Search

A free-standing, 3D, macro/microstructured atomic-cobalt/cobalt-oxide-reduced-graphene-oxide (Co/Co3O4-Gr) composite has been developed for complete water splitting. The self-assembled porous morphology associated with the metal/metal oxide active sites makes the whole surface of the electrode conducive toward catalyzing hydrogen and oxygen evolution in alkaline media at a low onset potential. The liquid-crystal-mediated free-standing electrocatalyst shows oxygen evolution at the onset potential of 1.38 V and at the potential of 1.66 V for a current density of 10 mA cm−2. These potentials are comparable to the corresponding values for Ru/C (1.46 and 1.62 V, respectively). In addition, the promising hydrogen evolution performance of our composite compared to Pt/C in alkaline media makes it an efficient bifunctional electrocatalyst for comprehensive water splitting, as well as provides guidance for future electrochemical energy material technologies. [ABSTRACT FROM AUTHOR]

The capture and storage of CO2 have been suggested as an effective strategy to reduce the global emissions of greenhouse gases. Hence, in recent years, many studies have been carried out to develop highly efficient materials for capturing CO2. Until today, different types of porous materials, such as zeolites, porous carbons, N/B-doped porous carbons or metal-organic frameworks (MOFs), have been studied for CO2 capture. Herein, the CO2 capture performance of new hybrid materials, graphene-organic frameworks (GOFs) is described. The GOFs were synthesized under mild conditions through a solvothermal process using graphene oxide (GO) as a starting material and benzene 1,4-diboronic acid as an organic linker. Interestingly, the obtained GOF shows a high surface area (506 m2 g−1) which is around 11 times higher than that of GO (46 m2 g−1), indicating that the organic modification on the GO surface is an effective way of preparing a porous structure using GO. Our synthetic approach is quite simple, facile, and fast, compared with many other approaches reported previously. The synthesized GOF exhibits a very large CO2 capacity of 4.95 mmol g−1 at 298 K (1 bar), which is higher those of other porous materials or carbon-based materials, along with an excellent CO2/N2 selectivity of 48.8. [ABSTRACT FROM AUTHOR]

Doping of graphene has emerged as a key strategy to improve the electrocatalytic performance of the oxygen reduction reaction (ORR). Activated graphene co-doped with iodine and nitrogen atoms (NIG) was developed in this work using a facile scalable approach. The onset potential, current density, and four-electron reduction pathway of the newly developed catalyst were significantly improved. The charge-transfer resistance of co-doped NIG was found to be much lower than nitrogen-doped graphene (NG); furthermore, the stability of NIG and its resistance to methanol crossover were also improved. The synergistically enhanced ORR performance of NIG was found to be a result of a high strain and size advantage of the larger iodine atom clusters (compared to nitrogen), which facilitate the simultaneous enrichment of anode electrons and O2 and H2O molecule transport at catalytic sites, inducing four-electron transfer in a single step. These results are promising for application in alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet-spinning to produce long lengths of micrometer-dimensional fibers and yarns are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO 'inks' in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non-solvent precipitation, dispersion destabilization, ionic cross-linking, and polyelectrolyte complexation. One-step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post-treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials. [ABSTRACT FROM AUTHOR]

Layered MoS2 prepared by liquid-phase exfoliation has been blended with single-walled carbon nanotubes (SWNTs) to form novel composite thin films for lithium battery applications. The films were formed by vacuum filtration of blended dispersions onto nitrocellulose membranes. The resulting composite films were transferred onto Cu foil electrodes via a facile filtration/wet transfer technique from nitrocellulose membranes. The morphology of the film was characterised by field emission scanning electron microscopy, which suggests that the MoS2-SWNT composite film shows good adherence to the Cu foil substrate. The MoS2-SWNT composite thin films show strong electrochemical performance at different charge-discharge rates. The capacity of a MoS2-SWNT composite film with thickness of 1 μm is approximately 992 mAh g−1 after 100 cycles. The morphology study showed that the MoS2-SWNT thin film retains structural integrity after 100 cycles, while the MoS2 thin film without SWNTs displays significant cracking. In addition, the novel composite thin film preparation and transfer protocols developed in this study could be extended to the preparation of various layered-material-based composite films, with the potential for new device designs for energy applications. [ABSTRACT FROM AUTHOR]

A series of Pt catalysts supported on Al2O3 that was doped with different amounts of CeO2 was developed, characterized, and tested in the aqueous-phase reforming (APR) of glycerol to H2. Catalyst 3Pt/3CeAl, which bore 3 wt % Pt on a support that contained 3 wt % CeO2, showed the highest carbon conversion to gas (85 %) and the highest H2 yield (80 %) for a feedstock of 1 wt % glycerol in water at 240 °C and 40 bar. A CeO2/Al2O3 support with only 1 wt % Pt also showed high H2 selectivity and carbon conversion to gas, as well as a much lower CH4 yield than the benchmark 3Pt/Al catalyst, clearly demonstrating that doping the support with 3 wt % CeO2 improved the APR of glycerol. H2 chemisorption results showed that the highest metal dispersion (58 %) and active surface area (4.3 m2 g−1) were achieved for the support that contained 3 wt % CeO2, and this effect appeared to be primarily responsible for the high H2 yield and carbon conversion to gas. No CO was observed in the product gas; therefore, this gas could potentially be used directly in proton exchange membrane fuel cells. Thus, including CeO2 in the Al2O3 catalyst support enhanced both the activity and selectivity towards H2 of a Pt catalyst for the APR of glycerol. [ABSTRACT FROM AUTHOR]

Proton-exchange membrane fuel cells (PEMFCs) are expected to provide a complementary power supply to fossil fuels in the near future. The current reliance of fuel cells on platinum catalysts is undesirable. However, even the best-performing non-noble metal catalysts are not as efficient. To drive commercial viability of fuel cells forward in the short term, increased utilization of Pt catalysts is paramount. We have demonstrated improved power and energy densities in a single PEMFC using a designed cathode with a Pt loading of 0.1 mg cm−2 on a mesoporous conductive entangled carbon nanotube (CNT)-based architecture. This electrode allows for rapid transfer of both fuel and waste to and from the electrode, respectively. Pt particles are bound tightly, directly to CNT sidewalls by a microwave-reduction technique, which provided increased charge transport at this interface. The Pt entangled CNT cathode, in combination with an E-TEK 0.2 mg cm−2 anode, has a maximum power and energy density of 940 mW cm−2 and 2700 mA cm−2, respectively, and a power and energy density of 4.01 W mgPt−1 and 6.35 A mgPt−1 at 0.65 V. These power densities correspond to a specific mass activity of 0.81 g Pt per kW for the combined mass of both anode and cathode electrodes, approaching the current US Department of Energy efficiency target. [ABSTRACT FROM AUTHOR]

The formation of liquid crystalline graphene oxide dispersions by J. M. Razal, G. G. Wallace, and co‐workers enables the production of fibers and yarns with excellent mechanical properties as well as high thermal and electrical conductivities. On page 5345, the dispersions are shown to be amenable to a range of solution‐based processing methods to create graphene‐based architectures. [ABSTRACT FROM AUTHOR]