Three-dimensional Graphene Architectures Research Articles

Boosting Effect of Nitrogen and Phosphorous Co-doped Three-Dimensional Graphene Architecture: Highly Selective Electrocatalysts for Carbon Dioxide Electroreduction to Formate

Boosting Effect of Nitrogen and Phosphorous Co-doped Three-Dimensional Graphene Architecture: Highly Selective Electrocatalysts for Carbon Dioxide Electroreduction to Formate

Synthesis of three-dimensional graphene architectures from chicken feather and its unusual dimensional crossover in electronic conductivity

Three-dimensional graphene architectures were synthesized from a new source, chicken feather, a bio-waste. Here ferric chloride (FeCl3) was used as a self-originator template, with a high C/O ratio (21:1). The introduction of Fe3＋ ion into the activated frame of carbon generated graphene nanostructure. X-ray photoelectron spectroscopy was used to analyse the defects in the prepared graphene. The obtained structures were found to be unique nanoplatelets and three-dimensional pyramid-like structure. Its DC conductivity has been tested within the temperature range of 20 to 300K and their temperature-dependent conduction mechanism was established. At ∼100 K and ∼50 K, a 3D–2D and Mott–ES type cross-over were observed respectively, with varied hopping length. The conductivity was found to be decreased with lowering temperature which was similarly observed in metals.

Electrocrystallization process of manganese oxide in graphene hydrogel

Electrodepositing manganese oxide in a three-dimensional graphene architecture has barely been explored, and therefore an exploratory but systematic investigation was conducted. A series of manganese oxide/graphene hydrogel electrodes were prepared by galvanostatic technique. The effects of electrodeposition condition, including current density, deposition time, Mn2+concentration and bath temperature, on the morphology and capacitive performance of the deposits were investigated. Nucleation and growth processes of the deposited manganese oxide were then deduced. An optimal capacitance of 452.5 F g−1 was got. This study could provide insight into the crystallization mechanism for electrochemical preparation of MnOx/graphene electrode for advanced energy storage/conversion devices.

Scalable synthesis of gyroid-inspired freestanding three-dimensional graphene architectures

Three-dimensional porous architectures of graphene are desirable for energy storage, catalysis, and sensing applications. Yet it has proven challenging to devise scalable methods capable of producing co-continuous architectures and well-defined, uniform pore and ligament sizes at length scales relevant to applications. This is further complicated by processing temperatures necessary for high quality graphene. Here, bicontinuous interfacially jammed emulsion gels (bijels) are formed and processed into sacrificial porous Ni scaffolds for chemical vapor deposition to produce freestanding three-dimensional turbostratic graphene (bi-3DG) monoliths with high specific surface area. Scanning electron microscopy (SEM) images show that the bi-3DG monoliths inherit the unique microstructural characteristics of their bijel parents. Processing of the Ni templates strongly influences the resultant bi-3DG structures, enabling the formation of stacked graphene flakes or fewer-layer continuous films. Despite the multilayer nature, Raman spectra exhibit no discernable defect peak and large relative intensity for the Raman 2D mode, which is a characteristic of turbostratic graphene. Moiré patterns, observed in scanning tunneling microscopy images, further confirm the presence of turbostratic graphene. Nanoindentation of macroscopic pillars reveals a Young's modulus of 30 MPa, one of the highest recorded for sp2 carbon in a porous structure. Overall, this work highlights the utility of a scalable self-assembly method towards porous high quality graphene constructs with tunable, uniform, and co-continuous microstructure.

Adsorption behavior of thorium on N,N,N′,N′-tetraoctyldiglycolamide (TODGA) impregnated graphene aerogel

As a kind of three-dimensional graphene architecture material with superhydrophobic, low density, high specific surface area and porosity, graphene aerogel (GA) can be used to immobilize extractant to constitute the solvent impregnated adsorbent. In this paper, the N,N,N′,N′-tetraoctyldiglycolamide impregnated graphene aerogel ( GA-TODGA) was prepared to remove the thorium from aqueous solution. It is found that the adsorption of thorium on GA-TODGA is strongly dependent on the concentration of TODGA in GA and HNO3 in aqueous solution. Compared with other solvent impregnated adsorbents, the adsorption capacity of GA-TODGA is much higher due to the high immobilization capacity of GA for TODGA. Furthermore, the GA-TODGA also possesses excellent stability and reusability, ensuring the application potential of using GA-TODGA in large scale.

Synthesis of three-dimensional graphene architectures by using an environmental-friendly surfactant as a reducing agent

Polyvinylpyrrolidone (PVP) modified reduced graphene aerogel (PVP-GA) was prepared through hydrothermal reduction and chemical reduction of graphene oxide (GO) in the presence of PVP. The structure of PVP-GA was characterized using XRD, FTIR, SEM, TEM and BET specific surface area. The results showed that GO was reduced effectively in the presence of PVP and the PVP molecules were absorbed onto the basal plane of reduced graphene oxide (rGO) through non-covalent interactions. The preparation process was carried out in aqueous media at 120 °C for 10 h without using any toxic reducing agent, thereby making it a facile, environmental-friendly and economical approach for the synthesis of a three-dimensional (3D) interconnected graphene macrostructure. The as-prepared monolithic 3D graphene exhibits a loose and high porous structure, which may find potential applications for adsorbent, shock absorber, catalyst carrier and hydrogen storage materials. In addition, it confirmed that simultaneous hydrothermal reduction and chemical reduction routes would be of value for preparing 3D nonporous graphene-based materials via the use of cheap and environmentally-friendly PVP as a reducing agent.

Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template

Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports.

Ultrahigh Performance of Novel Capacitive Deionization Electrodes based on A Three-Dimensional Graphene Architecture with Nanopores.

In order to achieve optimal desalination during capacitive deionization (CDI), CDI electrodes should possess high electrical conductivity, large surface area, good wettability to water, narrow pore size distribution and efficient pathways for ion and electron transportation. In this work, we fabricated a novel CDI electrode based on a three-dimensional graphene (3DG) architecture by constructing interconnected graphene sheets with in-plane nanopores (NP-3DG). As compared to 3DG, NP-3DG features a larger specific surface area of 445 m2 g−1 and therefore the higher specific capacitance. The ultrahigh electrosorptive capacity of NP-3DG predicted from Langmuir isotherm is 17.1 mg g−1 at a cell potential of 1.6 V. This can be attributed to the interconnected macropores within the graphene networks and nanopores on graphene sheets. Both of macropores and nanopores are favorable for enhancing CDI peroformance by buffering ions to reduce the diffusion distances from the external electrolyte to the interior surfaces and enlarging the surface area.

Silica-assistant synthesis of three-dimensional graphene architecture and its application as anode material for lithium ion batteries

A new approach for scalable synthesis of three-dimensional graphene (3d-G) with the assistant of silica is reported. Silica is generated on the surface of graphene oxide through a facile solution reaction. Graphene coated by silica is reduced through thermal reduction. 3d-G can be obtained after the subsequent etching process. The structures and morphologies of samples are investigated. It is demonstrated that the agglomeration of individual graphene sheets during the thermal reduction is effectively avoided under the perfect protection of silica. The electrochemical studies of the material show a significant enhancement in the specific capacity and rate capability of the lithium ion battery over commercially available graphite electrodes due to its unique 3D cross-linked graphene architecture. This method enables us to develop a facile and effective approach to scalable preparation of graphene.

Three-dimensional strutted graphene grown by substrate-free sugar blowing for high-power-density supercapacitors.

Three-dimensional graphene architectures in the macroworld can in principle maintain all the extraordinary nanoscale properties of individual graphene flakes. However, current 3D graphene products suffer from poor electrical conductivity, low surface area and insufficient mechanical strength/elasticity; the interconnected self-supported reproducible 3D graphenes remain unavailable. Here we report a sugar-blowing approach based on a polymeric predecessor to synthesize a 3D graphene bubble network. The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts. Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties. The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work.

Three-dimensional graphene architectures

Graphene has been widely explored for applications in electronics, sensors, actuators, catalysis and bio- or energy related systems. For these purposes, graphene materials usually have to be fabricated or assembled into desired micro-/nano-architectures for tuning and/or controlling their electrical, optical, mechanical, chemical or electrochemical properties. In this feature article, we review recent achievements in the studies of three-dimensional (3D) graphene architectures. The methodology for preparing these 3D graphene micro-/nano-architectures and their potential applications have been summarized.