Three-dimensional Graphene Hydrogel Research Articles

A novel 3-dimensional graphene-based cobalt-manganese bimetallic layered double hydroxide:Formation mechanism and performance in photo-assisted permonosulfate-activated degradation of sulfamethoxazole in aqueous solution

Sulfamethoxazole (SMX) is a common antibiotic used mainly for bacterial treatment. In this study, a novel three-dimensional cobalt-manganese bimetallic layered double hydroxide graphene hydrogel (CoMn-LDHs/rGO) has been prepared for photo-assisted permonosulfate (PMS)-activated degradation of SMX in water. Compared with the CoMn-LDHs/rGO + PMS and CoMn-LDHs/rGO + Vis systems, the degradation effect of CoMn-LDHs/rGO + PMS + Vis system is the best, and the degradation effect of CoMn-LDHs/rGO system could reach more than 98% under the optimal conditions. After 10 cycles, the catalytic degradation performance of CoMn-LDHs/rGO system remained good, while effectively preventing the leaching of metal ions. Based on the synergistic effect of photocatalysis and PMS oxidation, electron spin resonance spectroscopy and quenching experiments showed that three active substances (•OH, •SO4− and O2•−) were involved in the degradation of SMX. Density functional theory and liquid chromatography-mass spectrometry (LC-MS) results further proposed the SMX degradation transformation calculation. As expected, the study of the reaction mechanism of 3D CoMn-LDHs/rGO assisted PMS activation under visible light provides an efficient and rapid method for the sustainable degradation of pollutants in water system.

Toward the Improvement of Silicon-Based Composite Electrodes via an In-Situ Si@C-Graphene Composite Synthesis for Li-Ion Battery Applications

Using Si as anode materials for Li-ion batteries remain challenging due to its morphological evolution and SEI modification upon cycling. The present work aims at developing a composite consisting of carbon-coated Si nanoparticles (Si@C NPs) intimately embedded in a three-dimensional (3D) graphene hydrogel (GHG) architecture to stabilize Si inside LiB electrodes. Instead of simply mixing both components, the novelty of the synthesis procedure lies in the in situ hydrothermal process, which was shown to successfully yield graphene oxide reduction, 3D graphene assembly production, and homogeneous distribution of Si@C NPs in the GHG matrix. Electrochemical characterizations in half-cells, on electrodes not containing additional conductive additive, revealed the importance of the protective C shell to achieve high specific capacity (up to 2200 mAh.g-1), along with good stability (200 cycles with an average Ceff > 99%). These performances are far superior to that of electrodes made with non-C-coated Si NPs or prepared by mixing both components. These observations highlight the synergetic effects of C shell on Si NPs, and of the single-step in situ preparation that enables the yield of a Si@C-GHG hybrid composite with physicochemical, structural, and morphological properties promoting sample conductivity and Li-ion diffusion pathways.

CuBi2O4 surface-modified three-dimensional graphene hydrogel adsorption and in situ photocatalytic Fenton synergistic degradation of organic pollutants

A CuBi2O4/rGH composite catalyst was prepared by modifying CuBi2O4 on the surface of a three-dimensional graphene hydrogel (rGH) via a simple water bath method. The large specific surface area and particular surface adsorption properties of rGH were beneficial for adsorbing and enriching pollutant molecules and could then be further degraded by the in situ photocatalytic Fenton synergistic effect with the addition of H2O2. The introduction of graphene not only increases the surface area and improves the adsorption properties but also accelerates the transfer and separation efficiency of the interface photogenerated charge, thereby promoting the photocatalytic Fenton degradation performance. The adsorption performance and catalytic degradation performance of the 20 % CuBi2O4/rGH composite for phenol were 1.4 and 1.3 times higher than those of CuBi2O4, respectively. Meanwhile, the removal efficiency of phenol in the adsorption and in situ photocatalytic Fenton synergistic system was as high as 80 % within 20 min. In addition, the cross-linked network structure of the 3D graphene hydrogel could be better recycled, which has significant potential in practical applications. Quenching and EPR experimental results showed that hydroxyl radicals (·OH) were the most active species in the synergistic degradation process, and the mechanism of CuBi2O4/rGH adsorption and in situ photocatalytic Fenton degradation was proposed.

