Modulating the D-band center of mn and mitigating O vacancies with amino groups for enhanced long-cycle alkaline-manganese batteries

Manganese oxide is a promising cathode material for rechargeable batteries due to its high theoretical specific capacity. However, its practical application is hindered by its poor conductivity and rapid capacity decay caused by Jahn-Teller distortion during charging and discharging. This work introduces Na2EDTA during the synthesis of MnO2, and the amino group is introduced by adsorption to deposit to form N-doped MnO2. Alkaline N-doped MnO2 battery upshifts the d-band center of Mn, improves the conductivity of MnO2 and the formation energy of O vacancies during the charge-discharge process, and suppresses Jahn Teller distortion. As a result, N-doped MnO2 achieves a high capacity of up to 197mAh g-1 and excellent capacity retention of 94.2% over 250 cycles with slower voltage decay. This strategy enables the material with high cycling performance for single-electron discharge secondary alkaline manganese batteries.

RuSe2/CeO2heterostructure as a novel electrocatalyst for highly efficient alkaline hydrogen evolution

Constructing heterojunction to adjust the electronic structure of catalysts is a promising strategy for synergistically improving electrocatalytic activity. In addition, RuSe2is recognized as an effective alternative to Pt for boosting alkaline hydrogen evolution reaction (HER) on account of its outstanding catalytic properties. Herein, novel RuSe2/CeO2heterojunction electrocatalysts are fabricated through hydrothermal and thermal treatment methods. The optimal 50% RuSe2/CeO2heterojunction electrocatalyst exhibits a low HER overpotential of 16 mV to attain 10 mA cm-2current density and Tafel slope of 66.1 mV dec-1for hydrogen evolution in 1.0 M KOH. At the same time, the 50% RuSe2/CeO2heterojunction electrocatalyst also maintains a stable HER activity for 50 h or 3000 CV cycles. The experimental results show that formation of heterogeneous interface between RuSe2and CeO2results in the redistribution of electrons at the RuSe2/CeO2interface, thereby changing the electronic structure of RuSe2and enhancing the performance of the RuSe2/CeO2electrocatalyst. This work may provide a feasible way to design efficient hydrogen evolution heterojunction electrocatalysts by modulating the electronic structure in alkaline electrolytes.

Ultralow Ru Single Atoms Confined in Cerium Oxide Nanoglues for Highly-Sensitive and Robust H2 O2 -Related Biocatalytic Diagnosis

Exploring highly efficient, portable, and robust biocatalysts is a great challenge in colorimetric biosensors. To overcome the challenging states in creating single-atom biocatalysts, such as insufficient activity and stability, here, this work has engineered a unique CeO2 support as nanoglue to tightly anchor the Ru single-atom sites (CeO2 -Ru) with strong electronic coupling for achieving highly sensitive and robust H2 O2 -related biocatalytic diagnosis. The morphology and chemical/electronic structure analysis demonstrates that the Ru atoms are well-dispersed on CeO2 surface to form high-density active sites. Benefiting from the unique structure, the prepared CeO2 -Ru exhibits outstanding peroxidase (POD) like catalytic activity and selectivity to H2 O2 . Steady-state kinetic study results show that the CeO2 -Ru presents the highest Vmax and turnover number than the state-of-the-art POD-like biocatalysts. Consequently, the CeO2 -Ru discloses a high efficiency, good selectivity, and robust stability in the colorimetric detection of L-cysteine, glucose, and uric acid. Notably, the limit of detection (LOD) can reach 0.176 × 10-3 m for the L-cysteine, 0.095 × 10-3 m for the glucose, and 0.088 × 10-3 m for the uric acid via cascade reaction. This work suggests that the proposed unique CeO2 nanoglue will offer a new path to create single-atom noble metal biocatalysts and take a step closer to future biotherapeutic and biocatalytic applications.

Recent Advances in Cellulose-Based Hydrogels Prepared by Ionic Liquid-Based Processes

This review summarizes the recent advances in preparing cellulose hydrogels via ionic liquid-based processes and the applications of regenerated cellulose hydrogels/iongels in electrochemical materials, separation membranes, and 3D printing bioinks. Cellulose is the most abundant natural polymer, which has attracted great attention due to the demand for eco-friendly and sustainable materials. The sustainability of cellulose products also depends on the selection of the dissolution solvent. The current state of knowledge in cellulose preparation, performed by directly dissolving in ionic liquids and then regenerating in antisolvents, as described in this review, provides innovative ideas from the new findings presented in recent research papers and with the perspective of the current challenges.

