Layered transition metal dichalcogenide/carbon nanocomposites for electrochemical energy storage and conversion applications

Ternary (molybdenum disulfide/graphene)/carbon nanotube nanocomposites assembled via a facile colloidal electrostatic path as electrocatalysts for the oxygen reduction reaction: Composition and nitrogen-doping play a key role in their performance

Nanocomposites have garnered attention for their potential as catalysts in electrochemical reactions vital for technologies like fuel cells, water splitting, and metal-air batteries. This work focuses on developing three-dimensional (3D) nanocomposites through aqueous phase exfoliation, non-covalent functionalization of building blocks with surfactants and polymers, and electrostatic interactions in solution leading to the nanocomposites assembly and organization. By combining molybdenum disulfide (MoS2) layers with graphene nanoplatelets (GnPs) to form a binary 2D composite (MoS2/GnP), and subsequently incorporating multiwalled carbon nanotubes (MWNTs) to create ternary 3D composites, we explore their potential as catalysts for the oxygen reduction reaction (ORR) critical in fuel cells. Characterization techniques such as X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction elucidate material composition and structure. Our electrochemical studies reveal insights into the kinetics of the reactions and structure-activity relationships. Both the (MoS2/GnP)-to-MWNT mass ratio and nitrogen-doping of GnPs (N-GnPs) play a key role on the electrocatalytic ORR performance. Notably, the (MoS2/N-GnP)/MWNT material, with a 3:1 mass ratio, exhibits the most effective ORR activity. All catalysts demonstrate good long-term stability and methanol crossover tolerance. This facile fabrication method and observed trends offer avenues for optimizing composite electrocatalysts further.

Enhanced electrochemical performance of the MoS2/Bi2S3 nanocomposite-based electrode material prepared by a hydrothermal method for supercapacitor applications

Supercapacitors are widely used energy storage systems in the modern world due to their excellent electrochemical performance, fast charging capability, easy handling, and high power density. In the present work, pure MoS2 and MoS2/Bi2S3 nanocomposites with different compositions of bismuth were synthesized by the hydrothermal method. The structural properties of the electrode materials were studied using the XRD technique, which confirmed the formation of MoS2 and the secondary phase of Bi2S3 while increasing Bi substitution. The morphological studies of the synthesized electrode materials were performed using SEM, TEM, and HRTEM techniques, which indicated the 3D layered hierarchical structure of MoS2 nanospheres and the nanosheet-like structure of Bi2S3. The electrochemical properties of pristine MoS2 and MoS2/Bi2S3 nanocomposites were analysed by CV, CP, and EIS techniques using a 2 M KOH electrolyte in a three-electrode system. The CV curves show evidence of significant improvement in the electrochemical performance of MoS2/Bi2S3 composites compared to that of pure MoS2. The calculated specific capacitances of MoS2/Bi2S3 nanocomposites were relatively higher than those of pristine MoS2. The 20 mol% Bi added sample showed a maximum specific capacitance of 371 F g-1, compared to pristine MoS2 and other samples at a current density of 1 A g-1. The kinetics of the electrochemical process was studied. The Nyquist plots indicated that the Bi-added nanocomposites had lower Resr and RCT values, which resulted in high electrochemical performance. The experimental results revealed that Bi-substitution can further enhance the electrochemical energy storage performance of MoS2 for supercapacitor applications.

Recent Advancements in Chalcogenides for Electrochemical Energy Storage Applications

Energy storage has become increasingly important as a study area in recent decades. A growing number of academics are focusing their attention on developing and researching innovative materials for use in energy storage systems to promote sustainable development goals. This is due to the finite supply of traditional energy sources, such as oil, coal, and natural gas, and escalating regional tensions. Because of these issues, sustainable renewable energy sources have been touted as an alternative to nonrenewable fuels. Deployment of renewable energy sources requires efficient and reliable energy storage devices due to their intermittent nature. High-performance electrochemical energy storage technologies with high power and energy densities are heralded to be the next-generation storage devices. Transition metal chalcogenides (TMCs) have sparked interest among electrode materials because of their intriguing electrochemical properties. Researchers have revealed a variety of modifications to improve their electrochemical performance in energy storage. However, a stronger link between the type of change and the resulting electrochemical performance is still desired. This review examines the synthesis of chalcogenides for electrochemical energy storage devices, their limitations, and the importance of the modification method, followed by a detailed discussion of several modification procedures and how they have helped to improve their electrochemical performance. We also discussed chalcogenides and their composites in batteries and supercapacitors applications. Furthermore, this review discusses the subject’s current challenges as well as potential future opportunities.

