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Operating microbial fuel cells (MFCs) under extreme pH conditions offers a substantial benefit. Acidic conditions suppress the growth of undesirable methanogens and increase redox potential for oxygen reduction reactions (ORRs), and alkaline conditions increase the electrocatalytic activity. However, operating any fuel cells, including MFCs, is difficult under such extreme pH conditions. Here, we demonstrate a pH-universal ORR ink based on hollow nanospheres of manganese oxide (h-Mn

Lead iodide (PbI2) as a layered material has emerged as an excellent candidate for optoelectronics in the visible and ultraviolet regime. Micrometer-sized flakes synthesized by mechanical exfoliation from bulk crystals or by physical vapor deposition have shown a plethora of applications from low-threshold lasing at room temperature to high-performance photodetectors with large responsivity and faster response. However, large-area centimeter-sized growth of epitaxial thin films of PbI2 with well-controlled orientation has been challenging. Additionally, the nature of grain boundaries in epitaxial thin films of PbI2 remains elusive. Here, we use mica as a model substrate to unravel the growth mechanism of large-area epitaxial PbI2 thin films. The partial growth leading to uncoalesced domains reveals the existence of inversion domain boundaries in epitaxial PbI2 thin films on mica. Combining the experimental results with first-principles calculations, we also develop an understanding of the thermodynamic and kinetic factors that govern the growth mechanism, which paves the way for the synthesis of high-quality large-area PbI2 on other substrates and heterostructures of PbI2 on single-crystalline graphene. The ability to reproducibly synthesize high-quality large-area thin films with precise control over orientation and tunable optical properties could open up unique and hitherto unavailable opportunities for the use of PbI2 and its heterostructures in optoelectronics, twistronics, substrate engineering, and strain engineering.

Hotspot engineering has the potential to transform the field of surface-enhanced Raman spectroscopy (SERS) by enabling ultrasensitive and reproducible detection of analytes. However, the ability to controllably generate SERS hotspots, with desired location and geometry, over large-area substrates, has remained elusive. In this study, we sculpt artificial edges in monolayer molybdenum disulfide (MoS2) by low-power focused laser-cutting. We find that when gold nanoparticles (AuNPs) are deposited on MoS2 by drop-casting, the AuNPs tend to accumulate predominantly along the artificial edges. First-principles density functional theory (DFT) calculations indicate strong binding of AuNPs with the artificial edges due to dangling bonds that are ubiquitous on the unpassivated (laser-cut) edges. The dense accumulation of AuNPs along the artificial edges intensifies plasmonic effects in these regions, creating hotspots exclusively along the artificial edges. DFT further indicates that adsorption of AuNPs along the artificial edges prompts a transition from semiconducting to metallic behavior, which can further intensify the plasmonic effect along the artificial edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS2 surface (away from the cut edges) or along the natural (passivated) edges of the MoS2 sheet. To demonstrate the practical utility of this concept, we use our substrate to detect Rhodamine B (RhB) with a large SERS enhancement (∼104) at the hotspots for RhB concentrations as low as ∼10-10 M. The single-step laser-etching process reported here can be used to controllably generate arrays of SERS hotspots. As such, this concept offers several advantages over previously reported SERS substrates that rely on electrochemical deposition, e-beam lithography, nanoimprinting, or photolithography. Whereas we have focused our study on MoS2, this concept could, in principle, be extended to a variety of 2D material platforms.

Exploring efficient electrocatalysts for lithium-sulfur (Li-S) batteries is of great significance for the sulfur/polysulfide/sulfide multiphase conversion. Herein, we report nickel-iron intermetallic (Ni3Fe) as a novel electrocatalyst to trigger the highly efficient polysulfide-involving surface reactions. The incorporation of iron into the cubic nickel phase can induce strong electronic interaction and lattice distortion, thereby activating the inferior Ni phase to catalytically active Ni3Fe phase. Kinetics investigations reveal that the Ni3Fe phase promotes the redox kinetics of the multiphase conversion of Li-S electrochemistry. As a result, the Li-S cells assembled with a 70 wt % sulfur cathode and a Ni3Fe-modified separator deliver initial capacities of 1310.3 mA h g-1 at 0.1 C and 598 mA h g-1 at 4 C with excellent rate capability and a long cycle life of 1000 cycles at 1 C with a low capacity fading rate of ∼0.034 per cycle. More impressively, the Ni3Fe-catalyzed cells exhibit outstanding performance even at harsh working conditions, such as high sulfur loading (7.7 mg cm-2) or lean electrolyte/sulfur ratio (∼6 μL mg-1). This work provides a new concept on exploring advanced intermetallic catalysts for high-rate and long-life Li-S batteries.

