3D Mesoporous Graphene Research Articles

Mesoporous graphene-supported nanostructured nickel telluride for efficient electrocatalytic oxygen evolution reaction

The electrocatalytic oxygen evolution reaction (OER) imposes significant constraints on the operational overpotential of electrochemical energy devices, such as water electrolyzers, metal-air batteries, and fuel cells. However, the sluggish kinetics of OER reactions hinder these applications, which has prompted efforts to design more effective electrocatalysts. In this study, we have synthesized NiTe via in-situ growth into mesoporous graphene (MG), with varying nominal weight percentages (5- wt%, 10- wt%, and 15- wt%) of NiTe. The resulting NiTe/MG nanohybrids displayed hexagonally structured NiTe nanoparticles with a predominant (101) surface that promotes the OER kinetics. The wrinkled 3D mesoporous graphene scaffold facilitated the attachment and dispersion of NiTe particles of nanoscale on its surface, preventing their agglomeration. The porous characteristics of the MG significantly increased the high surface area of the NiTe/MG nanohybrids (583–671 m2 g−1), promoting enhanced accessibility of active sites and mass transport beneficial for the OER. Moreover, the altered electronic structure of the NiTe in the MG nanohybrid indicates enhancing O2 desorption during the OER. The optimized composition of the 10 wt% NiTe-loaded MG nanohybrid electrocatalyst demonstrates superior OER activity compared to other nanohybrids. It exhibits a small overpotential of 250 mV at 10 mA cm−2, a low Tafel slope of 63 mV dec−1 and maintained stability in 1 M KOH (pH = 14) as the electrolyte for a prolonged period. This enhanced OER activity is ascribed to the synergistic effect of MG’s high conductivity and the improved intrinsic activity of NiTe within the nanohybrid structure.

Well-dispersed cobalt magnetic nanoparticles incorporated into 3D mesoporous graphene

Well-dispersed cobalt magnetic nanoparticles incorporated into 3D mesoporous graphene

Efficient Electrochemical Oxygen Reduction to Hydrogen Peroxide Production from Nickel-Nitrogen-Doped Mesoporous Graphene Catalyst

Hydrogen peroxide(H2O2) is an excellent oxidizing agent with various uses in industrial bleaching, chemical synthesis, and wastewater treatment. Because of its wide range of applications, the global market demand is rapidly increasing. At present, over 95 % of H2O2 is produced through the anthraquinone process which is an environmentally unfriendly process. Therefore, numerous studies have focused on replacing this process for H2O2 with more eco-friendly processes. One of the alternative methods is the electrochemical production of H2O2 through oxygen reduction reaction(ORR), which offers an economical and environmentally friendly route to H2O2.The oxygen reduction reaction involves a multielectron transfer process in which O2 can be reduced to produce H2O in a four-electron process or undergo a two-electron pathway to form H2O2. However, the design of selective and active electrocatalysts remains a challenge due to competitive reaction pathways between two-electron and four-electron reduction.We develop 3D mesoporous graphene with high H2O2 production in neutral electrolytes by adjusting the pore size and regulating the atmosphere of Nickel single atom. This catalyst has 3D interconnected hollow N-doped graphene shells and Nickel single atoms will be atomically dispersed on N-doped graphene shells. The mesoporous structure with a large surface area accelerates mass transport. Moreover, electron-poor Nickel atoms yield high selectivity above 90 % and high activity for electrochemical oxygen reduction to produce H2O2 in neutral conditions. This result represents a benchmark for the two-electron ORR electrocatalyst in the neutral conditions.

