Youning Gong

Highly porous graphitic biomass carbon as advanced electrode materials for supercapacitors

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.

Facile Synthesis of Carbon Nanosphere/NiCo2O4 Core-shell Sub-microspheres for High Performance Supercapacitor.

This paper introduced a process to prepare the carbon nanosphere (CNS)/NiCo2O4 core-shell sub-microspheres. That is: 1) CNSs were firstly prepared via a simple hydrothermal method; 2) a layer of NiCo2O4 precursor was coated on the CNS surface; 3) finally the composite was annealed at 350 °C for 2 hours in the air, and the CNS/NiCo2O4 core-shell sub-microspheres were obtained. This core-shell sub-microsphere was prepared with a simple, economical and environmental-friendly hydrothermal method, and was suitable for large-scale production, which expects a promising electrode candidate for high performance energy storage applications. Electrochemical experiments revealed that the composite exhibited remarkable electrochemical performances with high capacitance and desirable cycle life at high rates, such as: 1) the maximum specific capacitance was up to 1420 F/g at 1 A/g; 2) about 98.5% of the capacitance retained after 3000 charge-discharge cycles; 3) the capacitance retention was about 72% as the current density increase from 1 A/g to 10 A/g.

Facile synthesis of hybrid CNTs/NiCo2S4 composite for high performance supercapacitors.

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.

Highly Sensitive, Durable, and Multifunctional Sensor Inspired by a Spider

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 spiders slit organs, while the high durability is inspired by the mechanical robustness of the spider silk. Similar to the spiders 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.

Direct determination of graphene amount in electrochemical deposited Cu-based composite foil and its enhanced mechanical property

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.

Construction of hierarchical TiO 2 nanorod array/graphene/ZnO nanocomposites for high-performance photocatalysis

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.