Amorphizing Metal Selenides-Based ROS Biocatalysts at Surface Nanolayer toward Ultrafast Inflammatory Diabetic Wound Healing

The microenvironments with high reactive-oxygen-species (ROS) levels, inflammatory responses, and oxidative-stress effects in diabetic ulcer wounds, leading to poor proliferation and differentiation of stem cells, severely inhibit their efficient healing. Here, to overcome the unbalanced multielectron reactions in ROS catalysis, we develop a cobalt selenide-based biocatalyst with an amorphous Ru@CoSe nanolayer for ultrafast and broad-spectrum catalytic ROS-elimination. Owing to the enriched electrons and more unoccupied orbitals of Ru atoms, the amorphous Ru@CoSe nanolayer-equipped biocatalyst displays excellent catalase-like kinetics (maximal reaction velocity, 23.05 μM s^-1; turnover number, 2.00 s^-1), which exceeds most of the currently reported metal compounds. The theoretical studies show that Ru atoms act as "regulators" to tune the electronic state of the Co sites and modulate the interaction of oxygen intermediates, thus improving the reversible redox properties of active sites. Consequently, the Ru@CoSe can efficiently rescue the proliferation of mesenchymal stem cells and maintain their angiogenic potential in the oxidative stress environment. In vivo experiments reveal the superior ROS-elimination ability of Ru@CoSe on the inflammatory diabetic wound. This study offers an effective nanomedicine for catalytic ROS-scavenging and ultrafast healing of inflammatory wounds and also provides a strategy to design biocatalytic metal compounds via bringing amorphous catalytic structures.

Phase Transformation from Amorphous RuSx to Ru-RuS2 Hybrid Nanostructure for Efficient Water Splitting in Alkaline Media

Ruthenium (Ru)-based materials, as a class of efficient hydrogen evolution reaction (HER) catalysts, play an important role in hydrogen generation by electrolysis of water in an alkaline solution for clean hydrogen energy. Hybrid nanostructure (HN) materials, which include two or more components with distinct functionality, show better performance than their individual materials, since HN materials can potentially integrate their advantages and overcome the weaknesses. However, it remains a challenge to construct Ru-based HN materials with desired crystal phases for enhanced HER performances. Herein, a series of new Ru-based HN materials (t-Ru-RuS₂, S-Ru-RuS₂, and T-Ru-RuS₂) through phase engineering of nanomaterials (PEN) and chemical transformation are designed to achieve highly efficient HER properties. Owing to the plentiful formation of heterojunctions and amorphous/crystalline interfaces, the t-Ru-RuS₂ HN delivers the most outstanding overpotential of 16 mV and owns a small Tafel slope of 29 mV dec^-1 at a current density of 10 mA cm^-2, which exceeds commercial Pt/C catalysts (34 mV, 38 mV dec^-1). This work shows a new insight for HN and provides alternative opportunities in designing advanced electrocatalysts with low cost for HER in the hydrogen economy.

Synergistic phase and crystallinity engineering in cubic RuSe2 catalysts towards efficient hydrogen evolution reaction

Herein, cubic RuSe2 electrocatalysts with different 1T phase ratios (ranging from 20.53% to 64.97%) and crystallinities (ranging from 1.72% to 89.10%) were developed by a fast and efficient microwave-assisted synthesis method.

2D Silicene Nanosheets for High-Performance Zinc-Ion Hybrid Capacitor Application

Supercapacitors possessing fast-charging characteristics and long lifespan are becoming increasingly important for powering portable and smart energy storage devices, and combining capacitive and battery-type materials into an integrated device is an effective method for increasing the overall performance of capacitors. Silicene is being designed as a cathode for the development of enhanced capacitance and ultra-cycle stable zinc-ion hybrid capacitors. Possessing a maximum areal capacity of 14 mF cm^-2, a maximum power density of 9 mW cm^-2, capacitance retention of 112% even after 10 000 cycles, and an unexpectedly high energy density of 23 mJ cm^-2, this achievement of the zinc-ion hybrid capacitor would be superior to that of previously reported silicon-based supercapacitors. The DFT calculations further reveal that Zn ions dominate the capacitive behavior of the silicene electrode. The support association between silicene and zinc-ion hybrid capacitors so that they can take advantage of each other's strengths, which takes electrochemical energy technology to a stage, offering a straightforward proposal for integration and implementation of silicon-based materials.

