Porous Graphene Materials Research Articles

The nanostructure preservation of 3D porous graphene: New insights into the graphitization and surface chemistry of non-stacked double-layer templated graphene after high-temperature treatment

Three-dimensional (3D) porous graphene materials with few layer nature and non-stacked structural feature afford significant advantages in high electrical conductivity, large surface area, and interconnected porous nanostructures. However, the structure evolution of porous graphene under high temperature is poorly understood. In this contribution, 3D double-layer templated graphene (DTG) composed of two non-stacked graphene layers with interlayer spacing around 15 nm and separated by a large quantity of protuberances, was employed as a special case to track the structure evolution of 3D porous graphene at high temperature. Compared with thermally reduced graphene oxide with easy graphitized nature, the unique non-stacked DTG structure was well preserved after a high-temperature annealing at 1600 °C. With limited self-healing of defects for graphene layers, and with preservation of mesosized protuberances that prevent graphene layers stacking during annealing, DTG is regarded as ‘hard carbon’ (‘non-graphitizable carbon’). The electron microscopy, Raman spectroscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, gravimetric elemental analysis, nitrogen/water physisorption, and probe reactions of electrochemical oxygen reduction reaction were employed to reveal the graphitization degree and surface chemistry of non-stacked DTG after high-temperature treatment.

Fe/Fe3C decorated 3-D porous nitrogen-doped graphene as a cathode material for rechargeable Li–O2 batteries

Fe/Fe3C decorated 3-D porous N-doped graphene (F-PNG) is designed and synthesized via a one-step carbonization route. During the process, MIL-100(Fe), a kind of metal organic frameworks (MOFs) plays a structure-directing role. It is found that F-PNG with 3-D porous structure is constituted by N-doped graphene and extremely small Fe/Fe3C particles uniformly distribute on the surface of graphene. This rationally designed F-PNG possesses excellent oxygen reduction reaction and oxygen evolution reaction bifunctional electrocatalytic activity. While the material is explored as a cathode of Li–O2 batteries, it exhibits excellent electrochemical performances, delivering a discharge voltage platform of ∼2.91V and a charge voltage platform of ∼3.52V at 0.1mAcm−2, showing a good cycle performance and having a discharge capacity of ∼7150mAhg−1carbon+catalyst at 0.1mAcm−2. The excellent performance of the F-PNG electrode is attributed to the good catalytic activity of uniformly distributed extremely small Fe/Fe3C particles and N-doped graphene, the high electronic conductivity, and the 3-D porous structure. These results indicate that F-PNG can be an excellent cathode material for Li–O2 batteries, and MOFs-assisted synthesis method would be a promising new strategy for the synthesis of 3-D porous graphene materials.

Convenient and controllable preparation of a novel uniformly nitrogen doped porous graphene/Pt nanoflower material and its highly-efficient electrochemical biosensing.

By employing dopamine as a nitrogen source and reducing agent, the block copolymer P123 as a pore forming agent, and graphene oxide as a carbon precursor, we present, for the first time, a convenient and controllable approach to the preparation of a novel uniformly nitrogen doped porous graphene (N-PGR) material. Using the prepared N-PGR as the supporting material, a novel nitrogen doped porous graphene/Pt nanoflower material (Pt/N-PGR) was obtained by a green and simple method. The characterization results of scanning electron microscopy (SEM), element mapping, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that Pt nanoflowers are uniformly dispersed on nitrogen doped porous graphene. Electrochemical measurements show that Pt/N-PGR-900/GCE exhibits improved electrocatalytic activity towards H2O2 reduction and glucose oxidation. Linear responses are found for H2O2 and glucose in the range of 0.5-40 326 μM and 0.5-133.5 mM with the detection limit (S/N = 3) of 0.2 μM and 0.05 mM, respectively. In addition, Pt/N-PGR-900/GCE exhibits high sensitivity and good anti-interference ability. The superior catalytic activity and selectivity make Pt/N-PGR a promising nanomaterial for application in electrochemical biosensing studies.

CaO‐Templated Growth of Hierarchical Porous Graphene for High‐Power Lithium–Sulfur Battery Applications

Structural hierarchy plays an important role in the biological world and for functional materials with optimized properties and high efficiency. As promising candidates for various energy storage systems, hierarchical porous carbon/graphene materials have been intensively investigated over the past decades, while the favorable regulation of their hierarchical porosity remains a challenge. Herein, porous CaO serves as both the catalyst and template for a versatile chemical vapor deposition (CVD) of hierarchical porous graphene. The gas atmosphere during CVD and nanostructure of adopted catalysts impact significantly on the graphitization degree and hierarchical porosity of resultant materials. The as‐fabricated material exhibits abundant microsized in‐plane vacancies, mesosized wrinkled pores, and macrosized strutted cavities, thereby contributing to a strong surface entrapment, short ion diffusion pathways, rapid mass transport, low interfacial resistance, and robust framework. It is demonstrated as a favorable scaffold for lithium–sulfur battery cathodes with superior rate capability, high coulombic efficiency, and excellent stability. A high capacity of 357 (656 ) is manifested at the current rate of 5.0 C, exhibiting a 74% retention of the capacity at 0.1 C. The first use of CaO‐templated CVD growth of graphene reported herein opens up new perspectives on the effective fabrication of hierarchical porous graphene materials on metal oxide catalysts with promising applications in energy storage, catalysis, adsorption, drug delivery, and so on.