Fabrication and Performance Test of Flexible Supercapacitors Based on Three-Dimensional Graphene Hydrogel

Flexible supercapacitors have attracted more and more attention and research because they can be used as energy storage devices for future flexible electronic devices. In the existing research, graphene has been used to make supercapacitor electrodes, but usually these electrodes have very low specific capacitance or flexibility. Here, a three-dimensional graphene hydrogel for the fabrication of flexible supercapacitors was presented, and the preparation of flexible supercapacitors based on three-dimensional graphene hydrogels was given. Through the research, we find that the prepared flexible supercapacitor has excellent capacitance characteristics, such as high specific capacitance of 168F/g and excellent mechanical flexibility. This study shows that the three-dimensional graphene macro structure has great potential in the preparation of high-performance flexible energy storage devices.

Adsorption and in-situ photocatalytic synergy degradation of 2,4-dichlorophenol by three-dimensional graphene hydrogel modified with highly dispersed TiO2 nanoparticles

A highly dispersed TiO2 nanoparticle-modified three-dimensional graphene hydrogel composite (TiO2-rGH) was successfully prepared by a hydrothermal method. Based on adsorption and photocatalytic degradation at the same active site, the synergistic system exhibited excellent catalytic degradation performance, which could fully mineralize the 2,4-dichlorophenol (40 mg/L) solution after 20 min. The reaction rate constants were 8 and 13 times those of TiO2 and rGH, respectively. Meanwhile, the assembly of two-dimensional graphene sheets with hybrid TiO2 nanoparticles to construct the three-dimensional graphene hydrogel structure not only increases the specific surface area of the composite but also builds more charge transport channels. The results showed that the specific surface area of TiO2-rGH was 151.46 m2/g, which was approximately 5 times that of rGH, and the adsorption activity for 2,4-dichlorophenol was doubled. In addition, the photocurrent density of TiO2-rGH was 11 times that of TiO2 nanoparticles; thus, the TiO2-rGH composites exhibited better adsorption and photocatalytic degradation performance than rGH and TiO2. More importantly, the three-dimensional graphene hydrogel composite has excellent stable degradation performance and solves the problem that the catalyst is difficult to recycle, showing great potential in practical applications.

Cubi2o4 Surface-Modified Three-Dimensional Graphene Hydrogel Adsorption and In-Situ Photocatalytic Fenton Synergistic Degradation of Organic Pollutants

Cubi2o4 Surface-Modified Three-Dimensional Graphene Hydrogel Adsorption and In-Situ Photocatalytic Fenton Synergistic Degradation of Organic Pollutants

Adsorption and <i>In-Situ</i> Photocatalytic Synergy Degradation of 2,4-Dichlorophenol by Three-Dimensional Graphene Hydrogel Modified with Highly Dispersed TiO <sub>2</sub> Nanoparticles

Adsorption and <i>In-Situ</i> Photocatalytic Synergy Degradation of 2,4-Dichlorophenol by Three-Dimensional Graphene Hydrogel Modified with Highly Dispersed TiO <sub>2</sub> Nanoparticles

Reduction Self-Assembly of Three-Dimensional Graphene Hydrogels: Implication as Adsorbents

We have prepared a three-dimensional (3D) graphene hydrogel with a specific surface area that is comparable to the theoretical specific surface area of two-dimensional graphene. Graphene oxide was ...

An aqueous zinc-ion hybrid super-capacitor for achieving ultrahigh-volumetric energy density

Zinc-ion hybrid super-capacitors are regarded as promising safe energy storage systems. However, the relatively low volumetric energy density has become the main bottlenecks in practical applications of portable electronic devices. In this work, the zinc-ion hybrid super-capacitor with high volumetric energy density and superb cycle stability had been constructed which employing the high-density three-dimensional graphene hydrogel as cathode and Zn foil used as anode in 1 mol/L ZnSO4 electrolyte. Benefiting from the abundant ion transport paths and the abundant active sites for graphene hydrogel with high density and porous structure, the zinc-ion hybrid super-capacitor exhibited an extremely high volumetric energy density of 118.42 Wh/L and a superb power density of 24.00 kW/L, as well as an excellent long cycle life (80% retention after 30,000 cycles at 10 A/g), which was superior to the volumetric energy density of the reported zinc-ion hybrid super-capacitors. This device, based on the fast ion adsorption/desorption on the capacitor-type graphene cathode and reversible Zn2+ plating/stripping on the battery-type Zn anode, which will inspire the development of zinc-ion hybrid super-capacitor in miniaturized devices.

Three-Dimensional Graphene Hydrogel Decorated with SnO2 for High-Performance NO2 Sensing with Enhanced Immunity to Humidity.

