Three-dimensional Graphene Sponge Research Articles

A green cross-linking method for the preparation of renewable three-dimensional graphene sponges for efficient adsorption of Congo red dye

Graphene-based materials possess significant potential for the treatment of dye wastewater due to their exceptional adsorption properties toward stubborn pollutants. However, their utilization is hindered by high preparation costs, low yields, environmental pollution during synthesis, and challenges in regenerating the adsorbent. This study proposes a novel approach to address these limitations by developing nitrogen-doped three-dimensional (3D) polyvinyl alcohol cross-linked graphene sponges (N-PGA) using a cross-linking method with ammonium carbonate. This method offers a relatively mild and environmentally friendly approach. Ammonium carbonate serves as both a reducing and modifying agent, facilitating the formation of the intrinsic structure of N-PGA and acting as a nitrogen source. Meanwhile, polyvinyl alcohol (PVA) is utilized as the cross-linking agent. The results demonstrate that N-PGA exhibits a favorable internal 3D hierarchical porous structure and possesses robust mechanical properties. The measured specific surface area (BET) of N-PGA was as high as 406.538 m2·g–1, which was favorable for its efficient adsorption of Congo red dye molecules. At an initial concentration of 50 mg·L–1, N-PGA achieved an impressive removal rate of 89.6% and an adsorption capacity of 112 mg·g–1 for Congo red (CR) dye. Furthermore, it retained 79% of its initial adsorption capacity after 10 cycles, demonstrating excellent regeneration performance. In summary, the synthesized N-PGA displays remarkable efficacy in the adsorption of CR dye in wastewater, opening up new possibilities for utilizing 3D porous graphene nanomaterials as efficient adsorbents in wastewater treatment.

Three-dimensional petal-like graphene Co3.0Cu1.0 metal organic framework for oxygen evolution reaction

Recently, metal-organic framework (MOF), as a non-noble metal material, has been widely studied for its great potential in catalysis. In this work, a group of hydrothermal growth of CoCu bimetallic active center organic frameworks on three-dimensional graphene sponge (3DGS-CoCu-MOF) were designed, and fabricated as an electrocatalyst for oxygen evolution reaction (OER). A series of electrochemical experiments showed that in the 0.1 mol L−1 KOH electrolyte, the overpotential of the optimal 3DGS-Co3.0Cu1.0-MOF was 460 mV, the slope of Tafel curve was 172 mV dec−1, the charge transfer resistance (Rct) was16.38 Ω cm−2, ECSA was 12.5 cm−2, and Rf was 176.06. After the test of 20000 s, the current density still maintains 95.07%. The better electrocatalytic performance and the long-term electrochemical durability indicated that the 3DGS-Co3.0Cu1.0-MOF material possessed good OER performance. The optimal 3DGS-Co3.0Cu1.0-MOF employed three-dimensional graphene sponge as the conductive substrate, bimetallic active center acted as the main body of the catalyst, and made full use of the synergistic effect of the bimetallic center. Therefore it is a promising catalyst material for the electrolysis of water.

A freestanding all-solid-state polymeric membrane Cu2+-selective electrode based on three-dimensional graphene sponge

A novel freestanding all-solid-state polymeric membrane Cu2+-selective electrode (Cu2+-ISE) is proposed based on three-dimensional graphene sponge (3D GS). The 3D GS electrode has been characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and contact angle measurements. Experiments show that 3D GS possesses a large electrical double layer capacitance, good conductivity, and high hydrophobicity. Based on these superior properties, 3D GS has been applied as both electrode substrate and solid contact for construction of a freestanding all-solid-state polymeric membrane Cu2+-ISE. The 3D GS-based Cu2+-ISE shows a good Nernstian response ranging from 1.0 × 10−8 to 7.9 × 10−4 M with a low detection limit of 2.5 × 10−9 M. Moreover, the proposed Cu2+-ISE exhibits a stable potential response with a reduced water layer at the sensing membrane/3D GS interface and is not affected by interferences from light, O2 and CO2.

