Nanosheet Networks Research Articles

Novel Flexible Transparent Conductive Films with Enhanced Chemical and Electromechanical Sustainability: TiO2 Nanosheet-Ag Nanowire Hybrid.

Flexible transparent conductive films (TCFs) of TiO2 nanosheet (TiO2 NS) and silver nanowire (Ag NW) network hybrid were prepared through a simple and scalable solution-based process. The as-formed TiO2 NS-Ag NW hybrid TCF shows a high optical transmittance (TT: 97% (90.2% including plastic substrate)) and low sheet resistance (Rs: 40 Ω/sq). In addition, the TiO2 NS-Ag NW hybrid TCF exhibits a long-time chemical/aging and electromechanical stability. As for the chemical/aging stability, the hybrid TCF of Ag NW and TiO2 NS reveals a retained initial conductivity (ΔRs/Rs < 1%) under ambient oxidant gas over a month, superior to that of bare Ag NW (ΔRs/Rs > 4000%) or RuO2 NS-Ag NW hybrid (ΔRs/Rs > 200%). As corroborated by the density functional theory simulation, the superb chemical stability of TiO2 NS-Ag NW hybrid is attributable to the unique role of TiO2 NS as a barrier, which prevents Ag NW's chemical corrosion via the attenuated adsorption of sulfidation molecules (H2S) on TiO2 NS. With respect to the electromechanical stability, in contrast to Ag NWs (ΔR/R0 ∼ 152.9%), our hybrid TCF shows a limited increment of fractional resistivity (ΔR/R0 ∼ 14.4%) after 200 000 cycles of the 1R bending test (strain: 6.7%) owing to mechanically welded Ag NW networks by TiO2 NS. Overall, our unique hybrid of TiO2 NS and Ag NW exhibits excellent electrical/optical properties and reliable chemical/electromechanical stabilities.

Carbon fabric supported 3D cobalt oxides/hydroxide nanosheet network as cathode for flexible all-solid-state asymmetric supercapacitor.

Owing to a lack of electroactive sites and poor conductivity, Co oxides/hydroxides nanosheet network electrodes usually show low experimental capacity, hardly meeting the demand for high energy density needed for an asymmetric supercapacitor. Herein, we demonstrate a surface capacity enhancement of a 3D cobalt oxides/hydroxides nanosheet network cathode through a simple cyclic voltammetry electro-deposition method. By optimizing the electro-deposition parameters, the as-prepared Co oxides/hydroxides nanosheet network electrode delivers a significantly high capacity of 427 C g-1 at the current density of 1 A g-1 and excellent rate ability of 79.8% at the current density of 10 A g-1, as well as outstanding cycling life. A detailed voltammetric analysis using the power-law relationship and Trasatti's method shows that both the large surface area, high pore volume and polycrystalline nature contribute to the enhancement of the surface capacity. In addition, the assembled asymmetric all-solid-state supercapacitor also presents a volume energy density of 2.78 mW h cm-3 at a power density of 14 mW cm-3 and excellent cycling stability. In addition, our prepared asymmetric supercapacitor shows super flexibility and was used to light up a heart-shaped logo. This work may provide valuable insights into the design and fabrication of electrode materials with improved capacity and rate ability.

Co2P nanoparticles encapsulated in 3D porous N-doped carbon nanosheet networks as an anode for high-performance sodium-ion batteries

A novel Co2P-3D PNC composite with Co2P NPs encapsulated in 3D porous N-doped carbon nanosheet networks was synthesized by a cobalt nitrate-induced PVP-blowing method combined with an in situ phosphidation process. The resultant Co2P-3D PNC anode delivers high specific capacity, enhanced rate capability, and improved cycling stability.

Sustained antibacterial activity of berberine hydrochloride loaded supramolecular organoclay networks with hydrogen-bonding junctions.

