Overcoming Ion Transport Barrier by Plasma Heterointerface Engineering: Epitaxial Titanium Carbonitride on Nitrogen-Doped TiO2 for High-Performance Sodium-Ion Batteries

Multiscale Interface Engineering of Sulfur-Doped TiO2 Anode for Ultrafast and Robust Sodium Storage

Sodium-ion batteries (SIBs) are a promising electrochemical energy storage system; however, their practical application is hindered by the sluggish kinetics and interfacial instability of anode-active materials. Here, to circumvent these issues, we proposed the multiscale interface engineering of S-doped TiO2 electrodes with minor sulfur/carbon inlaying (S/C@sTiO2), where the electrode-electrolyte interface (SEI) and electrode-current collector interface (ECI) are tuned to improve the Na-storage performance. It is found that the S dopant greatly promotes the Na+ diffusion kinetics. Moreover, the ether electrolyte generates much less NaF in the cycled electrode, but relatively richer NaF in the SEI in comparison to fluoroethylene carbonate-contained ester electrolyte, leading to a thin (9 nm), stable, and kinetically favorable SEI film. More importantly, the minor sodium polysulfide intermediates chemically interact with the Cu current collector to form a Cu2S interface between the electrode and the Cu foil. The conductive tree root-like Cu2S ECI serves not only as active sites to boost the specific capacity but also as a 3D "second current collector" to reinforce the electrode and improve the Na+ reaction kinetics. The synergy of S-doping and optimized SEI and ECI realizes large specific capacity (464.4 mAh g-1 at 0.1 A g-1), ultrahigh rate capability (305.8 mAh g-1 at 50 A g-1), and ultrastable cycling performance (91.5% capacity retention after 3000 cycles at 5 A g-1). To the best of our knowledge, the overall SIB performances of S/C@sTiO2 are the best among all of the TiO2-based electrodes.

Plasma-Induced 2D Electron Transport at Hetero-Phase Titanium Oxide Interface

Interfaces of metal oxide heterojunctions display a variety of intriguing physical properties that enable novel applications in spintronics, quantum information, neuromorphic computing, and high-temperature superconductivity. One such LaAlO3 /SrTiO3 (LAO/STO) heterojunction hosts a 2D electron liquid (2DEL) presenting remarkable 2D superconductivity and magnetism. However, these remarkable properties emerge only at very low temperatures, while the heterostructure fabrication is challenging even at the laboratory scale, thus impeding practical applications. Here, a novel plasma-enabled fabrication concept is presented to develop the TiO2 /Ti3 O4 hetero-phase bilayer with a 2DEL that exhibits features of a weakly localized Fermi liquid even at room temperature. The hetero-phase bilayer is fabricated by applying a rapid plasma-induced phase transition that transforms a specific portion of anatase TiO2 thin film into vacancy-prone Ti3 O4 in seconds. The underlying mechanism relies on the screening effect of the achieved high-density electron liquid that suppresses the electron-phonon interactions. The achieved "adiabatic" electron transport in the hetero-phase bilayer offers strong potential for low-loss electric or plasmonic circuits and hot electron harvesting and utilization. These findings open new horizons for fabricating diverse multifunctional metal oxide heterostructures as an innovative platform for emerging clean energy, integrated photonics, spintronics, and quantum information technologies.

Highly Stable Sb/C Anode for K+ and Na+ Energy Storage Enabled by Pulsed Laser Ablation and Polydopamine Coating

Potassium- and sodium-ion batteries (PIBs and SIBs) have great potential as the next-generation energy application owing to the natural abundance of K and Na. Antimony (Sb) is a suitable alloying-type anode for PIBs and SIBs due to its high theoretical capacity and proper operation voltage; yet, the severe volume variation remains a challenge. Herein, a preparation of N-doped carbon-wrapped Sb nanoparticles (L-Sb/NC) using pulsed laser ablation and polydopamine coating techniques, is reported. As the anode for PIB and SIB, the L-Sb/NC delivers superior rate capabilities and excellent cycle stabilities (442.2 and 390.5 mA h g^-1 after 250 cycles with the capacity decay of 0.037% and 0.038% per cycle) at the current densities of 0.5 and 1.0 A g^-1 , respectively. Operando X-ray diffraction reveals the facilitated and stable potassiation and sodiation mechanisms of L-Sb/NC enabled by its optimal core-shell structure. Furthermore, the SIB full cell fabricated with L-Sb/NC and Na₃ V₂ (PO₄ )₂ F₃ shows outstanding electrochemical performances, demonstrating its practical energy storage application.

