rGO Nanosheets Research Articles

Reduced graphene oxide decorated CuO@NiO nanocomposite and their improved photosensitive activity for photodetection applications

In our proposed work, pure rGO and CuO@NiO/rGO (CNR) nanocomposites (NCs) with different ratios of CuO@NiO:rGO (90:10, 75:25 and 50:50) were synthesized and explored by XRD, SEM with EDX, TEM, XPS, UV–visible, PL and utilized to measure the current – voltage characteristics under dark and illumination conditions. TEM analysis indicates ultra-thin nanosheets of rGO with lengths of several tens of micrometer and CuO@NiO particle sizes is ∼50 nm. XPS analysis showed the presence of element and chemical states for Cu, Ni, O, and C in CNR-(50:50) sample. The energy gap (Eg) of pure rGO is 3.99eV whereas the CNR for 90:10, 75:25 and 50:50 NCs energy gap (Eg) values are viz., 1.43eV, 1.41eV and 1.39eV. The diode characteristic of CNR-(50:50)/n-Si exhibit lower ideality factor (n = 1.96), higher barrier height (ΦB = 0.80eV) under illumination condition. The CNR-(50:50)/n-Si photodiode exhibits higher photosensitivity (PS), responsivity (R), External Quantum Efficiency (EQE) and detectivity (D*) values of 956.45 %, 656.29 mA/W, 367.6/1 % and 5.72 × 1012 (Jones) respectively.

Nanofiber-Reinforced MXene/rGO Composite Aerogel for a High-Performance Piezoresistive Sensor and an All-Solid-State Supercapacitor Electrode Material.

The assembly of two-dimensional (2D) nanomaterials into a three-dimensional (3D) aerogel can effectively prevent the problem of restacking. Here, nanofiber-reinforced MXene/reduced graphene oxide (rGO) conductive aerogel is prepared via the hydrothermal reduction of GO using pyrrole and in situ composite with MXene. Combined with low-content 2D conductive nanosheets (MXene and rGO) as "brick", conductive polypyrrole as "mortar", and one-dimensional (1D) nanofiber as "rebar", a strong interfacial cross-linking of MXene and rGO nanosheets is realized through covalent and noncovalent bonds to synergistically improve its mechanical performance. Based on the prepared MXene/rGO aerogel, a high-performance piezoresistive sensor with a sensitivity of up to 20.80 kPa-1 in a wide pressure range of 15.6 kPa is obtained, and it can withstand more than 5000 cyclic compressions. Besides, the sensor shows a stable output and can be applied to monitor various human motion signals. In addition, an all-solid-state supercapacitor electrode is also fabricated, which shows a high area-specific capacitance of up to 274 mF/cm2 at a current density of 1 mA/cm2.

In situ oxidation of reduced graphene oxide membranes by peracetic acid for dye desalination

Graphene oxide (GO) membranes with tunable interlayer spacings are of interest for dye removal from salty textile wastewater, and the membranes are often reduced to improve their stability, which inevitably lowers water permeance. Herein, we demonstrate that reduced GO (rGO) membranes can be facilely modified using peracetic acid (PAA) in situ to dramatically enhance water permeance while retaining dye rejection. Specifically, PAA-modified membranes (PrGO) are synthesized by vacuum-filtering hydrazine-reduced rGO nanosheets onto Nylon substrate and then exposing them to PAA solutions. The effects of the rGO layer thickness, PAA content, and PAA exposure time on the membrane chemistry, nanostructures, and salt/dye separation properties are thoroughly examined. For example, the PAA oxidation of a 100 nm-thick rGO membrane for 10 min increases water permeance by 180 %, from 35 to 93 Liter m−2 h−1 bar−1, and decreases Na2SO4 rejection from 10 % to 3.3 % while retaining the rejection of Congo red at ≈99.7 %. The PrGO membranes exhibit stable water permeance and >99 % dye rejection in multi-cycle tests in a crossflow system, surpassing state-of-the-art GO membranes and showcasing their potential for practical applications.

