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The rational construction and preparation of efficient, stable, and economic electrocatalysts for the oxygen reduction reaction (ORR) are necessary for fuel cells. In this work, we fabricated a porous carbon skeleton structure consisting of bimetallic organic framework (BMMOF)-derived N-doped microspheres linked with graphene oxide (GO) conducting network (denoted as UA-Co/RSC@NGF, where "UA" stands for ultrasound-assisted, "RSC" stands for resin microspheres, and "NGF" stands for N-doped graphene framework) as an efficient ORR catalyst by an ultrasound-assisted and one-step pyrolysis method. In this configuration, benefiting from the support of carbon microspheres and the strong synergistic coupling with GO, the structure of UA-Co/RSC@NGF is stabilized, and the large specific surface area enhances the density of active sites. With UA-Co/RSC@NGF as the catalyst, significant ORR properties were achieved with a high half-wave potential (E1/2, 0.90 V), an onset potential (Eonset, 1.03 V), and a large limited current density (5.37 mA cm−2). The durability and methanol resistance of UA-Co/RSC@NGF in alkaline media outperform commercially available Pt/C. This study may open a pathway for rationally designing multidimensional composite-structured carbon-based ORR catalysts for energy-related applications. [ABSTRACT FROM AUTHOR]

The exploration of economical, highly efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) is critical for large-scale industrial applications of clean energy conversion devices. Herein, a facile operation strategy is presented to construct the C-Fe/Fe3O4 nanoparticles embedded in the N-doped graphene framework (denoted as C-Fe/Fe3O4@NGF), which is derived from the introduction of ascorbic acid modified Fe/Zn-MOF guests into the graphene sheet host as a co-precursor and carbonized to obtain a high-performance catalyst. In this configuration, ascorbic acid with moderate acidity can corrode the surface of the MOFs to some extent, thus facilitating the exposure of active sites. As such, the optimized C-Fe/Fe3O4@NGF demonstrates superior ORR performance with a high onset potential (Eonset) of 0.96 V and half-wave potential (E1/2) of 0.86 V for the ORR. More importantly, the durability and methanol-resistance of C-Fe/Fe3O4@NGF outnumbers those of commercial Pt/C in alkaline media. The presented strategy opens a new avenue for developing highly active MOF-derived electrocatalysts for diverse applications. [ABSTRACT FROM AUTHOR]

All-inorganic cesium lead halide (CsPbX3, X=Cl, Br, I) perovskite nanocrystals (NCs) have attracted increasingly research interest as highly efficient light absorbers in optoelectronic devices for their outstanding optical properties. Here, a CsPbBr3 NCs/graphene hybrid photodetector was demonstrated for efficient ultraviolet light detection, in which CsPbBr3 NCs served as a light absorber, and graphene acted as a carrier transport expressway. The device exhibited high hole and electron mobilities of 1.7 × 103 cm2/V s and 6.4 × 103 cm2/V s in the dark. Under 405 nm illumination, the device showed high responsivity, specific detectivity, external quantum efficiency with maximum values of 3.4 A/W, 7.5 × 108 Jones, 103%, respectively, and short rise/decay times of 7.9/125 ms. The hybrid PD has important prospects in the photodetection applications of optical communication, biological imaging, remote sensing, and other multifunction optoelectronics. [ABSTRACT FROM AUTHOR]

A novel highly ordered three-dimensional nanoflower-like α-Fe 2 O 3 /coal-based graphene (α-Fe 2 O 3 /CG) composite was fabricated through a simple and controllable hydrothermal synthesis strategy. The nanoflower-like α-Fe 2 O 3 /CG provides abundant mesoporous morphology, efficient conductive network and rapid electron transfer, as well as unique structural features that all contribute to improved electrochemical performance. Here, α-Fe 2 O 3 /CG composites have been investigated as advanced anode in the lithium-ion batteries. The electrochemical performance indicated that nanocomposite of α-Fe 2 O 3 /CG exhibited a high capacity (1000 mAh g−1) after 100 cycles at 0.2 A g−1. In addition, the as-designed composite exhibited excellent cycling stability and even at 5 A g−1, the specific capacity of it still can achieve 425 mAh g−1. • A similar nanoflower structure was synthesized by a simple hydrothermal method. • The nanoflower structure benefits the diffusion of ions and transportation of electrons. • The composite showed excellent cycle stability, rate performance and high initial specific capacity. [ABSTRACT FROM AUTHOR]