Solar-driven water evaporation has been proposed as a renewable and sustainable strategy for the generation of clean water from seawater or wastewater. To enable such technologies, development of photothermal materials that enable efficient solar steam generation is essential. The current challenge is to manufacture such photothermal materials cost-effectively and at scale. Furthermore, the photothermal materials should be strongly hydrophilic and environmentally stable. Herein, we demonstrate facile and scalable fabrication of carbon nanotube (CNT)-based photothermal nanocomposite foam by igniting an ethanol solution of ferric acetylacetonate [Fe(acac)3] absorbed within nickel (Ni) foam under ambient conditions. The Fe(acac)3 precursor provides carbon and the zero-valent iron catalyst for growing CNTs on the Ni foam, while ethanol facilitates the dispersion of Fe(acac)3 on the Ni foam and supplies heat energy for the growth of CNTs by its burning. A forest of dense and uniform CNTs decorated with Fe2O3 nanoparticles is generated within seconds. The resultant Fe2O3/CNT/Ni nanocomposite foam exhibits "superhydrophilicity" and high light absorption capacity, ensuring rapid transport and fast evaporation of water within the entire foam. Efficient light-to-heat conversion causes the surface temperature of the foam to reach ∼83.1 °C under 1 sun irradiation. The average water evaporation rates of such foam are as high as ∼1.48 and ∼4.27 kg m-2 h-1 with light-to-heat conversion efficiencies of ∼81.3 and ∼93.8% under 1 sun and 3 sun irradiation, respectively. Moreover, the versatile and scalable combustion synthesis strategy presented here can be realized on various substrates, exhibiting high adaptability for different applications.

High specific capacity materials that can store potassium (K) are essential for next-generation K-ion batteries. One such candidate material is phosphorene (the 2D allotrope of phosphorus (P)), but the potassiation capability of phosphorene has not yet been established. Here we systematically investigate the alloying of few-layer phosphorene (FLP) with K. Unlike lithium (Li) and sodium (Na), which form Li3P and Na3P, FLP alloys with K to form K4P3, which was confirmed by ex situ X-ray characterization as well as density functional theory calculations. The formation of K4P3 results in high specific capacity (∼1200 mAh g-1) but poor cyclic stability (only ∼9% capacity retention in subsequent cycles). We show that this capacity fade can be successfully mitigated by the use of reduced graphene oxide (rGO) as buffer layers to suppress the pulverization of FLP. We studied the performance of rGO and single-walled carbon nanotubes (sCNTs) as buffer materials and found that rGO being a 2D material can better encapsulate and protect FLP relative to 1D sCNTs. The half-cell performance of FLP/rGO could also be successfully reproduced in a full-cell configuration, indicating the possibility of high-performance K-ion batteries that could offer a sustainable and low-cost alternative to Li-ion technology.

Graphene is the thinnest known two-dimensional (2D) material. This thinness is responsible for graphene's well-known optical transparency. In addition to being transparent to light, its extreme thinness and nonpolar nature also render graphene partially transparent to van der Waals and electrostatic interactions. This enables media present on opposite sides of a graphene sheet to sense or feel each other and be influenced by each other. Such crosstalk between materials separated by an impermeable barrier is impossible for typical barrier or coating materials that are usually thick enough to completely screen out such interactions. In this article, we review graphene's partial transparency to atomic interactions at the liquid-solid, solid-solid, and liquid-liquid interfaces. We compare graphene with other 2D materials such as hexagonal boron nitride and show that the extent of graphene's transparency is strongly dependent on the nature and interaction range of the materials placed on opposite sides of the graphene layer. We end with recommendations for future research to better understand the underlying science and to develop practical applications of this exciting phenomena.