Investigating the influence of oxygen-functionalized graphene nanosheets as an efficient multifunctional material for supercapacitor and electrocatalytic water splitting applications

Graphene oxide (GO) has received great research attention to develop its efficiency in electrochemical applications, particularly supercapacitor (SC) and water splitting systems. However, the presence of various oxygen moieties in GO drastically reduces the utilization of the material for commercial usages. In this work, we demonstrate the use of different sources to reduce graphene oxide (GO) nanosheets. The partially reduced GO not only improves the electronic conductivity but also boosts the interaction between the sp2- and sp3-hybridized carbon atoms. Benefiting from the partial reduction process, RGO is applied for the SC test in the three-electrode system and reveals a specific capacitance of 151.1 F g−1 at 1 A g−1 with a long cycle life. Furthermore, the asymmetric solid-state device can also be constructed from an M-GO cathode with an activated carbon anode, which displays a specific capacitance of 54.4 F g−1 at 1 A g−1, with a maximum energy density of 19.3 W h kg−1. Besides, the electrochemical water splitting performance of the partially reduced GO in KOH solution was also explored, confirming the effectiveness of the reduction process. This work highlights the successful preparation of RGO nanosheets, which may open a new route to constructing high-performance energy storage and conversion devices.

A switchable dual-mode film with designed intercalated and hierarchical structures for highly efficient passive radiation cooling and solar heating

A single-mode solar heating (SH) and passive radiative cooling (PRC) have been fast developed in outdoor thermal management. However, they hardly change with the temperature fluctuations of the hot and cold seasons. Herein, a flexible and stable dual-mode film with photo responsibility was engineered by integrating heating coating and cooling coating on the opposite surfaces of a porous polypropylene (PP) membrane. Flip the surfaces of the dual-mode film-facing solar light to switch between PRC and SH. The cross-linked heating side was fabricated from reduced graphene oxide (rGO) nanosheets intercalated with carbon black (CB) particles via spraying. A thick intercalated film can enhance solar absorptivity (96.4 %) and low infrared emissivity (8.0 %) due to the multiple solar reflections and adsorption between the interlayers, leading to high solar heating. The cooling side was derived from polyvinylidene fluoride (PVDF) coating embedded micro-nano Al2O3 particles via water vapor-induced phase separation (VIPS). The hierarchical coating with a pore size of 8.4 ± 0.1 µm and roughness of 4.0 ± 0.3 µm exhibits high solar reflectivity (92.2 %) and infrared emissivity (96.9 %), resulting in excellent passive radiative cooling. The net heating power (Pheating) and net cooling power (Pcooling) of the dual-mode film are 845.9 and 96.7 W m−2. Moreover, the dual-mode film exhibits outdoor thermoregulation capacity upon covering buildings, cars, and ice. In outdoor environments under solar radiation of 611 ∼ 716 W m−2, it has a temperature increase/decrease of 17.8/5.3 °C to the ambient temperature. Owing to the scalable fabrication processes and excellent thermoregulation characteristics, the dual-mode film is promising for applications in personal thermal management, energy-efficient buildings, in-car temperature control, and food freezing-thawing.

Samarium-doped vanadium pentoxide nanorods anchored reduced graphene oxide nanocomposite as a bi-functional electrode material for supercapacitor and direct methanol oxidation fuel cell applications

In this work, we demonstrate a novel, facile synthesis of reduced graphene oxide nanosheets decorated samarium-doped vanadium pentoxide (RGO/Sm:V2O5) nanocomposite material and explore its application toward supercapacitor and direct methanol oxidation process. As-fabricated material and electrode were well-characterized to evaluate its surface morphology and functionalities. Results indicate a maximum capacitance value of 544 F/g for RGO/Sm:V2O5 modified electrode than the 2% Sm:V2O5 (346 F/g) and V2O5 (133 F/g) modified electrodes. In addition, an excellent Rct value (3.2 Ω) was achieved for the RGO-loaded Sm:V2O5 electrode than the 2% Sm:V2O5 electrode (4.7Ω). The RGO/Sm:V2O5 electrode also shows higher cyclic efficiency (98 %) at the 1000th cycle than the non-RGO loaded Sm:V2O5 electrodes. Furthermore, the fabricated electrodes were also examined for the direct methanol oxidation performances, and the results indicate a higher current density value of 181 mA/cm2 for RGO/Sm:V2O5 electrode than 2% Sm:V2O5 electrode (139 mA/cm2). The excellent electrochemical performance of the RGO/Sm: V2O5 electrode is mainly due to the presence of RGO nanosheet in the synthesized nanocomposite material. Therefore, as-prepared material can be applied as an excellent alternative electrode material for energy storage and conversion systems.

