Quick responding humidity sensor based on polyaniline/reduced graphene oxide composite

Effect of grain boundary interfaces on electrochemical and thermoelectric properties of a Bi2Te3/reduced graphene oxide composites

Improved strength and toughness of semi-aromatic polyamide 6T-co-6(PA6T/6)/GO composites via in situ polymerization

Impact of enhanced interfacial strength on physical, mechanical and tribological properties of copper/reduced graphene oxide composites: Microstructural investigation

The poly(butylene succinate) (PBS)/graphene oxide (GO) composites containing different GO contents were prepared. The dispersion of GO was investigated using optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results showed that GO exhibited good dispersion in the polar PBS matrix. The rheological measurements showed that the presence of GO induced largely increased melt viscosity for the composites. Specifically, high content of GO formed the percolated network structure. The non-isothermal crystallization kinetics was investigated using differential scanning calorimetry. The results showed that the non-isothermal crystallization behavior of PBS was influenced by GO content and cooling rate. At relatively small content, GO dramatically accelerated the crystallization of PBS. More integrated PBS crystalline structure was achieved by introducing GO. The nucleation effect of GO in the composites was proved further by the variation of isothermal crystallization morphologies.

One-pot synthesis of NiFe layered double hydroxide/reduced graphene oxide composite as an efficient electrocatalyst for electrochemical and photoelectrochemical water oxidation

We apply direct ink writing for the three-dimensional (3D) printing of polyaniline/reduced graphene oxide (PANI/RGO) composites with PANI/graphene oxide (PANI/GO) gel as printable inks. The PANI/GO gel inks for 3D printing are prepared via self-assembly of PANI and GO in a blend solvent of N-methyl-2-pyrrolidinone and water, and offer both shaping capability, self-sustainability, and electrical conductivity after reduction of GO. PANI/RGO interdigital electrodes are fabricated with 3D printing, and based on these electrodes, a planar solid-state supercapacitor is constructed, which exhibits high performance with an areal specific capacitance of 1329 mF cm-2. The approach developed in this work provides a simple, economic, and effective way to fabricate PANI-based 3D architectures, which leads to promising application in future energy and electric devices at micro-nano scale.

Spindle-shaped microstructure of α-Fe2O3 was successfully synthesized by a simple hydrothermal method. The α-Fe2O3/graphene oxide (GO) composites was prepared using a modified Hummers’ strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the α-Fe2O3 particles. The average crystallite sizes of the α-Fe2O3 and α-Fe2O3/GO samples are ca. 27 and 24 nm, respectively. The possible growth of α-Fe2O3 onto GO layers led to a higher absorbance capacity for visible light by α-Fe2O3/GO than α-Fe2O3 composite. The photocatalytic degradation of toluene over the α-Fe2O3 and α-Fe2O3/GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the α-Fe2O3/GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of α-Fe2O3/GO could be promisingly applied in photo-driven air purification.

A Co3O4/reduced graphene oxide (rGO) composite was prepared by a convenient PVP (polyvinylpyrrolidone)-assisted method under reflux conditions. The prepared composite material consists of uniform Co3O4 nanoparticles (NPs about 100 nm), which are tightly enwrapped by rGO in the presence of PVP. This has been confirmed through observations by field emission scanning electron microscopy and transmission electron microscopy. The Co3O4/rGO composite exhibits superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, which is higher than that of the previously reported pure rGO and Co3O4 NPs. The anode was able to deliver a discharge capacity of 860 mA h g−1 during the 120th cycle at 40 mA g−1. The superior electrochemical performance of the Co3O4/rGO composite is attributed to its unique nanostructure, which closely combines the conductive graphene network with the uniformly dispersed Co3O4 NPs. X-ray absorption near-edge spectroscopy (XANES) was used to analyze the Co oxidation state of the Co3O4/rGO composite electrode.

In this paper, δ-MnO2 with layered structure was prepared by a facile liquid phase method, and exfoliated MnO2 nanosheet (e-MnO2) was obtained by ultrasonic exfoliation, whose surface was negatively charged. Then, positive charges were grafted on the surface of MnO2 nanosheets with a polycation electrolyte of polydiallyl dimethylammonium chloride (PDDA) in different concentrations. A series of e-MnO2@reduced graphene oxide (rGO) composites were obtained by electrostatic self-assembly combined with hydrothermal chemical reduction. When PDDA was adjusted to 0.75 g/L, the thickness of e-MnO2 was ~1.2 nm, and the nanosheets were uniformly adsorbed on the surface of graphene, which shows layer-by-layer morphology with a specific surface area of ~154 m2/g. On account of the unique heterostructure, the composite exhibits good electrochemical performance as supercapacitor electrodes. The specific capacitance of e-MnO2-0.75@rGO can reach 456 F/g at a current density of 1 A/g in KOH electrolyte, which still remains 201 F/g at 10 A/g. In addition, the capacitance retention is 98.7% after 10000 charge-discharge cycles at 20 A/g. Furthermore, an asymmetric supercapacitor (ASC) device of e-MnO2-0.75@rGO//graphene hydrogel (GH) was assembled, of which the specific capacitance achieves 94 F/g (1 A/g) and the cycle stability is excellent, with a retention rate of 99.3% over 10000 cycles (20 A/g).