The environmental risk from antibiotics is an issue of increasing concern. So, carboxymethyl β-cyclodextrin-functionalized montmorillonite nanosheets were for the first time successfully synthesized through a cheap, environmentally friendly and scalable approach and confirmed by FTIR, XRD and TGA. FE-SEM investigation showed that the resulting functional material could be further self-assembled into dense supramolecular organoclay networks (D-networks). The antibacterial properties of the D-networks loaded with natural berberine hydrochloride (BBH) were investigated toward E. coli and S. aureus by using colony growth on agar plates, bacterial growth curves based on optical densities, and confocal and fluorescence microscopy. Our studies demonstrated that the BBH loaded D-network antibacterial activity was concentration dependent and significantly exceeded that of free BBH. FE-SEM observation confirmed that E. coli and S. aureus can directly contact the D-networks and confocal and fluorescence microscopy showed that free BBH was only very poorly internalized, while the BBH released from the BBH-loaded D-network could be internalized efficiently into bacterial cells, resulting in an increment of the intracellular BBH level compared with the free BBH group. Time-dependent antibacterial activity was observed and it was found that the BBH-loaded D-network dispersion at the BBH dosage of 600 μg mL-1 almost completely suppressed the growth of E. coli, leading to a viability loss of up to 98.45 ± 1.22%, while the BBH-loaded D-network dispersion at the BBH concentration of 250 μg mL-1 exhibited a growth inhibition of 97.81 ± 0.83% toward S. aureus over three days. Our results suggest that supramolecular organoclay networks, in the future, may function as promising antibacterial drug carrier systems to promote BBH delivery in E. coli and S. aureus, which can reduce the environmental risk of antibiotics.

CTAB-assisted growth of self-supported Zn2GeO4 nanosheet network on a conductive foam as a binder-free electrode for long-life lithium-ion batteries.

The Ge-based compounds show great potential as replacements for traditional graphite anode in lithium-ion batteries (LIBs). However, large volume changes and low conductivity of such materials result in a poor electrochemical cycling and rate performance. Herein, we fabricate a self-supported and three-dimensional (3D) sponge-like structure of interlinked Zn2GeO4 ultrathin nanosheets anchored vertically on a nickel foam (ZGO NSs@NF) via a simple hydrothermal process assisted by cetyltrimethyl ammonium bromide (CTAB). Such robust self-supported hybrid structures greatly improve the structural tolerance of the active materials and accommodate the volume variation that occurs during repeated electrochemical cycling. As expected, the self-supported ZGO NSs@NF composites demonstrate an excellent lithium storage with a high discharge capacity, a long cycling life, and a good rate capability when used as binder-free anodes for LIBs. A high reversible discharge capacity of 794 mA h g-1 is maintained after 500 cycles at 200 mA g-1, corresponding to 81% capacity retention of the second cycle. Further evaluation at a higher current density (2 A g-1) also delivers a reversible discharge capacity (537 mA h g-1) for this binder-free anode. This novel 3D structure of the self-supported ultrathin nanosheets on a conductive substrate, with its volume buffer effect and good interfacial contacts, can stimulate the progress of other energy-efficient technologies.

From 1D nanotube arrays to 2D nanosheet networks on silver-coated textiles: new insights into the factors determining the performance of a core–shell hierarchical structure for wearable supercapacitors

Investigating the factors that determine the performance of the electrodes with different sub-structure helps to extend the application of wearable energy storage devices.

Highly sensitive CO sensor based on ZnO/MWCNT nano sheet network grown via hydrothermal method

Zinc Oxide/Multiwall Carbon Nanotube (ZnO/MWCNT) nano sheet network is grown by an in situ hydrothermal method on glass substrate. MWCNT is added to ZnO precursors during hydrothermal process with different percentage of additive MWCNTs. Interdigitated Ag electrode is deposited on glass substrate beforehand. CO gas is used as the target gas and sensitivity of the sensors is tested with dry air as carrier gas. The sensors show considerable high sensitivity and fast response to CO at around 100 °C operating temperature which is promising for industrial applications. This sensor is having advantage of being small in size, very thin structure, very low working temperature, fast response and recovery time and sensitive to low ppm CO gas. Sensors with more additives MWCNTs show stronger responses to CO gas. Sensors with 2 wt% additive MWCNTs showed the sensitivity of 1.6 and sensors with 6 wt% additive MWCNTs showed the sensitivity of 2.5–5 ppm of CO gas. Samples were characterized utilizing Field Emission Scanning Electron Microscopy (FE-SEM), X-Ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET) surface area measurement.

