Reduced Graphene Oxide Foam Research Articles

Initial Study of Reduced Graphene Oxide Foams Modified by Mn and Bi as Capacitive Electrode Materials

In a view of application of porous materials in wearable electronics and self-powered systems, reduced graphene oxide (rGO) foams modified by Mn or/and Bi were produced in this study to be used as electrodes for supercapacitors. The hydrothermal method and the freeze-drying processes were used for the preparation of the materials further morphologically, elementally and structurally analyzed. Based on the electrochemical characterization, Bi-modified rGO foam was found to be more a promising material for capacitive electrodes in comparison to the other prepared materials.

Reduced graphene oxide foams modified with caffeic acid for water decontamination: Capture and safe storage of Hg2+

Graphene-based materials are attractive adsorbents for water decontamination. In this work, we have produced eco-friendly reduced graphene oxide (rGO)-based sorbents by the hydrothermal reduction of graphene oxide (GO) in presence of caffeic acid (CA) and further modification with chitosan (CA_CS). Scanning electron microscopy observations show porous macrostructures that turn more compact after CA or CA_CS modification. The specific surface area achieves a maximum value of 293 m2 g−1 for the pristine rGO foam. The macropores are mainly distributed in a range between 1–170 µm. The Hg2+ removal efficiency of the rGO-based foams was investigated across several different parameters. The foam modified with caffeic acid exhibited the most promising performance, demonstrating the highest removal efficiency at pH 4–6, with a maximum sorption capacity of 2.79 mg/g as determined by the Sips equation. Kinetic analysis indicates that intraparticle diffusion and the sorption itself are the rate-limiting steps. The notable sorption efficiency, the low desorption rate, and the applicability in real complex water matrices, including tap water, position rGO_CA as a viable material for efficiently capturing Hg(II) from large volumes of water and securely storing it in a small solid volume.

Decoration of Ag Species into Reduced Graphene Oxide Foam as a Superelastic and Robust Host toward Stable Zn Metal Anodes under Dwell-Fatigue Condition.

Deep-sea equipment usually operates under dwell-fatigue condition, which means the equipped energy storage devices must survive under the changing pressure. Special mechanical designs should be considered to maintain the electrochemical performance of electrodes under this extreme condition. In this work, an effective assembly strategy is proposed to accommodate the dwell-fatigue loading using Ag decorated reduced graphene oxide (rGO) foam (denoted as AGF) as a superelastic and robust Zn host. The wet-press assembly process enables the formation of highly porous and robust framework. The strong synergetic effect between rGO and Ag further guarantees AGF's superelasticity and ultrahigh mechanical strength. Meanwhile, the homogeneously distributed Ag species on the rGO sheets act as zincophilic sites to effectively facilitate Zn plating. Furthermore, AGF offers enough space to address the expansion during the charge and discharge cycles. As expected, the symmetrical cell using this AGF@Zn host demonstrates a long lifespan over 400h at a depth-of-discharge of 50%. It is worth mentioning that the superelastic AGF host realizes stable Zn plating/stripping under varying pressures.

Electrochemically Modulated Multi-Metal Sulfides/3D-Graphene Scaffold for Sustainable Energy Generation and Storage

