Enhanced capacitive deionization of defect-containing MoS2/graphene composites through introducing appropriate MoS2 defect

Boosting Capacitive Deionization in MoS2 via Interfacial Coordination Bonding and Intercalation-Induced Spacing Confinement

Capacitive deionization (CDI) is a green and promising technology for seawater desalination, with its capacity and industrial application being severely hindered by efficient electrode materials. Layered molybdenum disulfide (MoS2) has garnered significant attention for CDI applications, while its performance is hampered by weak surface hydrophilicity, high interfacial resistance, and sluggish electron transport. Herein, we introduce an interfacial and intercalation dual-engineering strategy by covalently functionalizing the hydrophilic pyridine groups within the 1T-MoS2 layer (Py-MoS2); an electron-rich interface with an expanded interlayer spacing has been achieved synergistically. A state-of-the-art high desalination capacity of 43.92 mg g-1 and exceptional cycling stability have been achieved, surpassing all of the reported existing MoS2-based CDI electrodes. Comprehensive characterization and theoretical modeling reveal that covalently engineered pyridine groups enhance ion affinity via interfacial coordination, accelerate charge transfer, and expand ion-accessible sites within the MoS2 interlayer spacing through intercalation-induced structural modulation. These synergistic effects dramatically boost the ion adsorption kinetics, mass transfer efficiency, and salt ion uptake capacity within Py-MoS2 for CDI application. Our work presents an interfacial and intercalation dual-engineering strategy to promote the seawater desalination of 2D materials, paving new insights for next-generation high-performance CDI electrode development.

Template-Assisted Epitaxial Growth of Ordered SnO2 Nanorods Arrays with Different Hollow Structures for High-Performance Sodium Storage

Anode materials for sodium ion batteries (SIBs) are confronted with severe volume expansion and poor electrical conductivity. Construction of assembled structures featuring hollow interior and carbon material modification is considered as an efficient strategy to address the issues. Herein, a novel template-assisted epitaxial growth method, ingeniously exploiting lattice matching nature, is developed to fabricate hollow ordered architectures assembled by SnO2 nanorods. SnO2 nanorods growing along [100] direction can achieve lattice-matched epitaxial growth on (110) plane of α-Fe2O3. Driven by the lattice matching, different α-Fe2O3 templates possessing different crystal plane orientations enable distinct assembly modes of SnO2, and four kinds of hollow ordered SnO2@C nanorods arrays (HONAs) with different morphologies including disc, hexahedron, dodecahedron and tetrakaidecahedron (denoted as Di-, He-, Do-, and Te-SnO2@C) are achieved. Benefiting from the synergy of hollow structure, carbon coating and ordered assembly structure, good structural integrity and stability and enhanced electrical conductivity are realized, resulting in impressive sodium storage performances when utilized as SIB anodes. Specifically, Te-SnO2@C HONAs exhibit excellent rate capability (385.6 mAh·g-1 at 2.0 A·g-1) and remarkable cycling stability (355.4 mAh·g-1 after 2000 cycles at 1.0 A·g-1). This work provides a promising route for constructing advanced SIB anode materials through epitaxial growth for rational structural design.

Engineering Faradaic Electrode Materials for High-Efficiency Water Desalination

Water desalination technologies play a key role in addressing the global water scarcity crisis and ensuring a sustainable supply of freshwater. In contrast to conventional capacitive deionization, which suffers from limitations such as low desalination capacity, carbon anode oxidation, and co-ion expulsion effects of carbon materials, the emerging faradaic electrochemical deionization (FDI) presents a promising avenue for enhancing water desalination performance. These electrode materials employed faradaic charge-transfer processes for ion removal, achieving higher desalination capacity and energy-efficient desalination for high salinity streams. The past decade has witnessed a surge in the advancement of faradaic electrode materials and considerable efforts have been made to explore optimization strategies for improving their desalination performance. This review summarizes the recent progress on the optimization strategies and underlying mechanisms of faradaic electrode materials in pursuit of high-efficiency water desalination, including phase, doping and vacancy engineering, nanocarbon incorporation, heterostructures construction, interlayer spacing engineering, and morphology engineering. The key points of each strategy in design principle, modification method, structural analysis, and optimization mechanism of faradaic materials are discussed in detail. Finally, this work highlights the remaining challenges of faradaic electrode materials and present perspectives for future research.

Effect of point defects on the band alignment and transport properties of 1T-MoS2/2H-MoS2/1T-MoS2 heterojunctions

Defects, which are an unavoidable component of the material preparation process, can have a significant impact on the properties of two-dimensional devices. In this work, we investigated theoretically the effects of different types and positions of point defects on band alignment and transport properties of metallic 1T-phase MoS2/semiconducting 2H-phase MoS2 junctions. We found that the Schottky barriers of junctions depend on the type of defects and their locations while showing anisotropic characteristics along the zigzag and armchair directions of 2H-phase MoS2. Moreover, defects in the central scattering region can generate local impurity states and introduce new transmission peaks, while defects at the interface do not generate impurity-state-related transmission peaks. Together, these defect-related peaks and Schottky barriers jointly affect the transport properties of the junctions. Understanding the complex behaviors of defects in devices can make the process of material preparation more efficient by avoiding harm.