A facile, one-step hydrothermal route was exploited to prepare SnO2-decorated reduced graphene oxide hydrogel (SnO2/RGOH) with three-dimensional (3D) porous structures for NO2 gas detection. Various material characterizations demonstrate the effective deoxygenation of graphene oxide and in situ growth of rutile SnO2 nanoparticles (NPs) on 3D RGOH. Compared with the pristine RGOH, the SnO2/RGOH displayed much lower limit of detection (LOD) and an order of magnitude higher sensitivity, revealing the distinct impact of SnO2 NPs in improving the NO2-sensing properties. An exceptional low theoretical LOD of 2.8 ppb was obtained at room temperature. The p-n heterojunction formed at the interface between RGOH and SnO2 facilitates the charge transfer, improving both the sensitivity in NO2 detection and the conductivity of hybrid material. Considering that existing SnO2/RGO-based NO2 sensors suffer from great vulnerability to humidity, here we employed integrated microheaters to effectively suppress the response to humidity, with nearly unimpaired response to NO2, which boosted the selectivity. Notably, a flexible NO2 sensor was constructed on a liquid crystal polymer substrate with endurance to mechanical deformation. This work indicates the feasibility of optimizing the gas-sensing performance of sensors by combining rational material hybridization, 3D structural engineering with temperature modulation.

A portable solar-driven ratiometric photo-electrochromic visualization biosensor for detection of ochratoxin A

Photoelectrochemical (PEC) biosensors have been widely studied and applied due to unique advantages. But the requirement of electrochemical workstation and light source limits the development of portable PEC biosensors. In this work, a portable solar-driven visualization PEC biosensor has been successfully developed to completely get rid of instruments requirement. This biosensor is fabricated onto a small ITO electrode which may be divided into two modules, one is the detection module and the other is the reference module. Each module is composed of two regions. Co, N-TiO2/3DGH (three-dimensional graphene hydrogel) nanocomposite is used to construct the photoelectric sensing region and the electrochromic material Prussian Blue (PB) is used in the visual region. The quantification is through the chromaticity ratio of visual regions on the two modules. Based on this, the proposed portable visual biosensor has been successfully applied to the detection of ochratoxin A (OTA). A good linear range (1 ng/mL–500 ng/mL) was obtained with a detection limit of 0.29 ng/mL. Due to its high accuracy and portability, the sensor will bring bright prospects for research in the fields of bioanalysis, food testing and so on.

Electro-Oxidation and Simultaneous Determination of Indole-3-Acetic Acid and Salicylic Acid on Graphene Hydrogel Modified Electrode.

A selective and sensitive electrochemical sensor was developed for simultaneous detection of phytohormones indole-3-acetic acid (IAA) and salicylic acid (SA). The sensing interface was fabricated on a porous, three-dimensional networked graphene hydrogel (GH) modified glassy carbon electrode (GCE). The electrocatalytic behavior of IAA and SA on the surface of the modified electrode (GH/GCE) was investigated by cyclic voltammetry and linear sweep voltammetry. Results show that the oxidation reactions of IAA and SA occur at different potentials, which enable their simultaneous detection at the sensing interface. Under optimal conditions, the GH/GCE exhibited good selectivity and stability and its response, unaffected by various interferents, was linear in the range of 4 to 200 μM of IAA and SA. The limit of detection (S/N = 3) achieved were 1.42 μM for IAA and 2.80 μM for SA. The sensor performance was validated by measuring for IAA and SA in real vegetable samples with satisfactory results.

Cover Feature: Exploring Battery‐Type ZnO/ZnFe2O4 Spheres‐3D Graphene Electrodes for Supercapacitor Applications: Advantage of Yolk−Shell over Solid Structures (ChemElectroChem 23/2019)

The Cover Feature illustrates a binder-free electrode design on Ni foam with a uniquely nano-structured electroactive material: yolk–shell ZnO/ZnFe2O4 nanospheres matrixed in three-dimensional graphene hydrogel. The design results in a fourfold increase in the specific capacitance in comparison to that of solid metal oxide spheres. More information can be found in the Article by S. K. Jhajharia et al. on page 5819 in Issue 23, 2019 (DOI: 10.1002/celc.201901269).