A new low moduli dielectric elastomer nano-structured composite with high permittivity exhibiting large actuation strain induced by low electric field

Dielectric elastomers (DEs) are able to deform significantly in response under an external electric field. DE actuators have promising applications in many emerging fields such as biomimetic robots, haptic devices, tunable lens, and loudspeakers. Practical applications of DE devices are limited by the extremely high electric field and the high pre-stretch. Herein, we have designed and fabricated a new type of soft DE composites of partially reduced graphene oxide (RGO)/polystyrene-b-poly (n-butyl acrylate)-b-polystyrene triblock copolymer (SBAS). An extremely soft SBAS was tailor-made as the elastic matrix. A facile colloidal blending method, i.e. simply mixing the SBAS latex with GO aqueous dispersion, was used to fabricate the nano-structured composite with a segregated network of RGO nano-sheets. The design strategy led to the DE composite film of 1.5 wt% RGO/SBAS owning low modulus (0.51 MPa), high relative permittivity (∼11) and relatively high dielectric breakdown strength (33 kV/mm). The DE composite film exhibited 21.3% maximum area actuation strain at relatively low electric field strength 33 kV/mm without pre-stretch.

Electrodeposited ZnO morphology transformations under the influence of SeO2 additive: Rods, disks, nanosheets network

In this study various morphologies of ZnO including rods, disks, and nanosheets network were synthesised by electrodeposition method. The influence of the SeO2 additive concentration on morphological, structural, and optical properties of ZnO was studied by using scanning electron microscopy, X-ray diffractometry (XRD), energy-dispersive X-ray analysis (EDX), optical (UV–Vis) and photoluminescence (PL) spectroscopy methods. The formation of the disk-like ZnO structure with a diameter of ca. 300–500nm and thickness ca. 80–100nm was observed when 0.03mmol/L of SeO2 was added to the solution. Further increase of dopant concentration up to 0.2mmol/L in the solution yielded a highly-porous network structure composed of thin nanosheets with a wall thickness of ca. 20nm. According to the XRD results, all structures were composed of ZnO, rod-like crystals were strongly c-axis oriented, whereas disks and nanosheets network structures were a-axis oriented. EDX analysis revealed that Se was present in the disks and nanosheets structures. PL study of the rod sample showed UV emission at ~370nm, whereas the disks and nanosheets network showed intense deep-level emission band centred at ~540nm. The disks and nanosheets exhibited total transmittance of ∼80–90% in the region of 380–780nm, whereas transmittance of the rods was increasing from 5% to 50% in this region. According to haze factor calculations, samples possessed scattering ability of 20% for disks, 45% for sheets and ca. 50% for rods. The probable mechanism for the formation of ZnO structures was discussed in detail.

Facile Synthesis of Ag‐Decorated Ni3S2 Nanosheets with 3D Bush Structure Grown on rGO and Its Application as Positive Electrode Material in Asymmetric Supercapacitor

AbstractA facile and cost‐effective route is developed for synthesizing 3D bush structure of Ag nanoparticles‐decorated Ni3S2 grown on reduced graphene oxide (rGO) for the first time. In this composite, Ni3S2 exhibits nanosheet networks with porous feature. The electrochemical measurements display that the as‐prepared rGO/Ag/Ni3S2 composite possesses a superior areal capacitance of 5920 mF cm−2 at current density of 5 mA cm−2. 77.5% of the initial areal capacitance is retained as current density increased from 5 to 20 mA cm−2. Encouragingly, this electrode exhibits excellent cycle performance with 94% capacitance retention after 3000 cycles at a current density of 30 mA cm−2, whereas for rGO/Ni3S2 composite electrode, only 84.7% of the initial value is maintained. The enhanced conductivity and unique structure of rGO/Ag/Ni3S2 composite attribute to its superior electrochemical performance. In addition, an aqueous asymmetric supercapacitor is fabricated using rGO/Ag/Ni3S2 composite as positive electrode and the nitrogen‐doped graphene as negative electrode. The assembled device delivers high energy density of 28.7 Wh kg−1 at a power density of 425 W kg−1. This work may prompt the development and application of active materials decorated with highly conductive nanoparticles in supercapacitors.