Synergistic effect of intercalation and EDLC electrosorption of 2D/3D interconnected architectures to boost capacitive deionization for water desalination via MoSe2/mesoporous carbon hollow spheres

Transition-metal dichalcogenides can be used for capacitive deionization (CDI) via pseudocapacitive ion intercalation/de-intercalation due to their unique two-dimensional (2D) laminar structure. MoS₂ has been extensively studied in the hybrid capacitive deionization (HCDI), but the desalination performance of MoS₂-based electrodes remains only 20-35 mg g^-1 on average. Benefiting from the higher conductivity and larger layer spacing of MoSe₂ than MoS₂, it is expected that MoSe₂ would exhibit a superior HCDI desalination performance. Herein, for the first time, we explored the use of MoSe₂ in HCDI and synthesized a novel MoSe₂/MCHS composite material by utilizing mesoporous carbon hollow spheres (MCHS) as the growth substrate to inhibit the aggregation and improve the conductivity of MoSe₂. The as-obtained MoSe₂/MCHS presented unique 2D/3D interconnected architectures, allowing for synergistic effects of intercalation pseudocapacitance and electrical double layer capacitance (EDLC). An excellent salt adsorption capacity of 45.25 mg g^- 1 and a high salt removal rate of 7.75 mg g^- 1 min^-1 were achieved in 500 mg L^- 1 NaCl feed solution at an applied voltage of 1.2 V in batch-mode tests. Moreover, the MoSe₂/MCHS electrode exhibited outstanding cycling performance and low energy consumption, making it suitable for practical applications. This work demonstrates the promising application of selenides in CDI and provides new insights for ration design of high-performance composite electrode materials.

Recent advances in hierarchical MoS2/graphene-based materials for supercapacitor applications

Hierarchical MoS₂/graphene (MoS₂/G) has been widely researched in energy storage via supercapacitors. The combination of MoS₂ with graphene not only provides high conductivity but also enhances the structural stability, which are critical factors determining the electrochemical performance for energy storage. In this review, the recent development of various hierarchical MoS₂/G nanostructures in supercapacitor applications is summarized by classifying the materials into MoS₂/G nanospheres, MoS₂/G nanosheets, and MoS₂/G-based ternary composite. The description of the structural characteristics and electrochemical performance gives a clear and profound understanding of hierarchical MoS₂/G nanostructures as a supercapacitor material. In addition, further research prospects of hierarchical MoS₂/G are suggested.

Enhanced capacitive deionization properties of activated carbon doped with carbon nanotube-bridged molybdenum disulfide

The shortage of freshwater supplies has restricted societal development. Capacitive deionization (CDI) is an emerging technology for desalination of seawater or brackish water, the performance of which is highly dependent on electrode materials. In this work, a molybdenum disulfide/carbon nanotube composite (CNTs-b-MoS₂) with high capacitance was successfully synthesized using a hydrothermal method. The composite exhibited a specific capacitance of 112.79 F g^-1. To reduce costs and determine the practicality of using CNTs-b-MoS₂ for CDI, we combined activated carbon (AC) with CNTs-b-MoS₂ as a CDI electrode. The research demonstrated that after doping with 5% (mass ratio) CNTs-b-MoS₂, the specific capacitance and electrosorption capacity of AC were significantly improved and the maximum desalination capacity of CNTs-b-MoS₂/AC reached 8.19 mg g^-1. The low dosage of CNTs-b-MoS₂ combined with the high specific surface area of AC avoided the shortcomings of CNTs-b-MoS₂, namely low specific surface area and high cost. Moreover, the outstanding conductivity of CNTs-b-MoS₂ improved the conductivity and enhanced the adsorption capacity of AC, giving CNTs-b-MoS₂/AC potential as an advanced, low-cost CDI electrode material.

MoS2 and MoS2 Nanocomposites for Adsorption and Photodegradation of Water Pollutants: A Review

The need for fresh and conveniently treated water has become a major concern in recent years. Molybdenum disulfide (MoS₂) nanomaterials are attracting attention in various fields, such as energy, hydrogen production, and water decontamination. This review provides an overview of the recent developments in MoS₂-based nanomaterials for water treatment via adsorption and photodegradation. Primary attention is given to the structure, properties, and major methods for the synthesis and modification of MoS₂, aiming for efficient water-contaminant removal. The combination of MoS₂ with other components results in nanocomposites that can be separated easily or that present enhanced adsorptive and photocatalytic properties. The performance of these materials in the adsorption of heavy metal ions and organic contaminants, such as dyes and drugs, is reviewed. The review also summarizes current progress in the photocatalytic degradation of various water pollutants, using MoS₂-based nanomaterials under UV-VIS light irradiation. MoS₂-based materials showed good activity after several reuse cycles and in real water scenarios. Regarding the ecotoxicity of the MoS₂, the number of studies is still limited, and more work is needed to effectively evaluate the risks of using this nanomaterial in water treatment.

Recent progress of hierarchical MoS2 nanostructures for electrochemical energy storage

Hierarchical MoS2 nanostructures are of increasing importance in energy storage via batteries or supercapacitors. Herein, the various hierarchical MoS2 materials as electrochemical electrode are reviewed in detail by classifying the...