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Advances in the optoelectronics and information industries have allowed modern electronic devices to undergo a continuous trend toward miniaturization and integration, which poses significant chall...

A simple and effective process has been reported to prepare the silver (Ag)/graphene composite with excellent mechanical and electrical properties based on high-quality graphene (HQG). The HQG was fabricated via hot pressing of reduced graphene oxide (RGO) from chemical exfoliation, while the Ag/HQG composite was obtained by using spark plasma sintering (SPS) treatment under high temperature (1500 °C) and moderate pressure (40 MPa). With low oxygen-containing functional groups and defect density, the HQG dispersed homogeneously in the composite after high-energy ball milling. In comparison to pure Ag, the as-prepared Ag/RGO composite exhibited a great enhancement of 11% electrical conductivity and 42% micro-hardness with an optimal RGO adding content (1 wt%). The Ag/HQG composite is expected to open up a new way for the novel Ag-based electrical contact materials, and further to broaden its applications in micro-electronics and switching power. Keywords: Graphene, Silver, Composite, Electrical property, Mechanical property

In this study, a novel brick-like NiCo2O4 material was synthesized via a facile hydrothermal method. The as-prepared NiCo2O4 material possessed high porosity with the BET specific surface area of 58.33 m2/g, and its pore size distribution was in a range of 5–15 nm with a dominant pore diameter of 10.7 nm. The electrochemical performance of the NiCo2O4 was further investigated as anode material for lithium-ion battery. The NiCo2O4 anode possessed a high lithium storage capacity up to 2353.0 mAh/g at the current density of 100 mA/g. Even at the high rate of 1 A/g, a reversible capacity of ∼600 mAh/g was still retained, and an average discharge capacity of ∼1145 mAh/g could be recovered when the current density was reduced back to 150 mA/g. Due to the simple and cost-effective process, the NiCo2O4 bricks anode material shows great potential for further large-scale applications on the area of lithium-ion battery.

The electrochemical performance of lithium ion batteries depend largely on the structural properties of electrode materials. In this work, we propose an approach to synthesize lithium-rich layered oxides (LLOs) materials using a manganese dioxide (MnO2) template strategy, which could control the structure and particle size of final products via choosing different MnO2 templates. Through precisely optimizing, we successfully prepare cross-linked nanorods (CLNs) and agglomerate microrods (AMs) Li1.2Ni0.15Co0.1Mn0.55O2 cathode materials by using carbon-decorated MnO2 nanowires and MnO2 nanorods as templates, respectively. The lithium ion battery based on the CLNs exhibits excellent performance, delivering a high capacity of 286.2 mAh g−1 at 0.1 C and 237.5 mAh g−1 at 1 C. In addition, the device remains 98% and 89% of its initial capacity after 50 cycles at 0.1 C and 100 cycles at 1 C, respectively. The remarkable electrochemical performance can be mainly attributed to the cross-linked nanorods structure which can provide relatively shorter lithium ion diffusion length, larger reaction surface and more internal cavity. This universal structure engineering strategy may shed light on new material structures for high performance lithium-rich layered oxide cathode materials.

The photocatalytic performance of heterostructure photocatalysts is limited in practical use due to the charge accumulation at the interface and its low efficiency in utilizing solar energy during photocatalytic process. In this work, a ternary hierarchical TiO2 nanorod arrays/graphene/ZnO nanocomposite is prepared by using graphene sheets as bridge between TiO2 nanorod arrays (NRAs) and ZnO nanoparticles (NPs) via a facile combination of spin-coating and chemical vapor deposition techniques. The experimental study reveals that the graphene sheets provide a barrier-free access to transport photo-excited electrons from rutile TiO2 NRAs and ZnO NPs. In addition, there generates an interface scattering effect of visible light as the graphene sheets provide appreciable nucleation sites for ZnO NPs. This synergistic effect in the ternary nanocomposite gives rise to a largely enhanced photocurrent density and visible light-driven photocatalytic activity, which is 2.6 times higher than that of regular TiO2 NRAs/ZnO NPs heterostructure. It is expected that this hierarchical nanocomposite will be a promising candidate for applications in environmental remediation and energy fields.

Limited by the Boltzmann distribution of electrons, the sub-threshold swing (SS) of conventional MOSFETs cannot be less than 60 mV dec−1. This limitation hinders the reduction of power dissipation of the devices. Herein, we present high-performance In2O3 nanowire (NW) negative capacitance field-effect transistors (NC-FETs) by introducing a ferroelectric P(VDF-TrFE) layer in a gate dielectric stack. The fabricated devices exhibit excellent gate modulation with a high saturation current density of 550 μA μm−1 and an outstanding SS value less than 60 mV dec−1 for over 4 decades of channel current. The assembled inverter circuit can demonstrate an impressive voltage gain of 25 and a cut-off frequency of over 10 MHz. By utilizing the self-aligned fabrication scheme, the device can be ultimately scaled down to below 100 nm channel length. The devices with 200 nm channel length exhibit the best performances, in which a high on/off current ratio of >107, a large output current density of 960 μA μm−1 and a small SS value of 42 mV dec−1 are obtained at the same time. All these would not only evidently demonstrate the potency of NW NC-FETs to break through the Boltzmann limit in nanoelectronics, but also open up a new avenue to low-power transistors for portable products.