Porous nanosheet network architecture of CoP@Ni(OH)2 composites for high performance supercapacitors

A CoP@Ni(OH)2 composite with porous nanosheet networks was directly synthesized on carbon cloth, which avoids the usage of any binders and additives. Benefiting from the CoP nanosheet core that could provide fast electron transport pathway and distinctive nano-architecture, this composite achieved a specific capacitance of 1989 F g−1 at a current density of 2.0 A g−1, good rate capability and cyclic stability. Furthermore, an aqueous asymmetrical CoP@Ni(OH)2//AC supercapacitor (ASC) was also successfully assembled. The ASC device exhibited good electrochemical properties including a 1.8 V potential window, a high specific capacitance of 220 F g−1 at a current density of 1 A g−1 and long-term cycling performance. In the meantime, the ASC device also achieved a high energy density of 89.6 Wh kg−1 at a power density of 0.91 kW kg−1. These results suggest that nano-architectured CoP@Ni(OH)2 composite has great potential for application in energy storage device.

Hierarchical Porous NC@CuCo Nitride Nanosheet Networks: Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting and Selective Electrooxidation of Benzyl Alcohol

AbstractHighly active and stable bifunctional electrocatalysts for overall water splitting are important for clean and renewable energy technologies. The development of energy‐saving electrocatalysts for hydrogen evolution reaction (HER) by replacing the sluggish oxygen evolution reaction (OER) with a thermodynamically favorable electrochemical oxidation (ECO) reaction has attracted increasing attention. In this study, a self‐supported, hierarchical, porous, nitrogen‐doped carbon (NC)@CuCo2Nx/carbon fiber (CF) is fabricated and used as an efficient bifunctional electrocatalyst for both HER and OER in alkaline solutions with excellent activity and stability. Moreover, a two‐electrode electrolyzer is assembled using the NC@CuCo2Nx/CF as an electrocatalyst at both cathode and anode electrodes for H2 production and selective ECO of benzyl alcohol with high conversion and selectivity. The excellent electrocatalytic activity is proposed to be mainly due to the hierarchical architecture beneficial for exposing more catalytic active sites, enhancing mass transport. Density functional theoretical calculations reveal that the adsorption energies of key species can be modulated due to the synergistic effect between CoN and CuN. This work provides a reference for the development of high‐performance bifunctional electrocatalysts for simultaneous production of H2 and high‐value‐added fine chemicals.

Two‐Step Synthesis of Hierarchical Dual Few‐Layered Fe3O4/MoS2 Nanosheets and Their Synergistic Effects on Lithium‐Storage Performance

AbstractOwing to unique lamellar nanostructures, 2D inorganic materials are considered as promising candidates in energy storage and conversion. In this paper, a facile two‐step synthesis is developed to fabricate 3D hierarchical dual Fe3O4/MoS2 nanosheets (HD‐FMNs), in which few‐layered MoS2 nanosheets are anchored in 3D Fe3O4 nanosheet network to form the heterojunction structure. Furthermore, it is proved that the synergistic effects on both electron/lithium‐ion transport kinetics and mechanical cycling stability benefit from Fe3O4/MoS2 nanosheet incorporation in 3D HD‐FMN anode for lithium‐ion batteries (LIBs), resulting in the dramatically enhanced performance. The Fe3O4 nanosheet incorporation effectively improves the electronic conductivity due to its half‐metal characteristic, while the defect‐rich structure in the MoS2 nanosheets can facilitate the lithium ion transport. When tested as potential anode materials, 3D HD‐FMNs exhibit a high reversible capacity (650 mAh g−1) at current rate of 5 C (1 C = 1 A g−1) after superior long‐term cycles (1000 times), as well as an excellent rate capability even at high current rates. The outstanding electrochemical property of 3D HD‐FMNs allows their application in high‐performance anode materials for next‐generation LIBs. This strategy also opens a new way to design the novel 2D composite materials for electrochemical devices.

N/S Co-Doped 3 D Porous Carbon Nanosheet Networks Enhancing Anode Performance of Sodium-Ion Batteries.

