Shaozao Tan

Large‐Scale Fabrication of Pseudocapacitive Glass Windows that Combine Electrochromism and Energy Storage

Multifunctional glass windows that combine energy storage and electrochromism have been obtained by facile thermal evaporation and electrodeposition methods. For example, WO3 films that had been deposited on fluorine-doped tin oxide (FTO) glass exhibited a high specific capacitance of 639.8u2005Fu2009g(-1). Their color changed from transparent to deep blue with an abrupt decrease in optical transmittance from 91.3% to 15.1% at a wavelength of 633u2005nm when a voltage of -0.6u2005V (vs. Ag/AgCl) was applied, demonstrating its excellent energy-storage and electrochromism properties. As a second example, a polyaniline-based pseudocapacitive glass was also developed, and its color can change from green to blue. A large-scale pseudocapacitive WO3-based glass window (15×15u2005cm(2)) was fabricated as a prototype. Such smart pseudocapacitive glass windows show great potential in functioning as electrochromic windows and concurrently powering electronic devices, such as mobile phones or laptops.

Worm-like amorphous MnO2 nanowires grown on textiles for high-performance flexible supercapacitors

A novel class of amorphous MnO2 nanowires with a worm-like (WL) nanostructure was prepared by electrodeposition and a possible formation mechanism was proposed. The specific capacitance of WL amorphous MnO2 was 2–3 times larger than that of its crystalline cotton-like MnO2 counterpart. The unique WL amorphous nanostructure is believed to significantly facilitate the electrochemical performance of MnO2. Flexible solid-state symmetric supercapacitors assembled with WL-MnO2 electrodes exhibited a high energy density of 6.3 W h kg−1. These results demonstrate that the amorphous WL nanostructure grown on carbon fabric can serve as a promising electrode material for flexible and portable energy storage devices.

Significantly Enhanced Photocatalytic Activities and Charge Separation Mechanism of Pd-Decorated ZnO–Graphene Oxide Nanocomposites

Electron-hole recombination is one of the major factors limiting the efficiency of ZnO-based photocatalysts. In this work, a 2-fold enhancement strategy was employed to suppress electron-hole recombination and boost photocatalytic efficiency. First, significantly enhanced photocatalytic activity of ZnO by introducing graphene oxide (GO) was systematically investigated. Hybrid photocatalysts with different weight ratios of ZnO to GO (from 0.95:0.05 to 0.70:0.30) were synthesized and characterized. The results indicated that when the proportion ratio of ZnO to GO reached 0.85:0.15, the as-synthesized ZnO-GO nanocomposite exhibited the maximum photocatalytic efficiency on methylene blue with an apparent rate constant κapp almost 10 times faster than that of pure ZnO under UV illumination. GO was suggested to enhance the photocatalytic activity of ZnO because of its great capability in dye adsorption and charge separation. Second, Pd nanoparticles were introduced to decorate ZnO-GO to produce generally better photocatalyst ZnO-GO-Pd nanocomposites. The junction between Pd and ZnO was believed to also effectively separate the photogenerated charges due to the metal-semiconductor diode effect. These two systems of ZnO-GO and ZnO-GO-Pd nanocomposites are expected to have a broad range of applications in environmental conservation.

Freestanding CNT–WO3 hybrid electrodes for flexible asymmetric supercapacitors

Freestanding carbon nanotube (CNT)–tungsten oxide (WO3) hybrid films as the negative electrode of asymmetric supercapacitors (ASCs) are synthesized via a facile vacuum filtration and a subsequent physical vapor deposition method. With pure CNT films as the paired positive electrodes, these flexible ASC devices have been fabricated to demonstrate excellent electrochemical performance. Their cyclic voltammetry curves barely change when the ASC device is flat, bent, or twisted. Their volumetric capacitance reaches a high value of 2.6 F cm−3 at a scan rate of 10 mV s−1. Due to the extended operating voltage of 1.4 V, the ASC device reaches a power density of 30.6 mW cm−3 and an energy density of 0.59 mW h cm−3. After 50u2006000 cycles, the capacitance retention of the ASC is still 75.8%, which shows its excellent stability and ultra-long lifetime. When these ASC devices are connected in series as power sources, a commercial blue light-emitting diode can be lighted up and a commercial mobile-phone can be charged. In short, the novel ASC device with perfect flexibility and stability can be applied as one of the most promising next-generation power supplies.

Reduced graphene oxide for fiber-optic humidity sensing

Graphene-based electrical chemical vapor sensors can achieve extremely high sensitivity, whereas the comparatively slow sensing response and recovery, the research focused on only low concentration detection, have been known as drawbacks for many applications requiring rapid and high concentration detection. Here we report a novel graphene-based fiber-optic relative humidity (RH) sensor relying on fundamentally different sensing mechanism. The sensor can achieve power variation of up to 6.9 dB in high relative humidity range (70-95%), and display linear response with correlation coefficient of 98.2%, sensitivity of 0.31 dB/%RH, response speed of faster than 0.13%RH/s, and good repeatability in 75-95%RH. Theoretical analysis of sensing mechanism can explain the experimental result, and reveal the broad applying prospect of the sensor for other kinds of chemical vapor detection. This novel graphene-based optical sensor provides a beneficial complement to the existing electrical ones, and will promote the employment of graphene in chemical sensing techniques.

