Facile preparation of Co3O4 nanoparticles incorporating with highly conductive MXene nanosheets as high-performance anodes for lithium-ion batteries

Unveiling the In Situ Evolution of Li2O-Rich Solid Electrolyte Interface on CoOx Embedded Carbon Fibers as Li Anode Host

Modification of three-dimensional (3D) carbon hosts with metal oxides has been considered as advantageous for the formation of Li2O-rich solid electrolyte interface (SEI), which can show fast Li+ diffusion, and meanwhile alleviate dendrite problems caused by fragility and nonuniformity of native SEIs. However, the lack of convincing experimental evidence has made it difficult to unveil the true origin of oxygen in Li2O-rich SEIs until now. Herein, CoOx embedded carbon nanofibers (CNF-CoOx) are successfully prepared as high-performance Li anode hosts. By employing 18O isotope labeling, the role of CoOx during SEI evolution is elucidated, revealing that CoOx contributes significantly to Li2O formation by delivering oxygen. Benefiting from the rich Li2O content, the as-formed SEIs greatly improve the Li+ migration kinetics, and therefore, the CNF-CoOx@Li anode can exhibit excellent cycling stability in half, symmetrical, and full cells.

MXene as Promising Anode Material for High-Performance Lithium-Ion Batteries: A Comprehensive Review

Broad adoption has already been started of MXene materials in various energy storage technologies, such as super-capacitors and batteries, due to the increasing versatility of the preparation methods, as well as the ongoing discovery of new members. The essential requirements for an excellent anode material for lithium-ion batteries (LIBs) are high safety, minimal volume expansion during the lithiation/de-lithiation process, high cyclic stability, and high Li+ storage capability. However, most of the anode materials for LIBs, such as graphite, SnO2, Si, Al, and Li4Ti5O12, have at least one issue. Hence, creating novel anode materials continues to be difficult. To date, a few MXenes have been investigated experimentally as anodes of LIBs due to their distinct active voltage windows, large power capabilities, and longer cyclic life. The objective of this review paper is to provide an overview of the synthesis and characterization characteristics of the MXenes as anode materials of LIBs, including their discharge/charge capacity, rate performance, and cycle ability. In addition, a summary of the potential outlook for developments of these materials as anodes is provided.

Microwave-assisted upcycling of plastic waste to high-performance carbon anode for lithium-ion batteries

The increasing demand for high-performance lithium-ion batteries (LIBs) has emphasized the need for affordable and sustainable materials, prompting the exploration of waste upcycling to address global sustainability challenges. In this study, we efficiently converted polypropylene (PP) plastic waste from used centrifuge tubes into activated polypropylene carbon (APC) using microwave-assisted pyrolysis. The synthesis of APC was optimized using response surface methodology/central composite design (RSM/CCD). Based on the RSM results, the optimal conditions for PP plastic conversion into carbon were determined as follows: HNO3 concentration of 3.5 M, microwave temperature of 230 °C, and holding time of 25 min. Under these conditions, the obtained intensity ratio of Id/Ig in PP carbon was 0.681 ± 0.013, with an error of 6.81 ± 0.013 % between predicted and actual values. The physicochemical studies, including FESEM-EDX, XRD, and Raman spectroscopy, confirmed the successful synthesis of APC samples. The APC 800 material exhibited a well-organized three-dimensional structure characterized by large pores and mesopores, enabling fast ion transport in the electrode. As a result, the APC 800 electrode demonstrated an initial discharge capacity of 381.0 mAh/g, an improved initial coulombic efficiency of 85.1%, and excellent cycling stability after 100 cycles. Notably, the APC 800 electrode displayed remarkable rate performance, showing a reversible capacity of 355.1 mAh/g when the current density was reset to 0.2 A/g, highlighting its high electrochemical reversibility. The outstanding characteristics of APC 800 as an anode electrode material for high-performance lithium-ion batteries suggest a promising future for its application in the field.