A facile and scalable method is realized for the in situ synthesis of N/S co-doped 3 D porous carbon nanosheet networks (NSPCNNs) as anode materials for sodium-ion batteries. During the synthesis, NaCl is used as a template to prepare porous carbon nanosheet networks. In the resultant architecture, the unique 3 D porous architecture ensures a large specific surface area and fast diffusion paths of both electrons and ions. In addition, the import of N/S produces abundant defects, increased interlayer spacings, more active sites, and high electronic conductivity. The obtained products deliver a high specific capacity and excellent long-term cycling performance, specifically, a capacity of 336.2 mA h g-1 at 0.05 A g-1 , remaining as large as 214.9 mA h g-1 after 2000 charge/discharge cycles at 0.5 A g-1 . This material has great prospects for future applications of scalable, low-cost, and environmentally friendly sodium-ion batteries.

Liquid Exfoliation of Interlayer Spacing-Tunable 2D Vanadium Oxide Nanosheets: High Capacity and Rate Handling Li-Ion Battery Cathodes

With a layered crystal structure and good Li+ storage performance, vanadium pentoxide (V2O5) is potentially a high-energy and cost-effective cathode material for Li-ion batteries (LiBs). Networks of two-dimensional V2O5 nanosheets (2D V2O5 NS), with large interlayer distance, are ideal for enhancing the Li+ diffusion kinetics and thus for building high power LiBs. However, the lack of a simple, scalable and environmentally friendly route to nanosheet production still hinders the development of V2O5 applications. Here we demonstrate, liquid-phase exfoliation (LPE) of commercial V2O5 powder in environmental friendly solvents (water and ethanol) to achieve large quantities of 2D V2O5 NS colloidal solutions. The V2O5 NS are of high-quality, orthorhombic whose interlayer spacing can be well manipulated, ranging from 4.4 Å to 11.5 Å in ethanol and water, respectively. Ultrasonic aerosol printing of V2O5 NS/single-wall carbon nanotube (SWCNT) blended solutions resulted in large-area, flexible, and binder-free hybrid electrodes, which showcase a high discharge capacity of 370 mAh g-1 at 0.05 C, high energy density (1110 Wh kg-1) and power density (4350 W kg-1), etc. These properties can be attributed to the synergistic effects between the expanded hydrated NS and the conductive SWCNT matrix; the latter improves the reversible phase transition reactions of the NS, enhances the ion diffusion kinetics, maintains the electrode’s mechanical integrity and provides electron transport pathways. We believe the LPE/aerosol printing approach is environmentally green, general and scalable, and could be extended to other layered transitional metal oxides or dichalcogenides for fabrication of corresponding flexible, binder-free, conductive composites for energy storage systems.

Fast charge rate supercapacitors based on nitrogen-doped aligned carbon nanosheet networks

Achieving high electrochemical energy density while retaining high power density still remains a great challenge for porous carbons as the electrodes for supercapacitors. We report a facile and scalable synthesis of N-doped aligned carbon nanosheet network (N-ACN10) with high surface area and efficient 3D ion and electron transport pathways. Moreover, 3D interconnected nanochannels parallel to the graphene planes are beneficial for the increased ion accessible surface area and fast ion diffusion. Benefiting from fast ion and electron transport kinetics, the N-ACN10 electrode exhibits excellent frequency response with a scan rate up to 5Vs−1, high capacitance of 331Fg−1 at 2mVs−1 and superior rate capability (203Fg−1 at 5Vs−1), as well as excellent cycling stability (98% of capacitance retention after 10,000 cycles) in 6M KOH. More importantly, the assembled N-ACN10//N-ACN10 supercapacitors exhibit outstanding electrochemical performances in 1M Na2SO4 and EMIMBF4 electrolytes with maximum energy densities of 20.6 and 120.4Whkg−1 based on the mass of total active material, respectively.

