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The enhanced lithiophilic properties and the rigid array structure of Al2O3-CNTA/3DG synergistically induce dendrite-free and stable Li anode. The LOBs full battery assembled with the Al2O3-CNTA/3DG-Li anode and CNTA/3DG cathode achieves a long-term cycling stability.

The structural deterioration caused by the relatively weak out-of-plane bending stiffness and the chemically-active edge area of graphene limits its outperformance in strengthening for Al matrix composites (AMCs). Introducing one-dimensional (1D) carbon nanotubes (CNTs) to graphene/metal system is one of the promised strategies to complement the weakness of 2D graphene and make full use of the outstanding intrinsic properties of the both reinforcements. To date, such synergistic strengthening and toughening mechanisms are largely unknown. In this study, AMCs reinforced by a novel hybrid reinforcement, i.e., graphene nanosheets decorated with Cu nanoparticles and CNTs (Cu@GNS-CNTs), are fabricated by an in-situ synthesis method. The combined contrast experiments validated that the organically integrated reinforcing structure promotes the intrinsic load bearing capacity of GNS and the strain hardening capability of the Al matrix simultaneously. As a result, the composites achieved excellent tensile strength and uniform elongation with almost no loss. The strengthening mechanism originated primarily from the hybrid reinforcement exhibits superior load-transfer, fracture inhibition and dislocation storage capability by controlling the interface reaction to construct an effective interface structure without damaging the reinforcement. Our work identifies a promising structural modification strategy for 2D materials and provides mechanistic insights into the synergistic strengthening effect of graphene/CNTs hybrid reinforcement. [Display omitted] [ABSTRACT FROM AUTHOR]

The construction and application of traditional high-strength 7075 aluminum alloy (Al7075) through selective laser melting (SLM) are currently restricted by the serious hot cracking phenomenon. To address this critical issue, in this study, Si is employed to assist the SLM printing of high-strength Al7075. The laser energy density during SLM is optimized, and the effects of Si element on solidification path, relative density, microstructure and mechanical properties of Al7075 alloy are studied systematically. With the modified solidification path, laser energy density, and the dense microstructure with refined grain size and semi-continuous precipitates network at grain boundaries, which consists of fine Si, β-Mg2Si, Q-phase and θ-Al2Cu, the hot cracking phenomenon and mechanical properties are effectively improved. As a result, the tensile strength of the SLM-processed Si-modified Al7075 can reach 486 ± 3 MPa, with a high relative density of ~ 99.4%, a yield strength of 291 ± 8 MPa, fracture elongation of (6.4 ± 0.4)% and hardness of 162 ± 2 (HV0.2) at the laser energy density of 112.5 J/mm3. The main strengthening mechanism with Si modification is demonstrated to be the synergetic enhancement of grain refinement, solution strengthening, load transfer, and dislocation strengthening. This work will inspire more new design of high-strength alloys through SLM.

Single-atom catalysts (SACs) have demonstrated catalytic efficacy toward lithium polysulfide conversion in Li–S batteries. However, achieving high-density M–Nxsites with rational design by a simple method is still challenging to date. Herein, an ultrathin porous 3D carbon-supported single-atom catalyst (SACo/NDC) is synthesized with a salt-template strategy via a facile freeze-drying and one-step pyrolysis procedure and serves well as a sulfur host. The well-defined 3D carbon structure can effectively alleviate volume stress and confine polysulfides inside. Moreover, the dispersed Co–Nxsites exhibit strong chemical adsorption function and valid catalytic efficiency to LiPSs redox conversion. As a result, the SACo/NDC cathodes display enhanced long-term cycling stability and better rate capability.