Transition metal-based compounds (TMCs), especially sulfides and phosphides represent a class of promising non-precious metal oxygen electrocatalysts (OER and ORR) due to their advantages of abundance, low cost, and environmental friendliness. The effective modulation of electronic structure from synergistic interactions between the constituents and the favourable adsorption of crucial intermediates during electrochemical reactions is possible while using multi-metal transition metal-based sulfides and phosphides. Moreover, recent studies report that TMCs with heteroatom-doped carbonaceous materials display excellent bifunctional ORR/OER properties in alkaline environment, benefitting from the fast interfacial electron transfer and the synergistic effects originating from the chemical coupling between metallic atoms and carbon materials. In this regard, Graphene could effectively enhance the electrical properties and limit the volume expansion of the TMCs, improving the durability of the catalyst. However, there are several challenges associated processing of these catalysts or catalyst systems in a scalable route. Designing these scalable electrodes as porous structures is critical for their effective utilization in energy systems. Electrodeposition is an ideal and sustainable strategy that eliminates the calcination step in electrode processing and saves time. In the case of metal sulfides, adopting electrodeposition over 3D foams like of graphene will help to eliminatesimultaneous steps and reduce the toxic gas evolution during heating of precursors. The electrochemical processing will also help to achieve structural designs capable of delivering higher catalytic sites and a controlled ratio of metal elements, enabling excellent catalytic performance for the composition. More importantly, a sturdy interaction between the substrates and the deposited coatings, forming composite structures gives the electrocatalysts exceptional durability.Herein, we report an electrodeposition process of ternary, quaternary, and quinary transition metal-based sulfide electrocatalysts for OER and ORR in alkaline media. We will be discussing the versatile deposition process for multi-metal sulfides over 3D porous graphene foams materialized by chemical vapour deposition. The detailed electrochemical characterization of the catalyst compositions will be supported by first principle-based investigations on oxygen electrochemistry over modelled catalyst surfaces. Finally, the the practical application of rechargeable structural batteries using these transition metal-based catalysts will be demonstrated along with the performance factors.References Jaime et al, All-Electrochemical Nanofabrication of Stacked Ternary Metal Sulfide/Graphene Electrodes for High-Performance Alkaline Batteries, Small 2022, 18, 2106403Xue et al, Structure and performance of the LiFePO4cathode material: from the bulk to the surface, Nanoscale 2020, 12, 4816.Wang et al ,One-Pot Growth of 3D Reduced Graphene Oxide Foams Embedded with NiFe Oxide Nanocatalysts for Oxygen Evolution Reaction, Electrochem. Soc. 2016 ,163 F3158

Super expanded freestanding 3D graphene foam as a versatile platform for CO2 capture and hydrogenation

A robust fabrication process has been developed to produce super-expanded freestanding 3D reduced graphene oxide foams (SE-rGO) with an outstanding porous architecture and stable geometry for effective capture (from the atmosphere) and the conversion of CO2 into fuel. The 3D SE-rGO foam was prepared using salicylic acid-induced exfoliation of graphene layers based on a template-assisted process. The foam was then coated with a thin layer of polydopamine (pDA) to enhance its physical and functional properties. The morphology and structural integrity of the foam were examined using SEM, XRD, XPS, and TGA. Owing to its unique 3D porous architecture and large specific surface area (767 m2/g, SSA), the foam displayed excellent multifunctional attributes, namely high CO2 adsorption capacity (4.17 mmol/g) and catalytic support for effective CO2 hydrogenation to formate. The key catalytic activity was made possible by coating the foam with palladium nanoparticles. The coated foam showed outstanding hydrogenation of CO2 to formate with a maximum yield of 24.3% at 120 °C. Given its potential, this graphene foam can be a promising and versatile material for both CO2 capture and CO2 hydrogenation.

Effective degradation of tetracycline via recyclable free-standing three-dimensional copper-based graphene as a persulfate catalyst.

Water pollution by antibiotics is a serious and growing problem. Given this challenge, a free-standing three-dimensional (3D) reduced graphene oxide foam supported copper oxide nanoparticles (3D-rGO-CuxO) was synthesized using GO as a precursor and applied as an efficient persulfate activator for tetracycline (TC) degradation. The influences of CuxO mass, solution pH, persulfate dosage, and common anions on the TC degradation were investigated in detail. Analytical techniques indicated that the 3D-rGO-CuxO showed a cross-linking three-dimensional network structure, and CuxO particles with irregular shapes were uniformly loaded on graphene pore walls. The XPS and Auger spectra of Cu confirmed that Cu2O was the main component in solid copper compounds. The addition of CuxO was vitally important for the activation of the oxidation system, and the removal rate reached 98% with a CuxO load of 7:1. The pH showed little influence on the activation effect on TC degradation. For common anions, Cl- and CO32- had little influence on the system, while humic acid had a great inhibitory effect. The EPR test and quenching experiment revealed that the active substances in the oxidative degradation process mainly include SO4-·, ·OH, 1O2, and reactive Cu(III). Additionally, the 3D-rGO-CuxO material proved highly stable according to the replicated test results and was promising for the remediation of antibiotic-contaminated water.