Thermodynamic Transformation of Crystalline Organic Hybrid Iron Selenide to FexSey@CN Microrods for Sodium Ion Storage

Carbon-coated metal chalcogenide composites have been demonstrated as one type of promising anode material for sodium-ion batteries (SIBs). However, combining carbon materials with micronanoparticles of metal chalcogenide always involve complicated processes, such as polymer coating, carbonization, and sulfidation/selenization. To address this issue, herein, we reported a series of carbon-coated FexSey@CN (FexSey = FeSe2, Fe3Se4, Fe7Se8) composites prepared via the thermodynamic transformation of a crystalline organic hybrid iron selenide [Fe(phen)2](Se4) (phen = 1,10-phenanthroline). By pyrolyzing the bulk crystals of [Fe(phen)2](Se4) at different temperatures, FexSey microrods were formed in situ, where the nitrogen-doped carbon layers were coated on the surface of the microrods. Moreover, all the as-prepared FexSey@CN composites exhibited excellent sodium-ion storage capabilities as anode materials in SIBs. This work proves that crystalline organic hybrid metal chalcogenides can be used as a novel material system for the in situ formation of carbon-coated metal chalcogenide composites, which could have great potential in the application of electrochemical energy storage.

Superstructured Nanocrystals/Dual-Doped Mesoporous Carbon Anodes for High-Performance Sodium-Ion Batteries

Two-dimensional ordered superstructures have been attracting considerable attention due to their interesting properties and potential applications. However, designing ideal functional superstructures with excellent electrochemical properties is still a major challenge, and an in-depth understanding of the structure-activity relationship of electrodes remains to be achieved. To elucidate this critical issue, herein, we rationally designed and synthesized for the first time superstructured TiO₂/dual-doped mesoporous carbon anodes using confined space and surface coassembly strategies. Our method primarily relied on the larger interlayer space few-layered MXene and its negatively charged surface, allowing hexamethylenetetramine intercalation and surface electrostatic adsorption. The superstructured TiO₂/dual-doped mesoporous carbon was successfully assembled by the thermal decomposition of a confined carbon precursor. Subsequently, the comparison of Na⁺-storage properties of various anodes was carried out based on the results of structural characterization techniques and electrochemical analysis methods. The results showed that the optimized anode (N/O-C@TiO₂-20) can deliver a reversible capacity of 165 mA h g^-1 after 1000 cycles at a current density of 1 A g^-1, indicating excellent electrochemical properties. The enhancement can be attributed to the synergistic effect of carbon domains, defective nanocrystals, and a covalently coupled interface between TiO₂ and mesoporous carbon. Our work not only offered a new strategy for the assembly and regulation of superstructures to promote the electrochemical performance but also enlightened the rational design of advanced anodes for sodium-ion battery application.

High-Efficacy Hierarchical Dy2O3/TiO2 Nanoflower toward Wastewater Reclamation: A Combined Photoelectrochemical and Photocatalytic Strategy

Developing a sustainable photocatalyst is crucial to mitigate the foreseeable energy shortage and environmental pollution caused by the rapid advancement of global industry. We developed Dy₂O₃/TiO₂ nanoflower (TNF) with a hierarchical nanoflower structure and a near-ideal anatase crystallite morphology to degrade aqueous rhodamine B solution under simulated solar light irradiation. The prepared photocatalyst was well-characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, diffuse reflectance UV-vis spectra, and X-ray photoelectron spectroscopy. Further analysis was performed to highlight the photoelectrochemical activity of the prepared photocatalysts such as electrochemical impedance spectroscopy, linear sweep voltammetry, photocurrent response, and a Mott-Schottky study. The crystalline Dy₂O₃/TNF exhibits superb photocatalytic activity attributed to the improved charge transfer, reduced recombination rate of the electron-hole pairs, and a remarkable red-shift in light absorption.