• The 0.4 wt% GNSs/Al-Si composite foam sshow the energy absorption capacity of 6.8 ± 0.7 MJ/m3. • The graphene nanosheets could provide more pore nucleation sites and protect the liquid films. • The growth of Si precipitates was pronounced inhibited by the graphene nanosheets. The integrity and regularity of pore morphology play an important role in determining the mechanical properties of the metallic foam materials. The conventional methods on refining pore morphology are mainly focused on the optimization of fabrication techniques, however, they are usually inconvenient and complicated. Recently, incorporating nano reinforcement is considered to be a suitable way to fabricate metallic composite foams accompanied by optimized pore morphology and enhanced mechanical properties. In this work, through a facile and rapid powder metallurgy foaming method, the aluminum-silicon (Al-Si) alloy composite foams reinforced by graphene nanosheets (GNSs) are successfully fabricated. The microstructure analyses reveal that, for the Al-Si alloy foams incorporating the GNSs (GNSs/Al-Si composite foams), the pore size is transformed to be smaller, the pore size distributions become more homogeneous and the pore shape is also refined to a regular and roundish state. Meanwhile, the shape of Si precipitates is found transforming from an irregular long strip (length of ~20 μm, width of ~5 μm) to a fine particle state (diameter of ~5 μm). Moreover, the compressive testing results show that, the 0.4 wt% GNSs/Al-Si composite foams own the optimal compression stress of 11.7 ± 0.5 MPa, plateau stress of 10.0 ± 1.0 MPa and energy absorption capacity of 6.8 ± 0.7 MJ/m3, which have improvement of 58.1%, 53.8% and 51.1% in comparison with the Al-Si alloy foams counterpart, respectively. The present findings may pave a new way for developing new generation of metallic composite foams that with stable microstructure and excellent mechanical performance. [Display omitted] [ABSTRACT FROM AUTHOR]

As widely used protective materials, the application of Al foams is still limited by their low intrinsic mechanical properties caused by the brittleness of struts. The introduction of Mg is recently demonstrated effective to improve the mechanical performance of Al foams; however, the mechanism of Mg modification is still not clear. In this work, Al–Mg foams are developed through a powder metallurgy process with excellent compression performance and high energy absorption capacity. The effects of Mg modification on the cell structure, toughness, and deformation behavior are investigated systematically. As a result, the small cell size of ~ 1.8 mm and the high sphericity of 0.92 are achieved with 5% of Mg addition, delivering high compression stress of 8.5 ± 0.43 MPa and energy absorption capacity of 6.9 ± 0.36 MJ/m3, simultaneously. The synergistic mechanism for the improved mechanical performance is also demonstrated to be the combination of stress transfer and plastic deformation behavior of cells. The results provide a new strategy to develop high-performance foam materials by improving toughness and further promote the practical application.

[Display omitted] • Strong NIR absorption of 2D C and LSPR feature of Cu NPs co-enhance photothermy. • 2D C/Cu2 exhibits a remarkable photothermal conversion efficiency of 65.05 %. • Synergetic effect of photothermy and ion release can effectively sterilize. • 2D C/Cu shows broad-spectrum bactericidal activity without apparent toxicity. Low photothermal conversion efficiency restricts the antibacterial application of photothermal materials. In this work, two-dimensional carbon nanosheets (2D C) were prepared and decorated with Cu nanoparticles (2D C/Cu) by using a simple soluble salt template method combined with ultrasonic exfoliation. The photothermal conversion efficiency of 2D C/Cu system can be optimized by changing the content of Cu nanoparticles, where the 2D C/Cu2 showed the best photothermal conversion efficiency (η) of 65.05 % under 808 nm near-infrared light irradiation. In addition, the photothermal performance can affect the release behavior of Cu ions. This superior photothermal property combined with released Cu ions can endow this 2D hybrid material with highly efficient antibacterial efficacy of 99.97 % ± 0.01 %, 99.96 % ± 0.01 %, 99.97 % ± 0.01 % against Escherichia coli , Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus, respectively, because of the synergetic effect of photothermy and ion release. In addition, this 2D hybrid system exhibited good cytocompatibility. Hence, this study provides a novel strategy to enhance the photothermal performance of 2D materials and thus will be beneficial for development of antibiotics-free antibacterial materials with safe and highly efficient bactericidal activity. [ABSTRACT FROM AUTHOR]

W atoms/clusters are employed to in situassist the development of layered vertically aligned carbon nanotube arrays (VACNTs) through hot-filament-assisted chemical vapor deposition (HFCVD) with liquid binary Fe3O4/AlOxcatalysts. The hot W filament was utilized to in situevaporate atomic W and form W clusters on Fe catalysts, which have a strong impact on the growth of layered VACNT arrays. The migration and Ostwald ripening of Fe catalysts are found to be suppressed immediately with more W clusters deposition during CNT growth. Through controlling the deposition of W clusters, the electrochemical energy storage performance of as-prepared layered VACNT arrays is also tunable as electrodes of ion-based supercapacitors. The layered VACNT arrays can achieve a high capacity of 83.1 mF cm–2and possess desirable rate performance due to the suitable hot filament condition (55 W for 90 s). This work provides a new perspective to in-depth understand the behavior of W filament during HFCVD and the significant role of the in situgenerated W clusters on the growth of CNTs by maintaining the catalytic activity and structure of catalysts.