Abstract Nano-Fe 2 O 3 particles on a nickel substrate have been obtained by electrodeposition technique adjusting the ratio of electrolyte solvent (DMF and water), and then it was used as the working electrode to obtain the C-GQDs/α-Fe 2 O 3 composite material via second-step electrodeposition with the coal-based graphene quantum dots (C-GQDs) solution which had been prepared from Taixi anthracite powder as the electrolyte. The lithium-ion storage performance of C-GQDs/α-Fe 2 O 3 composites as the anode in the lithium-ion battery was studied, and the results show that the composites exhibited excellent cyclability and rate capability. When the current density was 1 A/g, the specific capacitance of C-GQDs/α-Fe 2 O 3 composites was up to 1582.5 mAh/g, and it could maintain 1320 mAh/g after 110 cycles. The specific capacitance was 1091 mAh/g at a high current density (5 A/g). [ABSTRACT FROM AUTHOR]

We fabricated a highly sensitive infrared (IR) layer-heterojunction field effect phototransistor (LH-FEpT) by integrating poly [2-methoxy-5-(20-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV)/PbSe quantum dots composite with monolayer graphene. The phototransistor exhibited high photosensitive in a wide spectral range from visual to infrared. The graphene/MEH-PPV/PbSe QDs based FEpT (GMQ-FEpT) show high carrier mobility (μ) up to 1800 cm 2 V −1 s −1 , high photo responsivity (R) about 133 A/W at a light intensity (4.9 mW/cm 2 ), high external quantum efficiency (EQE) (up to 2×10 4 %) and high specific detectivity (D*) (9.8×10 10 Jones) under illumination of 808 nm laser. [ABSTRACT FROM AUTHOR]

[Display omitted] • Small size FeS 2 encapsulated by N, S co-doped carbon shells and distributed on S-doped graphene. • FeS 2 was produced and S was successfully doped into the carbon skeleton by a one-step vulcanisation process. • The unique two-carbon encapsulated structure can greatly limit the volume expansion of FeS 2 during charging and discharging. • The successful introduction of heteroatoms can cause more defects, which provides more reaction sites for electrochemical reactions and improves the rate of charge transfer. FeS 2 is considered a promising anode candidate for LIBs (lithium-ion batteries) due to its low cost and high theoretical capacity. However, the large volume expansion and low conductivity of FeS 2 limit its further applications. In this work, a novel FeS 2 -based materials with two-carbon encapsulated structure has been designed to solve the above problems. This unique structure is constructed of spindle-shaped FeS 2 nanoparticles embedded in N/S co-doped carbon shell and covered by three-dimensional sulfur-doped graphene (FeS 2 @NSC/SG). The FeS 2 @NSC/SG composite shows excellent lithium storage performance benefiting from the unique two-carbon encapsulated structure. FeS 2 @NSC/SG electrode delivers a reversible capacity of 944.6 mAh·g−1 after 120 cycles at 0.1 A·g−1 when it is used as anode for LIBs. Even at 5 A·g−1, the capacity of FeS 2 @NSC/SG electrode remains 270.8 mAh·g−1 after 500 cycles. The excellent rate performance of FeS 2 @NSC/SG electrode is attributed to the electrochemical behavior dominated by the capacitive behavior and this strategy will provide new ideas for potential electrode materials. [ABSTRACT FROM AUTHOR]

Scalable and sustainable photocatalytic technology can convert CO 2 to valuable hydrocarbons, which requires highly efficient and inexpensive photocatalyst with a broad light absorption range, high stability and fast carrier separation efficiency. Herein, a nanostructure with 2D/2D conformation consisting of BiVO 4 and coal-based graphene oxide (CGO) were fabricated by hydrothermal method, which achieves efficient photoreduction of CO 2 to CH 3 OH. Surprisingly, this nanostructure exhibits a significantly enhanced photocurrent density (0.95 mA/cm2), good CO 2 adsorption capacity (1.34 cm3/gSTP) and medium stability. Moreover, the optimized 10-CGO/BiVO 4 composite shows moderate CO 2 conversion activity with a CH 3 OH production of 537.78 μmol/g h under light irradiation, which is approximately 6.47 times higher than that of BiVO 4 nanosheets. The enhanced photocatalytic activity can be attributed to the following three points: broadened visible light absorption ability, unique ultra-thin structure and abundant surface active sites; effective photocarriers separation efficiency and reduced interfacial resistance at their heterojunction between BiVO 4 and CGO nanosheets; CGO as co-catalyst with an electron-transfer path coupling with CGO can expedite the separation speed of carriers of photocatalyst, reduce the interface resistance and enrich surface active sites. This work provides inspiration for high performance binary photocatalyst in solar-chemical energy conversion process. The illustration of a possible charge transfer in CGO/BiVO 4 compound for photocatalytic reduction of CO 2 to CH 3 OH. [Display omitted] • CGO/BiVO 4 nanostructure is fabricated by a simple hydrothermal method. • The 2D/2D nanojunction expand visible light harvesting, improve carriers separation. • Fast and directional transfer of carrier is achieved by CGO. • CGO/BiVO 4 has stronger CO 2 adsorption capacity, providing more active sites. [ABSTRACT FROM AUTHOR]

