Materials Today Advances最新文献

Elemental germanium (Ge) is considered a high-capacity anode material for lithium-ion batteries (LIBs). However, it suffers from severe capacity degradation and inherent material instability owing to inevitable volumetric changes during the alloying/dealloying reactions with lithium. In this study, we report a hierarchical architecture comprising Ge nanoparticles in electrospun carbon fibers (Ge@C) coated with an in situ grown NiCo₂O₄ (NCO) layer to enhance the structural stability and electrochemical reversibility of Ge. The Ge@C@NCO fibers possess unique features, including well-dispersed Ge in nitrogen-doped porous carbon network that serves as a conductive volumetric buffer. This configuration allows for effective volume accommodation and improved electronic conductivity. Moreover, the porous NCO contributed to enhanced reversible capacity and rapid ionic transfer during electrochemical reactions. As a result, the Ge@C@NCO anode exhibited an ultrahigh specific capacity of 981.7 mAh g⁻¹ and excellent capacity retention over 200 cycles under a current density of 1 A g⁻¹, indicating superior lithium storage properties compared to pure Ge. Additionally, it retained approximately 80 % of initial capacity after 300 cycles even at 5 A g⁻¹, demonstrating fast charging capability. The outstanding performance of this hierarchical structure presents a new path for designing alloying-based anodes for high-energy-density LIBs.

Thermal insulation is crucially important to the safety and reusability of aerospace vehicles. Fabrication of thermal insulation materials with light weight, high mechanical strength and low thermal conductivity remains challenging. In this study, porous polymer derived silicon oxycarbide (SiOC) ceramics with hierarchical structures mimicking cuttlebones were prepared through stereolithography additive manufacturing followed by pyrolysis. The compressive strength of SiOC ceramics with ridges (“R” structures) alongside the sinusoidal walls (“S” structures) (RS-SiOC, 13.37 ± 0.86 MPa for 7-RS-SiOC) mimicking those of cuttlebone was much higher than that of SiOC ceramics with just sinusoidal walls (S–SiOC, 8.43 ± 0.81 MPa), while the density of RS-SiOC with 7 ridges (7-RS-SiOC) and S–SiOC were 0.40 g/cm³ and 0.39 g/cm³, respectively. Our results revealed that the tailored “S” and “R” structures of biomimetic 7-RS-SiOC ceramics, together with the amorphous network of SiOC assembled in the layer-by-layer manner, rendered the high mechanical strength. In addition, the 7-RS-SiOC sample exhibited a low thermal conductivity of 0.12 W/(m·K) at room temperature. The back temperature of the 7-RS-SiOC sample was 179.5 °C when exposed to 800 °C for 1200 s, showing excellent thermal insulation capability. The state-of-the-art biomimetic design of lightweight SiOC ceramics likely offers a solution to high-performance thermal insulation for aerospace vehicles.

Nanostructured manganese oxides (MnO_x) have shown incredible promise in constructing next-generation energy storage and catalytic systems. However, it has proven challenging to integrate with other low-dimensional materials due to harsh deposition conditions and poor structural stability. Here, we report the deposition of layered manganese dioxide (δ-MnO₂) on bilayer epitaxial graphene (QEG) using a simple three-step electrochemical process involving no harsh chemicals. Using this process we can synthesize a 50 nm thick H–MnO₂ film in 1.25s. This synthetic birnessite is inherently water-stabilized, the first reported in the literature. We also confirm that this process does not cause structural damage to the QEG, as evidenced by the lack of D peak formation. This QEG heterostructure enhanced MnO₂'s redox active gas sensing, enabling room temperature detection of NH₃ and NO₂. We also report on transforming this δ-MnO₂ to other MnO_x compounds, Mn₂O₃ and Mn₃O₄, via mild annealing. This is confirmed by Raman spectroscopy of the films, which also confirms limited damage to the QEG substrate. To our knowledge, this is the first synthesis of Mn₂O₃ and Mn₃O₄ on pristine graphene substrates. Both methods demonstrate the potential of depositing and transforming multifunctional oxides on single-crystal graphene using QEG substrates, allowing for the formation of nanostructured heterostructures previously unseen. Additionally, the electrochemical nature of the deposition presents the ability to scale the process to the QEG wafer and adjust the solution to produce other powerful multifunctional oxides.

Carbon-based nanomaterials are key to developing high-performing electrochemical sensors with improved sensitivity and selectivity. Nonetheless, limitations in their fabrication and integration into devices often constrain their practical applications. Moreover, carbon nanomaterials-based electrochemical devices still face problems such as large background currents, poor stability, and slow kinetics. To advance towards a new class of carbon nanostructured electrochemical transducers, we propose the in-situ polymerization and carbonization of furfuryl alcohol (FA) on porous silicon (pSi) to produce a tailored and highly stable transducer. The thin layer of polyfurfuryl alcohol (PFA) that conformally coats the pSi scaffold transforms into nanoporous carbon when subjected to pyrolysis above 600 °C. The morphological and chemical properties of PFA-pSi were characterized by scanning electron microscopy, and Raman and X-ray photoelectron spectroscopies. Their stability and electrochemical performance were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in [Fe(CN)₆]^3-/4-, [Ru(NH₃)₆]^2+/3+, and hydroquinone. PFA-pSi showed superior electrochemical performance compared to screen-printed carbon electrodes while also surpassing glassy carbon electrodes in specific aspects. Besides, PFA-pSi has the additional advantage of easy tuning of the electroactive surface area. To prove its potential for biosensing purposes, a DNA sensor based on quantifying the partial pore blockage of the pSi upon target hybridization was built on PFA-pSi. The sensor showed a limit of detection of 1.4 pM, outperforming other sensors based on the same sensing mechanism.