A series of NiCo2P-based electrocatalysts, which were wrapped by CeO2whose oxygen vacancies (VO) are partially filled with phosphorus atoms (named as NiCo2Px/PxFVo-CeO2, where xrefers to the consumption of NaH2PO2·H2O), have been fabricated to improve the electrocatalytic reactivity of NiCo2P toward hydrogen evolution in alkaline solution. In the novel catalysts, the P atoms fill the oxygen vacancies, elevate the chemical valence state of Ni2+and Co3+, and increase the hydride acceptors, which reinforcing the promoting effect of CeO2in the hydrogen evolution reaction (HER). Moreover, the negatively charged P atoms capture the positively charged protons more easily, benefiting the Volmer step during HER. Furthermore, the synergistic effect between oxygen vacancies and the filled P atoms accelerates the migration rate of electrons/ions and increases the electrochemical active area. All of the above are advantageous to the hydrogen evolution of NiCo2Px/PxFVo-CeO2in alkaline electrolyte. As a result, the overpotential as low as 33.6 mV is achieved for NiCo2P0.3/P0.3FVo-CeO2in alkaline media to drive a current density of 10 mA cm–2. The reactivity is superior to that of Pt/C at a large current density along with a Tafel slope of 61.24 mV dec–1and long-term durability, which giving a new technology for efficient transition-metal catalyst candidates toward HER in alkaline solution.

Solid polymer electrolytes (SPEs) are highly promising for realizing high-capacity, low-cost, and safe Li metal batteries. However, the Li dendritic growth and side reactions between Li and SPEs also plague these systems. Herein, a fluorinated lithium salt coating (FC) with organic-inorganic gradient and soft–rigid feature is introduced on Li surface as an artificial protective layer by the in-situreaction between Li metal and fluorinated carboxylic acid. The FC layer can improve the interface stability and wettability between Li and SPEs, assist the transport of Li ions, and guide Li nucleation, contributing to a dendrite-free Li deposition and long-lifespan Li metal batteries. The symmetric cell with FC-Li anodes exhibits a high areal capacity of 1 mAh cm−2at 0.5 mA cm−2, and an ultra-long lifespan of 2000 h at a current density of 0.1 mA cm−2. Moreover, the full cell paired with the LiFePO4cathode exhibits improved cycling stability, remaining 83.7% capacity after 500 cycles at 1 C. When matching with the S cathode, the FC layer can prevent the shuttle effect, contributing to stable and high-capacity Li–S battery. This work provided a promising way for the construction of stable all-solid-state lithium metal batteries with prolonged lifespan.

Conductive epoxy composites are of great interest due to their applications in electronics. They are usually made by mixing powdered conductive fillers with epoxy. However, the conductivity of the composite is limited by the low filler content because increasing filler content causes processing difficulties and reduces the mechanical properties of the epoxy host. We describe here the use of ultra-stiff graphene foams (uGFs) as three-dimensional (3D) continuous conductive fillers for epoxy resins. The powder metallurgy method was used to produce the dense uGFs monoliths that resulted in a very high filler content of 32 wt % in the uGF–epoxy composite, while the density of epoxy was only increased by 0.09 g/cm3. The composite had an electrical conductivity of 41.0 ± 6.3 S/cm, which is among the highest of all of the polymer-based composites with non-conductive polymer matrices and comparable with the conductive polymer matrices reported to date. The compressive modulus of the composite showed a remarkable improvement of >1700% compared to pure epoxy. We have demonstrated that the 3D uGF filler substantially improves the conductivity and reinforces the polymer matrix with a high filler content while retaining a density similar to that of the epoxy alone.