An ideal separator of lithium-ion battery (LIB) should have a zero ionic resistance. Low ionic resistance (high ionic conductivity) will greatly help to realize very fast ion diffusion and superhigh rate capability of LIBs. The most effective technique to achieve low ionic resistance of separator is to reduce its thickness or increase its porosity. Paradoxically, the low thickness and high porosity will inevitably decrease the mechanical strength of separators. Inspired by the hierarchical structures of abalone shell, we demonstrate in this work an ultrathin silica-anchored layered (PVdF/PE/PVdF) porous fiber separator prepared via electrospinning. The separator displays both ultrathin thickness (∼20 μm thick) and high mechanical strength of ∼11.2 MPa, as well as high porosity, which results in high electrolyte uptake (∼380%) and ionic conductivity (∼2.5 mS cm–1). When such thin separator was deployed in a LiFePO4/Li cell, and the cell can deliver an initial discharge capacity of 134.3 mA h g–1 at a high ...

High specific capacity anode materials such as silicon (Si) are increasingly being explored for next-generation, high performance lithium (Li)-ion batteries. In this context, Si films are advantageous compared to Si nanoparticle based anodes since in films the free volume between nanoparticles is eliminated, resulting in very high volumetric energy density. However, Si undergoes volume expansion (contraction) under lithiation (delithiation) of up to 300%. This large volume expansion leads to stress build-up at the interface between the Si film and the current collector, leading to delamination of Si from the surface of the current collector. To prevent this, adhesion promotors (such as chromium interlayers) are often used to strengthen the interface between the Si and the current collector. Here, we show that such approaches are in fact counter-productive and that far better electrochemical stability can be obtained by engineering a van der Waals "slippery" interface between the Si film and the current collector. This can be accomplished by simply coating the current collector surface with graphene sheets. For such an interface, the Si film slips with respect to the current collector under lithiation/delithiation, while retaining electrical contact with the current collector. Molecular dynamics simulations indicate (i) less stress build-up and (ii) less stress "cycling" on a van der Waals slippery substrate as opposed to a fixed interface. Electrochemical testing confirms more stable performance and much higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) as compared to conventional nickel current collectors.

Single-layer rhenium disulfide (ReS2) is a unique material with distinctive, anisotropic electronic, mechanical, and optical properties and has the potential to be used as an anode in alkali-metal-ion batteries. In this work, first principles calculations were performed to systematically evaluate the potential of monolayer pristine and defective ReS2 as anodes in lithium (Li)- and sodium (Na)-ion batteries. Our calculations suggest that there are several potential adsorption sites for Li and Na on pristine ReS2, owing to its low-symmetry structure. Additionally, the adsorption of Li and Na over pristine ReS2 is very strong with adsorption energies of −2.28 and −1.71 eV, respectively. Interestingly, the presence of point defects causes significantly stronger binding of the alkali-metal atoms with adsorption energies in the range −2.98 to −3.17 eV for Li and −2.66 to −2.92 eV for Na. Re single vacancy was found to be the strongest binding defect for Li adsorption, whereas S single vacancy was found to be th...

A major concern for exposed steel in structural applications is susceptibility to atmospheric corrosion. The International Organization for Standardization classifies atmospheric environments into ...

Transition-metal dichalcogenide (TMD) nanolayers show potential as high-performance catalysts in energy conversion and storage devices. Synthetic TMDs produced by chemical-vapor deposition (CVD) methods tend to grow parallel to the growth substrate. Here, we show that with the right precursors and appropriate tuning of the CVD growth conditions, ReS2 nanosheets can be made to orient perpendicular to the growth substrate. This accomplishes two important objectives; first, it drastically increases the wetted or exposed surface area of the ReS2 sheets, and second, it exposes the sharp edges and corners of the ReS2 sheets. We show that these structural features of the vertically grown ReS2 sheets can be exploited to significantly improve their performance as polysulfide immobilizers and electrochemical catalysts in lithium-sulfur (Li-S) batteries and in hydrogen evolution reactions (HER). After 300 cycles, the specific capacity of the Li-S battery with vertical ReS2 catalyst is retained above 750 mA h g(-1), with only ∼0.063% capacity decay per cycle, much better than the baseline battery (without ReS2), which shows ∼0.184% capacity decay per cycle under the same test conditions. As a HER catalyst, the vertical ReS2 provides very small onset overpotential (100 mV) and an exceptional exchange-current density (∼67.6 μA/cm(2)), which is vastly superior to the baseline electrode without ReS2.