• MAPbI 3 /RGO material with high TCR and low heat capacity synthesized by composite engineering. • The hot carrier injection is introduced to enhance the bolometric effect in graphene. • The responsivity and the response time of the terahertz detector are synchronously improved. Thermal photodetectors, such as bolometers, are the most promising option for detecting infrared (IR) to terahertz (THz) radiation at room temperature. Previous studies have shown that graphene has great potential for broadband thermal photodetection because of its distinctive optical and electrical properties. However, the responsivity of graphene photodetector is limited by the weak absorption and the finite temperature coefficient of resistance (TCR). Here, we synthesize the methylamine lead iodide perovskite (MAPbI 3)/graphene oxide (RGO) composite material, exhibiting high TCR of −0.89%K−1 and low heat capacity at room temperature. The composite is designed to construct a sensitive and fast IR to THz bolometer. The MAPbI 3 /RGO detector shows significant performance breakthroughs, with the responsivity as high as 805 mA/W, the response time of about 700 μs, at 220 GHz, which are about an order of magnitude higher than those of pure RGO detector. These results suggest that compositing engineering gives a new approach to the technological innovation of THz detectors. [ABSTRACT FROM AUTHOR]

• A MOF-derived route was reported to synthesize Fe/Fe 3 C@NC-Gs ORR electrocatalysts. • The loading amount of Fe influenced the properties of Fe/Fe 3 C@NC-Gs. • Fe/Fe 3 C@NC-G-2 shows obvious mesoporous, which gives positive impact on ORR activity. • Fe/Fe 3 C@NC-G-2 could catalyze ORR via a direct 4e− pathway. • Fe/Fe 3 C@NC-G-2 presents admirable catalytic activity for ORR. It is of significance to replace Pt-based electrocatalyst with high activity and low price non-noble metal oxygen reduction reaction (ORR) electrocatalysts for large-scale application of fuel cells. Herein, we display a kind of core–shell hybrid composed of Fe/Fe 3 C@nitrogen-doped carbon decorated on graphene (denoted as Fe/Fe 3 C@NC-Gs) as the efficient ORR electrocatalyst. The optimal-performing Fe/Fe 3 C@NC-G-2 catalyst presents an outstanding ORR performance in terms of a high onset potential (E onset) of 0.97 V (vs. RHE) and half-wave potential (E 1/2) of 0.88 V (vs. RHE), respectively, possible to rival those of the commercially available Pt/C in an alkaline electrolyte solution. Besides, the Fe/Fe 3 C@NC-G-2 catalyst manifests better stability and methanol tolerance than those of commercially available Pt/C, which is of importance for the excogitation and fabrication of novel electrocatalysts originated from non-precious metals. Accordingly, it is confirmed that the integration of Fe/Fe 3 C@NC and graphene enables plentiful active sites stemmed from different active species of Fe 3 C, Fe, and NC and intrinsic hierarchically porous structure with intimate contact of various components, which would give Fe/Fe 3 C@NC-G-2 a positive impact on ORR activity. [ABSTRACT FROM AUTHOR]

