Efficiency above 6% in poly(3‐hexylthiophene):phenyl‐C‐butyric acid methyl ester photovoltaics via simultaneous addition of poly(3‐hexylthiophene) based grafted graphene nanosheets and hydrophobic block copolymers

A combination of reduced graphene oxide (rGO) nanosheets grafted with regioregular poly(3‐hexylthiophene) (P3HT) (rGO‐g‐P3HT) and P3HT‐b‐polystyrene (PS) block copolymers was utilized to modify the morphology of P3HT:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) active layers in photovoltaic devices. Efficiencies greater than 6% were acquired after a mild thermal annealing. To this end, the assembling of P3HT homopolymers and P3HT‐b‐PS block copolymers onto rGO‐g‐P3HT nanosheets was investigated, showing that the copolymers were assembled from the P3HT side onto the rGO‐g‐P3HT nanosheets. Assembling of P3HT‐b‐PS block copolymers onto the rGO‐g‐P3HT nanosheets developed the net hole and electron highways for charge transport, thereby in addition to photoluminescence quenching the charge mobility (μ_h and μ_e) values increased considerably. The best charge mobilities were acquired for the P3HT₅₀₀₀₀:PC71BM:rGO‐g‐P3HT₅₀₀₀₀:P3HT₇₀₀₀‐b‐PS₁₀₀₀ system (μ_h = 1.9 × 10^?5 cm² V^–1 s^–1 and μ_e = 0.8 × 10^?4 cm² V^–1 s^–1). Thermal annealing conducted at 120 °C also further increased the hole and electron mobilities to 9.8 × 10^?4 and 2.7 × 10^?3 cm² V^–1 s^–1, respectively. The thermal annealing acted as a driving force for better assembly of the P3HT‐b‐PS copolymers onto the rGO‐g‐P3HT nanosheets. This phenomenon improved the short circuit current density, fill factor, open circuit voltage and power conversion efficiency parameters from 11.13 mA cm^?2, 0.63 V, 62% and 4.35% to 12.98 mA cm^?2, 0.69 V, 68% and 6.09%, respectively. © 2019 Society of Chemical Industry     

Ag-doped nickel ferrites and their composite with rGO: Synthesis,characterization, and solar light induced degradation of coloured and colourless effluents

Nickel ferrites (NF), silver doped nickel ferrites (AgNF), and a composite of silver doped nickel ferrites with reduced graphene oxide (AgNF@rGO) were prepared through the co-precipitation method. The X-ray diffraction analysis was carried out to confirm the structure of prepared materials, and the crystallite size of prepared ferrites was less than 10 nm. FT-IR spectroscopy was performed for the confirmation of functional groups present in the synthesized materials. The surface morphology of prepared samples was investigated via scanning electron microscopy. Optical analysis was carried out with the help of UV–Visible spectroscopy. Thermogravimetric analysis was performed to check the thermal stability. The photocatalytic degradation of methylene blue under solar light irradiation was studied. The AgNF@rGO composite showed 76% degradation of coloured compound (methylene blue) and 50% degradation of colourless compound (benzimidazole). The enhanced photocatalytic degradation efficacy of AgNF@rGO was ascribed to the reduced graphene oxide sheets, which provided a large surface area and the ability to trap electrons from the conduction band. As a result, the decreased recombination rate of electrons and holes enhanced the degradation ability of the composite based photocatalyst. A scavenging experiment was also performed to determine the most photoactive species taking part in the degradation process. In comparison among all prepared samples, AgNF@rGO showed the maximum photocatalytic activity. It was because of the large surface area of the AgNF@rGO. It was investigated that AgNF@rGO is the most effective catalyst for the degradation of coloured and colourless organic pollutants.     

Hydrothermal synthesis of Ag2CO3-TiO2 loaded reduced graphene oxide nanocomposites with highly efficient photocatalytic activity

Abstract

In this work, a growth of Ag₂CO₃-TiO₂ NPs over GO sheets and reduction of GO were simultaneously achieved by the hydrothermal process at 130 °C for 4?h. The photocatalytic activity of the as-prepared Ag₂CO₃-TiO₂ NPs decorated reduced graphene oxide (Ag₂CO₃-TiO₂/rGO) composite was studied by the degradation of methylene blue (MB) solution under visible light irradiation. A remarkable enhancement in the photocatalytic activity of the TiO₂ was achieved after sensitizing with Ag₂CO₃ and loading in rGO sheets which is attributed to the reduced charge recombination, enhanced dye adsorption, and the improvement in the light harvesting capacity of the composite.     