Lithium-Chemical Synthesis of Highly Conductive 3D Mesoporous Graphene for Highly Efficient New Generation Solar Cells

In this study, a highly conductive three-dimensional mesoporous graphene (3DMG), which was synthesized by our discovered reaction of lithium (Li) liquid and CO gas, was demonstrated as a promising electrode material for the hole transport material (HTM) free perovskite solar cell (PSC) and the dye-sensitized solar cell (DSSC), achieving high energy conversion efficiencies of 8.60% and 9.19%, respectively. The DSSC efficiency is higher than that (7.96%) of a DSSC with a standard Pt counter electrode. Furthermore, it was found that the electrical conductivity of 3DMG played a critical role in the PSC, but the DSSC performance was dependent on both its surface area and electrical conductivity. This would provide a novel approach to synthesize ideal electrode materials for energy devices.

Ultrahigh benzene adsorption capacity of graphene-MOF composite fabricated via MOF crystallization in 3D mesoporous graphene

Highly porous composites were synthesized via facile crystallization of a metal-organic framework (MOF) in mesopores of a three-dimensional (3D) graphene (MG). First, MG was prepared via facile thermal exfoliation of graphite oxide in air, which enabled sufficient separation of graphene sheets in the form of an interconnected 3D structure. Next, aluminum-based MOF [MOF520: Al8(OH)8(BTB)4(HCOO)4, BTB = 4,4′,4”-benzene-1,3,5-tryil-tribenzoate] was predominantly crystallized in mesopores of 3D structure having a large pore volume. The resulting MG-MOF composites possessed specific surface areas and pore volumes between those of MG (640 m2/g and 3.0 cm3/g) and MOF (3160 m2/g and 1.3 cm3/g). The composite consisting of MG and MOF with a weight ratio of 1:2 showed almost twice-larger benzene adsorption capacity, i.e., 24.5 mmol/g at 20 °C and relative pressure close to unity, in comparison to that of pure MOF. Although at the same conditions the pure MG captured an ultrahigh amount of benzene, i.e., 33.6 mmol/g, adsorption of this adsorbate at low and moderate relative pressures was much lower than that on pure MOF. Thus, the MG-MOF composites featured much better benzene adsorption performance in a wide range of relative pressures as compared to pure MG and MOF, respectively. Additionally, the composites featured better thermal stability in comparison to the pristine MOF. The use of MG in this synthesis method afforded the well-dispersed, small crystals of MOF, which is essential for the design of MOF-based composites.

All-Carbon Supercapacitor, Fullerene-Grafted 3D Graphene As Electrical Energy Storage Material

Supercapacitors have the potential to replace Li ion batteries as the next-generation electrical energy storage technology in demanding applications due to their high power density and excellent cycling stability. Graphene-based supercapacitor electrodes are very attractive because they feature high surface area, high electrical conductivity, and chemical inertness; however their capacitance is limited by their low density of states at the Fermi level (ca. 1 e- per 100 C atoms). To overcome the current charge storage limitations of graphene-based supercapacitors, researchers at Lawrence Livermore National Laboratory have developed an all-carbon composite graphene/fullerene supercapacitor combining the high charge storage capacitance of fullerenes (up to 6 e- per C60) with the high electrical conductivity of 3D mesoporous graphene macro-assemblies (GMAs) (Figure 1). Fig. 1: Fullerene-grafted 3D graphene bulk material. Funding was provided by Lawrence Livermore National Laboratory Directed Research and Development (LDRD) Grant 17-ERD-017. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. IM Release Number LLNL-ABS-741683. Figure 1

In-situ space-confined catalysis for fabricating 3D mesoporous graphene and their capacitive properties

Abstract A one-step strategy for preparing 3D mesoporous graphene networks (3DMGNs) based on the concepts of space-confined effect, catalytic effect and chemical activation is reported in this work. The soluble salts act as the in-situ templates to confine the thickness of 3D graphene layers. Meanwhile, the Fe-catalysts greatly improve the graphitization of the graphene matrix, which are easy to be removed by acid treatment. In addition, the KOH activation introduces abundant mesopores into the graphene networks, which facilities the electrolyte permeation. Thus, when using as electrode materials for supercapacitor, the as-obtained 3DMGNs with high electron conductivity, large surface area and hierarchical porous structure exhibit excellent capacitive properties, including high specific capacitance (215 F g−1 at 0.5 A g−1) and superior rate performance (168 F g−1 at 50 A g−1).