Modulation of the Morphological Architecture of Mn2O3 Nanoparticles to MnCoO Nanoflakes by Loading Co3+ Via a Co-Precipitation Approach for Mosquitocidal Development

The spread of many infectious diseases by vectors is a globally severe issue. Climate change and the increase of vector resistance are the primary sources of rising mosquito populations. Therefore, advanced approaches are needed to prevent the dispersal of life-threatening diseases. Herein, Mn₂O₃ NPs and MnCoO nanocomposites were presented as mosquitocidal agents. The synthesized samples were prepared by a co-precipitation route and characterized using different techniques indicating the change of host Mn₂O₃ structure to 2D MnCoO nanoflakes with Co³⁺ integration. The thermal decomposition of the nanoparticles was examined by TGA analysis, showing high stability. The energy gap (Eg) of Mn₂O₃ was estimated within the visible spectrum of the value 2.95 eV, which reduced to 2.80 eV with doping support. The impact of Mn₂O₃ and MnCoO on immature stages was investigated by semithin photomicrographs exhibiting significant changes in the midgut, fat tissue and muscles of the third larval instar. Moreover, the external deformations in pupae were examined using scanning electron microscopy (SEM).

Towards Greener and More Sustainable Synthesis of MXenes: A Review

The unique properties of MXenes have been deemed to be of significant interest in various emerging applications. However, MXenes provide a major drawback involving environmentally harmful and toxic substances for its general fabrication in large-scale production and employing a high-temperature solid-state reaction followed by selective etching. Meanwhile, how MXenes are synthesized is essential in directing their end uses. Therefore, making strategic approaches to synthesize greener, safer, more sustainable, and more environmentally friendly MXenes is imperative to commercialize at a competitive price. With increasing reports of green synthesis that promote advanced technologies and non-toxic agents, it is critical to compile, summarize, and synthesize the latest development of the green-related technology of MXenes. We review the recent progress of greener, safer, and more sustainable MXene synthesis with a focus on the fundamental synthetic process, the mechanism, and the general advantages, and the emphasis on the MXene properties inherited from such green synthesis techniques. The emerging use of the so-called green MXenes in energy conversion and storage, environmental remediation, and biomedical applications is presented. Finally, the remaining challenges and prospects of greener MXene synthesis are discussed.

Preparation and lithium storage of core-shell honeycomb-like Co3O4@C microspheres

Core-shell honeycomb-like Co₃O₄@C microspheres were synthesized via a facile solvothermal method and subsequent annealing treatment under an argon atmosphere. Owing to the core-shell honeycomb-like structure, a long cycling life was achieved (a high reversible specific capacity of 318.9 mA h g^-1 was maintained at 5C after 1000 cycles). Benefiting from the coated carbon layers, excellent rate capability was realized (a reversible specific capacity as high as 332.6 mA h g^-1 was still retained at 10C). The design of core-shell honeycomb-like microspheres provides a new idea for the development of anode materials for high-performance lithium-ion batteries.

Constructing Bimetallic ZIF-Derived Zn,Co-Containing N-Doped Porous Carbon Nanocube as the Lithiophilic Host to Stabilize Li Metal Anodes in Li-O2 Batteries

Li metal, because of its ultrahigh theoretical capacity, has attracted extensive attention. However, uncontrollable dendritic Li formation and infinite electrode dimensional variation hinder application of Li anodes. Herein, Zn,Co bimetallic zeolitic imidazolate frameworks (ZIFs) were synthesized and further pyrolyzed to obtain Zn,Co-containing N-doped porous carbon nanocube (Zn/Co-N@PCN), which was further applied as lithiophilic host to construct the lithiated Zn/Co-N@PCN (Li-Zn/Co-N@PCN). Zn vapor produced many pores on the carbon framework during calcination process that could store enough Li and thus inhibit the huge electrode volume change. Additionally, there were abundant lithiophilic groups in Zn/Co-N@PCN, such as N- or Co/Zn-based species, which were beneficial to uniform Li deposition. Moreover, the stable and conductive carbon-based matrix could ensure superior and reproducible Li plating/stripping behavior in Zn/Co-N@PCN over cycling. As a result, the Li-Zn/Co-N@PCN anode showed a steady and high columbic efficiency of around 99.0 % for 600 cycles at 0.5 mA cm^-2 . The Li-Zn/Co-N@PCN-based Li-O₂ battery could continuously work beyond 200 cycles, superior to a cell with a Li-Cu anode. These results in this work provide a novel way for construction of the advanced Li-based anodes and the corresponding high-performance Li-O₂ batteries.

