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Abstract Metal‐organic frameworks recently have been burgeoning and used as precursors to obtain various metal–nitrogen–carbon catalysts for oxygen reduction reaction (ORR). Although rarely studied, Mn–N–C is a promising catalyst for ORR due to its weak Fenton reaction activity and strong graphitization catalysis. Here, we developed a facile strategy for anchoring the atomically dispersed nitrogen‐coordinated single Mn sites on carbon nanosheets (MnNCS) from an Mn‐hexamine coordination framework. The atomically dispersed Mn–N4 sites were dispersed on ultrathin carbon nanosheets with a hierarchically porous structure. The optimized MnNCS displayed an excellent ORR performance in half‐cells (0.89 V vs. reversible hydrogen electrode (RHE) in base and 0.76 V vs. RHE in acid in half‐wave potential) and Zn–air batteries (233 mW cm−2 in peak power density), along with significantly enhanced stability. Density functional theory calculations further corroborated that the Mn–N4–C12 site has favorable adsorption of *OH as the rate‐determining step. These findings demonstrate that the metal‐hexamine coordination framework can be used as a model system for the rational design of highly active atomic metal catalysts for energy applications.

All-inorganic metal halide perovskite is promising for highly efficient and thermally stable perovskite light-emitting diodes (PeLEDs). However, there is still great room for improvement in the film quality, including low coverage and high trap density, which play a vital role in achieving high-efficiency PeLEDs. In this work, lead acetate (Pb(Ac)2) was introduced into the perovskite precursor solution as an additive. Experimental results show that perovskite films deposited from a one-step anti-solvent free solution process with increased surface coverage and reduced trap density were obtained, leading to enhanced photoluminescence (PL) intensity. More than that, the valence band maximum (VBM) of perovskite films was reduced, bringing about a better energy level matching the work function of the hole-injection layer (HIL) poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS), which is facilitated for the hole injection, leading to a decrease in the turn-on voltage (Vth) of PeLEDs from 3.4 V for the control device to 2.6 V. Finally, the external quantum efficiency (EQE) of the sky blue PeLEDs (at 484 nm) increased from 0.09% to 0.66%. The principles of Pb(Ac)2 were thoroughly investigated by using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). This work provides a simple and effective strategy for improving the morphology of perovskite and therefore the performance of PeLEDs.

Rational design and facile preparation of low-cost and efficient catalysts for the selective converting of biomass-derived monosaccharides into high value-added chemicals is highly demanded, yet challenging. Herein, we first demonstrate a N doped defect-rich carbon (NC-800-5) as metal-free catalyst for the selective oxidation of d-xylose into d-xylonic acid in alkaline aqueous solution at 100 °C for 30 min, with 57.4% yield. The doped graphitic N is found to be the active site and hydroxyl ion participating in the oxidation of d-xylose. Hydroxyl ion and d-xylose first adsorb on NC-800-5 surface, and the aldehyde group of d-xylose is catalyzed to form germinal diols ion. Then, C–H bond break to yield carboxylic group. Furthermore, NC-800-5 catalyst shows high stability in recycled test.

Abstract Room‐temperature sodium–sulfur (RT/Na–S) batteries are regarded as promising large‐scale stationary energy storage systems owing to their high energy density and low cost as well as the earth‐abundant reserves of sodium and sulfur. However, the diffusion of polysulfides and sluggish kinetics of conversion reactions are still major challenges for their application. Herein, we developed a powerful and functional separator to inhibit the shuttle effect by coating a lightweight three‐dimensional cellulose nanofiber‐derived carbon aerogel on a glass fiber separator (denoted NSCA@GF). The hierarchical porous structures, favorable electronic conductivity, and three‐dimensional interconnected network of N,S‐codoped carbon aerogel endow a multifunctional separator with strong polysulfide anchoring capability and fast reaction kinetics of polysulfide conversion, which can act as the barrier layer and an expanded current collector to increase sulfur utilization. Moreover, the hetero‐doped N/S sites are believed to strengthen polysulfide anchoring capability via chemisorption and accelerate the redox kinetics of polysulfide conversion, which is confirmed from experimental and theoretical results. As a result, the assembled Na–S coin cells with the NSCA@GF separator showed a high reversible capacity (788.8 mAh g−1 at 0.1 C after 100 cycles) and superior cycling stability (only 0.059% capacity decay per cycle over 1000 cycles at 1 C), thereby demonstrating the significant potential for application in high‐performance RT/Na–S batteries.