As a promising bifunctional electrocatalyst for water splitting, NiFe-layered double hydroxide (NiFe LDH) demonstrates an excellent activity toward oxygen evolution reaction (OER) in alkaline solution. However, its hydrogen evolution reaction (HER) activity is challenged owing to the poor electronic conductivity and insufficient electrochemical active sites. Therefore, a three-dimensional self-supporting metal hydroxide/oxide electrode with abundant oxygen vacancies is prepared by electrodepositing CeOxnanoparticles on NiFe LDH nanosheets. According to the density functional theory calculations and experimental studies, the oxygen vacancies at the NiFe LDH/CeOxinterface can be introduced successfully because of the positive charges accumulation resulting from the local electron potential difference between NiFe LDH and CeOx. The oxygen vacancies accelerate the electron/ion migration rates, facilitate the charge transfer, and increase the electrochemical active sites, which give rise to an efficient activity toward HER in alkaline solution. Furthermore, NF@NiFe LDH/CeOxneeds a lower potential of 1.51 V to drive a current density of 10 mA cm–2in overall water splitting and demonstrates a superior performance compared with the benchmark Pt/C and RuO2, which is indicated to be a promising bifunctional electrode catalyst.

Electrically splitting water to H2and O2is a preferred method for energy storage as long as no CO2is emitted during the supplied electrical input. Here we report a laser-induced graphene (LIG) process to fabricate efficient catalytic electrodes on opposing faces of a plastic sheet, for the generation of both H2and O2. The high porosity and electrical conductivity of LIG facilitates the efficient contact and charge transfer with the requisite electrolyte. The LIG-based electrodes exhibit high performance for hydrogen evolution reaction and oxygen evolution reaction with excellent long-term stability. The overpotential reaches 100 mA/cm2for HER, and OER is as low as 214 and 380 mV with relatively low Tafel slopes of 54 and 49 mV/dec, respectively. By serial connecting of the electrodes with a power source in an O-ring setup, H2and O2are simultaneously generated on either side of the plastic sheet at a current density of 10 mA/cm2at 1.66 V and can thereby be selectively captured. The demonstration provides a promising route to simple, efficient, and complete water splitting.

The cathodic oxygen reduction reaction (ORR) is essential in the electrochemical energy conversion of fuel cells. Here, through the NH3atmosphere annealing of a graphene oxide (GO) precursor containing trace amounts of Ru, we have synthesized atomically dispersed Ru on nitrogen-doped graphene that performs as an electrocatalyst for the ORR in acidic medium. The Ru/nitrogen-doped GO catalyst exhibits excellent four-electron ORR activity, offering onset and half-wave potentials of 0.89 and 0.75 V, respectively, vsa reversible hydrogen electrode (RHE) in 0.1 M HClO4, together with better durability and tolerance toward methanol and carbon monoxide poisoning than seen in commercial Pt/C catalysts. X-ray adsorption fine structure analysis and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy are performed and indicate that the chemical structure of Ru is predominantly composed of isolated Ru atoms coordinated with nitrogen atoms on the graphene substrate. Furthermore, a density function theory study of the ORR mechanism suggests that a Ru-oxo-N4structure appears to be responsible for the ORR catalytic activity in the acidic medium. These findings provide a route for the design of efficient ORR single-atom catalysts.

An automated metal powder three-dimensional (3D) printing method for in situsynthesis of free-standing 3D graphene foams (GFs) was successfully modeled by manually placing a mixture of Ni and sucrose onto a platform and then using a commercial CO2laser to convert the Ni/sucrose mixture into 3D GFs. The sucrose acted as the solid carbon source for graphene, and the sintered Ni metal acted as the catalyst and template for graphene growth. This simple and efficient method combines powder metallurgy templating with 3D printing techniques and enables direct in situ3D printing of GFs with no high-temperature furnace or lengthy growth process required. The 3D printed GFs show high-porosity (∼99.3%), low-density (∼0.015g cm–3), high-quality, and multilayered graphene features. The GFs have an electrical conductivity of ∼8.7 S cm–1, a remarkable storage modulus of ∼11 kPa, and a high damping capacity of ∼0.06. These excellent physical properties of 3D printed GFs indicate potential applications in fields requiring rapid design and manufacturing of 3D carbon materials, for example, energy storage devices, damping materials, and sound absorption.

The drive for significant advancement in battery capacity and energy density inspired a revisit to the use of Li metal anodes. We report the use of a seamless graphene–carbon nanotube (GCNT) electrode to reversibly store Li metal with complete dendrite formation suppression. The GCNT-Li capacity of 3351 mAh g–1GCNT-Liapproaches that of bare Li metal (3861 mAh g–1Li), indicating the low contributing mass of GCNT, while yielding a practical areal capacity up to 4 mAh cm–2and cycle stability. A full battery based on GCNT-Li/sulfurized carbon (SC) is demonstrated with high energy density (752 Wh kg–1total electrodes, where total electrodes = GCNT-Li + SC + binder), high areal capacity (2 mAh cm–2), and cyclability (80% retention at >500 cycles) and is free of Li polysulfides and dendrites that would cause severe capacity fade.

