectively. The results showed that the release rate of 5-FU from the KGM/PCCNT4 aerogel using PCCNT could be effectively controlled, suggesting potential applications for it as a drug carrier in targeted delivery in the biomedical filed.

Research Advances of Amorphous Metal Oxides in Electrochemical Energy Storage and Conversion

Amorphous metal oxides (AMOs) have aroused great enthusiasm across multiple energy areas over recent years due to their unique properties, such as the intrinsic isotropy, versatility in compositions, absence of grain boundaries, defect distribution, flexible nature, etc. Here, the materials engineering of AMOs is systematically reviewed in different electrochemical applications and recent advances in understanding and developing AMO-based high-performance electrodes are highlighted. Attention is focused on the important roles that AMOs play in various energy storage and conversion technologies, such as active materials in metal-ion batteries and supercapacitors as well as active catalysts in water splitting, metal-air batteries, and fuel cells. The improvements of electrochemical performance in metal-ion batteries and supercapacitors are reviewed regarding the enhancement in active sites, mechanical strength, and defect distribution of amorphous structures. Furthermore, the high electrochemical activities boosted by AMOs in various fundamental reactions are elaborated on and they are related to the electrocatalytic behaviors in water splitting, metal-air batteries, and fuel cells. The applications in electrochromism and high-conducting sensors are also briefly discussed. Finally, perspectives on the existing challenges of AMOs for electrochemical applications are proposed, together with several promising future research directions.

Cobalt tungsten oxide hydroxide hydrate (CTOHH) on DNA scaffold: an excellent bi-functional catalyst for oxygen evolution reaction (OER) and aromatic alcohol oxidation

CTOHH-DNA, a newly developed catalyst utilized for both electrocatalytic OER and aromatic alcohol oxidation reaction with excellent activities.

Scalable Fabrication of Core-Shell Sb@Co(OH)2 Nanosheet Anodes for Advanced Sodium-Ion Batteries via Magnetron Sputtering

Antimony (Sb) has captured extensive attention as a promising anode for sodium-ion batteries (SIBs) due to its high theoretical capacity and moderate sodiated potential but is held back from practical applications owing to its pulverization induced by dramatic volumetric variations during the (de)sodiation process. Herein, we report a core-shell Sb@Co(OH)₂ nanosheet anode fabricated via magnetron sputtering Sb onto the mass-productive Co(OH)₂ substrate anchored on stainless-steel mesh, which is scalable and suitable for flow-line production. In SIBs, the Sb@Co(OH)₂ anode displays superior rate performance (383.5 mAh/g at 30 A/g), high discharge capacity, and excellent stability. Compared with the sputtered Sb film electrode, the improved performance of the core-shell Sb@Co(OH)₂ nanosheet anode can be attributed to the open framework of the Co(OH)₂ substrate, not only accelerating the ion and electron transfer but also serving as the buffer for alleviating the volumetric variation and the supporting scaffold for prohibiting the aggregation. More importantly, the (de)sodiation mechanism of the Sb@Co(OH)₂ anode was explored by operando ( in situ) X-ray diffraction, and the similar alloying-dealloying processes (Sb ↔ Na _xSb ↔ Na₃Sb) for the 1st, 13th, and 30th cycles illustrate the excellent stability of the electrode.

An ordered mesoporous carbon nanosphere-encapsulated graphene network with optimized nitrogen doping for enhanced supercapacitor performance

Developing a simple strategy to simultaneously overcome the aggregation of graphene nanosheets and endow the ordered mesoporous carbon with the high conductivity required for a practical supercapacitor remains a great challenge. Herein, a strategy involving ethanol dispersive mixing, followed by co-carbonization was developed to prepare a N-doped ordered mesoporous carbon nanosphere-encapsulated graphene network (N-OMCN@GN), where the ordered mesoporous carbon nanosphere (OMCN) was inserted into the interlayers of graphene nanosheets and an optimized nitrogen doping level of up to 11.7 at% was simultaneously achieved. The as-prepared N-OMCN@GN possesses hierarchically porous architectures with largely accessible surfaces, short ion access/diffusion length with fast ion transfer, and a sphere (electron reservoir)-encapsulated plane (electron highway) configuration for convenient electron transfer. As a result, the N-OMCN@GN supercapacitor exhibited a high specific capacitance of 242.3 F g-1 at 1 A g-1 and excellent cycling stability with a capacitance retention of 95% at 5 A g-1 after 10 000 cycles. This study would pave the way to excavate the synergistic effects of graphene and OMCN for energy storage applications.

Facile synthesis of a hierarchical CuS/CuSCN nanocomposite with advanced energy storage properties

Facile fabrication of a CuS/CuSCN nanocomposite electrode for a supercapacitor with a high specific capacitance (1787.3 F g⁻¹).