Abstract With the rapid development of wearable and intelligent flexible electronic devices (FEDs), the demand for flexible energy storage/conversion devices (ESCDs) has also increased. Rechargeable flexible metal‐air batteries (MABs) are expected to be one of the most ideal ESCDs due to their high theoretical energy density, cost advantage, and strong deformation adaptability. With the improvement of the device design, material assemblies, and manufacturing technology, the research on the electrochemical performance of flexible MABs has made significant progress. However, achieving the high mechanical flexibility, high safety, and wearable comfortability required by FEDs while maintaining the high performance of flexible MABs are still a daunting challenge. In this review, flexible Zn‐air and Li‐air batteries are mainly exemplified to describe the most recent progress and challenges of flexible MABs. We start with an overview of the structure and configuration of the flexible MABs and discuss their impact on battery performance and function. Then it focuses on the research progress of flexible metal anodes, gel polymer electrolytes, and air cathodes. Finally, the main challenges and future research perspectives involving flexible MABs for FEDs are proposed.

In this work, rutin (RT)–loaded zein–carboxymethyl starch (CMS) nanoparticles were successfully prepared by the antisolvent precipitation method. The effect of CMS on composite nanoparticles at different concentrations was studied. When the ratio of zein–RT–CMS was 10:1:30, the encapsulation efficiency (EE) was the highest, reaching 73.5%. At this ratio, the size of the composite nanoparticles was 196.47 nm, and the PDI was 0.13, showing excellent dispersibility. The results of fluorescence spectroscopy, FTIR, XRD, and CD showed that electrostatic interaction, hydrogen bonding, and hydrophobic interaction were the main driving forces for the formation of nanoparticles. It can be seen from the FE–SEM images that the zein–RT–CMS nanoparticles were spherical. With the increase in the CMS concentration, the particles gradually embedded in the cross–linked network of CMS (10:1:50). After RT was loaded on zein–CMS nanoparticles, the thermal stability and pH stability of RT were improved. The results showed that zein–CMS was an excellent encapsulation material for bioactive substances.

Summary: The large-scale application of economically efficient electrocatalysts for hydrogen evolution reaction (HER) is limited in view of the high cost of polymer binders (Nafion) for immobilizing of powder catalysts. In this work, nitrogen-doped molybdenum carbide nanobelts (N-Mo2C NBs) with porous structure are synthesized through a direct pyrolysis process using the pre-prepared molybdenum oxide nanobelts (MoO3 NBs). Nanocellulose instead of Nafion-bonded N-Mo2C NBs (N-Mo2C@NCs) exhibits superior performance toward HER, because of excellent dispersibility and multiple exposed catalytically active sites. Furthermore, the conductive film composed of N-Mo2C NBs, graphene nanosheets, and nanocellulose (N-Mo2C/G@NCs) is fabricated by simple vacuum filtration, as flexible and editable electrode, which possesses excellent performance for scale HER applications. This work not only proposes the potential of nanocellulose to replace Nafion for binding powder catalysts, but also offers a facile strategy to prepare flexible and conductive films for a wide variety of nanomaterials. : Catalysis; Electrochemical Energy Conversion; Nanomaterials Subject Areas: Catalysis, Electrochemical Energy Conversion, Nanomaterials

Developing convenient deuterium labeling procedures is important in organic synthesis and the pharmaceutical industry. Here, the authors report a mild photocatalytic strategy for controllable deuteration of halides using D2O as the reagent and porous CdSe nanosheets as the catalyst.

Polysaccharides were isolated from Phyllostachys acuta leaves by microwave-assisted extraction under various temperatures and time. The obtained polysaccharides were characterized by acid hydrolysis, the Folin-Ciocalteu method, and Fourier transform infrared spectroscopy (FTIR). The major monosaccharides presented in the extracts were arabinose (258.0 mg/g to 414.5 mg/g), galactose (167.0 mg/g to 289.2 mg/g), and glucose (157.4 mg/g to 246.7 mg/g) along with some mannose, fructose, and xylose. The total phenol yield of the bamboo leaves was 0.31 mg/g to 0.73 mg/g. The FTIR spectra revealed that the polysaccharides mostly consisted of β-glycosidic linkages. For the cytotoxicity, the presence of polysaccharides considerably elevated the multiplication of HepG2 cells and showed no growth inhibition for the samples. For the antioxidant activities, the polysaccharides exhibited excellent abilities both in the diphenyl picrylhydrazyl radical potential (DPPH) assay and ferric reducing antioxidant potential (FRAP) assay. The results suggest that bamboo leaf polysaccharides have great potential to be applied in the food, healthcare, and pharmaceutical fields.