Self-assembled 3D mesoporous graphene oxides (MEGOs) as adsorbents and recyclable solids for CO2 and CH4 capture

Various graphene derivatives have been extensively synthesized and used in several research areas. Currently, however, very few examples of graphene derivatives that exhibit mesoporosity have been reported. In this work, we describe a facile method based on a self-assembly process of two-dimensional (2D) graphene oxides in aqueous solutions to produce three-dimensional (3D) mesoporous graphene oxide (MEGO) solids. The resulting MEGO solids exhibit exceptionally narrow mesopore distributions (2.4nm), high surface areas, large pore volumes and high thermal stabilities (>450°C). The MEGOs were used as adsorbents for CO2 and CH4; they showed good adsorption performance, particularly for CO2 at high pressures and remarkable recyclability, suggesting this material is a potential candidate to be used as adsorbent in precombustion process.

An efficient photocatalytic system containing Eosin Y, 3D mesoporous graphene assembly and CuO for visible-light-driven H2 evolution from water

In the present work, 3D mesoporous graphene assembly was fabricated in a hydrothermal process using triethylenetetramine molecules as cross-linkers. And CuO nanoparticles were introduced in the graphene assembly via in-situ photodeposition. Then, a photocatalytic system containing Eosin Y as a sensitizer, graphene assembly as a supporter material and electron transfer channel, and CuO nanoparticles as an active center of H2 evolution from water was prepared. Meanwhile, photocatalytic hydrogen evolution from water over the as-prepared photocatalytic system was explored under visible irradiation. Furthermore, for practical purposes, the durability of the photocatalytic system was also studied. And the photocatalytic mechanism was preliminarily discussed. The experimental results indicate that the as-prepared photocatalytic system is an efficient photocatalyst for visible-light-driven H2 evolution from water. The rate of H2 evolution over the photocatalytic system is up to 5.85 mmol g−1 h−1 under optimal conditions, which is 2.3 times higher than that over reduced graphene oxide loaded with CuO. The 3D porous graphene assembly plays an important role in the photocatalytic process. It can not only efficiently enhance the electron transfer in the photocatalytic system, but also result in fast diffusion of sacrificial reagent and timely release of H2 bubbles. This work provides us with new possibility for designing an efficient Pt-free visible photocatalyst for H2 evolution from water.

Fullerene-Grafted 3D Graphene As Electrical Energy Storage Material

Supercapacitors have the potential to replace Li ion batteries as the next-generation electrical energy storage technology in demanding applications due to their high power density and excellent cycling stability. Graphene-based supercapacitor electrodes are particularly promising because they feature high surface area, good electrical conductivity, and chemical inertness. Researchers at Lawrence Livermore National Laboratory have developed tailored fullerene-grafted 3D mesoporous graphene macro-assemblies (GMAs) (Figure 1) for electrical energy storage applications by anchoring fullerene molecules to the 3D graphene backbone. Fullerene-grafted graphene (C60-GMA) materials promise to overcome the current charge storage limitations of carbon-based supercapacitors by combining the high charge storage capacitance of fullerenes with the high electrical conductivity of 3D-GMAs. In fact, the charge storage capacitance of fullerene (223 mAh/g) is similar or higher than that of today’s standard lithium ion battery electrode materials (177 mAh/g for LiFePO4). Funding was provided by Lawrence Livermore National Laboratory Directed Research and Development (LDRD) Grant 17-ERD-017. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. IM Release Number LLNL-ABS-716277. Figure 1. Fullerene-grafted 3D graphene bulk material Figure 1

Direct conversion of coordination compounds into Ni2P nanoparticles entrapped in 3D mesoporous graphene for an efficient hydrogen evolution reaction

5 nm-sized Ni2P nanoparticles entrapped in 3D mesoporous graphene (Ni2P@mesoG) were synthesized in situ via [Ni2(EDTA)] thermolysis, followed by phosphidation.