A series of nanocomposites were prepared from graphene platelets (GPL) and a flexible biobased epoxy thermoset matrix derived from cashew nut shell liquid. The loading of GPL in the biobased thermoset matrix ranged from 0.1 to 0.8 wt % and resulted in increased tensile strength and Young’s modulus (17 to 33 MPa and 474 to 1700 MPa, respectively). Increases in mode I fracture toughness for KIC and GIC ranged from 0.6 to 1.9 MPa·m1/2 and 906 to 1734 J/m2, respectively. Furthermore, dynamic mechanical analysis revealed that GPL incorporation resulted in increases in the α-transition temperature (peak of the loss modulus) from 27 to 50 °C and increases the storage modulus from 1000 to 2000 MPa. Also, introduction of GPL increased the onset of degradation (Td3%) for the biobased thermoset matrix by 30 °C. Results of this work demonstrate that incorporation of graphene platelets enhances all measured physical and thermal properties of the cashew nut shell derived epoxy resin and enables higher performance appli...

Two-dimensional sheets of transition metal dichalcogenides are an emerging class of atomically thin semiconductors that are considered to be "air-stable", similar to graphene. Here we report that, contrary to current understanding, chemical vapor deposited transition metal dichalcogenide monolayers exhibit poor long-term stability in air. After room-temperature exposure to the environment for several months, monolayers of molybdenum disulfide and tungsten disulfide undergo dramatic aging effects including extensive cracking, changes in morphology, and severe quenching of the direct gap photoluminescence. X-ray photoelectron and Auger electron spectroscopy reveal that this effect is related to gradual oxidation along the grain boundaries and the adsorption of organic contaminants. These results highlight important challenges associated with the utilization of transition metal dichalcogenide monolayers in electronic and optoelectronic devices. We also demonstrate a potential solution to this problem, featuring encapsulation of the monolayer sheet by a 10-20 nm thick optically transparent polymer (parylene C). This strategy is shown to successfully prevent the degradation of the monolayer material under accelerated aging (i.e., high-temperature, oxygen-rich) conditions.

The performance of graphene field-effect transistors is limited by the drastically reduced carrier mobility of graphene on silicon dioxide (SiO2) substrates. Here we demonstrate an ultrasensitive ultraviolet (UV) phototransistor featuring an organic self-assembled monolayer (SAM) sandwiched between an inorganic ZnO quantum dots decorated graphene channel and a conventional SiO2/Si substrate. Remarkably, the room-temperature mobility of the chemical-vapor-deposition grown graphene channel on the SAM is an order-of-magnitude higher than on SiO2, thereby drastically reducing electron transit-time in the channel. The resulting recirculation of electrons (in the graphene channel) within the lifetime of the photogenerated holes (in the ZnO) increases the photoresponsivity and gain of the transistor to ∼10(8) A/W and ∼3 × 10(9), respectively with a UV to visible rejection ratio of ∼10(3). Our UV photodetector device manufacturing is also compatible with current semiconductor processing, and suitable for large volume production.

The recent interest and excitement in graphene has also opened up a pandora's box of other two-dimensional (2D) materials and material combinations which are now beginning to come to the fore. One family of these emerging 2D materials is transition metal dichalcogenides (TMDs). So far there is very limited understanding on the wetting behavior of "monolayer" TMD materials. In this study, we synthesized large-area, continuous monolayer tungsten disulfide (WS2) and molybdenum disulfide (MoS2) films on SiO2/Si substrates by the thermal reduction and sulfurization of WO3 and MO3 thin films. The monolayer TMD films displayed an advancing water contact angle of ∼83° as compared to ∼90° for the bulk material. We also prepared bilayer and trilayer WS2 films and studied the transition of the water contact angle with increasing number of layers. The advancing water contact angle increased to ∼85° for the bilayer and then to ∼90° for the trilayer film. Beyond three layers, there was no significant change in the measured water contact angle. This type of wetting transition indicates that water interacts to some extent with the underlying silica substrate through the monolayer TMD sheet. The experimentally observed wetting transition with numbers of TMD layers lies in-between the predictions of one continuum model that considers only van der Waals attractions and another model that considers only dipole-dipole interactions. We also explored wetting as a function of aging. A clean single-layer WS2 film (without airborne contaminants) was shown to be strongly hydrophilic with an advancing water contact angle of ∼70°. However, over time, the sample ages as hydrocarbons and water present in air adsorb onto the clean WS2 sheet. After ∼7 days, the aging process is completed and the advancing water contact angle of the aged single-layer WS2 film stabilizes at ∼83°. These results suggest that clean (i.e., nonaged) monolayer TMDs are hydrophilic materials. We further show that substitution of sulfur atoms by oxygen in the lattice of aged monolayer WS2 and MoS2 films can be used to generate well-defined 'hydrophobic-hydrophilic' patterns that preferentially accumulate and create microdrop arrays on the surface during water condensation and evaporation experiments.

