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Gaseous promotors have readily been adopted during the direct synthesis of graphene over insulators to enhance the growth quality and/or boost the growth rate. The understanding of the real functions of carbon-containing promotors has still remained elusive. In this study, we identify the critical roles of a representative CO2 promotor played in the direct growth of graphene. The comparative experimental trials validate CO2 as an effective modulator to decrease graphene nucleation density, improve growth kinetics, and mitigate adlayer formation. The first-principles calculations illustrate that the generation of gas-phase OH species in CO2-assisted system helps decrease the energy barriers of CH4 decomposition and carbon attachment to the growth front, which might be the key factor to allow high-quality direct growth. Such a CO2-promoted strategy enables the conformal coating of graphene film over curved insulators, where the sheet resistance of grown graphene on quartz reaches as low as 1.26 kΩ·sq−1 at an optical transmittance of ∼ 95.8%. The fabricated endoscope lens based on our conformal graphene harvests an apoptosis of 82.8% for noninvasive thermal therapy. The work presented here is expected to motivate further investigations in the controllable growth of high-quality graphene on insulating substrates. [ABSTRACT FROM AUTHOR]

The practical application of lithium–sulfur (Li–S) batteries has been handicapped by the notorious polysulfide shuttling and sluggish sulfur conversion kinetics. Although the functional modification of separator is readily proposed as an effective strategy to optimize the Li–S redox reactions, the excessive material dosage and invalid structural design still result in inferior electrocatalyst utilization. Herein, generic graphene‐metal selenide heterostructures (Gr‐MxSey, M = Mo, W, Mn, Cu and Zn) are controllably grown on commercial glass fiber (GF) separator employing a sequential low‐temperature chemical vapor deposition procedure. Such a tailored reservoir can not only render ample active sites but also realize the synergy of polar and catalytic framework, which maximizes the electrochemical functions in alleviating shuttle effect and guiding Li2S nucleation/decomposition. The thus‐derived Gr‐MxSey/GF separator affording favorable heatproof feature endows the Li–S battery with an outstanding cycling stability (100% capacity retention over 100 cycles at 0.2 C). Furthermore, the flexible Li–S pouch cell based on this new separator delivers good device performance (with a capacity decay of 0.25% per cycle over 100 cycles). This study offers comprehensive insight into the reliable separator design toward working Li–S batteries. [ABSTRACT FROM AUTHOR]

Direct synthesis of high-quality graphene on dielectric substrates without a transfer process is of vital importance for a variety of applications. Current strategies for boosting high-quality graphene growth, such as remote metal catalyzation, are limited by poor performance with respect to the release of metal catalysts and hence suffer from a problem with metal residues. Herein, we report an effective approach that utilizes a metal-containing species, copper acetate, to continuously supply copper clusters in a gaseous form to aid transfer-free growth of graphene over a wafer scale. The thus-derived graphene films were found to show reduced multilayer density and improved electrical performance and exhibited a carrier mobility of 8500 cm2 V−1 s−1. Furthermore, droplet-based hydrovoltaic electricity generator devices based on directly grown graphene were found to exhibit robust voltage output and long cyclic stability, in stark contrast to their counterparts based on transferred graphene, demonstrating the potential for emerging energy harvesting applications. The work presented here offers a promising solution to organize the metal catalytic booster toward transfer-free synthesis of high-quality graphene and enable smart energy generation. [ABSTRACT FROM AUTHOR]

Graphene films, fabricated by chemical vapor deposition (CVD) method, have exhibited superiorities in high crystallinity, thickness controllability, and large‐scale uniformity. However, most synthesized graphene films are substrate‐dependent, and usually fragile for practical application. Herein, a freestanding graphene film is prepared based on the CVD route. By using the etchable fabric substrate, a large‐scale papyraceous freestanding graphene fabric film (FS‐GFF) is obtained. The electrical conductivity of FS‐GFF can be modulated from 50 to 2800 Ω sq−1 by tailoring the graphene layer thickness. Moreover, the FS‐GFF can be further attached to various shaped objects by a simple rewetting manipulation with negligible changes of electric conductivity. Based on the advanced fabric structure, excellent electrical property, and high infrared emissivity, the FS‐GFF is thus assembled into a flexible device with tunable infrared emissivity, which can achieve the adaptive camouflage ability in complicated backgrounds. This work provides an infusive insight into the fabrication of large‐scale freestanding graphene fabric films, while promoting the exploration on the flexible infrared camouflage textiles. [ABSTRACT FROM AUTHOR]