Nanocellulose has become an important renewable component for composite inks, owing to its desirable physical properties, reinforcing capabilities, and tunable self-assembly behavior. However, it is difficult to improve the rheological performance of the nanocellulose-based composite to meet the requirement for 3D printing high resolution microarchitectures. Herein, a strategy is proposed that incorporation of amphiphilic molecular surfactant into nanocellulose gel can increase the molecular interaction via hydrophobic bonds and enhance the ink viscoelasticity. Following the design, a composite ink is formulated by adding xylan and Nonaethylene glycol monododecyl ether (C12E9) within nanocellulose gel. A new printing program is designed to achieve vertical writing of the composite ink and obtain free-standing micropillars and microhemispheres with high resolution in dozens of micrometers. The microhemisphere on an atomic force microscope (AFM) cantilever can be used as colloidal probe. This work proves that nanocellulose composite ink is a candidate for 3D printing functional devices with special microstructures. [ABSTRACT FROM AUTHOR]

A new type of a mesoporous carbon-coated bismuth (Bi@C) composite in the form of nanorods is fabricated and used as anode material in a potassiumion battery (KIB). The rod-like Bi core is composed of nanoparticles and confined by a shell of amorphous carbon. The KIB with such Bi@C anode exhibits a high storage capacity of 425 mAh g-1 at 0.2 A g-1. The mesoporous Bi@C, with a large surface area and an appropriate pore size is in close contact with the electrolyte and facilitates the diffusion of K+ ions. The carbon shell soothes the mechanical stresses owing to the volumetric changes of the anode during charging and discharging of the battery, preventing the degradation of active material and delivering a cyclic stability of over 500 cycles. This superior performance demonstrates the importance of a structural design that can offer a new pathway to anode development in KIB as well as in other energy storage devices. [ABSTRACT FROM AUTHOR]

Deuterium labeling is of great value in organic synthesis and the pharmaceutical industry. However, the state-of-the-art C-H/C-D exchange using noble metal catalysts or strong bases/acids suffers from poor functional group tolerances, poor selectivity and lack of scope for generating molecular complexity. Herein, we demonstrate the deuteration of halides using heavy water as the deuteration reagent and porous CdSe nanosheets as the catalyst. The deuteration mechanism involves the generation of highly active carbon and deuterium radicals via photoinduced electron transfer from CdSe to the substrates, followed by tandem radicals coupling process, which is mechanistically distinct from the traditional methods involving deuterium cations or anions. Our deuteration strategy shows better selectivity and functional group tolerances than current C-H/C-D exchange methods. Extending the synthetic scope, deuterated boronic acids, halides, alkynes, and aldehydes can be used as synthons in Suzuki coupling, Click reaction, C-H bond insertion reaction etc. for the synthesis of complex deuterated molecules. [ABSTRACT FROM AUTHOR]

The present study investigated the impact of regeneration process on the crystalline structure and enzymatic hydrolysis behaviors of microcrystalline cellulose (MCC) regenerated from ionic liquid 1-butyl-3-methylimidazolium chloride. The crystalline structures of these regenerated samples were analyzed by X-ray diffraction. Results suggested that almost amorphous cellulose was obtained by regenerating MCC in acetone (DRC-a), while partial cellulose II structure could be found in these regenerated samples from water and ethanol. Additionally, the enzymatic hydrolysis behaviors of MCC and its regenerated samples were comparatively studied. Results showed that above 90% of cellulose could be converted into glucose within 4 h for DRC-a and regenerated cellulose without drying (WRC-w) as compared to that of MCC (9.7%). Therefore, the regeneration process could significantly influence the crystallinity and digestibility of cellulose. [ABSTRACT FROM AUTHOR]

Novel polyimide-Yb complexes (PIYbCs) with high dielectric constant, low dielectric loss and low AC conductance were developed in this study. The PIYbCs were successfully prepared by thermal conversion from bipyrimidine contained polyamic acid with different amounts of Yb. The PIYbCs (molar ratio of Yb to bipyrimidine units=1:1) have shown high dielectric constant (above 150), low dielectric loss (below 0.04) and low AC conductance (lower than 7 x 10-7) at wide operational frequencies (100 Hz-100 kHz). The excellent dielectric properties could be well tuned by controlling the amount of polyimide complexing ytterbium (Yb) and obtained without sacrificing the mechanical properties and thermal stability. The excellent dielectric properties of PIYbCs can be attributed to the long-range and fast polaron delocalization among Yb (III) and the bipyrimidine units on the PI molecular backbones. The outstanding dielectric, mechanical and thermal properties make PIYbCs as promising candidate for high-technology electronic applications. [ABSTRACT FROM AUTHOR]