Flexible thermoelectric generators (FTEGs), which can overcome the energy supply limitations of wearable devices, have received considerable attention. However, the use of toxic Te-based materials and fracture-prone electrodes constrains the application of FTEGs. In this study, a novel Ag2Se and Poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS)/multi-walled carbon nanotube (MWCNT) FTEG with a high output performance and good flexibility is developed. The thermoelectric columns formulated in the work are environmentally friendly and reliable. The key enabler of this work is the use of embedded EGaIn electrodes, which increase the temperature difference collected by the thermoelectric column, thereby improving the FTEG output performance. Additionally, the embedded EGaIn electrodes could be directly printed on polydimethylsiloxane (PDMS) molds without wax paper, which simplifies the preparation process of FTEGs and enhances the fabrication efficiency. The FTEG with embedded electrodes exhibits the highest output power density of 25.83 μW/cm2 and the highest output power of 10.95 μW at ΔT = 15 K. The latter is 31.6% higher than that of silver-based FTEGs and 2.5% higher than that of covered EGaIn-based FTEGs. Moreover, the prepared FTEG has an excellent flexibility (>1500 bends) and output power stability (>30 days). At high humidity and high temperature, the prepared FTEG maintains good performance. These results demonstrate that the prepared FTEGs can be used as a stable and environmentally friendly energy supply for wearable devices.

In the detection of metal defects by ultrasonic Lamb waves, the commonly used medical coupling agent is volatile, poor stability, and the coupling effect is easily affected. It is vital to find the coupler materials with better performance. This paper develops sodium alginate hydrogel and acrylamide hydrogel with higher curing degree, and compares them with deionized water and medical coupling agent. At the same time, epoxy glue and organic silicone, which commonly used as adhesives in the aerospace field are selected for performance research. Firstly, analyzing FTIR spectra of the three hydrogels. The results showed that the hydrogel composition are correct and subsequent experiments are reliable. Secondly, the performance characteristics of 6 couplings are studied from 5 aspects of acoustic impedance, ultrasonic energy transfer efficiency, stability, temperature characteristics and oxidation resistance. The results show that the acrylamide gel developed in this paper has higher viscosity and stability than the medical coupling agent, and has a wider application. Based on the five performance studies, it can be concluded that in the measurement environment of long-term fixed sensors in the industrial and aerospace fields, organic silicone can not only play the role of bonding sensors and insulation, but have the advantages of strong stability, high ultrasonic energy transfer efficiency, temperature tolerance, oxidation resistance, etc. It is the optimal coupling material in ultrasonic testing for complex environments. The research in this paper provides a reference for the selection of optimal coupling agent materials for more complex applications, which has important engineering significance.

Composites of transition metal oxide and conducive polymer have shown great potential in optimizing the electrochemical performance of supercapacitors. Specifically, NiCo2O4/polyaniline (PANI) composites are especially promising, due to the synergetic effect of the two components. Here, we demonstrate the synthesis of a nickel foam-based NiCo2O4-PANI composite, where the PANI is polymerized in situ in aqueous acid, achieving co-doping of Ni2+ and Co2+ in the polymer. The synthesized composite was characterized using X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Electrochemical studies indicate that the composite exhibits an ultrahigh specific capacitance of 15.5 F.cm(-2) (3108 F.g(-1)) at a current density of 1 mA.cm(-2). In addition, the capacitance retention rate is 96.1% after 1000 charge-discharge cycles at 20 mA.cm(-2). Besides, such substrate-dependent design eliminates the electrode adhesion step in assembly compared to the substrate-free nanocomposite. A dual-electrode device made of NiCo2O4-PANI and activated charcoal exhibits a maximum energy density of 77.57 Wh.kg(-1) at 800 W.kg(-1). All these properties suggest that the materials and the synthesis route used for this NiCo2O4-PANI composite represent a promising strategy to make supercapacitor electrodes.

In this paper, a series of Co3O4-Ag photocatalysts with different Ag loadings were synthesized by facile hydrothermal and in situ photoreduction methods and fully characterized by XRD, SEM, TEM, FTIR spectroscopy, XPS, UV-vis and PL techniques. The catalysts were used for the degradation of methyl orange (MO). Compared with the pure Co3O4 catalyst, the Co3O4-Ag catalysts showed better activity; among these, the Co3O4-Ag-0.3 catalyst demonstrated the most efficient activity with 96.4% degradation efficiency after 30 h UV light irradiation and high degradation efficiency of 99.1% after 6 h visible light irradiation. According to the corresponding dynamics study under UV light irradiation, the photocatalytic efficiency of Co3O4-Ag-0.3 was 2.72 times higher than that of Co3O4 under identical reaction conditions. The excellent photocatalytic activity of Co3O4-Ag can be attributed to the synergistic effect of strong absorption under UV and visible light, reduced photoelectron and hole recombination rate, and decreased band gap due to Ag doping. Additionally, a possible reaction mechanism over the Co3O4-Ag photocatalysts was proposed and explained.