In situ self-assembled N-rich carbon on pristine graphene as a highly effective support and cocatalyst of short Pt nanoparticle chains for superior electrocatalytic activity toward methanol oxidation

Highly conductive cocatalysts with great promotion effects are critical for the development of pristine graphene supported Pt-based catalysts for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). However, identification of these cocatalysts and controlled fabrication of Pt/cocatalyst/graphene hybrids with superior catalytic performance present great challenges. For the first time, pristine graphene supported N-rich carbon (NC) has been controllably fabricated via ionic-liquid-based in situ self-assembly for in situ growth of small and uniformly dispersed Pt NP chains to improve the MOR catalytic activity. It is discovered that the NC serves simultaneously as a linker to facilitate in situ nucleation of Pt, a stabilizer to restrict its growth and aggregation, and a structure-directing agent to induce the formation of Pt NP chains. The obtained nanohybrid shows a much higher forward peak current density than commercial Pt/C and most reported noncovalently functionalized carbon (NFC) supported Pt catalysts, a lower onset potential than almost all commercial Pt/C and NFC supported Pt, and greatly enhanced durability compared to graphene supported Pt NPs and commercial Pt/C. The superior catalytic performance is ascribed to the uniformly dispersed, small-diameter, and short Pt NP chains supported on highly conductive G@NC providing high ECSA and improved CO tolerance and the NC with high content of graphitic N greatly enhancing the intrinsic activity and CO tolerance of Pt and offering numerous binding sites for robustly attaching Pt. This work not only identifies and controllably fabricates a novel cocatalyst to significantly promote the catalytic activity of pristine graphene supported Pt but provides a facile and economical strategy for the controlled synthesis of high-performance integrated catalysts for the MOR in DMFCs.

1,4,5,8-Naphthalenetetracarboxylic dianhydride grafted phthalocyanine macromolecules as an anode material for lithium ion batteries

For solving the problems of high solubility in electrolytes, poor conductivity and low active site utilization of organic electrode materials, in this work, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) grafted nickel phthalocyanine (TNTCDA-NiPc) was synthesized and used as an anode material for lithium ion batteries. As a result, the dispersibility, conductivity and dissolution stability are improved, which is conducive to enhancing the performance of batteries. The initial discharge capacity of the TNTCDA-NiPc electrode is 859.8 mA h g^-1 at 2 A g^-1 current density, which is much higher than that of the NTCDA electrode (247.4 mA h g^-1). After 379 cycles, the discharge capacity of the TNTCDA-NiPc electrode is 1162.9 mA h g^-1, and the capacity retention rate is 135.3%, which is 7 times that of the NTCDA electrode. After NTCDA is grafted to the phthalocyanine macrocyclic system, the dissolution of the NTCDA in the electrolyte is reduced, and the conductivity and dispersion of the NTCDA and phthalocyanine ring are also improved, so that more active sites of super lithium intercalation from NTCDA and phthalocyanine rings are exposed, which results in better electrochemical performance. The strategy of grafting small molecular active compounds into macrocyclic conjugated systems used in this work can provide new ideas for the development of high performance organic electrode materials.

Doping strategy, properties and application of heteroatom-doped ordered mesoporous carbon

To date, tremendous achievements have been made to produce ordered mesoporous carbon (OMC) with well-designed and controllable porous structure for catalysis, energy storage and conversion. However, OMC as electrode material suffers from poor hydrophilicity and weak electrical conductivity. Numerous attempts and much research interest have been devoted to dope different heteroatoms in OMC as the structure defects to enhance its performance, such as nitrogen, phosphorus, sulphur, boron, and multi heteroatoms. Unfortunately, the "how-why-what" question for the heteroatom-doped OMC has not been summarized in any published reports. Therefore, this review focuses on the functionalization strategies of heteroatoms in OMC and the corresponding process characteristics, including in situ method, post treatment method, and chemical vapor deposition. The fundamentally influencing mechanisms of various heteroatoms in electrochemical property and porous structure are summarized in detail. Furthermore, this review provides an updated summary about the applications of different heteroatom-doped OMC in supercapacitor, electrocatalysis, and ion battery during the last decade. Finally, the future challenges and research strategies for heteroatom-doped OMC are also proposed.

The green one-step electrodeposition of oxygen-functionalized porous g-C3N4 decorated with Fe3O4 nanoparticles onto Ni-foam as a binder-free outstanding material for supercapacitors

In this study, the binder-free high-performance nanocomposite of Fe₃O₄/oxygen-functionalized g-C₃N₄ was fabricated through a one-pot electrophoretic-electrochemical (EP-EC) process.