Reduced graphene oxide nanosheets as electron sink for MnFe2O4 nanoparticles: A synergistically boosted supercapacitance

Spinel ferrite structures have shown promise for energy storage. However, they are insulators and need a conductive substrate for better charge transfer. Here, we utilized a simple hydrothermal technique to in-situ coat a nickel foam with few-layer nanosheets of reduced graphene oxide (rGO) decorated with manganese ferrite (MnFe2O4) nanoparticles. We then studied the supercapacitance/pseudocapacitance properties of the rGO/MnFe2O4 composite. X-ray diffraction patterns, energy-dispersive X-ray maps, and X-ray photoelectron spectra of the composite were investigated to confirm its structural, elemental, and surface chemical composition, respectively. Scanning electron microscopy and transmission electron microscopy images demonstrated the decoration of rGO nanosheets with MnFe2O4 nanoparticles. In a three-electrode setup, the rGO/MnFe2O4 nanocomposite exhibits a specific capacitance per loaded material mass (2446 F/g at 1 A/g) which is higher than the sum of rGO (304 F/g) and MnFe2O4 (1084 F/g) electrodes, suggesting a synergistic effect between rGO and MnFe2O4. The energy density and power density of the rGO/MnFe2O4 electrode were also calculated 58.24 Wh/kg and 260.82 W/kg (at 1 A/g), respectively. We found that the resistance of the rGO/MnFe2O4 electrode (2.53 Ω) is much lower than the MnFe2O4 electrode (6.15 Ω), and the interfacial resistance of the rGO/MnFe2O4 electrode with electrolyte was found low, confirming the rGO role as a conductive substrate for insulating MnFe2O4 nanoparticles. We also showed that surface-related capacitance, rather than pseudocapacitance, is more dominant in the rGO/MnFe2O4 composite electrode than in the separate rGO and MnFe2O4 electrodes. We also demonstrated the practical performance of the rGO/MnFe2O4 electrode in a two-electrode setup. Finally, density functional theory calculations showed the considerable potential drop (16.5 eV) between MnFe2O4 and graphene that leads to a strong built-in electric field from graphene towards MnFe2O4. This indicates the role of graphene as a wide electron sink for MnFe2O4 nanoparticles that results in better charge distribution and storage.

Reduced graphene oxide encapsulated octahedral NiSe2 nanocrystals with dominant {111} crystal facets for efficient hydrogen evolution reaction

Regulating the exposed crystal facets of electrocatalysts is an effective means to enhance their electrocatalytic activity. However, related studies have focused mainly on traditional noble metals or metal oxides based electrocatalysts, while the research on crystal facets dependent electrocatalytic activity of metal selenides is still very rare. Here, crystal facets effect of cubic NiSe2 in electrocatalytic HER was studied. It was shown that octahedral NiSe2 nanocrystals dominated by active {111} crystal facets exhibited significantly enhanced HER activity. Moreover, by encapsulating the octahedral NiSe2 nanocrystals into reduced graphene oxide (rGO) nanosheet networks, further improvement in their HER activity could be achieved. First principles calculations and experimental characterization indicated that {111} crystal facts of NiSe2 had abundant surface active sites and ideal catalytic reaction energy barriers. This study not only expands the research on crystal facets-dependent HER activity, but also gains a deep understanding of the electrocatalytic mechanism.