Witnessing compositional evolution and identifying the catalytically active moiety of electrocatalysts is of paramount importance in Li–S chemistry. Nevertheless, this field remains elusive. We report the scalable salt‐templated synthesis of Se‐vacancy‐incorporated MoSe2 architecture (SeVs‐MoSe2) and reveal the phase evolution of the defective precatalyst in working Li–S batteries. The interaction between lithium polysulfides and SeVs‐MoSe2 is probed to induce the transformation from SeVs‐MoSe2 to MoSeS. Furthermore, operando Raman spectroscopy and ex situ X‐ray diffraction measurements in combination with theoretical simulations verify that the effectual MoSeS catalyst could help promote conversion of Li2S2 to Li2S, thereby boosting the capacity performance. The Li–S battery accordingly exhibits a satisfactory rate and cycling capability even with and elevated sulfur loading and lean electrolyte conditions (7.67 mg cm−2; 4.0 μL mg−1S). This work elucidates the design strategies and catalytic mechanisms of efficient electrocatalysts bearing defects. [ABSTRACT FROM AUTHOR]

Direct growth of large area uniform graphene on functional insulating materials is essential for engineering versatile applications of graphene. However, the existing synthesis approaches can hardly avoid the generation of non-uniform multilayer graphene along the gas flow direction, affording huge challenges for further scaling up. Herein, by exploiting the molten state of soda-lime glass, we have accomplished the direct growth of large area uniform (up to 30 cm × 6 cm) graphene via a facile chemical vapor deposition route on low cost soda-lime glass. The use of molten glass eliminates the chemically active sites (surface corrugations, scratches, defects), and improves the mobility of carbon precursors, affording uniform nucleation and growth of monolayer graphene. Intriguingly, thus-obtained graphene acts as an ideal coating layer for the surface crystallographic modification of soda-lime glass, making it epitaxy substrates for synthesizing high-quality PbI2 nanoplates and continues films. Accordingly, a prototype photodetector was fabricated to present excellent photoelectrical properties of high responsivity (∼ 600 on/off current ratio) and fast response speed (18 µs). This work hereby paves ways for the batch production and the direct applications of graphene glass as platforms for constructing high performance electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Owing to the lattice match, aligned CH3NH3PbI3 perovskite array films composed of CH3NH3PbI3 microribbons with the length at the sub-millimeter scale were fabricated on ST cut quartz which showed a fast photo-response. This method provides a simple and flexible approach to grow oriented crystalline CH3NH3PbI3 arrays at the millimeter scale. [ABSTRACT FROM AUTHOR]

Witnessing compositional evolution and identifying the catalytically active moiety of electrocatalysts is of paramount importance in Li-S chemistry. Nevertheless, this field remains elusive. We report the scalable salt-templated synthesis of Se-vacancy-incorporated MoSe 2 architecture (SeVs-MoSe 2 ) and reveal the phase evolution of the defective precatalyst in working Li-S batteries. The interaction between lithium polysulfides and SeVs-MoSe 2 is probed to induce the transformation from SeVs-MoSe 2 to MoSeS. Furthermore, operando Raman spectroscopy and ex situ X-ray diffraction measurements in combination with theoretical simulations verify that the effectual MoSeS catalyst could help promote conversion of Li 2 S 2 to Li 2 S, thereby boosting the capacity performance. The Li-S battery accordingly exhibits a satisfactory rate and cycling capability even with and elevated sulfur loading and lean electrolyte conditions (7.67 mg cm -2 ; 4.0 μL mg -1 S ). This work elucidates the design strategies and catalytic mechanisms of efficient electrocatalysts bearing defects., (© 2021 Wiley-VCH GmbH.)

Electrocatalysts remain vitally important for the rational management of intermediate polysulfides (LiPSs) in the realm of Li-S batteries. In terms of transition-metal-based candidates, in situ evolution of electrocatalysts in the course of an electrochemical process has been acknowledged; nevertheless, consensus has not yet been reached on their real functional states as well as catalytic mechanisms. Herein, we report an all-chemical vapor deposition design of the defective vanadium diselenide (VSe 2 )-vertical graphene (VG) heterostructure on carbon cloth (CC) targeting a high-performance sulfur host. The electrochemistry induces the sulfurization of VSe 2 to VS 2 at Se vacancy sites, which propels the adsorption and conversion of LiPSs. Accordingly, the VSe 2 -VG@CC/S electrode harvests an excellent cycling stability at 5.0 C with a capacity decay of only 0.039% per cycle over 800 cycles, accompanied by a high areal capacity of 4.9 mAh cm -2 under an elevated sulfur loading of 9.6 mg cm -2 . Theoretical simulation combined with operando characterizations reveals the key role played by the Se vacancy with respect to the electrocatalyst evolution and LiPS regulation. This work offers insight into the rational design of heterostructure sulfur hosts throughout defect engineering.