“Pottery” of Porous Graphene Materials

Porous graphene “pottery” is prepared via a process imitating traditional pottery preparation technology. This method is simple, cheap, scalable, and eco-friendly. The “pottery” of porous graphene materials has an ultrahigh mass density, a large SSA, good conductivity, and unique anisotropic electrical and mechanical properties, promising for the practical applications in supercapacitors. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A highly nitrogen-doped porous graphene – an anode material for lithium ion batteries

Highly porous nitrogen-doped graphene material obtained via melamine–formaldehyde resin as a cross-linker demonstrates excellent electrochemical properties in Li-ion batteries.

Micelle-template synthesis of nitrogen-doped mesoporous graphene as an efficient metal-free electrocatalyst for hydrogen production.

Synthesis of mesoporous graphene materials by soft-template methods remains a great challenge, owing to the poor self-assembly capability of precursors and the severe agglomeration of graphene nanosheets. Herein, a micelle-template strategy to prepare porous graphene materials with controllable mesopores, high specific surface areas and large pore volumes is reported. By fine-tuning the synthesis parameters, the pore sizes of mesoporous graphene can be rationally controlled. Nitrogen heteroatom doping is found to remarkably render electrocatalytic properties towards hydrogen evolution reactions as a highly efficient metal-free catalyst. The synthesis strategy and the demonstration of highly efficient catalytic effect provide benchmarks for preparing well-defined mesoporous graphene materials for energy production applications.

ChemInform Abstract: Recent Advances in Porous Graphene Materials for Supercapacitor Applications

AbstractReview: 224 refs.

Fabrication of 3-Dimensional Porous Graphene Materials for Lithium Ion Batteries

A 3-dimensional porous graphene material (PGM) has been synthesized using a simple two-step process: hydrothermal reaction and calcination. Hydrothermal reaction of graphene oxide (GO) in the presence of resorcinol and glutaraldehyde leads to covalent grafting of partially reduced GO with glutaraldehyde and the deposition of phenolic resin. Subsequent calcination of the composite consisting of phenolic resin deposited on partially reduced GO in the presence of KOH produces structurally stable, highly porous graphene material with a specific surface area of ∼1,066±2m2g−1. When used as an active electrode material in a lithium battery, the PGM exhibits an initial discharge capacity of ∼1,538 mAh g−1, which is significantly higher than those of graphite and other carbonaceous materials reported previously. More importantly, when cycled at higher discharge/charge rates, the PGM-based electrodes still deliver large capacities and excellent cycling performance, demonstrating great potential for high-performance lithium-ion batteries. The attractive electrochemical performance of the PGM is attributed to its unique porous structure with large specific surface area and the presence of more disordered carbon atoms produced by the KOH activation.

Recent advances in porous graphene materials for supercapacitor applications

Driven by the environmental problems and energy crisis, the development of clean and renewable energy materials as well as their devices is urgently demanded. Supercapacitors, also called electrochemical capacitors, which store energy using either ion adsorption or fast surface redox reactions, are supposed to be a promising candidate for alternative electrical energy storage devices due to their high power density, exceptional cycle life, and low maintenance cost. The performance of supercapacitors is highly dependent on the properties of electrode materials. Graphene based materials exhibit great potential application for supercapacitors because of their unique structure and excellent intrinsic physical properties. Introducing porous structures to graphene is an effective strategy to obtain high surface area and high specific capacitance. In this review, we provide a brief summary of the recent developments about the synthesis and application of porous graphene materials for supercapacitors.

Porous graphene nanoarchitectures: an efficient catalyst for low charge-overpotential, long life, and high capacity lithium-oxygen batteries.

The electrochemical performance of lithium-oxygen (Li-O2) batteries awaits dramatic improvement in the design of porous cathode electrodes with sufficient spaces to accommodate the discharge products and discovery of effective cathode catalysts to promote both oxygen reduction reactions and oxygen evolution reactions. Herein, we report the synthesis of porous graphene with different pore size architectures as cathode catalysts for Li-O2 batteries. Porous graphene materials exhibited significantly higher discharge capacities than that of nonporous graphene. Furthermore, porous graphene with pore diameter around 250 nm showed the highest discharge capacity among the porous graphene with the small pores (about 60 nm) and large pores (about 400 nm). Moreover, we discovered that addition of ruthenium (Ru) nanocrystals to porous graphene promotes the oxygen evolution reaction. The Ru nanocrystal-decorated porous graphene exhibited an excellent catalytic activity as cathodes in Li-O2 batteries with a high reversible capacity of 17,700 mA h g(-1), a low charge/discharge overpotential (about 0.355 V), and a long cycle life up to 200 cycles (under the curtaining capacity of 1000 mAh g(-1)). The novel porous graphene architecture inspires the development of high-performance Li-O2 batteries.