Antibacterial properties of reduced graphene oxide fibers fabricated by hydrothermal method

The antibacterial activity of reduced graphene oxide fibers (rGOFs) fabricated by a one-step dimensionally confined hydrothermal technique was investigated on both Gram-positive and Gram-negative models of bacteria in this study. The surface morphology, microstructure, and chemical composition of the as-prepared rGOFs were determined using scanning electron microscopy (SEM), X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. SEM images showed the fiber to have an average diameter of 46.6 ± 0.53 μm, composed of rGO nanosheets with numerous sharp edges. XPS and Raman spectroscopy confirmed the presence of sp3-bonded carbon and structural defects in the samples. Antibacterial properties of rGOFs were tested and analyzed using agar well diffusion, colony counting method, SEM observation, and reactive oxygen species generation. The excellent broad-spectrum antibacterial ability of rGOFs is attributed to the physicochemical properties and unique surface morphological features of the samples, which could facilitate the development of rGOFs-based biomaterial for various biomedical and nano-technological applications such as a promising antibacterial agent or an implant/scaffold for nerve tissue engineering and regeneration.

Tailoring tin sulfide electrocatalyst with petroleum coke derived reduced graphene oxide for overall water splitting

Metal chalcogenides like Tin sulfide (SnS2) presents as viable alternative electrocatalysts for alkaline water splitting (AWS) due to their huge abundance, stability, and environment friendly nature. However, insufficient exposed active sites and poor conductivity severely impede its large-scale applications. In this work, an in-situ hybridization of hexagonal SnS2 with intercalation of reduced graphene oxide nanosheets (TS-rGOx) overcomes the problem of SnS2 stacking. It further enhances the interlayer spacing thereby boosting the number of active sites. The resulting TS-rGOx exhibited excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities demanding low overpotential of 313 mV and 196.2 mV at 20 mA/cm2 with long term durability upto 60 h, which can be attributed to enhanced interlayer spacing of SnS2, abundant active sites and higher conductivity resulting from the in-situ hybridization and intercalation of rGO nanosheets. This work opens a prospect towards the design and application of efficient SnS2 based heterostructuredelectrocatalystfor AWS.

ZIF-67 derived CoNi@carbon/RGO composites with abundant heterogeneous interfaces for electromagnetic wave absorption

The controllable structure design and composition regulation play a key role in the development of electromagnetic wave (EMW) absorbing material. Herein, CoNi@carbon/RGO absorbing materials were successfully prepared by direct pyrolysis of ZIF-67/Ni(OH)2/GO precursor. The CoNi@carbon/RGO-15 sample achieves an RLmin value of −46.14 dB and an effective absorption bandwidth (EAB) of 1.15 GHz (thickness 4.1 mm) at a low frequency with a filling amount of only 10 wt%. When the thickness is 1.5 mm, the RLmin reaches −41.09 dB and the EAB reaches 5.41 GHz, covering most of the Ku bands. After the pyrolysis, the carbon layer, Co and Ni nanoparticles, and RGO nanosheets form a three-dimensional porous structure, which builds up abundant heterogeneous interfaces and conductive networks. These factors can enhance impedance matching, dielectric, and magnetic loss. This indicates that CoNi@carbon/RGO is the potential lightweight EMW absorbing material with high performance.

Encapsulating Si particles in multiple carbon shells with pore-rich for constructing free-standing anodes of lithium storage

Silicon based (Si-based) materials are considered to be the most promising anode materials for lithium-ion batteries (LIBs) due to their high specific capacity. However, the issues of poor electrical conductivity and volume expansion during cycling have not been effectively addressed. The optimum remedy is to select specific materials to establish an exceptional conductive and volume buffer structure to assist the Si materials to develop its excellent lithium storage properties. Here, Si particles were encapsulated into porous carbon fibers containing ultrafine Co particles (CP) to obtained Si-x@CP-y film. Among them, the addition of Si particles and the void structure was precisely regulated to achieve a superior electrode with a high specific capacity. Subsequently, the two-dimensional conductive material reduced graphene oxide (rGO) nanosheets were further incorporated to obtain Si-2@CP-2@rGO films with core@multi-shell structure. The final electrode was equipped with one-, two-, and three-dimensional electronic pathways to allow rapid electron transport, and featured with multi-layer buffer structure and reserved pores that could effectively mitigate volume changes. As expected, the free-standing Si-2@CP-2@rGO electrode delivered a high specific capacity of 1221.2 mAh/g after 100 cycles at 0.1 A/g in a half cell, and the assembled full cell showed 249.0 mAh/g after 200 cycles at 0.2 A/g, which fulfilled the lightweight requirement for new energy storage devices.

