ABSTRACT
The heterostructure of transition-metal chalcogenides is a promising approach to boost alkali ion storage due to fast charge kinetics and reduction of activation energy. However, cycling performance is a paramount challenge that is suffering from poor reversibility. Herein, it is reported that Se-rich particles can chemically interact with local hexagonal ZnSe/MnSe@C heterostructure environment, leading to effective ions insertion/extraction, enabling high reversibility. Enlightened by theoretical understanding, Se-rich particles endow high intrinsic conductivities in term of low energy barriers (1.32 eV) compared with those without Se-rich particles (1.50 eV) toward the sodiation process. Moreover, p orbitals of Se-rich particles may actively participate and further increase the electronegativity that pushes the Mn d orbitals (dxy and dx2-y2) and donate their electrons to dxz and dyz orbitals, manifesting strong d-d orbitals interaction between ZnSe and MnSe. Such fundamental interaction will adopt a well-stable conducive electronic bridge, eventually, charges are easily transferred from ZnSe to MnSe in the heterostructure during sodiation/desodiation. Therefore, the optimized Se-rich ZnSe/MnSe@C electrode delivered high capacity of 576 mAh g-1 at 0.1 A g-1 after 100 cycles and 384 mAh g-1 at 1 A g-1 after 2500 cycles, respectively. In situ and ex situ measurements further indicate the integrity and reversibility of the electrode materials upon charging/discharging.
ABSTRACT
The development of electrochemically inexpensive, durable, and active electrocatalysts for the oxygen evolution reaction (OER) is attracting considerable attention. The heterogeneous interfacing might regulate the electronic structure and further improve the electrochemical activity. Herein, a Ce(OH)3 nanoparticle-interfaced Fe-doped nickel sulfide (Ce(OH)3@Fe-Ni3S2) electrocatalyst was prepared to improve the OER performance. The fabricated electrocatalyst displayed excellent intrinsic activity and long-term stability in 1 M KOH for the OER. The catalyst shows an ultralow overpotential of 195 mV at a current density of 10 mA cm-2 and a Tafel slope of 52 mV dec-1, which are remarkably smaller than those of the control samples. This excellent electrocatalytic activity is attributed to the incorporation of Ce(OH)3 nanoparticles on the surface of the Fe-Ni3S2 nanosheet, which increases the electrochemical activity and enlarges the active surface area of the catalyst. In comparison to previous nonprecious OER electrocatalysts, the prepared Ce(OH)3@Fe-Ni3S2 exhibits greater electrocatalytic activity and longer durability, allowing for the selection of new electrocatalysts for practical applications.
ABSTRACT
Photocatalytic hydrogen generation from direct water splitting is recognized as a progressive and renewable energy producer. The secret to understanding this phenomenon is discovering an efficient photocatalyst that preferably uses sunlight energy. Two-dimensional (2D) graphitic carbon nitride (g-C3N4)-based materials are promising for photocatalytic water splitting due to special characteristics such as appropriate band gap, visible light active, ultra-high specific surface area, and abundantly exposed active sites. However, the inadequate photocatalytic activity of pure 2D layered g-C3N4-based materials is a massive challenge due to the quick recombination between photogenerated holes and electrons. Creating 2D heterogeneous photocatalysts is a cost-effective strategy for clean and renewable hydrogen production on a larger scale. The 2D g-C3N4-based heterostructure with the combined merits of each 2D component, which facilitate the rapid charge separation through the heterojunction effect on photocatalyst, has been evidenced to be very effective in enhancing the photocatalytic performance. To further improve the photocatalytic efficiency, the development of novel 2D g-C3N4-based heterostructure photocatalysts is critical. This mini-review covers the fundamental concepts, recent advancements, and applications in photocatalytic hydrogen production. Furthermore, the challenges and perspectives on 2D g-C3N4-based heterostructure photocatalysts demonstrate the future direction toward sustainability.
ABSTRACT
Lithium-sulfur batteries are one of the most promising next-generation energy storage systems. The efficient interconversion between sulfur/lithium polysulfides and lithium sulfide is a performance-determining factor for lithium-sulfur batteries. Herein, a novel strategy to synthesize a unique tube-in-tube CNT-wired sulfur-deficient MoS2 nanostructure embedding cobalt atom clusters as an efficient polysulfide regulator is successfully conducted in Li-S batteries. It is confirmed that encapsulating MWCNTs into hollow porous sulfur-deficient MoS2 nanotubes embedded with metal cobalt clusters not only can accelerate electron transport and confine the dissolution of lithium polysulfide by physical/chemical adsorption, but also can catalyze the kinetics of polysulfide redox reactions. Based on DFT calculations, in situ spectroscopic techniques, and various electrochemical studies, catalytic effects of CNT/MoS2 -Co nanocomposite in Li-S battery are deeply investigated for the first time. The CNT/MoS2 -Co composite cathode exhibits a very remarkable rate capability (641 mAh g-1 at 5.0 C) and excellent cycling stability (capacity decay rate of 0.050% per cycle at 5.0 C) even at high sulfur mass loading of 3.6 mg cm-2 . More crucially, CNT/MoS2 -Co tube-in-tube nanostructures present a superior specific capacity of 650 mAh g-1 in a Li-S pouch cell at 0.2 C (4.0 mg cm-2 ).
ABSTRACT
BACKGROUND: Iron oxide nanocomposites have received a great attention for their application in various fields like physics, medicine, biology, and material science etc., due to their unique properties, such as magnetism, electrical properties, small size, biocompatibility and low toxicity. METHODS: Fe3O4/Ag3PO4@WO3 nanocomposites with different weight percent of Ag3PO4 were successfully prepared through fabricated Ag3PO4/Fe3O4 with WO3 via in situ fabrication method, electrospinning involved precursor solution preparation and spinning to enhance photocatalyst performance under simulated sunlight for the degradation of methylene blue (MB) and antibacterial activity against Staphylococcus aureus (S. aureus). RESULTS: The photocatalytic degradation of methylene blue (MB) under simulated light irradiation indicated that the nanocomposite with 0.25 mg of Ag3PO4 has the best activity. An additional advantage of these photocatalysts is magnetic recoverability, using external magnetic field and photocatalytic stability of the nanocomposites was evaluated for three cycles. In addition, using different scavengers, holes (h+) and superoxide radical (O 2 ·-) radicals and hydroxide radical (·OH) were identified the main oxidative species in the degradation reaction of methylene blue. CONCLUSIONS: The results reveal that Fe3O4/Ag3PO4@WO3-0.25 nanocomposites have photocatalytic and antibacterial activity against S. aureus. The photocatalyst and mechanism based on the enhancement of electron transfer processes between Ag3PO4 and WO3 nanoparticles.