The mesoporous CoTiO3 nanoparticles, which have been successfully prepared by a fast, simple and low-cost hydrothermal method, show good decolourisation and degradation of methylene blue (MB). The synthesised samples can be recovered easily from solution by a magnetic mass. Surface morphology, structure, composition, and optical characteristics of the prepared CoTiO3 were determined using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet–visible absorption measurements. The degradation percentage of MB was nearly 95% at an initial concentration of 10 ppm in 90 min. Such enhanced photocatalytic activities of synthesised CoTiO3 were attributed to a large specific surface area (54.22 m2 g−1) and defects density, which was useful for restraining surface recombination of photo-generated charge carriers. The recovery of CoTiO3 nanoparticles was about 85% and the degradation rate of MB remained 80% after five cycles. As a whole, the CoTiO3 nanocomposites give a synergistic effect in photocatalytic and magnetic behaviour and indicate that the synthesised samples have a promising potential particularly for water purification and environmental remediation.

In this work, NiCo2O4@TiO2 electrodes based on micro-region heterojunctions were synthesized by a simple one-step hydrothermal method. The material characteristics of resultant samples were characterized by XPS, XRD, SEM, HRTEM and BET. Compared with NiCo2O4 electrodes prepared with the same hydrothermal method, the NiCo2O4@TiO2 electrode shows higher electrochemical performance, cycling stability and lower charge transfer resistance. Specifically, the mass specific capacitances of NiCo2O4 and NiCo2O4@TiO2 electrodes are 564.3 F . g(-1) and 1085.7 F . g(-1) at current density of 5 A . g(-1) and retained 84.4% and 95.5% after 10,000 cycles, while the R-ct of NiCo2O4 and NiCo2O4@TiO2 are 1.72 Omega and 0.18 Omega, respectively. For practical applications of NiCo2O4@TiO2 electrode, a NiCo2O4@TiO2//AC two-electrode system was assembled and the performances were tested to achieve 255.9 F . g(-1) at current density of 2.5 A . g(-1) . Additionally, the corresponding energy density and power density were recorded as 91 wh/kg and 4 kw/kg. The superior electrochemical performance and cycle stability ofNiCo(2)O(4)@TiO2 electrode might be attributed to the higher specific surface and microregion heterojunctions for enormous future applications.

The optimized structure of composited materials decides the electrochemical performances of supercapacitors. Herein, the NiCo2O4@MnMoO4 particles with novel and functional structure were synthesized by two-step hydrothermal method process in this work, in which nickel foam (Ni foam) was employed as substrate. In the experiment process, the NiCo2O4 particles were prepared on the Ni foam and then the NiCo2O4@MnMoO4 particles were prepared on the NiCo2O4. According to the electrochemical tests, both the NiCo2O4 and NiCo2O4@MnMoO4 micro-particles prepared in this work have superior electrochemical performances including higher specific capacitances than most of the other NiCo2O4 and NiCo2O4@MnMoO4 researches. At the scan rate of 5 mA.cm(-2), the area specific capacitance of the NiCo2O4 electrode is 4.73 F cm(-2) (equivalent to 1152.4 F.g(-1) mass specific capacitance), while that of the NiCo2O4@MnMoO4 electrode is 16.40 F cm(-2) (equivalent to 2603.9 F.g(-1) mass specific capacitance). The cycling performance of the NiCo2O4 and NiCo2O4@MnMoO4 at the current density of 5 mA.cm(-2) were measured. After 3000 discharge-charge cycles, the specific capacitance of the NiCo2O4 micro-particles remains 112.2% of its initial value, and the NiCo2O4@MnMoO4 micro-particles remains 92.1%. The asymmetric supercapacitor is assembled by the NiCo2O4@MnMoO4 compounds and activated carbon (AC), which show high energy density of 44.16 Wh/kg at power density of 0.8 kW/kg. The results show that the NiCo2O4@MnMoO4 composite is an excellent candidate for electrode materials of energy storage devices. (C) 2018 Elsevier B.V. All rights reserved.

Triboelectric nanogenerators are widely used because of low cost, simple manufacturing process and high output performance. In this work, a flexible one-structure arched triboelectric nanogenerator (FOAT), based on common electrode to combine the single-electrode mode and contact-separation, was designed using silicone rubber, epoxy resin and flexible electrode. The peak-to-peak short circuit current of 18μA and the peak-to-peak open circuit voltage of 570V can be obtained from the FOAT with the size of 5×7 cm2 under the frequency of 3Hz and the pressure of 300N. The peak-to-peak short circuit current of FOAT is increased by 29% and 80%, and the peak-to-peak open circuit voltage is increased by 33% and 54% compared with single-electrode mode and contact-separation mode, respectively. FOAT realizes the combination of two generation modes, which improves the output performance of triboelectric nanogenerator (TENG). 62 light-emitting-diodes (LEDs) can be completely lit up and 2.2μF capacitor can be easily charged to 1.2V in 9s. When the FOAT is placed at different parts of the human body, the human motion energy can be harvested and be the sensing signal for motion monitoring sensor. Based on the above characteristics, FOAT exhibits great potential in illumination, power supplies for wearable electronic devices and self-powered motion monitoring sensor via harvesting the energy of human motion.