New Graphene Form of Nanoporous Monolith for Excellent Energy Storage.

Extraordinary tubular graphene cellular material of a tetrahedrally connected covalent structure was very recently discovered as a new supermaterial with ultralight, ultrastiff, superelastic, and excellent conductive characteristics, but no high specific surface area will keep it from any next-generation energy storage applications. Herein, we prepare another new graphene monolith of mesoporous graphene-filled tubes instead of hollow tubes in the reported cellular structure. This graphene nanoporous monolith is also composed of covalently bonded carbon network possessing high specific surface area of ∼1590 m(2) g(-1) and electrical conductivity of ∼32 S cm(-1), superior to graphene aerogels and porous graphene forms self-assembled by graphene oxide. This 3D graphene monolith can support over 10 000 times its own weight, significantly superior to CNT and graphene cellular materials with a similar density. Furthermore, pseudocapacitance-active functional groups are introduced into the new nanoporous graphene monolith as an electrode material in electrochemical capacitors. Surprisingly, the electrode of 3D mesoporous graphene has a specific capacitance of 303 F g(-1) and maintains over 98% retention after 10 000 cycles, belonging to the list for the best carbon-based active materials. The macroscopic mesoporous graphene monolith suggests the great potential as an electrode for supercapacitors in energy storage areas.

Batteries: 3D Mesoporous Graphene: CVD Self-Assembly on Porous Oxide Templates and Applications in High-Stable Li-S Batteries (Small 39/2015)

Batteries: 3D Mesoporous Graphene: CVD Self-Assembly on Porous Oxide Templates and Applications in High-Stable Li-S Batteries (Small 39/2015)

3D Mesoporous Graphene: CVD Self-Assembly on Porous Oxide Templates and Applications in High-Stable Li-S Batteries.

A nanostructured carbon with high specific surface area (SSA), tunable pore structure, superior electrical conductivity, mechanically robust framework, and high chemical stability is an important requirement for electrochemical energy storage. Porous graphene fabricated by chemical activation and liquid etching has a high surface area but very limited volume of electrochemically accessible mesopores. Herein, an effective strategy of in situ formation of hierarchically mesoporous oxide templates with small pores induced by Kirkendall diffusion and large pores attributed to evaporation of deliberately introduced volatile metal is proposed for chemical vapor deposition assembly of porous graphene frameworks (PGFs). The PGFs inherit the hierarchical mesoporous structure of the templates. A high SSA of 1448 m(2) g(-1), 91.6% of which is contributed by mesopores, and a mesopore volume of 2.40 cm(3) g(-1) are attained for PGFs serving as reservoirs of ions or active materials in electrochemical energy storage applications. When the PGFs are applied in lithium-sulfur batteries, a very high sulfur utilization of 71% and a very low fading rate of ≈0.04% per cycle after the second cycle are achieved at a current rate of 1.0 C. This work provides a general strategy for the rational construction of mesoporous structures induced by a volatile metal, with a view toward the design of hierarchical nanomaterials for advanced energy storage.

Simple coordination complex-derived three-dimensional mesoporous graphene as an efficient bifunctional oxygen electrocatalyst.

3D mesoporous graphene (mesoG) was synthesized from [Ni2(EDTA)] (EDTA = ethylenediaminetetraacetate). The material is comprised of interconnected 4 nm-sized hollow carbon shells composed of 3-4 layers of graphene and exhibits high bifunctional electrocatalytic activity as well as high durability for use in oxygen evolution and reduction reactions.

Freestanding 3D mesoporous graphene oxide for high performance energy storage applications

Freestanding 3D mesoporous graphene with enhanced capacitance for supercapacitors has been synthesized by carbon monoxide reduction, healing and activation.