R-3 Repository :: Browsing by Author "Ruan, Gedeng"

Browsing by Author "Ruan, Gedeng"

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Cobalt Nanoparticles Embedded in Nitrogen-Doped Carbon for the Hydrogen Evolution Reaction
(American Chemical Society, 2015) Fei, Huilong; Yang, Yang; Peng, Zhiwei; Ruan, Gedeng; Zhong, Qifeng; Li, Lei; Samuel, Errol L.G.; Tour, James M.; Smalley Institute for Nanoscale Science and Technology
There is great interest in renewable and sustainable energy research to develop low-cost, highly efficient, and stable electrocatalysts as alternatives to replace Pt-based catalysts for the hydrogen evolution reaction (HER). Though nanoparticles encapsulated in carbon shells have been widely used to improve the electrode performances in energy storage devices (e.g., lithium ion batteries), they have attracted less attention in energy-related electrocatalysis. Here we report the synthesis of nitrogen-enriched core–shell structured cobalt–carbon nanoparticles dispersed on graphene sheets and we investigate their HER performances in both acidic and basic media. These catalysts exhibit excellent durability and HER activities with onset overpotentials as low as ∼70 mV in both acidic (0.5 M H2SO4) and alkaline (0.1 M NaOH) electrolytes, and the overpotentials needed to deliver 10 mA cm–2 are determined to be 265 mV in acid and 337 mV in base, further demonstrating their potential to replace Pt-based catalysts. Control experiments reveal that the active sites for HER might come from the synergistic effects between the cobalt nanoparticles and nitrogen-doped carbon.
Growth of graphene films from non-gaseous carbon sources
(2015-08-04) Tour, James; Sun, Zhengzong; Yan, Zheng; Ruan, Gedeng; Peng, Zhiwei; Rice University; United States Patent and Trademark Office
In various embodiments, the present disclosure provides methods of forming graphene films by: (1) depositing a non-gaseous carbon source onto a catalyst surface; (2) exposing the non-gaseous carbon source to at least one gas with a flow rate; and (3) initiating the conversion of the non-gaseous carbon source to the graphene film, where the thickness of the graphene film is controllable by the gas flow rate. Additional embodiments of the present disclosure pertain to graphene films made in accordance with the methods of the present disclosure.
Nanocomposite oil sensors for downhole hydrocarbon detection
(2016-06-28) Tour, James M.; Hwang, Chih-chau; Lu, Wei; Ruan, Gedeng; Tomson, Mason B.; Kan, Amy; Wang, Lu; Wong, Michael S.; Kini, Gautam; Hirasaki, George J.; Miller, Clarence; Rice University; United States Patent and Trademark Office
Various embodiments of the present disclosure pertain to nanocomposites for detecting hydrocarbons in a geological structure. In some embodiments, the nanocomposites include: a core particle; a polymer associated with the core particle; a sulfur-based moiety associated with the polymer; and a releasable probe molecule associated with the core particle, where the releasable probe molecule is releasable from the core particle upon exposure to hydrocarbons. Additional embodiments of the present disclosure pertain to methods of detecting hydrocarbons in a geological structure by utilizing the nanocomposites of the present disclosure.