Elastic three-dimensional graphene sponge fabricated by the liquid crystals of controlled large graphene oxide sheets

Three-dimensional graphene (3DG) sponge has attracted increasing attention because it combines the unique properties of cellular materials and the excellent performance of graphene. Preparation of 3DG sponge depends mainly on the self-assembly of graphene oxide sheets. In the case of using uniform large graphene oxide and ultralarge graphene oxide sheets, the nematic liquid crystals (LCs) phases are formed at low concentration. After chemical reduction, the LCs of GO solution are converted to 3DG sponges with a high degree of orientation, offering a new methodology to regulate the controlled large GO sheets. The orientation of GO solution can be inherited by 3DG sponge, making the sponge to have a large-scale ordered network structure. The 3D elastic graphene sponges have low density and good elasticity, promising for the applications in strain sensing, shock damping, and energy cushioning. Our work explores a novel strategy for organizing the ordered alignment of controlled large GO sheets and exploring the relationship between the microstructures and mechanical properties of 3DG sponge.

Functionalized three-dimensional graphene sponges for highly efficient crude and diesel oil adsorption.

Modified Hummer's method has been used in this study to synthesize graphene oxide (GO) solution that was utilized for the fabrication of three-dimensional (3D) graphene sponges and their subsequent functionalization through a low-cost and facile vapor-based surface enhancement approach. The functionalized 3D-graphene sponge is an excellent absorbent, which can remove more than 3300wt.% of crude oil (calculated with respect to the original sorbent mass). The functionalization of the obtained graphene sponges with trichloro (1H,1H,2H,2H-perfluorooctyl)silane enhanced their wettability properties due to the super-hydrophobic nature of the resulting materials characterized by the contact angles in water greater than 150°. Furthermore, their elastic compression modulus (estimated by conducting a series of compression tests) was about 22.3kPa. The equilibrium modeling of the oil removal process, which was performed by plotting Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, confirmed the properties of the fabricated 3D graphene sponges as exceptional absorbents for crude and diesel oil, which could be attributed to the oleophilic nature of graphene. Moreover, the obtained 3D graphene sponges could be regenerated via heat treatment, which was conducted to release the adsorbed species. After five adsorption-desorption cycles, the sorption capacity of the produced 3D graphene sponges towards crude oil reached 95% of the initial value.

Fabrication of macroporous reduced graphene oxide composite aerogels reinforced with chitosan for high bilirubin adsorption.

Numerous adsorbents have been reported for the removal of bilirubin, which is a well-known endogenous toxin. Three-dimensional graphene sponges and aerogels have been fully studied in the adsorption field but little in hemoperfusion especially for bilirubin adsorption. In this study, macroporous reduced graphene oxide (GO) aerogels were fabricated by a chemical reduction method. Besides, chitosan was introduced in the aerogels during the reduction process to improve their mechanical properties. The graphene oxide composite aerogels reinforced with chitosan (rGO/CS) were investigated using scanning electron microscopy (SEM), Fourier Transform Infrared Spectrometry (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET). Furthermore, the mechanical properties test showed the reinforced mechanical strength of the rGO/CS aerogels. The adsorption performance of the aerogels for bilirubin was studied in detail, showing a high adsorption capacity (458.9 mg g−1) and a fast adsorption rate. Moreover, the low hemolysis ratio and negligible anticoagulant activity of rGO/CS aerogels suggested good blood compatibility. The mesoporous structure of the aerogels can provide good mechanical strength, and the macroporous structure of the rGO/CS aerogels shows a good adsorption capacity, which would have potential applications in bilirubin adsorption.

Three-Dimensional Graphene Sponge with Hierarchically Porous Structure for Electrochemical Supercapacitors

Supercapacitors is an electrochemical energy storage device typically used as sustainable power supply (such as electric vehicles and mobile electronic devices) due to their higher power density than batteries, higher energy density than conventional dielectric capacitors, and long life cycles. [1,2] Graphene, a two-dimensional (2D) one-atom-thick single layer of sp2-bonded carbon, is considered as an ideal electrode material in supercapacitors because of its superior electrical conductivity and exceptionally large specific surface area. Graphene sheets, unless well separated from each other, tend to form irreversible agglomerates through strong π-π stacking and van der Waals interaction.[3] Meanwhile, the electrochemical binders and additives are normally required to make graphene-based electrodes, which would have an adverse effect on the specific capacitance of the resulting electrodes. To tackle these challenges, three dimensional (3D) graphene networks with highly electrical conductivity and large specific surface area, short diffusion pathways for electrolyte ions and fast transport channels for electrons are very promising supercapacitor materials. To these aims, we have developed ways to synthesize a novel macroporous/nanoporous graphene sponge with tunable pore sizes. This 3D porous graphene sponge has i) an interconnected electrolyte-filled macroporous network that enables increase of contact surface between 3D network and electrolytic solution, and rapid ion transport, ii) short ion and electron transport lengths due to nanoporous structures, iii) a large electrode specific surface area and (iv) high electron conductivity in the electrode assembly. The structure characterization and capacitive properties of the 3D macroporous/nanoporous graphene sponge was investigated and discussed, indicating 3D porous graphene sponge as an ideal electrode materials for supercapacitors. Keywords：Graphene, 3D porous materials, supercapacitors, electrochemical energy

Sulfur Nanogranular Film-Coated Three-Dimensional Graphene Sponge-Based High Power Lithium Sulfur Battery.

