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Solid electrolytes (SEs) are milestones in the technology roadmaps for safe and high energy density batteries. The design of organic SEs is challenged by the need to have dynamic structural fluidity for ion motion. The presence of well-ordered one-dimensional (1D) channels and stability against phase transition in covalent organic frameworks (COFs) render them potential candidates for low-temperature SEs. Herein, we demonstrate two milestones using hydrazone COF as an SE: it achieves an ion conductivity of 10–5 S cm–1 at −40 °C with a Li+ transference number of 0.92 and also prevents the dissolution of small organic molecular electrode in all-solid-state batteries. Using 1,4-benzoquinone as the cathode, a lithium battery using hydrazone COF as a SE runs for 500 cycles at a steady current density of 500 mA g–1 at 20 °C. Considering that hydrazone COF is readily amenable to large-scale production and facile post-synthetic modification, its use in an all-solid-state battery is highly promising.

Unbiased search on the potential energy surface of medium-sized boron clusters, with B(80), B(74), and B(68) as representatives, was carried out using simulated annealing incorporated with first-principles molecular dynamics. These boron clusters thermodynamically prefer the B(12)-centered core-shell structures, which resemble the fragment of bulk boron solids. Though these core-shell clusters lack a descriptive symmetry and may not be the true global minima, the core-shell B(80) is about 25 meV/atom lower in energy than the widely assumed highly stable "magic" B(80) fullerene. The electronic states and photoelectron spectra of these clusters are closely correlated to the structural motif, which may be helpful for detecting the cluster configurations in experiments.

In nature, cellulose nanofibers form hierarchical structures across multiple length scales to achieve high-performance properties and different functionalities. Cellulose nanofibers, which are separated from plants or synthesized biologically, are being extensively investigated and processed into different materials owing to their good properties. The alignment of cellulose nanofibers is reported to significantly influence the performance of cellulose nanofiber-based materials. The alignment of cellulose nanofibers can bridge the nanoscale and macroscale, bringing enhanced nanoscale properties to high-performance macroscale materials. However, compared with extensive reviews on the alignment of cellulose nanocrystals, reviews focusing on cellulose nanofibers are seldom reported, possibly because of the challenge of aligning cellulose nanofibers. In this review, the alignment of cellulose nanofibers, including cellulose nanofibrils and bacterial cellulose, is extensively discussed from different aspects of the driving force, evaluation, strategies, properties, and applications. Future perspectives on challenges and opportunities in cellulose nanofiber alignment are also briefly highlighted.

The formation and kinetics of single and double vacancies in graphene chemical vapor deposition (CVD) growth on Cu(111), Ni(111), and Co(0001) surfaces are investigated by the first-principles calculation. It is found that the vacancies in graphene on the metal surfaces are dramatically different from those in free-standing graphene. The interaction between the vacancies and the metal surface and the involvement of a metal atom in the vacancy structure greatly reduce their formation energies and significantly change their diffusion barriers. Furthermore, the kinetic process of forming vacancies and the potential route of their healing during graphene CVD growth on Cu(111) and Ni(111) surfaces are explored. The results indicate that Cu is a better catalyst than Ni for the synthesis of high-quality graphene because the defects in graphene on Cu are formed in a lower concentration and can be more efficiently healed at the typical experimental temperature. This study leads to a deep insight into the atomic process of graphene growth, and the mechanism revealed in this study can be used for the experimental design of high-quality graphene synthesis.

CO2 hydrogenation has attracted great attention, yet the quest for highly-efficient catalysts is driven by the current disadvantages of poor activity, low selectivity, and ambiguous structure-performance relationship. We demonstrate here that C3N4-supported Cu single atom catalysts with tailored coordination structures, namely, Cu–N4 and Cu–N3, can serve as highly selective and active catalysts for CO2 hydrogenation at low temperature. The modulation of the coordination structure of Cu single atom is readily realized by simply altering the treatment parameters. Further investigations reveal that Cu–N4 favors CO2 hydrogenation to form CH3OH via the formate pathway, while Cu–N3 tends to catalyze CO2 hydrogenation to produce CO via the reverse water-gas-shift (RWGS) pathway. Significantly, the CH3OH productivity and selectivity reach 4.2 mmol g–1 h–1 and 95.5%, respectively, for Cu–N4 single atom catalyst. We anticipate this work will promote the fundamental researches on the structure-performance relationship of catalysts.

Now is the age of high-tech research and development. Different types of fibers have been produced in the last decades for the benefit of human needs. Core-shell nanofibers are a revolutionary development in the field of science and technology. Preparation of nanoscale fibers in a core-shell configuration, using two dissimilar materials, via a novel technique of electrospinning has presented unusual potential for use in many novel applications. The studies have addressed issues related to the technology involved and examined the suitability of the technique for producing unique nanoscale morphologies involving variety of materials. Numerous studies have been published on the preparation of core-shell nanofibers by electrospinning process for developing novel structures for new applications. No major review of the co-axial electrospinning process has appeared to the knowledge of the authors but is needed in order to develop a fuller understanding of the status of work in this field. After a brief introduction to the conventional electrospinning process, this paper focuses on the preparation and uses of core-shell fibers by electrospinning studies published to date. It attempts to categorize them in terms of the approaches adopted, and highlights the knowledge gained with respect to the material and process parameters that impact the size and the uniformity of the core-shell nanofibers obtained.

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