Nanomaterials for Hydrocarbon Exploration, Acid Gas Removal and Energy Devices
(2015-04-08) Ruan, Gedeng; Tour, James M.; Wilson, Lon J; Tomson, Mason B
This thesis discusses the synthesis and characterization of several different nanomaterials as well as their applications to oil and energy industries. The nanomaterials studied here include asphalt-derived high surface area activated porous carbon, commercial carbon black (CB), nanoporous metal compounds, graphene, and graphene nanoribbons (GNRs). Through proper design and functionalization, these nanomaterials exhibit interesting properties and their applications in hydrocarbon exploration, acid gas removal as well as energy devices are demonstrated. Firstly, the research activities toward the development of new absorbents for carbon dioxide (CO2) capture have been growing quickly. Despite the variety of existing materials with high surface areas and high CO2 uptake performances, the cost of the materials remains a dominant factor in slowing their industrial applications. In the first chapter we study preparation and CO2 uptake performance of highly porous carbon materials derived from a very inexpensive carbon source, asphalt. Carbonization of asphalt with potassium hydroxide (KOH) at high temperatures (600 - 750 ºC) yields asphalt-derived porous carbon materials (A-PC) with high surface areas of up to 2780 m2 g-1 and high CO2 uptake performance of 21 mmol g-1 or 93 wt% at 30 bar and 25 ºC. Furthermore, nitrogen doping and reduction with hydrogen yields active N-doped materials (A-NPC and A-rNPC) containing up to 9.3% nitrogen, making them nucleophilic porous carbons with further increase in CO2 uptake to 26 mmol g-1 or 114 wt% at 30 bar and 25 ºC for A-rNPC. This is the highest reported CO2 uptake among the family of the activated porous carbonaceous materials. The CO2 is released and the asphalt material is regenerated when the pressure is returned to 1 bar. Thus the porous carbon materials from asphalt have excellent properties for reversibly capturing CO2 at the well-head during the extraction of natural gas, a naturally occurring high pressure source of CO2. Through a pressure swing sorption process, the asphalt-derived material is a reversible capture medium that is highly efficient and very inexpensive. Secondly, crude oil is called as “sour” crude oil when the total sulfur level is larger than 0.5 %. The sour crude oil is corrosive to the oil production and transportation facilities and toxic to human health. Among these sulfur species, H2S is the one of main impurities in sour crude. Therefore it is important to develop a method to accurately measure the sulfur content which may help geologists evaluate the quality of the crude oil before large scale extraction. In the second chapter, we study polyvinyl alcohol functionalized carbon black (PVA-CB) nanoparticles which are stable under high temperature and high salinity conditions. After further being functionalized with H2S-sensitive fluorescence probe, the probe molecule-PVA-CB (FB-PVA-CB) can be used to determine the H2S content in H2S-containing oil in porous rock based on the fluorescent enhancement of the H2S-sensitive addends. Thirdly, a flexible 3-dimensional (3-D) nanoporous NiF2-dominant layer on poly(ethylene terephthalate) has been developed. The nanoporous layer itself can be freestanding without adding any supporting carbon materials or conducting polymers. By assembling the nanoporous layer into two-electrode symmetric devices, the inorganic material delivers battery-like thin-film supercapacitive performance with a maximum capacitance of 66 mF cm-2 (733 F cm-3 or 358 F g-1), energy density of 384 Wh kg-1 and power density of 112 kW kg-1. Flexibility and cyclability tests show that the nanoporous layer maintains its high performance under long-term cycling and different bending conditions. The fabrication of the 3-D nanoporous NiF2 flexible electrode could be easily scaled. Fourthly, in its monolayer form, graphene is a one-atom-thick two-dimensional material with excellent electrical, mechanical and thermal properties. Large-scale production of high-quality graphene is attracting an increasing amount of attention. Chemical vapor and solid deposition methods have been developed to grow graphene from organic gases or solid carbon sources. Most of the carbon sources used were purified chemicals that could be expensive for mass production. In this work, we have developed a less expensive approach using six easily obtained, low or negatively valued raw carbon-containing materials used without pre-purification (cookies, chocolate, grass, plastics, roaches, and dog feces) to grow graphene directly on the backside of a Cu foil at 1050 °C under H2/Ar flow. The non-volatile pyrolyzed species were easily removed by etching away the frontside of the Cu. Analysis by Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy and transmission electron microscopy indicates that the monolayer graphene derived from these carbon sources is of high quality. Fifthly, the preparation of polymer-functionalized graphene nanoribbons (PF-GNRs) in a one-pot synthesis is described. Multiwalled carbon nanotubes (MWCNTs) were intercalated by potassium under vapor- or liquid-phase conditions, followed by addition of vinyl monomers, resulting in PF-GNRs. Scanning electron microscopy, thermogravimetric mass spectrometry and X-ray photoelectron spectroscopy were used to characterize the PF-GNRs. Also explored here is the correlation between the splitting of MWCNTs, the intrinsic properties of the intercalants and the degree of defects and graphitization of the starting MWCNTs. The PF-GNRs could have applications in conductive composites, transparent electrodes, heat circuits and supercapacitors.
Porous carbon materials for CO2 separation in natural gas
(2017-10-03) Tour, James M.; Schipper, Desmond E.; Hwang, Chih-chau; Tour, Josiah; Jalilov, Almaz S.; Ruan, Gedeng; Li, Yilun; Rice University; United States Patent and Trademark Office
In some embodiments, the present disclosure pertains to materials for use in CO2 capture in high pressure environments. In some embodiments, the materials include a porous carbon material containing a plurality of pores for use in a high pressure environment. Additional embodiments pertain to methods of utilizing the materials of the present disclosure to capture CO2 from various environments. In some embodiments, the materials of the present disclosure selectively capture CO2 over hydrocarbon species in the environment.