Composite phase change material based on reduced graphene oxide/expanded graphite aerogel with improved thermal properties and shape-stability

Composite phase change materials (PCMs) based on reduced graphene oxide/expanded graphite (rGO/EG) aerogel were prepared by hydrothermal self-assembly and impregnation method. The morphology, chemical structure, thermal properties, and shape-stability of the composite PCMs based on rGO/EG aerogel were examined. The results show that rGO sheets form a three-dimensional (3D) network structure and EG particles are attached to rGO sheets and uniformly interspersed in the aerogel. The oxygen-containing functional groups remaining in rGO/EG aerogel promote heterogeneous crystallization of paraffin, leading to increased latent heat. The 3D thermally conductive pathway provided by rGO/EG aerogel improves the composite PCM's thermal conductivity up to 0.79 W·m⁻¹·K⁻¹, which is about 4 times of that of pure paraffin. The leakage of composite PCMs is remarkably improved at very high percentage of paraffin. Simulative light-thermal experiments reveal that the composite PCMs have the ability of conversion and storage of light-thermal energy. In short, 3D network structure of rGO, with the aid of EG, endows the composite PCMs with improved thermal properties, good shape-stability, and light-thermal storage performance.     

Rechargeable Na–SO2 Battery with Ethylenediamine Additive in Ether‐Based Electrolyte

Rechargeable metal–SO₂ batteries have drawn tremendous attention because it can accelerate SO₂ fixation/utilization and offer high energy density. Herein, a rechargeable Na–SO₂ battery based on an ether‐based liquid electrolyte with an ethylenediamine (EDA) additive is realized via the reversible formation/decomposition of Na₂S₂O₄. Experimental investigations reveal that the EDA additive provides three benefits by simultaneously decreasing the overall electrode polarization, increasing the full discharge capacity, and improving battery cyclability. At a current density of 250 mA g^?1, the full discharge capacity of the battery with the EDA additive is more than twice of a similar system in the absence of EDA. In addition to the significantly enhanced capacity, the as‐assembled Na–SO₂ battery demonstrates excellent cyclic stability after 200 cycles, which is equivalent to a total duration of 1600 h. Moreover, the corrosion resistance of Na anode is strengthened with the aid of EDA in the SO₂‐containing liquid electrolyte. This work will pave the way for Na–SO₂ batteries as a promising battery technology toward both pollutant gas utilization and energy storage.     

Lubricant‐Infused Anisotropic Porous Surface Design of Reduced Graphene Oxide Toward Electrically Driven Smart Control of Conductive Droplets' Motion

The study of Nepenthes pitcher plants‐bioinspired anisotropic slippery liquid‐infused porous surfaces (SLIPS) is currently in its infancy. The factors that influence their anisotropic self‐cleaning and electric response of a drop's motion and the mechanism have not been fully elucidated. In order to address these problems, two new types of anisotropic slippery surfaces have been designed by using directional, porous, conductive reduced graphene oxide (rGO) films, and different lubricating fluids (conductive and nonconductive), which are used to study the influencing factors and the mechanism of anisotropic self‐cleaning and electric‐responsive control of a drop's motion. The results demonstrate the anisotropic self‐cleaning property of these two types of SLIPS is closely related to the interaction between liquid drops, lubricating fluids and dirt, and the conductive lubricating fluids filling the rGO porous film can reduce the response voltage of the electrically driven reversible control of a drop's slide. The uniqueness of this research lies in the use of two different lubricating fluids and graphene materials to prepare anisotropic SLIPS, identify the key factors to achieve an electrically driven system. These studies are essential for advancing the application of electronically responsive SLIPS in the fields of liquid directional transportation, microfluidics, microchips, and other related research.     

Minimising non-selective defects in ultrathin reduced graphene oxide membranes with graphene quantum dots for enhanced water and NaCl separation

Reduced graphene oxide (rGO) membranes have been intensively evaluated for desalination and ionic sieving applications,benefiting from their stable and well-confined interlayer channels.However,rGO membranes generally suffer from low permeability due to the high transport resistance resulting from the narrowed two-dimensional (2D) channels.Although high permeability can be realized by reducing membrane thickness,membrane selectivity normally declines because of the formation of non-selective defects,in particular pinholes.In this study,we demonstrate that the non-selective defects in ultrathin rGO membranes can be effectively minimised by a facile posttreatment via surface-deposition of graphene quantum dots (GQDs).The resultant GQDs/rGO membranes obtained a good trade-off between water permeance (14 L·m-2·h-1·MPa-1) and NaCl rejection (91％).This work provides new insights into the design of high quality ultrathin 2D laminar membranes for desalination,molecular/ionic sieving and other separation applications.     