All-fiber-optic temperature sensor based on reduced graphene oxide

We demonstrate a novel all-fiber-optic temperature sensor based on a reduced graphene oxide (rGO) film coated onto a side-polished fiber (SPF). Significantly enhanced interaction between the propagating light and the rGO film can be obtained via strong evanescent field of the SPF. The strong light–graphene interaction results in temperature sensing with a maximum optical power variation of 11.3xa0dB in the SPF experimentally. The novel temperature fiber sensor has a linear correlation coefficient of 99.4%, a sensitivity of 0.134xa0dBxa0°C−1, a precision of better than 0.03u2009°C, and a response speed of better than 0.0228u2009°Cxa0s−1. Such an rGO-based all-fiber-optic temperature sensor is easy to fabricate, is compatible with fiber-optic systems, and possesses high potentiality in photonics applications such as all-fiber-optic temperature sensing networks.

Fabrication of a High-Stability Cross-Linked Quaternized Poly(epichlorolydrin)/PTFE Composite Membrane via a Facile Route

A novel cross-linked quaternized composite anion-exchange membrane based on poly(epichlorohydrin) (PECH) was prepared by a facile route. First, PECH was cross-linked with 2-methylimidazole and combined with a poly(tetrafluoroethylene) (PTFE) membrane to form cross-linked PECH/PTFE (CPECH/PTFE). Then, CPECH/PTFE was quaternized by 1-methylimidazole to obtain cross-linked quaternized PECH/PTFE (CQPECH/PTFE). (1)H NMR and Fourier transform infrared spectroscopic data indicated that CQPECH was successfully synthesized, and the CQPECH/PTFE membrane had a dense and homogeneous structure demonstrated by the field-emission scanning electron microscopy. The results showed that the use of 2-methylimidazole as the cross-link agent could avoid the solubility of the composite membrane in water and dimethyl sulfoxide. With an increase of 2-methylimidazole, the solubility of the PECH ionomer was decreased. M-3, one of the CQPECH/PTFE membranes, showed good thermal properties (stable below 250 °C under an N2 atmosphere), excellent mechanical strength (a tensile strength of 67.3 MPa), moderate water uptake of 45.3%, and very low swelling degree of 9.01% at 30 °C. Besides, M-3 showed a hydroxide conductivity of up to 27 mS/cm and good long-term stability in a 1 M KOH solution at 60 °C for 15 days. In addition, a single H2/O2 fuel-cell test using M-3 at 50 °C indicated a peak power density of 23 mW/cm(2). These results suggested that the CQPECH/PTFE membrane had a good perspective for application in an alkaline fuel cell.

Easy one-step hydrothermal synthesis of nitrogen-doped reduced graphene oxide/iron oxide hybrid as efficient supercapacitor material

AbstractHybrid material consisting of α-Fe2O3 and nitrogen-doped reduced graphene oxide (N-rGO/Fe2O3) for supercapacitor electrode material has been synthesized via an easy one-step hydrothermal method, where urea serves as nitrogen source, reducing agent and precipitant. As a result, the reduction and nitrogen doping of graphene oxide and the in situ formation of α-Fe2O3 are achieved simultaneously. The results show that the synthesized N-rGO/Fe2O3 composite exhibits much better electrochemical performance than the sample without nitrogen doping. Moreover, thanks to the positive synergetic effect between N-rGO and α-Fe2O3, the N-rGO/Fe2O3 composite shows superior electrochemical property, including high capacitance, excellent rate capability, and good cycle life. Consequently, the easy preparation approach in this work will be considered as an efficient pathway for the development of metal oxide or hydroxide/N-rGO electrode material for high-performance supercapacitors.n Graphical AbstractNitrogen-doped reduced graphene oxide/α-Fe2O3 (N-rGO/Fe2O3) composite was prepared via easy one-step hydrothermal method, where urea served as nitrogen source, reducing agent, and precipitant. The presence of N-rGO was favored for the smaller size and more homogenous distribution of Fe2O3 nanoparticle. Due to the nitrogen doping and positive synergistic effect between N-rGO and Fe2O3, the obtained composite exhibited superior electrochemical performance.

TiO2 nanowires for potential facile integration of solar cells and electrochromic devices

Self-powered systems usually consist of energy-acquisition components, energy-storage components and functional components. The development of nanoscience and nanotechnology has greatly improved the performance of all the components of self-powered systems. However, huge differences in the materials and configurations in the components cause large difficulties for integration and miniaturization of self-powered systems. Design and fabrication of different components in a self-powered system with the same or similar materials/configurations should be able to make the above goal easier. In this work, a proof-of-concept experiment involving an integrated self-powered color-changing system consisting of TiO2 nanowire based sandwich dye-sensitized solar cells (DSSCs) and electrochromic devices (ECDs) is designed and demonstrated. When sunlight illuminates the entire system, the DSSCs generate electrical power and turn the ECD to a darker color, dimming the light; by switching the connection polarity of the DSSCs, the lighter color can be regained, implying the potential application of this self-powered color-changing system for next generation sun glasses and smart windows.

Reduced graphene oxide for fiber-optic toluene gas sensing

A fiber-optic toluene gas sensor based on reduced graphene oxide (rGO) is demonstrated and its sensing property is investigated experimentally and theoretically. The rGO film is deposited on a side polished fiber (SPF), allowing the strong interaction between rGO film and propagating field and making the SPF sensitive to toluene gas. It is found that the sensor has good linearity and reversibility and can work at room temperature with the response and the recovery time of 256 s and the detection limit of 79 ppm. Moreover, a theoretical model for the sensor is established to analyze the sensing mechanism. Theoretical analysis indicates this type of sensor could work in a wide range of toluene gas concentration and shows that a significant rise in its sensitivity can be expected by adjusting the doping level or chemical potential of graphene.