Porous carbon materials for CO2 separation in natural gas
(2017-03-21) Tour, James M.; Schipper, Desmond E.; Hwang, Chih-chau; Tour, Josiah; Jalilov, Almaz S.; Ruan, Gedeng; Li, Yilun; Rice University; United States Patent and Trademark Office
In some embodiments, the present disclosure pertains to materials for use in CO2 capture in high pressure environments. In some embodiments, the materials include a porous carbon material containing a plurality of pores for use in a high pressure environment. Additional embodiments pertain to methods of utilizing the materials of the present disclosure to capture CO2 from various environments. In some embodiments, the materials of the present disclosure selectively capture CO2 over hydrocarbon species in the environment.
Production and use of flexible conductive films and inorganic layers in electronic devices
(2020-10-20) Tour, James M.; Yang, Yang; Ruan, Gedeng; Rice University; United States Patent and Trademark Office
Embodiments of the present disclosure pertain to methods of making conductive films by associating an inorganic composition with an insulating substrate, and forming a porous inorganic layer from the inorganic composition on the insulating substrate. The inorganic layer may include a nanoporous metal layer, such as nickel fluoride. The methods of the present disclosure may also include a step of incorporating the conductive films into an electronic device. The methods of the present disclosure may also include a step of associating the conductive films with a solid electrolyte prior to its incorporation into an electronic device. The methods of the present disclosure may also include a step of separating the inorganic layer from the conductive film to form a freestanding inorganic layer. Further embodiments of the present disclosure pertain to the conductive films and freestanding inorganic layers.
Rebar Graphene
(American Chemical Society, 2014) Yan, Zheng; Peng, Zhiwei; Casillas, Gilberto; Lin, Jian; Xiang, Changsheng; Zhou, Haiqing; Yang, Yang; Ruan, Gedeng; Raji, Abdul-Rahman O.; Samuel, Errol L.G.; Hauge, Robert H.; Yacaman, Miguel Jose; Tour, James M.; Richard E. Smalley Institute for Nanoscale Science and Technology
As the cylindrical sp2-bonded carbon allotrope, carbon nanotubes (CNTs) have been widely used to reinforce bulk materials such as polymers, ceramics, and metals. However, both the concept demonstration and the fundamental understanding on how 1D CNTs reinforce atomically thin 2D layered materials, such as graphene, are still absent. Here, we demonstrate the successful synthesis of CNT-toughened graphene by simply annealing functionalized CNTs on Cu foils without needing to introduce extraneous carbon sources. The CNTs act as reinforcing bar (rebar), toughening the graphene through both π–π stacking domains and covalent bonding where the CNTs partially unzip and form a seamless 2D conjoined hybrid as revealed by aberration-corrected scanning transmission electron microscopy analysis. This is termed rebar graphene. Rebar graphene can be free-standing on water and transferred onto target substrates without needing a polymer-coating due to the rebar effects of the CNTs. The utility of rebar graphene sheets as flexible all-carbon transparent electrodes is demonstrated. The in-plane marriage of 1D nanotubes and 2D layered materials might herald an electrical and mechanical union that extends beyond carbon chemistry.
Segregation of Amphiphilic Polymer-Coated Nanoparticles to Bicontinuous Oil/Water Microemulsion Phases
(American Chemical Society, 2017) Qi, Luqing; ShamsiJazeyi, Hadi; Ruan, Gedeng; Mann, Jason A.; Lin, Yen-Hao; Song, Chen; Ma, Yichuan; Wang, Le; Tour, James M.; Hirasaki, George J.; Verduzco, Rafael
Polymer-coated nanoparticles are interfacially active and have been shown to stabilize macroscopic emulsions of oil and water, also known as Pickering emulsions. However, prior work has not explored the phase behavior of amphiphilic nanoparticles in the presence of bicontinuous microemulsions. Here, we show that properly designed amphiphilic polymer-coated nanoparticles spontaneously and preferentially segregate to the bicontinuous microemulsion phases of oil, water, and surfactant. Mixtures of hydrophilic and hydrophobic chains are covalently grafted onto the surface of oxidized carbon black nanoparticles. By sulfating hydrophilic chains, the polymer-coated nanoparticles are stable in the aqueous phase at salinities up to 15 wt % NaCl. These amphiphilic, negatively charged polymer-coated nanoparticles segregate to the bicontinuous microemulsion phases. We analyzed the equilibrium phase behavior of the nanoparticles, measured the interfacial tension, and quantified the domain spacing in the presence of nanoparticles. This work shows a novel route to the design of polymer-coated nanoparticles which are stable at high salinities and preferentially segregate to bicontinuous microemulsion phases.