Carbon materials have attracted great attention for their diversified applications in supercapacitors, and different structures of carbon have been reported to exhibit dissimilar electrochemical properties. In the past, activated carbons, carbon nanotubes (CNTs), carbon nanofibers and graphene have been shown to have excellent electrochemical performances, but it still remains a problem on how to improve the capacitance of carbon-based materials effectively from the viewpoint of their giant commercial potential. Noticing that connecting chemical groups to carbon can provide large pseudo-capacitance, we hereby demonstrated that the position of the chemical groups also plays an important role in the pseudo-capacitance. In our work, we synthesized graphene nanoribbon (GNR), graphene oxide (GO) and functional MWCNTs and showed that GNR has larger capacitance (calculated to be 202 F/g at a scan rate of 5 mV/s) and energy density compared to CNTs and GO when using as electrode materials. Furthermore, the supercapacitor device based on as-synthesized GNR exhibits excellent cycle stability and rate capability which evident is potential in high performance supercapacitor. Revealing the source of the capacitance, we found that though GNR has less oxygen-containing groups, it has larger pseudo-capacitance than GO and CNTs due to the remarkable edge-riched structure with high activity in electrochemical reactions. This finding highlights the importance of edge structure in carbon-based pseudo supercapacitor and suggests a new insight for the development of pseudo-capacitance electrode materials.

Sensitivity, durability, and multifunction are the essential requirements for a high-performance wearable sensor. Here, we report a novel multifunctional sensor with high sensitivity and durability by using a buckled spider silk-like single-walled carbon nanotubes (SSL-SWNTs) film as the conducting network and a crack-shaped Au film as the sensitive transducer. Its high sensitivity is inspired by the crack-shaped structure of the spider's slit organs, while the high durability is inspired by the mechanical robustness of the spider silk. Similar to the spider's slit organs that can detect slight vibrations, our sensor also exhibits a high sensitivity especially to tiny strain. The proposed quantum tunneling model is consistent with experimental data. In addition, this sensor also responds sensitively to temperature with the sensitivity of 1.2%/°C. Because of the hierarchical structure like spider silk, this sensor possesses combined superiority of fast response (60 ms) and high durability (10 000 cycles). We also fabricate a wearable device for monitoring various human physiological signals. It is expect that this high-performance sensor will have wide potential applications in intelligent devices, fatigue detection, body monitoring, and human-machine interfacing.

Supercapacitor is a newly-developed device for electrochemical energy storage with high power density, long life span, as well as rapid capture and storage of energy. Carbon-based materials, from carbon nanospheres, nanotubes and nanofibers to graphene, are the most commonly used electrode materials for supercapacitors. Our group has engaged in the research of carbon nanomaterials over the past decade. Herein we summarize some typical carbon nanomaterials and their synthetic routes based on our published works, which is expected to provide the theoretical and experimental basis for further applications on carbon-based energy storage devices.

Supercapacitor is a new type of energy-storage device, and has been attracted widely attentions. As a two dimensional (2D) nanomaterials, graphene is considered to be a promising material of supercapacitor because of its excellent properties involving high electrical conductivity and large surface area. In this paper, the large-scale graphene is successfully fabricated via environmental-friendly electrochemical exfoliation of graphite, and then, the three dimensional (3D) graphene foam is prepared by using nickel foam as template and FeCl 3 /HCl solution as etchant. Compared with the regular 2D graphene paper, the 3D graphene foam electrode shows better electrochemical performance, and exhibits the largest specific capacitance of approximately 128 F/g at the current density of 1 A/g in 6 M KOH electrolyte. It is expected that the 3D graphene foam will have a potential application in the supercapacitors.

The amount of graphene (Gr) in a composite plays a key role in enhancing the performance of the composite. In general, an indirect method, that is, by adjusting the concentration of Gr (or GO) in the electrolyte, is used to study the influence of the graphene content on the properties of copper (Cu)–Gr composite foil. In this paper, we firstly propose a direct and accurate approach, that is, by using an instrumental carbon and sulfur analyzer, to determine the amount of Gr in the direct current electrodeposited Cu–Gr composite foil, and also obtain the relationship between the amount of Gr in the composite foils and the concentration of GO in the electrolyte. Further, mechanical property measurements reveal that: (1) the variations in the mechanical properties (involving the elastic modulus, hardness and tensile strength) of the Cu–Gr foils along with the concentration of GO in the electrolyte exhibit similar tendencies to that of the Gr content in the Cu–Gr foils. (2) According to current experimental conditions, the optimal values of the mechanical properties and the amount of Gr in the foils appears at a GO concentration of 0.5 g L−1 in the electrolyte. (3) When the GO concentration is less than 0.5 g L−1, the values of the mechanical properties and the amount of Gr in the foils present an approximately linear relationship; and beyond 0.5 g L−1, the values become unstable and declining, which can be attributed to an agglomeration of excess GO in the electrolyte which makes it difficult to be co-deposited into the foil.

