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Abstract: Edges of 2D transition metal dichalcogenides (TMDs) are well known as highly reactive sites, thus researchers have attempted to maximize the edge site density of 2D TMDs. In this work, metal‐organic framework (MOF) templates are introduced to synthesize few‐layered WS2 nanoplates (a lateral dimension of ≈10 nm) confined in Co, N‐doped hollow carbon nanocages (WS2_Co‐N‐HCNCs), for highly sensitive NO2 gas sensors. WS2 precursors are assembled in the surface cavity of Co‐based zeolite imidazole framework (ZIF‐67) and subsequent pyrolysis produced WS2_Co‐N‐HCNCs. During the pyrolysis, the carbonized ZIF‐67 are doped by Co and N elements, and the growth of WS2 is effectively suppressed, creating few‐layered WS2 nanoplates functionalized Co‐N‐HCNCs. The WS2_Co‐N‐HCNCs exhibit outstanding NO2 sensing characteristics at room temperature, in terms of response (48.2% to 5 ppm), selectivity, response and recovery speed, and detection limit (100 ppb). These results are attributed to the enhanced adsorption and desorption kinetics of NO2 on abundant WS2 edges, confined in the gas permeable HCNCs. This work opens up an efficient way for the facile synthesis of edge abundant few‐layered TMDs combined with porous carbon matrix via MOF templating route, for applications relying on highly active sites. [ABSTRACT FROM AUTHOR]

To date, lithium-oxygen batteries (LOBs) using porous carbon materials as the air cathode have been widely studied. However, a fundamental issue of carbon electrode still remains; the carbon surface is unstable and is highly reactive in contact with Li 2 O 2 , resulting in the formation of irreversible byproducts ( e.g. , Li 2 CO 3 ). To address this issue, we investigated the use of surface protection layers for improving the cycling stability of porous carbon-based LOB cathode. We employed atomic layer deposition (ALD) for conformal coating of two types of overlayers (In 2 O 3 and TiN), i.e. , oxide and nitride thin film, on an electrospun carbon nanopaper (CNp) membrane. The LOB cell with In 2 O 3 -coated CNp exhibited much enhanced cycling performance (over 140 cycles) compared with pristine CNp and TiN-coated CNp as control samples (less than 60 cycles for both cases). To further improve cell efficiency by reducing overpotentials, the surface of In 2 O 3 -coated CNp electrode was functionalized by catalytic RuO x nanoparticles, which enables stable and complete discharging and recharging reactions below 4.2 V for an extended period of 165 cycles. Interestingly, after each discharge, nanosheet-like Li 2 O 2 growth was observed on In 2 O 3 -coated CNps, which is advantageous for enhanced cycle life. This work demonstrates that use of a free-standing, high surface area carbon membrane, that is conformally encapsulated by a highly conductive and stable oxide protection layer, is essential for enhanced Li-O 2 cell performance by preventing direct contact between underneath carbon and electrolyte. [ABSTRACT FROM AUTHOR]

Pore-loaded WO3 nanofibers (NFs) functionalized with spherical catalyst films were achieved via electrospinning combined by the sacrificial templating route using layer-by-layer (LbL) catalyst assembled polystyrene (PS) colloids. The catalyst-loaded porous WO3 NFs exhibited significantly improved toluene and acetone detection capability for potential application in exhaled breath analysis. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have been increasingly studied due to sodium (Na) being an inexpensive ionic resource (Na) and their battery chemistry being similar to that of current lithium-ion batteries (LIBs). However, SIBs have faced substantial challenges in developing high-performance anode materials that can reversibly store Na+ in the host structure. To address these challenges, molybdenum sulfide (MoS2)-based active materials have been considered as promising anodes, owing to the two-dimensional layered structure of MoS2 for stably (de)inserting Na+. Nevertheless, intrinsic issues of MoS2—such as low electronic conductivity and the loss of active S elements after a conversion reaction—have limited the viability of MoS2 in practical SIBs. Here, we report MoS2 embedded in carbon nanofibers encapsulated with a reduced graphene oxide (MoS2@CNFs@rGO) composite for SIB anodes. The MoS2@CNFs@rGO delivered a high capacity of 345.8 mAh g−1 at a current density of 100 mA g−1 for 90 cycles. The CNFs and rGO were synergistically taken into account for providing rapid pathways for electrons and preventing the dissolution of S sources during repetitive conversion reactions. This work offers a new point of view to realize MoS2-based anode materials in practical SIBs. [ABSTRACT FROM AUTHOR]

• Synthesis of CA-CNF by insulating block electrospinning & carbonization. • Formation of cross-aligned network even after heat treatment. • Faster reaction kinetics and regular electron pathway of CA-CNF. • High-rate cyclability of CA-CNF (259.4 mAh g−1 at 3000 mA g−1). The conventional use of metallic current collector in an electrochemical cell results in decreased loading of active materials and hence limited capacity in consideration of all the inactive current collector components. In response to this trend, a number of conductive, free-standing materials have been proposed as electrodes, which would act as both current collector and active materials. Here, in this study, we have firstly developed the cross-aligned carbon nanofiber (CA-CNF) for efficient Li storage, especially at high current densities. Using the insulating block electrospinning, the nanofibers can be aligned in a certain direction, where it is viable to fabricate cross-aligned nanofibers in a cost-effective and scalable manner. Attributed to faster kinetics and regular electron pathway arising from CA-CNF, it exhibits an excellent high-rate cyclability (259.4 mAh g−1 at a current density of 3000 mA g−1). This work builds up a milestone in suggesting a cross-aligned carbon nanofibrous network as efficient Li storage, which can also be applied to various electrode materials embedded cross-aligned conductive composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]