Constructing central hollow cylindrical reduced graphene oxide foams with vertically and radially orientated porous channels for highly efficient solar-driven water evaporation and purification

Constructing central hollow cylindrical reduced graphene oxide foams with vertically and radially orientated porous channels for highly efficient solar-driven water evaporation and purification

Facile fabrication of flexible piezo-resistive pressure sensor array using reduced graphene oxide foam and silicone elastomer

Electronic skins have attracted significant interest due to their broad applications in our daily lives. Flexible pressure sensors form one of the essential parts of any electronic skin. Achieving high-performance electronic skins requires ways to make pressure sensor arrays with high sensitivity and good flexibility. We report on the facile fabrication of flexible piezo-resistive pressure sensor arrays with excellent mechanical stability, high sensitivity, and a wide working range (0–30 kPa) of pressure using reduced graphene oxide (rGO) on flexible PCB (FPCB). It shows a remarkable sensitivity of 0.13 kPa−1 in the pressure range < 10 kPa and 0.05 kPa−1 in the range of > 10 kPa, covering a broad spectrum of testing conditions. We demonstrated that it could provide a pressure map and intensity, giving tactile information of the pressure exerted on our prototype with a 4 × 4 array.

Uranium In Situ Electrolytic Deposition with a Reusable Functional Graphene-Foam Electrode.

Nuclear fission produces 400 GWe which represents 11% of the global electricity output. Uranium is the essential element as both fission fuel and radioactive waste. Therefore, the recovery of uranium is of great importance. Here, an in situ electrolytic deposition method to extract uranium from aqueous solution is reported. A functionalized reduced graphene oxide foam (3D-FrGOF) is used as the working electrode, which acts as both a hydrogen evolution reaction catalyst and a uranium deposition substrate. The specific electrolytic deposition capacity for U(VI) ions with the 3D-FrGOF is 4560mg g-1 without reaching saturation, and the Coulombic efficiency can reach 54%. Moreover, reduction of the uranium concentration in spiked seawater from 3ppm to 19.9 ppb is achieved, which is lower than the US Environmental Protection Agency uranium limits for drinking water (30 ppb). Furthermore, the collection electrode can be efficiently regenerated and recycled at least nine times without much efficiency fading, by ejecting into 2000ppm concentrated uranium solution in a second bath with reverse voltage bias. All these findings open new opportunities in using free-standing 3D-FrGOF electrode as an advanced separation technique for water treatment.

A generalizable strategy for constructing ultralight three-dimensional hierarchical network heterostructure as high-efficient microwave absorber

Using previous models and theories to construct and develop high-efficient microwave absorbers (MAs) should be a strategic and effective ways to optimize the electromagnetic wave attenuation. Herein, the ultralow density and flexible graphene oxide foam (GOF) and reduced graphene oxide foam (RGOF)/MoS2 nanosheets were designed and fabricated by the method of chemical vapor deposition and hydrothermal reaction. The obtained GOF and RGOF/MoS2 samples exhibited very excellent microwave absorption properties while their densities were merely 0.0082 and 0.0084 g•cm−3, respectively. More importantly, benefiting from the excellent synergistic effect between RGOF and MoS2, the designed RGOF/MoS2 well inherited the combined advantages of GOF and MoS2 in terms of strong absorption abilities, broad absorption bandwidth and thin matching thicknesses. The values of minimum reflection loss and effective frequency bandwidth for RGOF/MoS2 sample could reach up to −62.92 dB with the matching thickness of 2.27 mm and 4.48 GHz with the matching thickness of 2.12 mm, which were very desirable for high-performance MAs. Moreover, the obtained results indicated that the microwave absorption properties of RGOF/MoS2 sample could be further optimized by regulating the MoS2 content. Therefore, a new and effective strategy was proposed to develop high efficiency MAs with ultra-lightweight, wide-band, thin thickness and strong absorption capabilities.

Ultrahigh Sensitive Wearable Pressure Sensors Based on Reduced Graphene Oxide/Polypyrrole Foam for Sign Language Translation

AbstractPressure sensors have attracted worldwide attention due to their extensive application requirements in wearable devices, flexible touch display, soft robotics, and health monitoring. Although many pressure sensors have been developed, it still remains a grand challenge to achieve ultrahigh sensitivity with good stability in low‐pressure regions. Herein, the polypyrrole (PPy) is introduced to reduced graphene oxide foam (rGOF) via in situ solventless polymerization to manufacture rGO/PPyF, which significantly enhances the sensitivity and stability of the derived sensors. The as‐fabricated sensor demonstrates an ultrahigh sensitivity of 32.32 kPa−1 in the pressure region of 0–21 Pa, high resolution, and excellent cycling stability. Furthermore, the pressure sensor can transform different hand gestures to distinguishable electrical signals in sign language translation, which indicates that the pressure sensor has a bright application prospect in wearable devices and human–computer interaction.