In this study, we report a novel route via microwave irradiation to synthesize a bio-inspired hierarchical graphene--nanotube--iron three-dimensional nanostructure as an anode material in lithium-ion batteries. The nanostructure comprises vertically aligned carbon nanotubes grown directly on graphene sheets along with shorter branches of carbon nanotubes stemming out from both the graphene sheets and the vertically aligned carbon nanotubes. This bio-inspired hierarchical structure provides a three-dimensional conductive network for efficient charge-transfer and prevents the agglomeration and restacking of the graphene sheets enabling Li-ions to have greater access to the electrode material. In addition, functional iron-oxide nanoparticles decorated within the three-dimensional hierarchical structure provides outstanding lithium storage characteristics, resulting in very high specific capacities. The anode material delivers a reversible capacity of ~1024 mA · h · g(-1) even after prolonged cycling along with a Coulombic efficiency in excess of 99%, which reflects the ability of the hierarchical network to prevent agglomeration of the iron-oxide nanoparticles.

We demonstrate here the effect of electron beam induced deposited platinum on the electrical transport through multilayer graphene sheets. Platinum metal is deposited at different positions on the graphene multilayers, i.e., including as well as excluding the bottom contact sites and the change in electrical conductance of the same multilayer graphene sheets before and after platinum deposition is segregated. An improvement in electrical conductance is observed even if the metal is deposited at the part of the graphene sheets that does not touch the bottom gold electrodes, and hence this experimental approach directly demonstrates that the contact improvement is not the sole reason for the improved electrical conduction. The improvement in electrical performance of the graphene sheets is explained in terms of the doping of graphene sheets caused by the charge transfer between the deposited metal and the graphene and thereby modified density of states for electrical conduction. Metal deposition also leads to the increased interlayer interaction of the graphene sheets as revealed by the transmission electron microscopy analysis. Further, two types of breakdown behaviors viz. sharp and stepped breakdowns observed for these graphene devices are explained in terms of the effective graphene-metal contact area. These studies reveal the implications of top metal contact fabrication on graphene for electronic devices.

Conventional graphitic anodes in lithium-ion batteries cannot provide high-power densities due to slow diffusivity of lithium ions in the bulk electrode material. Here we report photoflash and laser-reduced free-standing graphene paper as high-rate capable anodes for lithium-ion batteries. Photothermal reduction of graphene oxide yields an expanded structure with micrometer-scale pores, cracks, and intersheet voids. This open-pore structure enables access to the underlying sheets of graphene for lithium ions and facilitates efficient intercalation kinetics even at ultrafast charge/discharge rates of100 C. Importantly, photothermally reduced graphene anodes are structurally robust and display outstanding stability and cycling ability. At charge/discharge rates of ~40 C, photoreduced graphene anodes delivered a steady capacity of ~156 mAh/g(anode) continuously over 1000 charge/discharge cycles, providing a stable power density of ~10 kW/kg(anode). Such electrodes are envisioned to be mass scalable with relatively simple and low-cost fabrication procedures, thereby providing a clear pathway toward commercialization.

Pioneering research in 2004 by Geim and Novoselov (2010 Nobel Prize winners in Physics) of the University of Manchester led to the isolation of a monolayer graphene sheet. Graphene is a single-atom-thick sheet of sp(2) hybridized carbon atoms that are packed in a hexagonal honeycomb crystalline structure. Graphene is the fundamental building block of all sp(2) carbon materials including single-walled carbon nanotubes, mutliwalled carbon nanotubes, and graphite and is therefore interesting from the fundamental standpoint as well as for practical applications. One of the most promising applications of graphene that has emerged so far is its utilization as an ultrasensitive chemical or gas sensor. In this article, we review some of the significant work performed with graphene and its derivatives for gas detection and provide a perspective on the challenges that need to be overcome to enable commercially viable graphene chemical sensor technologies.