Ultrahigh N-doped porous carbon graphene nanosheets (NPC@GNS) with two-dimensional (2D) multilayer sandwich framework are elaborately designed from ZIF-8 nanoparticles in situ grown on graphene oxide (GO) with 2-methyimidazole and polyvinyl pyrrolidone added as nitrogen precursor through a facile one-step fast pyrolysis and explored in lithium-ion batteries (LIBs). As the process-enhanced anode material, the NPC@GNS provide a high capacity of 906.6 mAh g−1 after 100 cycles at 0.5 A g−1, and an average capacity of 378.2 mAh g−1 after an extremely long cycling durability over 1000 cycles at 5 A g−1. It is worth noting that the superior electrochemical performance of the NPC@GNS electrode as the anode for LIBs confirms the reliability of the sufficient "point and plane" 2D sandwich framework, and a portion of the micropores and a large number of preferred mesoporous channels help to facilitate rapid charge transfer, which indicates that NPC@GNS is a vibrant material that plays a key role in contributing to the application in future energy storage. • A simple nitrogen-doped sandwich structure was synthesized in situ. • The preferred mesoporous structure benefits the diffusion of ions and transportation of electrons. • The composite showed excellent cycle stability, rate performance and high specific capacity. [ABSTRACT FROM AUTHOR]

Here we present a feasible way to fabricate a high-performance graphene phototransistor functionalized with Poly(3-hexylthiophene) (P3HT)/graphene bulk heterojunction by solution processing, which possesses the advantages of the high carrier mobility of graphene and the high visible light absorption of P3HT. The hole field-effect mobility for the device was 3.8 cm 2 V − 1 s −1 at room temperature. The photoresponsivity, external quantum efficiency and detectivity were 12 A/W, 3 × 10 3 % and 1.6 × 10 6 Jones at a illumination irradiance of 15 mW/cm 2 respectively. The phototransistor exhibited sensitive photoresponse with a rise time of 168 ms and a decay time of 121 ms. [ABSTRACT FROM AUTHOR]

Previous studies have shown that graphene's particular optical and electrical properties endow it with powerful potential in infrared (IR) photodetection. However, the responsivity of detectors is limited by the weak absorption and high thermal conductivity of graphene. Here, we report synchronous laser reduction to fabricate the intercalated MAPbI 3 /RGO composite to improve the photothermoelectric (PTE) performance and break through the barrier of responsivity of graphene photodetectors at room temperature. Combined with experimental phenomena and theoretical analysis, the introduction of MAPbI 3 improved the fundamental thermoelectric properties of the composite, such as absorption coefficient, thermal conductivity, Seebeck coefficient, and thermal sensitivity index, etc. The MAPbI 3 /RGO detector shows significant performance breakthroughs in sensitivity, noise-equivalent power (NEP) in the IR region, responsivity as high as 44.24 mV/W, and noise-equivalent power of 7.17 nW/√Hz at 980 nm. The fast and low-cost fabrication of inserting perovskite into multilayer graphene offers opportunities to decouple the carrier and phonon transmission in materials, thus promising for developing high-performance PTE photodetectors. [ABSTRACT FROM AUTHOR]

• The main innovations of the submitted manuscript are: • In order to apply the quasi-BIC metasurfaces in practice, the substrate needs to be added and the substrate itself will greatly destroy the up-down symmetry, in this paper, the tapered structure designed can recapture the electromagnetic field into the quasi-BIC metasurfaces and eliminate the adverse effects of substrate. • The tapered structure maintains the high absorption rate of the quasi-BIC metasurfaces with up-down asymmetry on graphene, and this structure will be applicable to the critical coupling under quasi-BIC condition for other two-dimensional materials. • The calculated results show that our tapered structure is applicable to different structures and substrates, it is universal and can be used to solve other problems when quasi-BIC or BIC structures with up-down asymmetry. Either the bound states in the continuum (BIC) or quasi-BIC structure can be used as Hermitian system when it has up-down symmetry (Cartesian coordinates in the out-plane or z direction), so that BICs is stable. However, out-plane symmetry is not guaranteed in all cases. We take the quasi-BIC structure to enhance the absorption of two-dimensional materials as an example, but not limited to the use of other BIC structures, to solve the problem of the asymmetric quasi-BIC metasurfaces in the z direction. Previously reported works have proposed to control critical coupling light absorption in two-dimensional materials such as monolayer graphene by quasi-BIC metasurfaces. However, in order to apply the quasi-BIC structure in practice, the substrate needs to be added and it will greatly destroy the out-plane symmetry, resulting in the reduction of the original high absorption rate of graphene. To solve the above problems, the tapered structure designed in this paper can recapture the electromagnetic field into the quasi-BIC structure and avoid the leakage of the field into the substrate. This structure maintains the high absorption rate of the original structure on graphene, and the calculated results show that our tapered structure is applicable to different structures and substrates. [ABSTRACT FROM AUTHOR]