Ultrahigh solar steam generation rate of a vertically aligned reduced graphene oxide foam realized by dynamic compression

Dynamic compression is proven to be an efficient strategy to adjust the water energy state in the channels of V-RGO foams. The V-RGO foam with a compressive strain of 47.1% exhibits a water evaporation rate of 3.39 kg m−2 h−1 under 1-sun irradiation.

Polyoxometalate-modified reduced graphene oxide foam as a monolith reactor for efficient flow catalysis of epoxide ring-opening reactions

A POM@rGO monolith reactor was constructed using a facile and broad-spectrum hydrothermal approach and it effectively catalyzes epoxide ring-opening reactions with 99% conversion and over 90% selectivity, reaching a turnover number (TON) of around 28 044 after 38 h catalysis.

Reduced graphene oxide foam templated by nickel foam for organ-on-a-chip engineering of cardiac constructs.

Myocardial tissue engineering has attracted increasing awareness for heart failure, and researchers are committed to developing an appropriate biological material to reconstruct myocardial tissues. Here, we applied a simple and high-throughput method to fabricate a three-dimensional (3D) partially reduced graphene oxide (PRGO) foam chip, whose structure, properties and biocompatibility confirmed that it is a suitable material for myocardial tissue engineering. The PRGO foam was produced based on a reduction reaction that occurred at the interface between the graphene oxide (GO) solution and Ni foam; as the Ni foam scaffold was dissolved in an HCl solution, the PRGO foam was harvested. After the PRGO foam was freeze-dried, its elasticity property was evaluated, and primary cardiomyocytes obtained from 2-day-old SD rats were cultured in the 3D foam. The results demonstrated good cell adherence, spreading, activity, organization and beating function in the PRGO foam during the long-term culturing process, which proved that the PRGO foam obtained by this method had application potential for myocardial tissue engineering.

Polyaniline/reduced graphene oxide foams as metal-free cathodes for stable lithium–oxygen batteries

Lithium–oxygen batteries (LOBs) are considered as next-generation energy storage devices owing to their high-energy densities, yet they generally suffer from low actual specific capacity and poor cycle performance. To solve these issues, a range of electrocatalysts have been introduced in the cathode to reduce the overpotential during charge/discharge cycles and minimize unwanted side reactions. Due to relative high costs and limited reserves of noble metals and their compounds, it is important to develop low-cost and efficient metal-free electrocatalysts. Here, we report a simple method to prepare three-dimensional porous polyaniline (PANI)/reduced graphene oxide foams (PPGFs) with different PANI contents via a two-step self-assembly process. When these foams are tested as the cathode in LOBs, the device using the PPGF with 50% PANI content exhibits a discharge capacity up to 36 010 mAh g−1 and an excellent cycling stability (260 cycles at 1000 mAh g−1 and 500 cycles at 500 mAh g−1), provid ing new insights into the design of next-generation metal-free cathodes for LOBs.

Ultralight covalently interconnected silicon carbide aerofoam for high performance thermally conductive epoxy composites

With the development of highly integrated electronic devices, there are growing demands for high performance thermal management materials with high thermal conductivity and electrical insulation. Herein, we report thermal properties of epoxy-based SiC aerofoam composites. A novel three-dimensional structure of covalently interconnected porous SiC (3D-SiC) aerofoam is successfully fabricated using 3D reduced graphene oxide foam as a template, and it was embedded in epoxy resin and cured to prepare thermoconductive composites. The formation of covalent SiC linkage and presence of interconnected 3D-SiC aerofoam resulted in thermal conductivity of the epoxy composites as high as 10.26 W·m−1·K−1 at 6.52 vol% of SiC, which calculated as thermal conductivity enhancement efficiency per 1 vol% of filler loading equals to 859%. The 3D-SiC/epoxy composites showed an excellent heat dissipation performance compared to that of a commercial thermal pad. The 3D-SiC/epoxy composite is a highly prospective candidate as next generation thermal dissipating material for electronic devices.