We compared the electrical conductivity of multiwalled-carbon-nanotube/polystyrene and graphene/polystyrene composites. The conductivity of polystyrene increases from ∼6.7 × 10(-14) to ∼3.49 S/m, with an increase in graphene content from ∼0.11 to ∼1.1 vol %. This is ∼2-4 orders of magnitude higher than for multiwalled-carbon-nanotube/polystyrene composites. Furthermore, we show that the conductivity of the graphene/polystyrene system can be significantly enhanced by incorporation of polylactic acid. The volume-exclusion principle forces graphene into the polystyrene-rich regions (selective localization) and generates ∼4.5-fold decrease in its percolation threshold from ∼0.33 to ∼0.075 vol %.

Water flow over carbon nanotubes has been shown to generate an induced voltage in the flow direction due to coupling of ions present in water with free charge carriers in the nanotubes. However, the induced voltages are typically of the order of a few millivolts, too small for significant power generation. Here we perform tests involving water flow with various molarities of hydrochloric acid (HCl) over few-layered graphene and report order of magnitude higher induced voltages for graphene as compared to nanotubes. The power generated by the flow of ∼0.6 M HCl solution at ∼0.01 m/sec was measured to be ∼85 nW for a ∼30 × 16 μm size graphene film, which equates to a power per unit area of ∼175 W/m(2). Molecular dynamics simulations indicate that the power generation is primarily caused by a net drift velocity of adsorbed Cl(-) ions on the continuous graphene film surface.

The majority of work in graphene nanocomposites has focused on polymer matrices. Here we report for the first time the use of graphene to enhance the toughness of bulk silicon nitride ceramics. Ceramics are ideally suited for high-temperature applications but suffer from poor toughness. Our approach uses graphene platelets (GPL) that are homogeneously dispersed with silicon nitride particles and densified, at ∼1650 °C, using spark plasma sintering. The sintering parameters are selected to enable the GPL to survive the harsh processing environment, as confirmed by Raman spectroscopy. We find that the ceramic's fracture toughness increases by up to ∼235% (from ∼2.8 to ∼6.6 MPa·m(1/2)) at ∼1.5% GPL volume fraction. Most interestingly, novel toughening mechanisms were observed that show GPL wrapping and anchoring themselves around individual ceramic grains to resist sheet pullout. The resulting cage-like graphene structures that encapsulate the individual grains were observed to deflect propagating cracks in not just two but three dimensions.

We report the use of graphene as an additive to improve the lubrication and cooling performance of semisynthetic metal-working fluids (MWFs) used in micromachining operations. Microturning experiments were conducted in the presence of MWFs containing varying concentrations of graphene platelets. Graphene-based MWF formulations performed significantly better as compared to conventional MWFs. Moreover, an analysis of the trends in the cutting forces and cutting temperatures, taken in conjunction with the trends in the wetting ability, thermal conductivity, and kinematic viscosity of the modified MWFs, establishes graphene as a superior additive over both single and multiwalled carbon nanotubes. The superior performance of graphene is attributed to the increased wettability of the cutting fluid that allows for penetration of the graphene platelets into the tool−workpiece interface. Once in that interface, the graphene platelets provide efficient lubrication because of the relative sliding of graphene layers ...

Lithium-ion batteries show poor performance for high power applications involving ultrafast charging/discharging rates. Here we report a functionally strain-graded carbon-aluminum-silicon anode architecture that overcomes this drawback. It consists of an array of nanostructures each comprising an amorphous carbon nanorod with an intermediate layer of aluminum that is finally capped by a silicon nanoscoop on the very top. The gradation in strain arises from graded levels of volumetric expansion in these three materials on alloying with lithium. The introduction of aluminum as an intermediate layer enables the gradual transition of strain from carbon to silicon, thereby minimizing the mismatch at interfaces between differentially strained materials and enabling stable operation of the electrode under high-rate charge/discharge conditions. At an accelerated current density of ∼51.2 A/g (i.e., charge/discharge rate of ∼40C), the strain-graded carbon-aluminum-silicon nanoscoop anode provides average capacities of ∼412 mAh/g with a power output of ∼100 kW/kg(electrode) continuously over 100 charge/discharge cycles.

We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ∼0.2% (with respect to the epoxy resin weight and ∼0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ∼3-5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ∼1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries.