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.

Energy from Garbage: Recycling Heavy Metal‐Containing Wastewater Adsorbents for Energy Storage

The global challenge of heavy metal contamination in wastewater necessitates efficient adsorbents, which, while they can effectively remove contaminants, ultimately become toxic waste themselves. Recycling wastewater adsorbents loaded with heavy metals is an alternative to their disposal as toxic garbage. This study presents a genuine recycling strategy for heavy metal‐loaded adsorbents, repurposing them as electrode materials for energy storage applications, that is, electrochemical capacitors, and thus synergistically tackles water purification and waste valorization. Graphene oxide was prepared via the improved Hummers’ method, and subsequently, a reduced graphene oxide (rGO) foam was hydrothermally synthesized. This rGO‐based foam adsorbed >95% of the Hg2+ ions in a 100 ppm solution, using a dose = 500 mg L−1, and up to 240 mg of Hg2+ ions/g on average at 25 °C, which are among the highest values reported so far. Electrochemically, the Hg‐loaded rGO (rGO/Hgads) exhibits mercury redox activity and a 15% increase in capacity as compared to pristine rGO in an aqueous cell. Overall, this demonstrates the potential of reprocessed wastewater adsorbents as efficient and sustainable electrodes for high‐power energy storage (time constant τ = 11 s), offering a compelling solution to add more value and extend the life cycle of waste materials.

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.

Electricity Generation by a Phototrophic Bacterium in a Glucose−Fed Double Chambered Microbial Fuel Cell Using a Fabricated 3D Anode Electrode

Study’s Novelty/Excerpt This study presents an approach to enhancing microbial fuel cell (MFC) performance by employing phototrophic bacteria (PTB) and sustainable electrode materials, specifically a 3D anode electrode fabricated from reduced graphene oxide (rGO) and nickel (Ni) foam. By integrating morphological, biochemical, and molecular techniques to identify the electrochemically active PTB, the research achieved a significant eight-fold increase in power density using rGO-Ni electrodes compared to conventional Ni electrodes. This work underscores the potential of utilizing sustainable materials and PTB to improve MFC efficiency and economic viability, offering a promising direction for sustainable bioelectricity generation. Full Abstract Over the past years, despite intensified research on microbial fuel cells (MFC), low power densities were recorded, reducing the productivity and economic viability of the process. This necessitated testing various MFC configurations, fabricating various electrodes, and evaluating various substrate types and species of electrogenic microorganisms to improve MFC performance. Despite the dual advantage of phototrophic bacteria (PTB), metabolizing organic waste substances and generating electricity, less research was conducted on the bacterium. Although a significant amount of energy is generated using unsustainable (fossil-based) materials in electrode fabrication, this study focuses on using sustainable materials like carbon cloth and graphite to fabricate a 3D anode electrode to exploit the maximum energy generated by PTB. The PTB used in this study was identified through morphological characteristics and biochemical tests (catalase and oxidase) and confirmed using a molecular technique: 16S rRNA sequencing. Preliminary results indicated that the PTB was gram-negative, spherical in shape, non−motile, and facultatively anaerobic bacterium. Analysis of the 16S rRNA partial sequence was conducted in GenBank databases. 100 significant sequences with the lowest and highest similarities of 84.10% and 98.76% were recorded, respectively. Of these, 13 strains had the highest similarities of >90%, all belonging to the genus Dysgonomonas, with D. oryzarvi Dy73 (98.76%) as the closest. Reduced graphene oxide (rGO) used as the anode was prepared using Hummer’s method by depositing the rGO on nickel (Ni) foam which changed the colour of Ni from grey to black after depositing and annealing. In addition to the SEM images, which showed a continuous multi−layered 3D scaffold on the Ni, the cyclic voltammetry (CV) analyses indicated an increase in the electrochemical activities of the rGO−Ni electrode compared to Ni. The CV also confirmed the bacterium to be electrochemically active. The 100 mL glucose−fed two−chamber MFC were separately run with the Ni and rGO–Ni as anode electrodes in a batch mode for 11 days, while carbon cloth was used as the cathode for both runs. An approximate 0.58 W/m2 power density was recorded for Ni, but eight−fold of Ni’s, 4.9 W/m2was generated by rGO−Ni. The study demonstrated that using fabricated 3D rGO–Ni as anode electrode can increase the microbial adhesion and power density of bacterium in MFC, thereby providing a more applicable and sustainable alternative to bioelectricity generation.

Multistage microcellular waterborne polyurethane composite with optionally low-reflection behavior for ultra-efficient electromagnetic interference shielding

Electromagnetic interference (EMI) shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components, precision instruments, and fifth-generation communication equipment. In this study, multistage microcellular waterborne polyurethane (WPU) composites were constructed via gradient induction, layer-by-layer casting, and supercritical carbon dioxide foaming. The gradient-structured WPU/iron-cobalt loaded reduced graphene oxide (FeCo@rGO) foam serves as an impedance-matched absorption layer, while the highly conductive WPU/silver loaded glass microspheres (Ag@GM) layer is employed as a reflection layer. Thanks to the incorporation of an asymmetric structure, as well as the introduction of gradient and porous configurations, the composite foam demonstrates excellent conductivity, outstanding EMI SE (74.9 dB), and minimal reflection characteristics (35.28 %) in 8.2–12.4 GHz, implying that more than 99.99999 % of electromagnetic (EM) waves were blocked and only 35.28 % were reflected to the external environment. Interestingly, the reflectivity of the composite foam is reduced to 0.41 % at 10.88 GHz due to the resonance for incident and reflected EM waves. Beyond that, the composite foam is characterized by low density (0.47 g/cm3) and great stability of EMI shielding properties. This work offers a viable approach for crafting lightweight, highly shielding, and minimally reflective EMI shielding composites.

One‐step preparation of binder‐free nickel‐containing graphene foam electrode for supercapacitors

AbstractIn this study, a nickel hydroxide (Ni(OH)2)‐modified reduced graphene oxide (rGO) foam electrode for supercapacitor application is presented. The electrode was prepared without using a binder through a one‐step process with three different ratios (NirGO1, NirGO2, and NirGo3). To compare the supercapacitor performance of the obtained graphene foam electrodes, rGO and rGO:carbon black (CB) standard electrodes with PVDF‐HFP binder were also prepared. All electrodes were then characterized structurally (XPS, EDS, RAMAN, XRD, and FT‐IR) and morphologically (SEM). Structural characterizations demonstrated that the Ni‐containing electrodes were in α‐Ni(OH)2:rGO structure. In addition, NirGO3 exhibited a specific capacitance of 800 F g−1 which is relatively the highest performance between the foam electrodes, while rGO:CB presented a specific capacitance of 900 F g−1. The results demonstrated that with the method proposed for electrode development, it was possible to obtain comparable results with the standard electrode rGO:CB.

Well-designed lamellar reduced graphene oxide-based foam for high-performance solar-driven water purification

Although solar steam generation is promising for seawater desalination, it is less effective in purifying wastewater with both salt/heavy metal ions and organic contaminants. It is thus imperative to develop multifunctional integrated solar-driven water purification systems with high solar-thermal evaporation and photocatalytic degradation efficiencies. Herein, a lamellar reduced graphene oxide (L-RGO) foam with the vertical lamellar structure is fabricated by bidirectional-freezing, lyophilization, and slight chemical reduction for water purification. The unique vertical lamellar structure not only accelerates upward transport of water for facilitating water evaporation but also endows the L-RGO foam with superb high elasticity for tuning the interlayer distance and varying interactions between the oxygen-containing groups and water molecules to adjust water energy state. As a result, the L-RGO foam achieves a superb water evaporation rate of 2.40 kg m−2 h−1 along with an energy efficiency of 95.3 % under the compressive strain of 44.7 % under 1-sun irradiation. Equally importantly, the decoration of L-RGO foam with polypyrrole is capable of efficiently degrading organic pollutants while retaining high solar steam generation performances, exhibiting great potential in the comprehensive treatment of various water sources for relieving freshwater crisis.

A metallated graphene oxide foam with a carbon nanotube shell for an enhanced capacitance device

Revealing the role of multimetal decoration in an M-rGO foam architecture for capacitance enhancement and a corresponding LED device.

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

Double Carbon Networks Reinforce the Thermal Storage and Thermal Transfer Properties of 1-Octadecanol Phase Change Materials.

Using thermal storage materials with excellent thermal properties in the energy utilization system enables efficient use of renewable energy sources. Organic phase change materials (PCMs) have the advantages of high heat storage density, no corrosion, and low cost, but low thermal conductivity and insufficient heat transfer capacity have always been the bottlenecks in their application. In this paper, melamine foam@ reduction graphene oxide (MF@rGO) and carbon foam@ reduction graphene oxide (CF@rGO) composite foams with double carbon networks were prepared by self-assembly method and further employed in 1-octadecinal (OD) PCMs. The microstructure, chemical composition, phase change behavior, thermal conductivity, and photothermal conversion performance of MF@rGO/OD and CF@rGO/OD were studied in detail using SEM, FTIR, Raman DSC, and LFA. The melting and solidification enthalpies of CF@rGO/OD composite PCMs were 208.3 J/g and 191.4 J/g, respectively, its thermal conductivity increased to 1.54 W/m·K, which is 6.42 times that of pure OD. The porous structure and high thermal conductivity of the double carbon network substantially enhance the efficiency of energy storage and release in composite PCMs. CF@rGO/OD composite PCMs have excellent heat storage performance and heat transfer capacity, and a wide range of application prospects in the fields of low-temperature solar heat storage, precision instrument temperature control, and intelligent buildings.

Hydrogel with dual networks making reduced GO connection and orientation for a bi-directional thermal conductive film

With the rapid development of modern electronic devices, materials having high thermal conductivities (TCs) both in in-plane and through-plane directions are specially needed for thermal management. Whereas, the construction of efficient thermal-conductive pathways in bi-directions is still a challenge. Herein, a facile gel-drying approach is developed, achieving the formation of bi-directional pathways with the assistance of a dual-network structure. During the process, cellulose nanocrystal (CNC) with a high intrinsic TC was mixed with gellable cellulose (CNF) to form CNF/2CNC dispersion which was then used as a matrix. Reduced graphene oxide (RGO) foam with a network structure was used as a filler. The RGO network was tightly wrapped by the formed CNF/2CNC cross-linking network, resulting in a hydrogel with a dual-network structure. After drying, the resultant RGO-foam-CNF/2CNC film not only has a long-range orientation path in the horizontal direction, but also maintained a connected path in the vertical direction. The resultant film with 18.5 wt% RGO exhibited high TCs of 14.06 W·m−1·K−1 and 2.47 W·m−1·K−1 simultaneous for in-plane and through-plane directions, which is 21.6 times and 9.88 times higher than those of a typical CNF film, respectively. This strategy offers a new avenue for the designs of soft, cuttable, environmentally friendly polymer composite films with high TCs in bi-directions.

Exploring the capture and desorption of CO2 on graphene oxide foams supported by computational calculations

In the last decade, the highest levels of greenhouse gases (GHG) in the atmosphere have been recorded, with carbon dioxide (CO2) being one of the GHGs that most concerns mankind due to the rate at which it is generated on the planet. Given its long time of permanence in the atmosphere (between 100 to 150 years); this has deployed research in the scientific field focused on the absorption and desorption of CO2 in the atmosphere. This work presents the study of CO2 adsorption employing materials based on graphene oxide (GO), such as GO foams with different oxidation percentages (3.00%, 5.25%, and 9.00%) in their structure, obtained via an environmentally friendly method. The characterization of CO2 adsorption was carried out in a closed system, within which were placed the GO foams and other CO2 adsorbent materials (zeolite and silica gel). Through a controlled chemical reaction, production of CO2 was conducted to obtain CO2 concentration curves inside the system and calculate from these the efficiency, obtained between 86.28 and 92.20%, yield between 60.10 and 99.50%, and effectiveness of CO2 adsorption of the materials under study. The results obtained suggest that GO foams are a promising material for carbon capture and the future development of a new clean technology, given their highest CO2 adsorption efficiency and yield.

Superior cycling performance of NiC2O4/rGO/NF composites for hybrid supercapacitors

In the energy storage systems, hybrid supercapacitor has a promising in the future, making up performance disparity between traditional capacitors and lithium ion batteries. In this work, a novel Nickle oxalate (NiC2O4) based composite by inducing reduced graphene oxide (rGO) and nickel foam (NF) has been constructed for battery-type supercapacitors, which exhibits significantly improved electrochemical properties. The NiC2O4/rGO/NF (NGN) composite possesses a superior capacity of 305 mAh g‐1 and better cycling stability which the specific capacitance of sample retained 91.32 % after 30,000 cycles. The NGN hybrid supercapacitors (NGN-HSC) assembled by NGN as the anode and the activated carbon (AC) as the cathode exhibits high energy density of 54.75 Wh kg−1 at 1800.05 W kg−1 power density, also outstanding cycling stability (72.07 % capacity is retained after 10,000 times). The work supplies a new approach to design electrodes with ultrahigh cycling stability.

Rapid Yet Efficient Reduction of Graphene Oxide Triggered by Semi-Molten Metals.

Reduced graphene oxide (rGO) has garnered extensive attention as electrodes, sensors, and membranes, necessitating the efficient reduction of graphene oxide (GO) for optimal performance. In this work, a swift reduction of GO that involves bringing GO foam in contact with semi-molten metals like tin (Sn) and lithium (Li) is presented. These findings reveal that the electrical resistance of GO foam is significantly diminished by its interaction with these metals, even in dry air. Taking inspiration from this technique, Sn foil is employed to encase the GO foam, followed by a calcination in 15 vol% H2 /Ar environment at 235°C to fabricate the rGO, which demonstrates a remarkably lower electrical resistivity of 0.42 Ω cm when compared to the chemically reduced GO via hydrazine hydrate (650 Ω cm). The reduction mechanism entails the migration of Sn on GO and its subsequent reaction with oxygen functional groups. SnO/Sn(OH)2 formed from the reaction can be subsequently reversed through reduction by H2 to Sn. Utilizing this rGO as the host material for a sulfur cathode, a lithium-sulfur battery is constructed that displays a specific capacity of 1146 mAh g-1 and maintains a capacity retention of 68.4% after 300 cycles at a rate of 0.2 C.

Persulfate enhanced removal of bisphenol A by copper oxide/reduced graphene oxide foam: Influencing factors, mechanism and degradation pathway

The CuO/reduced graphene oxide foam (CuO/RGF) with excellent recyclability was prepared via hydrothermal method followed by freeze drying treatment for bisphenol A (BPA) removal via activating peroxydisulfate (PDS). SEM, XRD, XPS, FT-IR, BET, and TG techniques were used to investigate the structure and property of CuO/RGF. The effect of degradation conditions (pH, PDS amount, Cl−, HCO3−, HA and FA) on BPA removal by CuO/RGF were investigated. The result presented that CuO nanosheet was inserted into the RGF carrier with three-dimensional structure. The degradation rate constant of BPA over CuO/RGF (0.00917 min−1) was 1.24 and 6.46 times higher than those of BPA over CuO (0.00714 min−1) and RGF (0.00142 min−1). More importantly, the pore structure of RGF can successfully limit the release of Cu (II) compared to pure CuO. According to quenching test as well as electron spin resonance (EPR) spectra, BPA degradation was triggered by 1O2, •OH and SO4•-, which was the combination of nonradical (1O2) and radical activation of PDS (•OH and SO4•-). The possible degradation route of BPA was proposed based on intermediates obtained by combining solid phase extraction pretreatment technique with high performance liquid-mass spectrometry. After assessing the viability of MCF-7 cells, we can see that the estrogenic activities of treated solution reduced without producing stronger endocrine disruptors.

Ferrihydrite − Graphene oxide foams as an efficient adsorbent for Arsenic(III) removal from an aqueous solution

We report the synthesis of a new range of ferrihydrite-graphene oxide (FH-GO) foams using chitosan as cross linker, with varying iron content (5 wt%, 10 wt%, and 20 wt% of FH) as highly efficient adsorbents for the removal of arsenic (III) (As(III)) in an aqueous solution. The sonochemical methods were adopted to synthesize various FH-GO foams and were further characterized by XRD, SEM, TEM, FTIR, Raman, and XPS techniques. The synthesized materials were used for the removal of As(III) in both batch and fixed bed absorbent column methods. The adsorption isotherm results showed that the 10 wt% of FH-GO foams demonstrated a superior adsorbent for the As(III) with high adsorption capacities than that of the other two FH-GO foams (5 wt% and 20 wt% of FH). Moreover, 10 wt% of FH-GO foams was also demonstrated to be nearly a complete (>98.4%) removal of As(III) ions at neutral pH 7. The adsorption isotherm fitted very well with the Langmuir model with the highest accuracy data for all the synthesized adsorbent materials. In addition, the fixed bed absorbent column method was also adopted for the removal of As(III) ions in the water sample, which showed >99.2% of removal efficiency. The outstanding adsorption capabilities, along with their easy and low-cost synthesis, make these kinds of adsorbents extremely capable for commercial applications in wastewater treatment and drinking water purification.

Preparation of hydrophobic and fire-retarding poly(lactic acid)/graphene oxide foams for oil/organic solvents absorption

Petroleum leakage, oil spill and toxic organic solvent emissions have become a global water contamination issue. To solve this problem, it is a promising solution to develop a simple and green strategy to prepare environmentally friendly and high absorption capacity absorbents from biodegradable polymers. Herein, in this work, PLA was used as the matrix to prepare the foam absorbent. Firstly, the flame retardant methoxy-phosphonitrilic trimer (HEPCP, FR) was synthesized. Then PLA composite foams were produced by melting PLA with FR, and mixing with GO through a freezing-dry method. The results showed that FR-PLA/5GO foam self-extinguished immediately when removing the ignition source, due to the fact that the incorporation of GO further improve the fire retardancy of FR-PLA foam. The porosity and the water contact angle of FR-PLA/5GO were gradually increased up to 94.0% and 127.4°, showing a lightweight, highly hydrophobic and homogeneous pore structure. Then the FR-PLA/5GO foam was used as the oil/organic solvent absorbent, which reached the saturated adsorption capacity within 10 s due to the high hydrophobicity and porosity. Meanwhile, the absorbent showed good recyclability, and the FR-PLA/5GO foam still maintained > 75.0% of its original capacity after 10 cycles of the evaporation−adsorption procedure. This work provides a method for developing a biodegradable absorbent for the oil/organic contaminant.

The Self-Supporting NiMn-LDHs/rGO/NF Composite Electrode Showing Much Enhanced Electrocatalytic Performance for Oxygen Evolution Reaction

The poor conductivity and instability of layered dihydroxides (LDHs) limit their widespread application in oxygen evolution reaction (OER). In this study, the composite electrode of NiMn-LDHs, reduced graphene oxide (rGO) and nickel foam (NF), i.e., NiMn-LDHs/rGO/NF, was prepared by a hydrothermal method. When subjected to oxygen evolution reaction (OER) catalytic performance in a solution of 1 M KOH, the NiMn-LDHs/rGO/NF composite catalyst exhibited an overpotential of only 140 mV at a current density of 10 mA cm−2 and a Tafel slope of 49 mV dec−1, which is not only better than the comparing RuO2/NF catalyst, but also better than most of the Mn-based and the Ni–Fe-containing bimetallic OER catalysts reported in the literature. The excellent electrocatalytic performance is ascribed to the efficient integration of ultrathin NiMn-LDH sheets, thin-layered rGO and NF, contributing significantly to the decrease in charge transfer resistance and the increase in electrochemically active surface area. Moreover, NF plays a role of current collector and a role of rigid support for the NiMn-LDHs/rGO composite, contributing extra conductivity and stability to the NiMn-LDHs/rGO/NF composite electrode.

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.