Ultra-high rate capability of nanoporous carbon network@V2O5 sub-micron brick composite as a novel cathode material for asymmetric supercapacitors

Vanadium Oxide: Phase Diagrams, Structures, Synthesis, and Applications

Vanadium oxides with multioxidation states and various crystalline structures offer unique electrical, optical, optoelectronic and magnetic properties, which could be manipulated for various applications. For the past 30 years, significant efforts have been made to study the fundamental science and explore the potential for vanadium oxide materials in ion batteries, water splitting, smart windows, supercapacitors, sensors, and so on. This review focuses on the most recent progress in synthesis methods and applications of some thermodynamically stable and metastable vanadium oxides, including but not limited to V₂O₃, V₃O₅, VO₂, V₃O₇, V₂O₅, V₂O₂, V₆O₁₃, and V₄O₉. We begin with a tutorial on the phase diagram of the V-O system. The second part is a detailed review covering the crystal structure, the synthesis protocols, and the applications of each vanadium oxide, especially in batteries, catalysts, smart windows, and supercapacitors. We conclude with a brief perspective on how material and device improvements can address current deficiencies. This comprehensive review could accelerate the development of novel vanadium oxide structures in related applications.

Construction of trifunctional electrode material based on Pt-Coordinated Ce-Based metal organic framework

The main challenge hindering the use of Pt nanoparticles (Pt NPs) for electrochemical applications is their high cost and agglomeration. Herein, a trifunctional electrode material based on a two-dimensional cerium-based metal organic framework (2D Ce-MOF) decorated with Pt NPs is constructed. The large specific surface area of the 2D Ce-MOF can effectively prevent the phenomenon of Pt NPs reaction. The strong synergy between Pt NPs and the 2D Ce-MOF not only significantly enhances electron transport efficiency, but also increases the number of electrochemically reaction reactive sites. As a result, the Ce-MOF@Pt presents excellent performance in the HER (Hydrogen Evolution Reaction), OER (Oxygen Evolution Reaction) and supercapacitor reactions. The Tafel slopes of OER and HER are 47.9 and 188.1 mV dec^-1, respectively. Meanwhile, Ce-MOF@Pt-0.05 shows a specific capacity of 1894F g^-1 at a current density of 1 A g^-1 and remains at 111.5% of the initial capacitance after 3000 cycles. In general, this study highlights the importance of Pt NPs in promoting the electrochemical performance of MOFs and reveals a new way to reduce electrocatalyst prices.

Ti3C2Tx (MXene)-wrapped V2O5/Fe2O3 composite for enhanced-performance supercapacitor

Among transition-metal-oxides, vanadium oxides and iron oxides have attracted much attention for electrochemical energy storage devices due to their high theoretical specific capacities and multiple variable valence states of V...

Mo-doped Co3O4 ultrathin nanosheet arrays anchored on nickel foam as a bi-functional electrode for supercapacitor and overall water splitting

Simple preparation, favorable price and environmental protection have been a long-term challenge in the field of electrochemistry. Herein, we studied and prepared a bifunctional Mo-doped Co₃O₄ ultrathin nanosheets, which has been validated as an effective binder-free electrode material for electrocatalytic water splitting and supercapacitors. The material has a large specific surface area, high electrical conductivity and exposure to more active sites, breaking down the limited performance and range of use of transition metal oxides. Benefiting from intriguing ultrathin property and conductivity, OER and HER process of 0.4Mo-Co₃O₄ have a small Tafel slope of 83.7 and 98 mV dec^-1, respectively. The current density at 10 mA cm^-2 show a low overpotential of 315 and 79 mV and significant stability. The water electrolytic device requires a potential of 1.64 V to reach 10 mA cm^-2, and the potential change is negligible after 12 h of continuous electrolysis. In addition, the manifest improved electrochemical performance of 0.3Mo-Co₃O₄ as supercapacitor electrode material shows high areal capacitance 2815 mF cm^-2 at 1 mA cm^-2, excellent rate performance (85% at 10 mA cm^-2) and retains 90% of the initial capacitance by cycling 5000 at a current density of 10 mA cm^-2. Moreover, 0.3Mo-Co₃O₄||0.3Mo-Co₃O₄ symmetrical supercapacitor has a maximum volumetric energy density of 1.25 mW h cm^-3 at a power density of 7.1 mW cm^-3 and superior cycle life. The influence of doping on electrochemical performance was studied by changing the content of doped metal ions, which is of great significance for the exploration of supercapacitor and electrocatalytic hydrolysis of bifunctional electrode materials.

Recent Advances in Design and Fabrication of Nanocomposites for Electromagnetic Wave Shielding and Absorbing

Electromagnetic (EM) pollution has raised significant concerns to human health with the rapid development of electronic devices and wireless information technologies, and created adverse effects on the normal operation of the sensitive electronic apparatus. Notably, the EM absorbers with either dielectric loss or magnetic loss can hardly perform efficient absorption, which thereby limits their applications in the coming 5G era. In such a context, the hotspot materials reported recently, such as graphene, MXenes, and metal-organic frameworks (MOF)-derived materials, etc., have been explored and applied as EM absorbing and shielding materials owing to their tunable heterostructures, as well as the facile incorporation of both dielectric and magnetic components. In this review, we deliver a comprehensive literature survey according to the types of EM absorbing and shielding materials, and interpret the connectivity and regularity among them on the basis of absorbing mechanisms and microstructures. Finally, the challenges and the future prospects of the EM dissipating materials are also discussed accordingly.