Free-standing robust three-dimensional (3D) rebar graphene foams (GFs) were developed by a powder metallurgy template method with multiwalled carbon nanotubes (MWCNTs) as a reinforcing bar, sintered Ni skeletons as a template and catalyst, and sucrose as a solid carbon source. As a reinforcement and bridge between different graphene sheets and carbon shells, MWCNTs improved the thermostability, storage modulus (290.1 kPa) and conductivity (21.82 S cm–1) of 3D GF resulting in a high porosity and structurally stable 3D rebar GF. The 3D rebar GF can support >3150× the foam’s weight with no irreversible height change, and shows only a ∼25% irreversible height change after loading >8500× the foam’s weight. The 3D rebar GF also shows stable performance as a highly porous electrode in lithium ion capacitors (LICs) with an energy density of 32 Wh kg–1. After 500 cycles of testing at a high current density of 6.50 mA cm–2, the LIC shows 78% energy density retention. These properties indicate promising applications with 3D rebar GFs in devices requiring stable mechanical and electrochemical properties.

Here we show that a versatile binary catalyst solution of Fe3O4/AlOxnanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlOxnanoclusters over Fe3O4crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg–1), high-power density capabilities (∼20,500 W kg–1at 29 Wh kg–1), and a large operating voltage window (4.3 to 0.01 V).

Large-area graphene has emerged as a promising material for use in flexible and transparent electronics due to its flexibility and optical and electronic properties. The anchoring of transition metal nanoparticles on large-area single-layer graphene is still a challenge. Here, we report an in situpreparation of carbon nano-onion-encapsulated Fe nanoparticles on rebar graphene, which we term rivet graphene. The hybrid film, which allows for polymer-free transfer and is strong enough to float on water with no added supports, exhibits high optical transparency, excellent electric conductivity, and good hole/electron mobility under certain tensile/compressive strains. The results of contact resistance and transfer length indicate that the current in the rivet graphene transistor does not just flow at the contact edge. Carbon nano-onions encapsulating Fe nanoparticles on the surface enhance the injection of charge between rivet graphene and the metal electrode. The anchoring of Fe nanoparticles encapsulated by carbon nano-onions on rebar graphene will provide additional avenues for applications of nanocarbon-based films in transparent and flexible electronics.

High-quality microsized ultrathin single-crystalline anatase TiO2nanosheets (MS-TiO2) with exposed {001} facets were synthesized by a facile and low-cost two-step process that combines a graphene oxide (GO)-assisted hydrothermal method with calcination. Both GO and HF play an important role in the formation of well dispersed MS-TiO2. As a novel microsized (1–4 μm) ultrathin two-dimensional (2D) material, MS-TiO2possesses much higher lateral size and aspect ratio compared to common 2D nanosized (30–60 nm) ultrathin TiO2nanosheets (NS-TiO2), resulting in excellent electronic conductivity and superior electron transfer and diffusion properties. Here, we fabricated MS-TiO2and NS-TiO2, both of which were incorporated with the TiO2nanoparticles (P25) to constitute the hybrid photoanode of dye-sensitized solar cells (DSSCs), and explored the effect of the lateral size (nano- and micro-) of ultrathin TiO2nanosheets on their electron transfer and diffusion properties. Benefiting from the faster electron transfer rate and short diffusion path of the MS-TiO2, the MS-TiO2/P25 gains the more superior performance compared to pure P25 and NS-TiO2/P25 in the application of DSSCs. Moreover, it is expected that the novel high aspect ratio MS-TiO2may be applied in diverse fields including photocatalysis, photodetectors, lithium-ion batteries and others concerning the environment and energy.

A simple and scalable method which combines traditional powder metallurgy and chemical vapor deposition is developed for the synthesis of mesoporous free-standing 3D graphene foams. The powder metallurgy templates for 3D graphene foams (PMT-GFs) consist of particle-like carbon shells which are connected by multilayered graphene that shows high specific surface area (1080 m2g–1), good crystallization, good electrical conductivity (13.8 S cm–1), and a mechanically robust structure. The PMT-GFs did not break under direct flushing with DI water, and they were able to recover after being compressed. These properties indicate promising applications of PMT-GFs for fields requiring 3D carbon frameworks such as in energy-based electrodes and mechanical dampening.