Soft-Hard segments regulated framework of Nitrogen-Doped reduced graphene oxide aerogel for efficient adsorption of pollutants

Graphene aerogel (GA) is recognized for its high porosity, rendering it a promising candidate for water treatment applications. However, its reuse potential is hampered due to inherent limitations. To address this, the present study introduces a nitrogen-doped graphene aerogel (NGA) developed by integrating polydopamine soft segments and polyaniline hard segments into the GA matrix. This approach promotes the formation of a cohesive and durable 3D network by bridging reduced graphene oxide (rGO) nanosheets, with the hard segments of polyaniline interposed among rGO layers to mitigate significant restacking, thereby enhancing surface area and adsorption sites. NGA demonstrates remarkable properties including strength (67 kPa), reversible compressibility under 64 % strain, low density (12.26 mg/cm3), and thermal stability (Tdecomposition = 679.6 °C in air), which collectively enhance its adsorption capacity and recyclability. This study further examines the influence of various factors such as pH, adsorbates (dyes and organic solvents), initial concentration, and cycle times on the aerogel’s adsorption efficacy. Additionally, simulation outcomes reveal that NGA’s adsorption kinetics and thermodynamics align more closely with the endothermic pseudo-first-order kinetic model, indicative of predominant physical adsorption mechanisms. Given its superior adsorption capabilities for pollutants, NGA holds significant promise for application in water treatment.

Room temperature gas sensor based on rGO/Bi2S3 heterostructures for ultrasensitive and rapid NO2 detection

Bismuth sulfide (Bi2S3) is a promising material for detecting NO2 molecules at room temperature thanks to its narrow and tunable bandgap. However, pure Bi2S3 suffers from some sensing blemish because of its low electroconductivity and poor charge transfer efficiency. Herein, we synthesized the high sensing response room temperature NO2 detection materials composed of Bi2S3 nanoflowers and reduced graphene oxide (rGO). The formed conductive network and heterojunctions between Bi2S3 nanoflowers and rGO nanosheets dramatically improve the conductivity and electron transfer efficiency. The excellent rGO/Bi2S3 sensor shows a high sensing response of 9.8 (approximately two times higher than that of the pure Bi2S3) and rapid response speed of 22 s (almost half of the pure Bi2S3) upon exposure to 1 ppm NO2 at room temperature. Meanwhile, the rGO/Bi2S3 sensor displays superb humidity-independent, selectivity, and stability. These improved NO2 sensing behaviors can be attributed to the heterointerfaces and the hybrid effects, which accelerate charge transfer efficiency between NO2 molecules and the surface of rGO/Bi2S3 heterostructure. To enable on-line detection of ambient hazardous gas, we designed a portable wireless NO2 detector based on rGO/Bi2S3 heterostructure. This study offer an insightful guidance for improving the NO2 sensing behaviors of metal chalcogenides.

Development of BaMnO3 nanoparticles embedded on rGO nanosheets via facile hydrothermal route to improve water oxidation

In light of environmental problems such as the depletion of hydrocarbon resources and global warming, the use of environment-friendly power production has become crucial nowadays. Hydrogen can serve as a globally friendly energy source because the byproduct of hydrogen combustion is only water. By a hydrothermal approach, we synthesized barium manganese oxide (BaMnO3) embedded on reduced graphene oxide (rGO) as a competent electrocatalyst for OER. We utilized X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive x-rays (EDX), Brunauer Emmette Teller (BET) and Raman to determine the crystal structure, morphology, elemental composition, surface area and lattice phenomena of the fabricated rGO/BaMnO3 nanocomposite. The BaMnO3 agglomerated nanoparticles were incorporated into the mesoporous hollow carbon nanosheets to form amorphous textured embedded rGO/BaMnO3. This enhanced the intrinsic reactivity of rGO/BaMnO3 nanocomposite for the oxygen evolution reaction (OER) in addition to increasing the effective surface area of the electrolyte. The electrochemical outcomes demonstrate that synthesized nanocomposite exhibited an impressive Tafel slope (36 mV dec−1), lowest overpotential (202 mV) and remarkable stability over 35 h. Therefore, the fabricated nanocomposite displayed exceptional efficiency in OER process as well as for numerous other future applications.