Three-Dimensional Nanoporous Fe2O3/Fe3C-Graphene Heterogeneous Thin Films for Lithium-Ion Batteries
(American Chemical Society, 2014) Yang, Yang; Fan, Xiujun; Casillas, Gilberto; Peng, Zhiwei; Ruan, Gedeng; Wang, Gunuk; Yacaman, Miguel Jose; Tour, James M.; Smalley Institute for Nanoscale Science and Technology
Three-dimensional self-organized nanoporous thin films integrated into a heterogeneous Fe2O3/Fe3C-graphene structure were fabricated using chemical vapor deposition. Few-layer graphene coated on the nanoporous thin film was used as a conductive passivation layer, and Fe3C was introduced to improve capacity retention and stability of the nanoporous layer. A possible interfacial lithium storage effect was anticipated to provide additional charge storage in the electrode. These nanoporous layers, when used as an anode in lithium-ion batteries, deliver greatly enhanced cyclability and rate capacity compared with pristine Fe2O3: a specific capacity of 356 μAh cm–2 μm–1 (3560 mAh cm–3 or ∼1118 mAh g–1) obtained at a discharge current density of 50 μA cm–2 (∼0.17 C) with 88% retention after 100 cycles and 165 μAh cm–2 μm–1(1650 mAh cm–3 or ∼518 mAh g–1) obtained at a discharge current density of 1000 μA cm–2(∼6.6 C) for 1000 cycles were achieved. Meanwhile an energy density of 294 μWh cm–2 μm–1(2.94 Wh cm–3 or ∼924 Wh kg–1) and power density of 584 μW cm–2 μm–1 (5.84 W cm–3 or ∼1834 W kg–1) were also obtained, which may make these thin film anodes promising as a power supply for micro- or even nanosized portable electronic devices.
Three-Dimensional Networked Nanoporous Ta2O5–x Memory System for Ultrahigh Density Storage
(American Chemical Society, 2015) Wang, Gunuk; Lee, Jae-Hwang; Yang, Yang; Ruan, Gedeng; Kim, Nam Dong; Ji, Yongsung; Tour, James M.; Richard E. Smalley Institute of Nanoscale Science and Technology
Oxide-based resistive memory systems have high near-term promise for use in nonvolatile memory. Here we introduce a memory system employing a three-dimensional (3D) networked nanoporous (NP) Ta2O5-x structure and graphene for ultrahigh density storage. The devices exhibit a self-embedded highly nonlinear I-V switching behavior with an extremely low leakage current (on the order of pA) and good endurance. Calculations indicated that this memory architecture could be scaled up to a ∼162 Gbit crossbar array without the need for selectors or diodes normally used in crossbar arrays. In addition, we demonstrate that the voltage point for a minimum current is systematically controlled by the applied set voltage, thereby offering a broad range of switching characteristics. The potential switching mechanism is suggested based upon the transformation from Schottky to Ohmic-like contacts, and vice versa, depending on the movement of oxygen vacancies at the interfaces induced by the voltage polarity, and the formation of oxygen ions in the pores by the electric field.
Unimolecular Submersible Nanomachines. Synthesis, Actuation, and Monitoring
(America Chemical Society, 2015) García-López, Víctor; Chiang, Pinn-Tsong; Chen, Fang; Ruan, Gedeng; Martí, Angel A.; Kolomeisky, Anatoly B.; Wang, Gufeng; Tour, James M.; Center for Theoretical Biological Physics
Unimolecular submersible nanomachines (USNs) bearing light-driven motors and fluorophores are synthesized. NMR experiments demonstrate that the rotation of the motor is not quenched by the fluorophore and that the motor behaves in the same manner as the corresponding motor without attached fluorophores. No photo or thermal decomposition is observed. Through careful design of control molecules with no motor and with a slow motor, we found using single molecule fluorescence correlation spectroscopy that only the molecules with fast rotating speed (MHz range) show an enhancement in diffusion by 26% when the motor is fully activated by UV light. This suggests that the USN molecules give ?9 nm steps upon each motor actuation. A non-unidirectional rotating motor also results in a smaller, 10%, increase in diffusion. This study gives new insight into the light actuation of motorized molecules in solution.

Browsing by Author "Ruan, Gedeng"

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