Effects of Anion Carriers on Capacitance and Self-Discharge Behaviors of Zinc Ion Capacitors

Pseudocapacitive behavior and ion hybrid capacitors can improve the energy density of supercapacitors, but research has only considered the reaction of cations during the electrochemical process, leading to a flawed mechanistic understanding. Here, the effects of various anions carriers on the electrochemical behaviors of titanium nitride-based zinc ion capacitor (Zn-TiN capacitor) were explored. DFT calculations revealed the stable structure of TiN-SO₄ after adsorbed process, enabling SO₄ ^2- participate in the electrochemical process and construct a two-step adsorption and intercalation energy storage mechanism, improving the capacitance and anti-self-discharge ability of the Zn-TiN capacitor, which delivered an ultrahigh capacitance of 489.8 F g^-1 and retained 83.92 % of capacitance even after 500 h resting time. An energy storage system involving anions in the electrochemical process can improve capacitance and anti-self-discharge ability of ion hybrid capacitors.

High-performance and flexible all-solid-state hybrid supercapacitor constructed by NiCoP/CNT and N-doped carbon coated CNT nanoarrays

The exploration of flexible supercapacitors with high energy density is a matter of considerable interest to meet the demand of wearable electronic devices. In this work, with carbon nanotubes (CNTs) grown on carbon cloth (CC) as flexible substrate, NiCoP nanoflake-surrounded CNT nanoarrays (NiCoP/CNT) and N-doped carbon coated CNT nanoarrays (CNT@N-C) were synthesized on CC and utilized as cathode and anode materials for constructing flexible all-solid-state hybrid supercapacitor. Both them exhibit excellent electrochemical performance. NiCoP/CNT/CC composites can deliver a specific capacitance of 261.4 mAh g^-1, and CNT@N-C/CC exhibits a high capacitance of 256 F g^-1 at the current density of 0.5 A g^-1. The hybrid supercapacitor built from the two well designed electrodes can provide a specific capacitance of 123.3 mAh g^-1 at current density 1 mA g^-1 within a potential window of 0-1.5 V and retain almost 85% of its initial capacitance after 5000 cycles. Furthermore, the flexible devices show the maximum energy density of 138.7 Wh kg^-1 and a power density of 6.25 kW kg^-1, obviously superior to some recent reported supercapacitor devices, indicating its potential in practical application.

Boosting Specific Energy and Power of Carbon-Ionic Liquid Supercapacitors by Engineering Carbon Pore Structures

Carbon-ionic liquid (C-IL) supercapacitors (SCs) promise to provide high capacitance and high operating voltage, and thus high specific energy. It is still highly demanding to enhance the capacitance in order to achieve high power and energy density. We synthesized a high-pore-volume and specific-surface-area activated carbon material with a slit mesoporous structure by two-step processes of carbonization and the activation from polypyrrole. The novel slit-pore-structured carbon materials provide a specific capacity of 310 F g⁻¹ at 0.5 A g⁻¹ for C-IL SCs, which is among one of the highest recorded specific capacitances. The slit mesoporous activated carbons have a maximum ion volume utilization of 74%, which effectively enhances ion storage, and a better interaction with ions in ionic liquid electrolyte, thus providing superior capacitance. We believe that this work provides a new strategy of engineering pore structure to enhance specific capacitance and rate performance of C-IL SCs.

Graphitic Carbon Quantum Dots Modified Nickel Cobalt Sulfide as Cathode Materials for Alkaline Aqueous Batteries

Carbon quantum dots (CQDs) as a new class of emerging materials have gradually drawn researchers' concern in recent years. In this work, the graphitic CQDs are prepared through a scalable approach, achieving a high yield with more than 50%. The obtained CQDs are further used as structure-directing and conductive agents to synthesize novel N,S-CQDs/NiCo₂S₄ composite cathode materials, manifesting the enhanced electrochemical properties resulted from the synergistic effect of highly conductive N,S-codoped CQDs offering fast electronic transport and unique micro-/nanostructured NiCo₂S₄ microspheres with Faradaic redox characteristic contributing large capacity. Moreover, the nitrogen-doped reduced graphene oxide (N-rGO)/Fe₂O₃ composite anode materials exhibit ultrahigh specific capacity as well as significantly improved rate property and cycle performance originating from the high-capacity prism-like Fe₂O₃ hexahedrons tightly wrapped by highly conductive N-rGO. A novel alkaline aqueous battery assembled by these materials displays a specific energy (50.2 Wh kg^-1), ultrahigh specific power (9.7 kW kg^-1) and excellent cycling performance with 91.5% of capacity retention at 3 A g^-1 for 5000 cycles. The present research offers a valuable guidance for the exploitation of advanced energy storage devices by the rational design and selection of battery/capacitive composite materials.

Facile self-templating synthesis of heteroatom-doped 3D porous carbon materials from waste biomass for supercapacitors

Heteroatom-doped 3D porous carbon has been synthesized by utilizing hydroxyapatite in pig bones as a self-template and used in symmetric supercapacitors exhibiting ultra-high energy density both in an aqueous electrolyte and organic electrolyte.