Influence of component content on the capacitance of magnetite/reduced graphene oxide composite

Calcium alginate (CaAlg) is a kind of biodegradable and eco-friendly functional material, and CaAlg/reduced graphene oxide (rGO) composites are expected to be applied as new textile, heat-generating, and flame-retardant materials. In this paper, the CaAlg/rGO composites were prepared by a sol-gel method and their morphological and thermal properties were studied. The results showed that the introduction of rGO can efficiently improve the thermal stability of CaAlg. Further study showed that rGO increased the carbon formation rate by 4.1%, indicating that the thermal stability was improved by the promotion of carbon formation. Moreover, the weight loss rate of the composites was faster at 180–200 °C than that of CaAlg, after which the rate was less comparatively, suggesting the better thermal stability of the composite. This maybe because the high heat transfer efficiency of rGO allowed the material to reach the temperature of the thermal decomposition of the glycan molecule chain within a short time, and then promoted carbon formation. The thermal cracking mechanism of the composites is proposed based on the experimental data.

Using silicon/reduced graphene oxide (Si/rGO) composites as lithium-ion battery (LIB) anodes can effectively buffer the volumetric expansion and shrinkage of Si. Herein, we designed and prepared Si/rGO-b with a sandwiched structure, formed by a duple combination of ammonia-modified silicon (m-Si) nanoparticles (NP) with graphene oxide (GO). In the first composite process of m-Si and GO, a core-shell structure of primal Si/rGO-b (p-Si/rGO-b) was formed. The amino groups on the m-Si surface can not only hybridize with the GO surface to fix the Si particles, but also form covalent chemical bonds with the remaining carboxyl groups of rGO to enhance the stability of the composite. During the electrochemical reaction, the oxygen on the m-Si surface reacts with lithium ions (Li+) to form Li2O, which is a component of the solid-electrolyte interphase (SEI) and is beneficial to buffering the volume expansion of Si. Then, the p-Si/rGO-b recombines with GO again to finally form a sandwiched structure of Si/rGO-b. Covalent chemical bonds are formed between the rGO layers to tightly fix the p-Si/rGO-b, and the conductive network formed by the reintroduced rGO improves the conductivity of the Si/rGO-b composite. When used as an electrode, the Si/rGO-b composite exhibits excellent cycling performance (operated stably for more than 800 cycles at a high-capacity retention rate of 82.4%) and a superior rate capability (300 mA h/g at 5 A/g). After cycling, tiny cracks formed in some areas of the electrode surface, with an expansion rate of only 27.4%. The duple combination of rGO and the unique sandwiched structure presented here demonstrate great effectiveness in improving the electrochemical performance of alloy-type anodes.

Improved room-temperature hydrogen storage performance of lithium-doped MIL-100(Fe)/graphene oxide (GO) composite

Profenofos substantially enhances the productivity of agricultural growth; however, it poses adverse ill effects on humans due to residual profenofos presence in water, resulting in severe contamination. Therefore, it is the need of the hour to develop a highly sensitive electrochemical sensor that can detect trace levels of profenofos in different kinds of water samples with enhanced accuracy. In this context, a detection strategy predicated upon the prescribed threshold of profenofos pesticide has been delineated. A UiO-67 metal-organic framework (MOF)/graphene oxide (GO) composite was synthesized via a solvothermal method and characterized using X-ray diffractometry, Fourier-transform infrared spectrometry, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, X-ray photoelectron spectrometry, cyclic voltammetry, electrochemical impedance spectroscopy, and Brunauer-Emmett-Teller analysis. The resultant sensor exhibited the capability to recognize profenofos across the detection range of 10.0 to 500.0 μM, with a notably low detection limit (LOD) of 0.09 μM and a high sensitivity of 1.8 × 10-3 μA μM-1 using the amperometric method. Importantly, the sensor manifested commendable performance attributes, encompassing favorable repeatability (RSD: 0.5%), resistance to interference (5%), and exceptional recovery rates (98.82-108.89%) when applied to drinking water, groundwater, and agricultural irrigation water samples. The integration of UiO-67 MOF with GO enhanced the sensitivity of the fabricated electrode by providing abundant active sites for profenofos interaction. This innovative methodology holds potential for alleviating the challenges associated with profenofos contamination, presenting a reliable and effective approach for detection and quantification in varied environmental contexts.

Metal‐organic frameworks (MOFs) often suffer from poor stability, making them suitable precursors for metal oxides/porous carbon catalysts in the oxygen evolution reaction via pyrolysis. High‐temperature treatment, however, leads to significant loss of active sites. To address this, Fe‐MOFs, FeCo‐MOFs, and FeCo‐MOFs/graphene oxide (GO) composites using a one‐pot hydrothermal method are synthesized and annealed at a low temperature of 300 °C. Characterization reveals that FeCo‐MOFs/GO composites possess unique nanowire structures mixed with a small amount of nanoflakes. It is believed that introducing graphene oxide plays a critical role in forming this structure, because the defects in GO provide numerous nucleation sites for nanowire growth. With high specific surface area and good stability, these nanostructures show a low overpotential of 261.5 mV at a current density of 10 mA cm−2 and a Tafel slope of 20.47 mV dec−1 in 1 mol L−1 KOH alkaline water electrolysis. Density functional theory calculations further indicate that the synergistic effect of Fe and Co atoms enhances the catalytic activity.