Application of three-dimensional graphene hydrogels for removal of ofloxacin from aqueous solutions

Antibiotics widely use around the world. There is an increasing demand for the removal of antibiotics from water due to their toxicity to living beings and the adsorption process regarded as a promising method for the removal of the antibiotic. Graphene hydrogel showed an adequate adsorption capacity for antibiotics via combined adsorption interaction mechanisms (e.g., π-π interaction, hydrogen bonding, and hydrophobic interaction). In this study, a one-step hydrothermal reduction method applied for the preparation of 3D porous graphene hydrogel adsorbents. The characteristic properties of synthesized graphene hydrogels were obtained using scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller. Graphene hydrogels used for removing ofloxacin as widespread fluoroquinolone antibiotic drugs from aqueous solutions. Residual ofloxacin concentration was achieved using a low-cost and straightforward smartphone fluorimeter set–up. This set-up can quantify and compare fluorescent intensity in several samples simultaneously, which is a significant advantage. These results demonstrate that graphene hydrogel is a promising adsorbent for the removal of ofloxacin pollutants from aqueous solutions. Also, image processing smartphone application is the right candidate for inexpensive, accessible, and fast monitoring of ofloxacin pollutants.

Aramid nanofiber-reinforced three-dimensional graphene hydrogels for supercapacitor electrodes

HypothesisSelf-assembled graphene hydrogels are notable in the field of electrochemical energy storage for their unique combination of excellent specific surface area, high porosity, and electrically conductive continuous network. However, graphene hydrogels suffer from poor mechanical integrity compared to layered architectures like graphene buckypapers, limiting their applications in practical devices. We propose the use of high strength, Kevlar®-derived polymeric nanofillers, aramid nanofibers (ANFs) as structural fillers to enhance graphene hydrogel’s shear modulus in the context of multifunctional (mechanical and electrochemical) architectures. ExperimentsGraphene hydrogels are fabricated using sol-gel self-assembly of graphene oxide (GO) nanosheets in presence of ammonium hydroxide. Colloidal dispersion of ANFs and GO are integrated using a novel combination of solvent exchange and dialysis approach to fabricate GO-ANF hydrogels with 0–15 wt.% of ANFs loading (dry weight basis). Shear modulus and electrochemical properties of resulting hydrogel composites are evaluated using rheology and symmetric supercapacitor cell. FindingsThe addition of 2 wt.% ANFs resulted in an 80% improvement in shear modulus compared to neat graphene hydrogel. Addition of ANFs resulted in gradual reduction of specific capacitance, with the specific capacitance of 190 F/g for neat graphene hydrogel, reducing to 128 F/g for an ANF loading of 15 wt.% (dry weight basis). This work shows the broader concept that adding high-strength nanofibers to a nanomaterial gel can add reinforcement provided that the gelation process itself is not disrupted.

A novel morphology of 3D graphene hydrogel nanotubes for high-performance nonenzymatic hydrogen peroxide sensor

A novel nanostructure of three-dimensional graphene hydrogel nanotubes (3DGHNTs) is successfully synthesized for the purpose of sensing non-enzymatic H2O2 in alkaline solution. The 3DGHNTs were fabricated using manganese dioxide nanotubes (MnO2 NTs) as the effective sacrificial template and without the use of any acids or a high temperature process. 3DGH with different percentages of MnO2 NTs ranging from 5 to 30% are prepared via a hydrothermal method. When the loading percentage of MnO2 NTs is 10%, the obtained 3DGHNTs-Mn10 nanocomposite exhibits a large specific surface area with high porosity, which enhance the electrochemical properties for H2O2 detection. The developed biosensor exhibits excellent sensitivity (220.4μAmM−1cm−2) with a wide linear detection range (25μM–22.57mM) and a low detection limit (4μM). The biosensor also shows a fast response time (less than 5s) and good selectivity as well as reproducibility and long-term stability. Hence, the prepared 3DGHNTs-Mn10 nanocomposite can be considered a promising electrode material for the detection of H2O2 in real sample.

Adsorption mechanism and effect of moisture contents on ciprofloxacin removal by three-dimensional porous graphene hydrogel.

The three-dimensional (3D) porous graphene hydrogel (GH) was synthetized by an environmentally friendly one-step hydrothermal reduction method. The characterization methods, such as Environmental scanning electron microscope, Contact angle, and Fourier transform infrared spectroscopy, were used to analyze the possible reduction mechanism. In order to investigate the relationship between adsorption properties of ciprofloxacin (CIP) and moisture content, GH with different moisture contents, was synthesized via different reaction variables (initial graphene oxide concentration, proportion of reductant, temperature, and reduction time). Besides, GH synthesis parameters were also optimized using variable control methods. More importantly, the multiple adsorption mechanisms of CIP on GH was also be investigated and summarized, indicating GH possesses a promising potential in practical application. These results indicate that GH may be an efficient adsorbent for antibiotic pollutants removal in water purification.