Facile fabrication of Fe3O4 octahedra with bimodal conductive network of nanoporous Cu and graphene nanosheets for high-performance anode in Li-ion batteries

Fe3O4/Cu@graphene (Fe3O4/Cu@G) nanocomposite is prepared through a facile fabrication of Fe3O4/Cu precursor by dealloying FeCuAl alloy followed by the reduction of coassembled aggregates of Fe3O4/Cu and graphene oxide. The obtained Fe3O4 octahedra are well enwrapped in nanoporous Cu network and graphene nanosheets. Benefitting from the bimodal conductive network of Cu and graphene, the Fe3O4/Cu@G composite exhibits much higher specific capacity and dramatically enhanced cycling stability compared with the pure Fe3O4 octahedra, Fe3O4/Cu, and Fe3O4@G composite. Moreover, the Fe3O4/Cu@G electrode shows satisfactory cycling reversibility even at a current rate up to 2000 mA g−1 for 800 cycles. Owing to the superiorities of high electrochemical performances and easy preparation, the Fe3O4/Cu@G composite shows encouraging application potential to be an advanced anode material for lithium storage.

Morphology Adjustable Silica Nanosheets for Immobilization of Gold Nanoparticles

AbstractA network of silica nanosheets composed of nanosheets of several nanometers in thickness and containing pores, whose dimensions are on the hundreds‐of‐nanometers scale, exhibits morphological self‐adjustment upon binding of nanoparticles at its surface. The loading of nanoparticles in the nanosheets caused an obvious rearrangement of the silica nanosheet network probably due to the incomplete silica framework of the nanosheets. This self‐adjustment of the structure leads to a fixing of the nanoparticles at the nanosheets’ interiors. In addition, the resulting gold nanoparticle‐loaded silica nanosheets show high performance for the catalytic reduction of nitrophenols with high conversion. The networked nanosheets described here may be used as a new supporting substrate for other metal nanoparticles and could be used for various catalytic processes.

Liquid exfoliation of interlayer spacing-tunable 2D vanadium oxide nanosheets: High capacity and rate handling Li-ion battery cathodes

With a layered crystal structure and good Li+ storage performance, vanadium pentoxide (V2O5) is potentially a high-energy and cost-effective cathode material for Li-ion batteries (LiBs). Networks of two-dimensional V2O5 nanosheets (2D V2O5 NS), with large interlayer distance, are ideal for enhancing the Li+ diffusion kinetics and thus for building high power LiBs. However, the lack of a simple, scalable and environmentally friendly route to nanosheet production still hinders the development of V2O5 applications. Here we demonstrate, liquid-phase exfoliation (LPE) of commercial V2O5 powder in environmental friendly solvents (water and ethanol) to achieve large quantities of 2D V2O5 NS dispersions. The V2O5 NS are of high-quality whose interlayer spacing can be well manipulated, ranging from 4.4Å to 11.5Å in ethanol and water (forming NS xerogel), respectively. Ultrasonic aerosol printing of V2O5 NS xerogel/single-wall carbon nanotube (SWCNT) blended dispersions resulted in large-area, flexible, and binder-free hybrid electrodes, which showcase a high discharge capacity of 370mAhg−1 at 0.05C, high energy density (555Whkg−1) and power density (2175Wkg−1), etc. These properties can be attributed to the synergistic effects between the expanded hydrated NS and the conductive SWCNT matrix; the latter improves the reversible phase transition reactions of the NS, enhances the ion diffusion kinetics, maintains the electrode's mechanical integrity and provides electron transport pathways. The Li+ storage mechanism was investigated, suggesting the capacity was majorly contributed by the non-diffusion controlled process (pseudocapacitive). We believe the LPE/aerosol printing approach is environmentally green, general and scalable, and could be extended to other layered transitional metal oxides or dichalcogenides for fabrication of corresponding flexible, binder-free, conductive composites for energy storage systems.

Microstructure and spatial distribution of corrosion products anodically grown on zinc in chloride solutions

Zinc substrates were electrochemically oxidized in NaCl solution to produce corrosion patinas. XRD, XPS and Raman analyses enabled the identification of simonkolleite and zinc oxide as the patina constituents. FIB-SEM imaging shows that the upper part of the patinas is a network of simonkolleite nanosheets with an open microstructure that is unlikely to act as a significant barrier for corrosion processes. STEM investigations and Raman mapping measurements reveal the presence of a ca. 20–400nm thin nanoporous ZnO-rich film below the simonkolleite and covering the zinc substrate. Under potentiostatic conditions, the reduced cathodic activity of the patina-covered zinc electrodes is assigned to this nanoporous ZnO layer.