The chiral metasurface possesses wide applications in terahertz (THz) band. It is still an important issue to control the chiral properties of metasuface by a simple and effective method. We design a reflective chiral THz metasurface that reflection medium in bottom is based on monolayer graphene on low resistance Si substrate. This structure allows a more reasonable approach to tune Fermi level (E F) of graphene compared with previous report. THz reflection change in graphene as varying E F can control in a large dynamic range the chiral properties of metasurface, inducing the state switch between 'On' and 'Off'. The dynamic control is also effective for various further applications such as vortex focusing and near field imaging. Significantly, we report for the first time the variation rule of reflection amplitude for reflecting suppressed circularly polarized light, with the change in rotation angle of top metal ring of metasurface. Based on this, we develop an innovation application, called full grayscale near field imaging (FGNFI) that can show full grayscale details compared with traditional near field imaging that can only show two grayscale states. Image 1 We propose a new structure that using monolayer graphene on surface of low resistivity silicon substrate acts as a reflection medium in reflective chiral terahertz metasurface. When bias voltage is applied between graphene and silicon, electrons and holes in silicon can be injected into graphene to tune the chirality between 'On' and 'Off' states. An innovation near field imaging application is developed by using the regular amplitude change of reflection suppressed circular polarization with metal ring rotation. The new application we developed can theoretically achieve the imaging with a series of grayscale values between the brightest to the dimmest states, which give more color details and thus is called full grayscale near field imaging (FGNFI). The tunable chirality 'On' and 'Off' can be used not only for traditional applications, but also for our newly developed FGNFI application. • A new graphene tuned recflective chiral terahertz metasurface is proposed. • Monolayer graphene on surface of low resistivity Si acts as a reflection medium. • Appling voltage between graphene and Si obtains the chirality On and Off states. • New application called full grayscale near field imaging (FGNFI) is developed. • FGNFI can achieve full grayscale details. [ABSTRACT FROM AUTHOR]

Chiral metasurfaces can achieve giant chiral optical responses and have been expanded from the optical band to other electromagnetic bands. Here, we propose a new method for dynamic terahertz circular dichroism (CD) manipulation in metasurfaces. By introducing a patterned and electrically doped graphene into the metamirror consists of double layer C-shaped split ring resonators (SRRs), efficient terahertz CD modulation is observed. Since the electrical doping of graphene changes the absorption loss of the metasuface cavity, the structure shows switching between a chiral metasurface and an ordinary metal mirror, which can be seen as "on" and "off" states. The calculation results show an efficient modulation of the terahertz CD in a large dynamic range. In addition, we also use the new method to design two metasurfaces for dynamic terahertz wavefront modulation and near-field digital imaging, both of which show a high-performance electrical switching. This method provides a new way for the design of active terahertz devices based on metasurfaces, and also promotes the applications of terahertz chiral metasurfaces in high-speed wireless communication and dynamic imaging. Image 1 [ABSTRACT FROM AUTHOR]

Although potassium-ion batteries (PIBs) are considered as promising candidate to lithum-ion batteries (LIBs) in the area where energy density is no longer the top priority, developing suitable anodes for PIBs is still a big challenge because of the large radius of potassium-ion, which limits the rate performace and cyclic stability. Herein, nitrogen/oxygen dual-doped hierarchically porous carbon/graphene composite (NOPC@G) has been prepared for potassium-ion storage. Thanks to the heteroatom-rich porous structure and conductive network induced by graphene, the ion diffusion and electronic transmission are enhanced, which make NOPC@G exhibit outstanding potassium storage performance in terms of high specific capacity (445 mAhg−1), high rate capability (112 mAhg−1 at 40 C) and excellent cyclic stability. Furthermore, when used as anode for potassium-ion capacitors (PICs), NOPC@G also exhibits an impressive electrochemical performance with a maximum energy density of 153 Wh kg−1 (with a power density of 120 W kg−1) and a maximum power density of 22.98 kW kg−1 (with an energy density of 57 Wh kg−1). The simple synthesis route combined with the desirable electrochemical performance makes NOPC@G a promising anode for potassium storage. [Display omitted] [ABSTRACT FROM AUTHOR]