Construction of 3D hierarchical porous NiCo2O4/graphene hydrogel/Ni foam electrode for high-performance supercapacitor

We report the utilization of three-dimensional graphene hydrogel embedded with Ni foam as a high-surface-area support and one-step electrodeposition of NiCo2O4 nanoflakes on the support for use as supercapacitor electrode, with dramatic improvements in the accessible electrode surface area and loading amount of pseudocapacitive material being achieved. The constructed NiCo2O4/graphene hydrogel/Ni foam ternary composite electrode possesses a hierarchical open-porous structure scaling from macropores to mesopores, which synergistically provides continuous electron path, commodious ion channel and large electrolyte-electrode interface, thus benefiting the improvement of overall energy storage properties of the supercapacitor electrode. Accordingly, the as-prepared electrode exhibits exceptional high capacitance of 3.84 F cm−2 at 2 mA cm−2 and excellent rate capability with 71.6% retention at 50 mA cm−2. Moreover, the assembled asymmetric supercapacitor using NiCo2O4/graphene hydrogel/Ni foam as positive electrode and graphene hydrogel/Ni foam as negative electrode renders a maximum energy density and power density of 65 Wh kg−1 and 18.9 kW kg−1, respectively, and a striking cycling stability with 92% capacitance retention after 5000 charge-discharge cycles. These desirable results suggest a great potential of hierarchical porous NiCo2O4/graphene hydrogel/Ni foam electrode for the high-performance supercapacitor application.

Na2MoO4 as both etcher for three-dimensional holey graphene hydrogel and pseudo-capacitive feedstock for asymmetric supercapacitors

Porous graphene hydrogel (pGH) have attracted considerable attention due to their unique properties and practical applications in the field of supercapacitors. Their exceptional porous structure (high degree of porosity, high pore volume and high specific surface area) combined with the inherent properties of graphene can fully broaden the ion channel and then improve the performance of the supercapacitor. Here a general and scalable synthesis method to prepare three-dimensional integrate electrode of porous graphene hydrogel (pGH) has been developed using Na2MoO4 as pore-making agent by a hydrothermal synthesis reaction. The as-prepared porous graphene hydrogel can be used as an electrode with a gravimetric capacitance of 473 F g−1, nearly three times that of the hydrogel electrode without puncturing pores, contributes to its highly specific area and ion channels. In addition, the nanocomposite of MoO3/GH can also works as positive electrode while the MoO3 nanoparticles produced during the hydrothermal process is an ideal material for pseudo-capacitance. At the same time, the sodium molybdate is added into the acidic electrolyte to interact with hydrogen ions to produce the pseudo-capacitance either. Then, an asymmetric supercapacitor (pGH||MoO3/GH) was fabricated by using pGH as negative electrode while MoO3/GH as positive electrode, and the maximum energy density is 40.34 W h kg−1 at a current density of 1 A g−1 while the power density is 565.13 W kg−1.

Surface-crumpled graphene hydrogels with macro- and microporous structures for ultrahigh-volumetric energy storage

Recent research has focused on three-dimensional graphene hydrogels with macroporous structure effectively applied for power supply. Here we report a novel surface-crumpled reduced graphene oxide hydrogel with hierarchical pores, through adjusting the temperature and time of hydrothermal reaction with the addition of 2-butanol molecules. Large amounts of micropores in the interior of the macroporous hydrogel skeleton, are attributed to the crispation on the edge of graphene sheets, forming the uniform tubes with the inner diameter of 1.74 nm confirmed by transmission electron microscopy. The pressed hydrogel electrode can provide an outstanding specific capacitance of 549 F cm-3 at 1.14 A cm−3 and high rate capability of 62.2% from 1.14 A cm−3 to 114 A cm−3. The assembled symmetric device can deliver a volumetric specific capacitance of 517 F cm-3 at 1.14 A cm−3, energy density of 71.9 Wh L−1 at 0.57 kW L−1, excellent cycling stability (98.6%) and coulomb efficiency (97.3%). The achievement of such remarkable performances can open up an exciting route to the hierarchically porous structure of graphene-based networks for highly efficient capacitive energy storage.