ChemInform Abstract: Porous Graphene Materials for Advanced Electrochemical Energy Storage and Conversion Devices

AbstractReview: 130 refs.

Tunable Hydrogen Separation in Porous Graphene Membrane: First-Principle and Molecular Dynamic Simulation

First-principle density functional theory (DFT) calculation and molecular dynamic (MD) simulation are employed to investigate the hydrogen purification performance of two-dimensional porous graphene material (PG-ESX). First, the pore size of PG-ES1 (3.2775 Å) is expected to show high selectivity of H2 by DFT calculation. Then MD simulations demonstrate the hydrogen purification process of the PG-ESX membrane. The results indicate that the selectivity of H2 over several other gas molecules that often accompany H2 in industrial steam methane reforming or dehydrogenation of alkanes (such as N2, CO, and CH4) is sensitive to the pore size of the membrane. PG-ES and PG-ES1 membranes both exhibit high selectivity for H2 over other gases, but the permeability of the PG-ES membrane is much lower than the PG-ES1 membrane because of the smaller pore size. The PG-ES2 membrane with bigger pores demonstrates low selectivity for H2 over other gases. Energy barrier and electron density have been used to explain the difference of selectivity and permeability of PG-ESX membranes by DFT calculations. The energy barrier for gas molecules passing through the membrane generally increase with the decreasing of pore sizes or increasing of molecule kinetic diameter, due to the different electron overlap between gas and a membrane. The PG-ES1 membrane is far superior to other carbon membranes and has great potential applications in hydrogen purification, energy clean combustion, and making new concept membrane for gas separation.

Porous Graphene Materials for Water Remediation

Water remediation has been a critical issue over the past decades due to the expansion of wastewater discharge to the environment. Currently, a variety of functional materials have been successfully prepared for water remediation applications. Among them, graphene is an attractive candidate due to its high specific surface area, tunable surface behavior, and high strength. This Concept paper summarizes the design strategy of porous graphene materials and their applications in water remediation, such as the cleanup of oil, removal of heavy metal ions, and elimination of water soluble organic contaminants. The progress made so far will guide further development in structure design strategy of porous materials based on graphene and exploration of such materials in environmental remediation.

Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures

In order to make full utilization of the high intrinsic surface area of graphene, recently, porous graphene materials including graphene nanomesh, crumpled graphene and graphene foam, have attracted tremendous attention and research interest, owing to their exceptional porous structure (high surface area, and high pore volume) in combination with the inherent properties of graphene, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Interestingly, porous graphene materials and their derivatives have been explored in a wide range of applications in the fields of electronic and photonic devices, energy storage, gas separation/storage, oil absorption and sensors. This article reviews recent progress in the synthesis, characterization, properties, and applications of porous graphene materials. We aim to highlight the importance of designing different porous structures of graphene to meet future challenges, and the trend on future design of porous graphene materials is analyzed.

Investigation of Gas Storage Properties of Graphene Material Prepared by Microwave-assisted Reduction of Graphene Oxide

Porous graphene material, named as MWRGO, has been prepared by microwave-assisted reduction method. Ex- tensive characterizations indicate that graphene oxide was effectively reduced and MWRGO has a porous and disordered stacking structure. It has a special surface area of 461.6 m 2 /g with pore size centered at 0.67 nm. H2 and CO2 adsorption properties of MWRGO were investigated, showing a H2 uptake of 0.52 wt% at 77 K and 1 atm and an absolute adsorption amount as high as 10.7 wt% at a higher pressure of 60 bar. The amount of CO2 adsorption at 273 K and 1 atm is 7.1 wt%. Keywords graphene; carbon materials; gas storage; microwave reduction; porous materials

Porous Graphene Materials for Advanced Electrochemical Energy Storage and Conversion Devices

Combining the advantages from both porous materials and graphene, porous graphene materials have attracted vast interests due to their large surface areas, unique porous structures, diversified compositions and excellent electronic conductivity. These unordinary features enable porous graphene materials to serve as key components in high-performance electrochemical energy storage and conversion devices such as lithium ion batteries, supercapacitors, and fuel cells. This progress report summarizes the typical fabrication methods for porous graphene materials with micro-, meso-, and macro-porous structures. The structure-property relationships of these materials and their application in advanced electrochemical devices are also discussed.