To meet the requirements of both high energy and power density with cycle durability of modern EVs, we prepared a novel nanosulfur granular assembled film coated on the three-dimensional graphene sponge (3D-GS) composite as a high-performance active material for rechargeable lithium sulfur batteries. Instead of conventional graphene powder, three-dimensional rGO sponge (3D-rGO) is employed for the composite synthesis, resulting in a sulfur film directly in contact with the underlying graphene layer. This significantly improves the overall electrical conductivity, strategically addressing challenges of conventional composites of low sulfur utilization and dissolution of polysulfides. Additionally, the synthesis mechanism of 3D-GS is elucidated by XPS and DFT analyses, where replacement of hydroxyl group of 3D-rGO sponge by sulfur (S8) is found to be thermodynamically favorable. As expected, 3D-GS demonstrates outstanding discharge capacity of 1080 mAh g(-1) at a 0.1C rate, and 86.2% capacity retention even after 500 cycles at a 1.0C rate.

Graphene Sponges Prepared from Clusters of Soap Bubbles with Hierarchical Pores

Graphene Sponges Prepared from Clusters of Soap Bubbles with Hierarchical PoresRujing Zhang, Yachang Cao, Hongwei ZhuSchool of Materials Science and Engineering, Key Laboratory of Materials Processing Technology, Tsinghua University, Beijing 100084, P. R. China Inspired by the light weight and porosity of the foams of soap bubbles, three-dimensional graphene sponges were fabricated using clusters of soap bubbles as templates. The structure was prepared by simply adding the dispersion of graphene oxide (GO) into a cluster of soap bubbles and stirring the mixture evenly, with subsequent vacuum freeze-drying and thermal annealing. Mass production can be realized since the synthesis process was simple and the raw material was easy to get. Typical hierarchical structure of the thermal-annealled GO (trGO) sponge was obtained with the stirring rate of 250 r min-1 and frozen by liquid nitrogen. SEM images showed the structure was ordered quasi-round pores with diameters as large as several hundred microns, having smaller slot pores on the walls. TEM characterization of the materials showed small pores in nanometer scale, with the diameters ranging from several nanometers to dozens of nanometers. Since the stirring rate in soap bubbles’ production could influence the volume of bubbles, and the freezing rate of bubbles after adding GO dispersion could affect the assembly of GO sheets, the finally obtained structure could be tuned by changing the stirring rate or freezing rate.With high sirring rates of 5000 r min-1 and 20000 r min-1, the obtained structure had no visible large ordered pores due to the collapse of thinner walls in bubbles with smaller volume. Spongy materials prepared with freezing medium as refrigerator were also fabricated, showing disordered pores with smooth walls, resulting from the rearrangement of GO sheets in the process of slow freezing. The thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were also conducted to character the residual impurities from the soap after thermal annealing. In the compression tests, trGO sponge prepared with the stirring rate of 250 r min-1 and frozen by refrigerator could recover completely under 30%-70% compression strain, revealing the ultra-flexibility and softness of the materials. Under cyclic compression, the stress-strain curves didn’t change obviously in 100 cycles. For materials frozen rapidly by liquid nitrogen, the compressive strain was bigger compared with trGO sponges prepared with refrigerator, since the collapse of relatively ordered assembly of graphene sheets had made the structure more compact. The spongy materials could absorb both water and oil, partly because of the visible large pores, and partly because of the residual oxygen-containing groups. The specific capacitance of the trGO sponge was measured as 15.8 F g-1, relatively lower than those three-dimensional graphene-based structures that have been reported, mainly due to the large amount of visible pores with the diameters as large as several hundred microns increasing the benefit surface area much less than pores in nanoscale. The ultra-light, super-flexible three-dimensional graphene sponge, with hierarchical ordered pores with the diameters ranging from several nanometers to hundreds of microns, showed potential applications in stroage media, absorbents, thermal insulation, sound insulation, etc. Figure (a) Optical image of laundry detergent bubbles.(b) Graphene sponge prepared with stirring rate of 250 r min-1 and frozen with liquid nitrogen