Improving visible light photocatalytic inactivation of E. coli by inducing highly efficient radical pathways through peroxymonosulfate activation using 3-D, surface-enhanced, reduced graphene oxide (rGO) aerogels

In this work, we synthesized highly porous reduced graphene oxide foams, presenting augmented antibacterial activity in presence/absence of peroxymonosulfate (PMS). To date, this is the first investigation of photocatalytic PMS disinfection by 3D-rGO materials. The foams were prepared through hydrothermal (3DG-W) and solvothermal method (3DG-EG), and analyzed by SEM, PXRD, FTIR, Raman spectroscopy and BET. Hydrothermally synthesized aerogels (3DG-W) were better organized and had higher specific surface area. The higher ratio of ID/IG in 3DG-W showed the greater removal of oxygen functional groups, larger density of structural defects and a smaller average size of the sp2 domains. Although in the dark PMS activation by 3DG and the subsequent bacterial inactivation likely proceeds via a non-radical pathway, under visible light, the bacterial inactivation rate for 3DG-W was ~3 times higher than that of 3DG-EG and radical pathways are dominant. The generated germicidal reactive species were identified using appropriate scavengers and accordingly, an overview of the occurring photocatalytic and PMS activation pathways is discussed, while the mechanisms leading to bacterial inactivation are hereby detailed.

A nanocomposite prepared from hemin and reduced graphene oxide foam for voltammetric sensing of hydrogen peroxide.

A foam consisting of reduced graphene oxide was synthesized by a one-pot hydrothermal method. The foam was used to prepare a nanocomposite with hemin which is formed via π-interactions. The nanocomposite was incorporated via aNafion film and then placed on a glassy carbon electrode (GCE). The modified GCE displays outstanding catalytic activity towards H2O2. It is assumed that this is due to (a) the redox-active center [Fe(III/II)] of hemin, and (b) the crosslinked macroporous structure of the foam. Both improve the electron transfer rate and electrochemical signals. Under the optimum experimental conditions and a working voltage of typically -0.41mV (vs. SCE), the sensor has a 2.8nM H2O2 detection limit, and the analytically useful range extends from 5nM to 5mM with a sensitivity of 50.5μAμM-1cm-2. The modified GCE has high sensitivity and fast response. It was utilized to quantify H2O2 in spiked environmental water samples. Graphical abstractSchematic representation of the electrochemical sensor based on a nanocomposite prepared from hemin and reduced graphene oxide foam, which can be applied to the determination of hydrogen peroxide in serum.

Cold direct pen writing of reduced graphene oxide foams for ultrasensitive micro-contact force probing

Pressure sensor has attracted great attention due to its wide applications in electronic skin, health monitor, and wearable devices. However, there is still an urgent challenge in sensing the weak force, especially in the micro-contact cases. Herein, a novel cold direct pen writing method has been developed for fabricating reduced graphene oxide microfoam (rGOMF) as a pressure sensing element. The as-fabricated rGOMF-based pressure sensor exhibits ultrahigh sensitivities of 0.19, 0.82, and 1.43 KPa−1 in the pressure ranges of 0–10, 10–25 and 25–40 Pa with a micro-contact area of 0.594 mm2, respectively, which satisfies the ultrasensitive probing of micro-contact force. Meanwhile, it shows a high stability over 1000 cycles of pressure testing with a fast response (100 ms) and high reversibility. Not limited to rGO, this method is also suitable for other two-dimensional nanomaterials. Thus, this approach is anticipated to be applied to a wide range of microfoam-based devices with advanced functions such as multifunctional sensing, water separation, energy conversion and storage.

Reduced graphene oxide foam supported CoNi nanosheets as an efficient anode catalyst for direct borohydride hydrogen peroxide fuel cell

Abstract Catalytic performance and NaBH4 utilization are two crucial concerns in the electrooxidation of NaBH4. To improve the inherent properties of regular performance and low fuel utilization of the transition metal Co and Ni, an efficient anode catalyst of ultra-thin CoNi nanosheets modified novel 3D self-supported reduced graphene oxide foam is prepared in this work. The alkaline condition borohydride oxidation reaction on the prepared catalyst is investigated in a typical three-electrode system. The prepared catalyst shows a high performance due to the large electrochemical active surface area, low activation energy (8.29 kJ·mol−1), and the small electrochemical impedance it embraced. Linear scan voltammetry recorded in a low concentration of NaBH4 suggests that borohydride oxidation is a first-order reaction on the prepared catalyst. Based on the unique structure of the catalyst, which is useful to capture the hydrogen and perform further oxidation of hydrogen, higher utilization of NaBH4 achieved on the catalyst. Besides, the prepared anode catalyst applied to a direct borohydride-hydrogen peroxide fuel cell (DBHPFC). The results of polarization curve and power density curves, as well as stability research, all indicate that the as-prepared catalyst is a highly efficient anode material for application in DBHPFC.