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Guo X.,Donghua University | Bi H.,Nanjing Southeast University | Zafar A.,Donghua University | Liang Z.,Graphene Energy | And 3 more authors.

Three-dimensional (3D) carbon nano-materials, e.g. a graphene sponge (GS) are promising candidates for the removal of pollutants and the separation of oil and water. A systematic study on how oils or organic solvents disperse in the porous structures of 3D carbon nano-materials, and the factors affecting their sorption process, would be beneficial for designing a superior sorbent with desirable porous structures. Here, confocal Raman spectroscopic imaging was utilized to explore the absorption and desorption processes of dodecane (a constituent in petroleum products) in 3D porous GS with different pore size. It was found that dodecane predominately locates within the interior pores composed of reduced graphene oxide (rGO) sheets, which provide storage spaces for the absorbed molecules. The larger pore GS has a higher absorption capacity and faster desorption rate compared to the smaller one, which is due to the higher pore volume and weaker interaction with the absorbed molecules. A possible mechanism was also proposed to explain the role of porous macrostructures on the absorption and desorption properties of GSs. © 2016 IOP Publishing Ltd. Source

Yu F.,Shihezi University | Yu F.,Key Laboratory of Materials Oriented Chemical Engineering of Xinjiang Uygur Autonomous Region | Zhang L.,Institute of Chemical and Engineering Sciences, Singapore | Li Y.,Shihezi University | And 3 more authors.
RSC Advances

Olivine-structured lithium ion phosphate (LiFePO4) is one of the most competitive candidates for fabricating energy-driven cathode material for sustainable lithium ion battery (LIB) systems. However, the high electrochemical performance is significantly limited by the slow diffusivity of Li-ion in LiFePO4 (ca. 10-14 cm2 s-1) together with the low electronic conductivity (ca. 10-9 S cm-1), which is the big challenge currently faced by us. To resolve the challenge, many efforts have been directed to the dynamics of the lithiation/delithiation process in LixFePO4 (0 ≤ x ≤ 1), mechanism of electrochemical modification, and synthetic reaction process, which are crucial for the development of high electrochemical performance for LiFePO4 material. In this review, in order to reflect the recent progress ranging from the very fundamental to practical applications, we specifically focus on the mechanism studies of LiFePO4 including the lithiation/delithiation process, electrochemical modification and synthetic reaction. Firstly, we highlight the Li-ion diffusion pathway in LixFePO4 and phase translation of LixFePO4. Then, we summarize the modification mechanism of LiFePO4 with high-rated capability, excellent low-temperature performance and high energy density. Finally, we discuss the synthetic reaction mechanism of high-temperature carbothermal reaction route and low-temperature hydrothermal/solvothermal reaction route. © the Partner Organisations 2014. Source

Nan H.,Nanjing Southeast University | Wang Z.,Nanjing Southeast University | Wang W.,Nanjing Southeast University | Liang Z.,Graphene Energy | And 8 more authors.
ACS Nano

We report on a strong photoluminescence (PL) enhancement of monolayer MoS2 through defect engineering and oxygen bonding. Micro-PL and Raman images clearly reveal that the PL enhancement occurs at cracks/defects formed during high-temperature annealing. The PL enhancement at crack/defect sites could be as high as thousands of times after considering the laser spot size. The main reasons of such huge PL enhancement include the following: (1) the oxygen chemical adsorption induced heavy p doping and the conversion from trion to exciton; (2) the suppression of nonradiative recombination of excitons at defect sites, which was verified by low-temperature PL measurements. First-principle calculations reveal a strong binding energy of ∼2.395 eV for an oxygen molecule adsorbed on a S vacancy of MoS2. The chemically adsorbed oxygen also provides a much more effective charge transfer (0.997 electrons per O2) compared to physically adsorbed oxygen on an ideal MoS2 surface. We also demonstrate that the defect engineering and oxygen bonding could be easily realized by mild oxygen plasma irradiation. X-ray photoelectron spectroscopy further confirms the formation of Mo-O bonding. Our results provide a new route for modulating the optical properties of two-dimensional semiconductors. The strong and stable PL from defects sites of MoS2 may have promising applications in optoelectronic devices. © 2014 American Chemical Society. Source

News Article | April 24, 2009
Site: venturebeat.com

Graphene Energy, an Austin, Tex. startup based on technology from the University of Texas and Virginia’s College of William and Mary, has taken a $500,000 seed round from Quercus Trust and 21Ventures. Ultracapacitors (insulating layers between conductors that house electric fields) are being explored by a variety of startups for their energy storage, usually as a component accompanying batteries in electric cars. Graphene is seeking to improve the technology by improving capacitance, or the amount of energy stored, and increasing the energy density of its capacitors. Other companies in the field include Apowercap Technologies, Eestor and Maxwell Technologies, all three of which hope to install their products in electric vehicles.

News Article | January 13, 2009
Site: gigaom.com

Graphene Energy, an Austin-based developer of ultracapacitor technology, has raised $500,000 in seed investment from Quercus Trust and 21Ventures. The investment represents yet another move by David Gelbaum’s Quercus Trust, which was the third-most active venture fund investing in cleantech in all of 2008, according to the Cleantech Group. Graphene Energy works with the strongest material ever tested — a one-atom thick sheet of graphite — to build ultracapacitors. The material, known as graphene, was hailed as the new silicon last year when researchers discovered that electrons could travel up to 100 times faster in graphene than silicon. Around the same time, a new generation of ultracapacitors emerged that aimed to seize the future of the auto industry. With ultra-fast charge times, they can absorb voltage drops and surges to extend battery life — or store electricity on their own. But capacity has lagged somewhere around 5 percent of battery’s storage capacity. Graphene Energy plans to solve this problem by stacking several sheets of graphene (pictured below), which it says could as much as double the capacity offered by today’s commercial ultracapacitors (usually made with activated carbon). The company, which emerged from research at the University of Texas, foresees applications in electric and hybrid vehicles, mobile devices, and wind- and solar-powered electric grids.

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