In this work, we established a one-step strategy to synthesize three-dimensional porous graphitic biomass carbon (PGBC) from bamboo char (BC), and studied its electrochemical performance as electrode materials for supercapacitors. Using potassium ferrate (K2FeO4) to fulfil the synchronous carbonization and graphitization of bamboo carbon, this method is less time-demanding, highly efficient and pollution-free, when compared with a conventional two-step strategy. The as-prepared PGBC sample possessed a porous structure with a large specific surface area (1732 m2 g−1) and abundant micropores, as well as a high graphitization degree demonstrated by XRD and Raman. Further electrochemical measurements revealed that the PGBC electrode exhibited a high specific capacitance of 222.0 F g−1 at 0.5 A g−1, and the solid-state symmetric supercapacitor in an aqueous electrolyte (KOH/PVA) presented considerable synergetic energy–power output properties with an energy density of 6.68 W h kg−1 at a power density of 100.2 W kg−1, and 3.33 W h kg−1 at 10 kW kg−1. Moreover, the coin-type symmetric supercapacitor in an ionic liquid electrolyte (EMIM TFSI) delivered a higher energy density of 20.6 W h kg−1 at a power density of 12 kW kg−1. This approach holds great promise to achieve low-cost, green and industrial-grade production of renewable biomass-derived carbon materials for advanced energy storage applications in the future.

A facile approach to fabricate low-cost hole-transport-material (HTM)-free perovskite solar cell(PSC) based on commercial P25 nanoparticles and bilayer hybrid carbon electrode under ambient condition is reported. The performance of such HTM-free PSCs are highly dependent on the thickness and morphology of the P25 based TiO 2 electron-transport layer(ETL), which can be adjusted by the amount of ethanol and ethyl cellulose in the paste. After optimization, a power conversion efficiency of 12.48% is obtained, which is enhanced by 20.46% compared with solar cells employing hydrothermal TiO 2 ETL. In addition, PSCs with P25 ETL also exhibit excellent long-term stability together with reduced hysteresis. With advantages of low-cost, high efficiency and facile fabrication process, commercial P25 nanoparticles based PSC is highly potential for future commercialization.

Two dimensional materials have promising benefits in photoelectronic devices, including facilitating charge transport and reducing defects in perovskite solar cells (PSCs) and photodetectors (PDs) through interface engineering. Herein, a two dimension polymeric material of graphitic carbon nitride quantum dots (g-CNQDs) interlayer is used to modify the SnO2/perovskite interface in both ambient PSCs and PDs to improve the overall performance. The introduction of g-CNQD layer improves the crystalline quality of sequential perovskite absorber with high phase purity, less grain boundaries, low trap states and suppressed carrier recombination due to the intrinsic cross-linkable feature and relatively smooth surface of g-CNQD. As a result, with optimal modification, fully air-processed PSC reached a champion power conversion efficiency of 21.23% with negligible hysteresis, and the PDs had remarkable performance enhancement. Moreover, our PSCs have good stability in ambient air, keeping over 90% of the initial efficiency after 30 days’ exposure.

In this work, a novel carbon nanotubes (CNTs)/NiCo2S4 composite for high performance supercapacitors was prepared via a simple chemical bath deposition combined with a post-anion exchange reaction. The morphologies and phase structures of the composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and low-temperature sorption of nitrogen (BET). The electro-chemical tests revealed that the CNT/NiCo2S4 composite exhibited high electrochemical performance, because the CNTs were used as a conductive network for the NiCo2S4 hexagonal nanoplates. Compared with pure NiCo2S4 and the mechanically mixed CNTs/NiCo2S4 composite, the CNTs/NiCo2S4 composite electrode material exhibited excellent supercapacitive performance, such as a high specific capacitance up to 1537 F/g (discharge current density of 1 A/g) and an outstanding rate capability of 78.1% retention as the discharge current density increased to 100 A/g. It is therefore expected to be a promising alternative material in the area of energy storage.

A kind of sandwich-like NiCo2O4/rGO/NiO heterostructure composite has been successfully anchored on nickel foam substrate via a three-step hydrothermal method with successive annealing treatment. The smart combination of NiCo2O4, reduced graphene oxide (rGO), and NiO nanostructure in the sandwich-like nano architecture shows a promising synergistic effect for supercapacitors with greatly enhanced electrochemical performance. For serving as supercapacitor electrode, the NiCo2O4/rGO/NiO heterostructure materials exhibit remarkable specific capacitance of 2644 mF cm−2 at current density of 1 mA cm−2, and excellent capacitance retentions of 97.5% after 3000 cycles. It is expected that the present heterostructure will be a promising electrode material for high-performance supercapacitors. Graphical Abstract