Hierarchical MXene/transition metal oxide heterostructures for rechargeable batteries, capacitors, and capacitive deionization

2D MXenes have attracted considerable attention due to their high electronic conductivity, tunable metal compositions, functional termination groups, low ion diffusion barriers, and abundant active sites. However, MXenes suffer from sheet stacking and partial surface oxidation, limiting their energy storage and water treatment development. To solve these problems and enhance the performance of MXenes in practical applications, various hierarchical MXene/transition metal oxide (MXene/TMO) heterostructures are rationally designed and constructed. The hierarchical MXene/TMO heterostructures can not only prevent the stacking of MXene sheets and improve the electronic conductivity and buffer the volume change of TMOs during the electrochemical reaction process. The synergistic effect of conductive MXenes and active TMOs also makes MXene/TMO heterostructures promising electrode materials for energy storage and seawater desalination. This review mainly introduces and discusses the recent research progress in MXene/TMO heterostructures, focusing on their synthetic strategies, heterointerface engineering, and applications in rechargeable batteries, capacitors, and capacitive deionization (CDI). Finally, the key challenges and prospects for the future development of the MXene/TMO heterostructures in rechargeable batteries, capacitors, and CDI are proposed.

3D porous carbon conductive network with highly dispersed Fe-Nxsites catalysts for oxygen reduction reaction

Intrinsic activity and reactive numbers are considered two important factors in oxygen reduction reaction (ORR) catalysts. Herein, we report the rational design and synthesis of a strongly coupled hybrid material comprising of FeZn nanoparticles (FeZn NPs) supported by a three-dimensional carbon conductive network (FeZn NPs@3D-CN) for increased ORR performance. Fe-N-C sites can offer high intrinsic activity owing to the unique bonding and oxygen vacancies, and the carbon conductive network facilitating the exposure to active sites, and increasing electron transport. Because of the synergetic effect of the conductive networks containing Fe-N-C and polyaniline, the catalysts exhibited ORR activity in an alkaline medium via a four-electron transfer process. FeZn NPs@3D-CN exhibited outstanding performance with a limited current density (6.2 mA cm^-2), the Tafel slope (81.19 mV dec^-1), and stability (23 mV negative shift after 2000 cycles), which were superior to those of 20% Pt/C (5.7 mA cm^-2, 75.1 mV dec^-1, 36 mV negative shift after 2000 cycles). This research highlights the effect of conductive networks expanding pathways and reducing the resistance of mass transport, which is a facile method to generate superior ORR electrocatalysts.

Urchin-like hierarchical ruthenium cobalt oxide nanosheets on Ti3C2Tx MXene as a binder-free bifunctional electrode for overall water splitting and supercapacitors

Synthesizing efficient electrode materials for water splitting and supercapacitors is essential for developing clean electrochemical energy conversion/storage devices. In the present work, we report the construction of a ruthenium cobalt oxide (RuCo₂O₄)/Ti₃C₂T_x MXene hybrid by electrophoretic deposition of Ti₃C₂T_x MXene on nickel foam (NF) followed by RuCo₂O₄ nanostructure growth through an electrodeposition process. Owing to the strong interactions between RuCo₂O₄ and Ti₃C₂T_x sheets, which are verified by density functional theory (DFT)-based simulations, RuCo₂O₄/Ti₃C₂T_x MXene@NF can serve as a bifunctional electrode for both water splitting and supercapacitor applications. This electrode exhibits outstanding electrocatalytic activity with low overpotentials of 170 and 68 mV at 100 A m^-2 toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The RuCo₂O₄/Ti₃C₂T_x MXene@NF-based alkaline water-splitting cell only requires 1.62 V to achieve a current density of 100 A m^-2, which is much better than that of RuO₂@NF and Pt/C@NF-assembled cells (1.75 V@100 A m^-2). The symmetric supercapacitor (SSC)-assembled electrode displays a high specific capacitance of 229 F g^-1 at 3 A g^-1. The experimental results, complemented with theoretical insights, provide an effective strategy to prepare multifunctional materials for electrocatalysis and energy storage applications.