RGO@TiO2-x Schottky heterojunction for enhanced bidirectional catalysis in polysulfide conversion

The shuttling and sluggish conversion kinetics of lithium polysulfides (LiPSs) lead to poor cycling performance and low energy efficiency in lithium-sulfur batteries (LSBs). In this work, a hierarchically structured nanocomposite, synthesized through a surfactant-directed hydrothermal growth following dopamine-protected pyrolysis, serves as a bidirectional catalyst for LSBs. This nanocomposite comprises N-doped reduced graphene oxide (rGO) nanosheets anchored with uniformly distributed TiO2-x nanoparticles via interfacial N-Ti and C-Ti bonding, resulting in the formation of abundant 2D/0D Schottky heterojunctions (rGO/TiO2-x). Density functional theory (DFT) calculations and in situ Raman characterizations demonstrate that rGO/TiO2-x effectively inhibits the shuttling of LiPSs with enhanced redox kinetics, achieving high utilization of the sulfur cathode and improving the overall reversibility. A high areal capacity is attained at a high sulfur loading and a low electrolyte/sulfur ratio. The initial specific capacity reaches 1010 mA h g−1 at a current density of 0.2C (1C = 1675 mA g−1), and a retention of 86.4 % is attained over 100 cycles. A light-emitting diode (LED) screen using two LSBs with rGO/TiO2-x demonstrates their high potential for practical applications.

Developing TiCo2O4 spinel based on rGO nanosheet to enhance electrochemical performance of OER activity

The reduction of fossil fuel reserves and the deterioration of environmental conditions have led to a worldwide concern with producing significant amounts of energy in a sustainable manner. The production of electrocatalysts for the oxygen evolution reaction (OER) is imperative for widespread commercialization of water electrolyzers. The electrocatalysts must exhibit improved electrocatalytic behavior while being cost-effective. This work presents simple hydrothermal route for producing a TiCo2O4 nanostructure with a spherical morphology, which is supported on reduced graphene oxide sheets (rGO). The nanocomposite has been subjected to an investigation of its morphological, structural and electrochemical characteristics. This material exhibits promise for electrochemical water splitting due to its significant electroactive surface area, distinctive morphology and metal ions (M+) synergetic effect on its electrocatalytic performance. The nanostructure of TiCo2O4/rGO-has been observed to exhibit robust electrocatalytic activity, underscoring the significance of the present study. Additionally, presented are the enduring stability of the OER, along with the reduced overpotential (269 mV@10 mA cm−2), decreased Tafel slope (37.56 mV dec-1) with greater electrochemical active surface area. Our finding suggests that the TiCo2O4/rGO nanohybrid exhibited high electrocatalytic efficiency and can be utilized in diverse electrochemical applications.

Three‐phase interfacial design in BaTiO3/rGO/polyetherimide composite enabling enhanced dielectric, thermal and mechanical properties