Design of best performing hexagonal shaped Ag@CoS/rGO nanocomposite electrode material for electrochemical supercapacitor application

The mixed metal/metal sulphide (Ag@CoS) with reduced graphene oxide (rGO) nanocomposite (Ag@CoS/rGO) was synthesized for the possible electrode in supercapacitors. Ag@CoS was successfully deposited on the rGO nanosheets by hydrothermal method, implying the growth of 2D Ag and CoS-based hexagonal-like structure on the rGO framework. The synthesized nanocomposite was subjected to structural, morphological and electrochemical studies. The XRD results show that the prepared nanocomposite material exhibits a combination of hexagonal and cubic phase due to the presence of CoS and Ag phases together. The band appearing at nearly 470.33 cm⁻¹ in FTIR spectra can be ascribed to the absorption of S–S bond in the Ag@CoS/rGO nanocomposite. The clear hexagonal structure was analysed by SEM and TEM with the grain sizes ranging from nanometer to micrometer. The electrode material exhibits excellent cyclic stability with a specific capacitance of 1580 F/g at a current density of 0.5 A/g without any loss of capacitive retention even after 1000 cycles. Based on the electrochemical performance, it can be inferred that the prepared novel nanocomposite material is very suitable for using as an electrode for electrochemical supercapacitor applications.     

A facile dissolution strategy facilitated by H2SO4 to fabricate a 2D metal-free g-C3N4/rGO heterojunction for efficient photocatalytic H2 production

A 2D g-C₃N₄(pPCN)/rGO heterojunction for photocatalytic hydrogen production is fabricated by a facile dissolution strategy facilitated by H₂SO₄. The bulk g-C₃N₄ (CN) can be directly exfoliated into ultrathin protonated g-C₃N₄ (PCN) nanosheets under the assistance of H₂SO₄, and PCN can be further modified by rGO in a dissolved state under the electrostatic self-assembly process. The nanocomposite exhibits a large surface area (146.47 m²/g) and intimate contact interfaces between pPCN and rGO due to the specific synthesis method. Based on the DRS, PL and photoelectrochemical analyses, the introduction of rGO can greatly improve the light absorption and photogenerated charge carrier separation and transfer of g-C₃N₄. The optimal pPCN/2 wt% rGO nanocomposite shows an efficient photocatalytic H₂ evolution rate of 715 μmol g^?1 h^?1 under visible light irradiation, which is 2.6 and 13 times higher than those obtained on pPCN and CN. In addition, a photocatalytic mechanism over a 2D pPCN/rGO heterojunction is proposed. This work offers a new effective strategy for fascinating gC₃N₄based nanocomposites with promising hydrogen generation.     

Enhanced photoelectrochemical water splitting in hierarchical porous ZnO/Reduced graphene oxide nanocomposite synthesized by sol-gel method

Today the utilization of solar energy to split water and its conversion to hydrogen and oxygen has been considered as a powerful way to solve the environmental crisis. Hierarchical porous nanostructured ZnO and ZnO/reduced graphene oxide (rGO) composite photoanodes are synthesized by innovated sol-gel method using triethylenetetramine (TETA) as a stabilizer. The hierarchical porous ZnO structure containing large agglomerates each consisting of tiny nanoparticles are formed. The X-ray diffraction analysis and Raman spectroscopy confirm the in-situ reduction of graphene oxide sheets during synthesis and formation of ZnO/rGO nanocomposite. Although the band gap and transmittance of the porous nanocomposites do not dramatically change by rGO addition, the main photoluminescence peak quenches entirely showing prolonging exciton lifetime. The ZnO/rGO porous structure achieved remarkably improved current density (1.02 mA cm^?2 at 1.5 V vs. Ag/AgCl) in 1 wt% rGO, up to 12 times higher compared to the bare ZnO (0.09 mA cm^?2 at 1.5 V vs. Ag/AgCl), which attributes to positive role of ZnO hierarchical porous structure and rGO electron separation/transportation. These findings provide new insights into the broad applicability of this methodology for promising future semiconductor/graphene composite in the field of photoelectrochemical water splitting.