Anchoring 1D nanochain-like Co3O4 on a 2D layered Ti3C2Tx MXene with outstanding electromagnetic absorption

3D superstructure Ti3C2Tx/Co3O4 nanochain composites were synthesized through electrostatic self-assembly, in which 1D Co3O4 nanochains were anchored on a 2D layered Ti3C2Tx surface.

Three-dimensional clusters of peony-shaped CuO nanosheets as a high-rate anode for Li-ion batteries

Copper oxide (CuO) has emerged as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity, low cost and low toxicity to the natural environment. However, the low electronic/ionic conductivity and the imponderable volume expansion problem during the charge and discharge process hinder its practical applications. Herein, we introduced three-dimensional clusters of peony-shaped CuO nanosheets (TCP-CuO) to tackle these problems by increasing the surface of the active material. The unique three-dimensional peony-liked structure not only alleviates the volume expansion problem, but also enhances the electron/ion conductivity. As a result, the TCP-CuO electrode possesses a reversible high capacity of 641.1 mA h g⁻¹ at 0.1 A g⁻¹ after 80 cycles as well as an outstanding rate performance of 531.6 mA h g⁻¹ at a rate of 5C (1C = 674 mA g⁻¹) and excellent cycling durability of 441.1 mA h g⁻¹ at 1 A g⁻¹ after 100 cycles. This work demonstrated a novel strategy for the construction of a well-designed structure for other advanced energy-storage technologies.

TCP-CuO possesses a unique three-dimensional peony-liked architecture which not only alleviates volume expansion problem, but also enhances electron/ion conductivity. As an anode in LIBs, TCP-CuO delivers excellent electrochemical performances.

Designed assembly of Ni/MAX (Ti3AlC2) and porous graphene-based asymmetric electrodes for capacitive deionization of multivalent ions

The contamination of aquatic ecosystems by fluoride and heavy metal ions constitute an environmental hazard and has been proven to be harmful to human health. This study explores the feasibility of using asymmetric capacitive deionization (CDI) electrodes to remove such toxic ions from wastewater. An asymmetric CDI cell was fabricated using 2D Ni/MAX as an anode and 3D porous reduced graphene oxide (pRGO) as a cathode for the electrosorption of F^-, Pb²⁺, and As(III) ions. A simple microwave process was used for the synthesis of Ni/MAX composite using fish sperm DNA (f-DNA) as a cross-linker between MAX nanosheets (NSs) and the metallic Ni nanoparticles (NPs). Further, pRGO anode was prepared through effective reduction of RGO using lemon juice as green reducing agent with the assist of f-DNA as a structure-directing agent for the formation of 3D network. With this tailored nanoarchitecture, pRGO and Ni/MAX electrodes exhibited a high specific capacitance of 760 and 385 F g^-1, respectively. The fabricated Ni/MAX and pRGO based CDI system demonstrated a high electrosorption capacity of 68, 76, and 51 mg g^-1 for the monovalent F^-, divalent Pb²⁺, and trivalent As(III) ions at 1.4 V in neutral pH. Furthermore, Ni/MAX//pRGO system was successfully applied for the removal of total F(T), Pb(T), and As(T) ions from real industrial wastewater and contaminated groundwater. The present findings indicate that the fabricated Ni/MAX//pRGO electrode has excellent electrochemical properties that can be exploited for the removal of anionic and cationic metal ions from aqueous solutions in a CDI based system.