AbstractAs core components in electric/electronic fields, dielectric materials have recently received ever‐increasing interests. Among them, polymer‐based dielectric composites have drawn ever‐increasing attentions due to their high‐temperature resistance and excellent processibility. However, state‐of‐art studies mostly focus on the modification of single‐phase filler, while the heterogeneous three phase interactions between fillers and polymer matrix are rarely studied. To fill this gap, in this study, a novel strategy of interfacial design and structural construction of three‐phase BaTiO3/rGO/polymer nanocomposites have been promoted to simultaneously build interfacial barriers between adjacent rGO nanosheets and to enhance the interfacial polarization of rGO nanosheets for improved dielectric, thermal and mechanical properties. The dielectric constant of 0.6 wt% BT/ARGO/PEI reached 644@1 kHz with a dielectric loss of only 0.218, while these values for 0.5 wt% ARGO/PEI composites are 471 and 0.489, respectively. Meanwhile, the breakdown strength almost doubled (from 48 kV·mm−1 to 87 kV·mm−1) upon the addition of BaTiO3 (BT) nanoparticles. Moreover, the introduced BT nanoparticles significantly enhanced the intermolecular frictions between different materials and contributed largely to promoted mechanical and thermal properties. We therefore speculate this work establishes a strong foundation for fabricating three heterogeneous‐phase high dielectric polymer materials with excellent dielectric, thermal and mechanical properties.Highlights Graphene oxide was modified by APTES and reduced by L‐Ascorbic Acid. Three‐phase BT/ARGO/PEI composites showed enhanced dielectric properties. The incorporated BT nanoparticles reduced the dielectric loss. The thermal and mechanical properties of BT/ARGO/PEI composites are optimized. Interfacial interactions between different phase of materials are studied.

Engineering of 3D architectures with yttrium on reduced-graphene oxide nanosheets for effective co-adsorption of tetracycline and phosphate

Effective removal of composite pollutants containing antibiotic and phosphorus is still facing challenges for the wastewater treatment. In this study, yttrium-hydroxide component was loaded onto the surface of reduced GO nanosheets via low-temperature hydrothermal method, to synthesize the 3D YrGO architectures. The optimized YrGO-8 hydrogels showed the maximum adsorption capacity of 226.45 mg/g for tetracycline (TC), and 33.403 mg/g for phosphate, which was higher than many other reported adsorbents. The characterization results demonstrated that the rGO nanosheets were successfully crosslinked by Y(III) to form a porous 3D structure, which was beneficial to the mass transfer and active sites exposure. The adsorption behaviors of TC or phosphate was suppressed by the co-existing phosphate ions or TC, with slower adsorption rate and lower adsorption amount. Importantly, column adsorption analyzed by Thomas model illustrated the rate basis of YrGO-8beads to capture TC/phosphate in an adsorbate diffusion rate. Moreover, the 3D YrGO-8 remained stable and high reusability in multi-uptake-release rounds via pH regulation. The mechanism study suggested that the sequence of adsorption process of TC followed the order of hydrogen bond (HB) > π – π electron donor–acceptor (EDA), n − π EDA > Y(III) bridging interactions, while the uptake of phosphate formed Y-O-P inner-sphere complexes prior to HB. This study proposes a novel insight into the development of 3D architectures for effectively simultaneous treatment of composite TC and phosphate pollution.

Facile synthesis of rGO nanosheet encapsulated Ni2V2O7 nanorods for energy storage applications

The less emission, environmental friendliness and less hazardous energy storage materials are most impotent to the clean energy system. Here we synthesis rGO anchored nickel vanadate nanorods for supercapacitor application. As a result, the Ni2V2O7 and rGO@Ni2V2O7 nanomaterials show a monoclinic structure from the XRD pattern. The vibrational of V–O–V and Ni–O along with the main peak of carbon materials indicates the rGO anchoring with Ni2V2O7 in the FTIR and Raman spectra. The SEM and TEM images illustrate a rod shaped Ni2V2O7 was attached over the rGO sheet surface. From the BET analysis, the rGO@Ni2V2O7 sample has a higher surface area than the Ni2V2O7 electrode. Further, the supercapacitor application of Ni2V2O7 and rGO@Ni2V2O7 electrodes shows 318 F/g and 624 F/g at 1 A/g capacitance values. Although, the rGO@Ni2V2O7 electrode shows higher power (771 W/kg) and energy density (22.28 Wh/kg) values than the NiV2O7 electrode. Moreover, the rGO@Ni2V2O7 exhibits a 95% of capacitance retention value even at the 1000th cycle. Moreover, the prepared rGO@Ni2V2O7 has less Rct value of 4.72 Ω) than the Ni2V2O7 electrode (9.86 Ω). The attachment of rGO can provide a higher surface area, higher conductivity and lower resistivity to the Ni2V2O7 electrode. According to these results, the rGO@Ni2V2O7 electrode is the more suitable for supercapacitor electrodes.