3D Graphene Aerogel Research Articles

Enhanced electrochemical performance of ion-beam-treated 3D graphene aerogels for lithium ion batteries

High energy light-ion (3.8MeV He) bombardment is used to introduce lattice defects in a 3-dimensional (3D) interconnected network of graphene aerogels (GAs). When these materials are used as anodes for lithium ion batteries, we observe improved percentage reversible capacity and cycle stability compared to those without ion-beam treatment. Furthermore, all ion-beam treated 3D graphene samples exhibit substantially higher Coulombic efficiencies, suggesting at beneficial role of vacancy-type defects in stabilizing solid-electrolyte interphases. Although 3D graphene exhibits initial reversible capacities that are 2–3 times higher than that of graphite (∼372mAh/g), fast capacity fading is observed but becomes more stable after ion-beam treatment. Our experimental results demonstrate that ion-beam treatment is an effective route to tune and produce good-performance graphene electrodes, and that vacancy-type defects help to promote reversible lithium storage capacity in graphene. We further observe that 3D GAs irradiated to the highest dose studied (1016cm−2) fail rapidly upon electrochemical cycling, likely caused by the excessive ion-beam damage and graphene restacking. Raman I(D)/I(D′) signature is considered linked to defect type in graphene and thus is proposed, for the first time, as an indicator of the reversible capacity for GAs.

One-step Synthesis of Pt Nanoparticles Highly Loaded on Graphene Aerogel as Durable Oxygen Reduction Electrocatalyst

Synthesis of highly active and durable Pt based catalysts with a high metal loading for fuel cells’ applications still remains a big challenge. The three-dimensional (3D) graphene aerogel (GA) not only possess the intrinsic property of graphene, but also have abundant pore architecture for anchoring metal nanoparticles, thus would be suitable as metal catalysts’ support. This work reports a simple and mild one-step co-reduction synthesis of Pt nanoparticles highly loaded on 3D GA and the use as durable oxygen reduction catalyst. Both X-ray diffraction and TEM measurements confirm that Pt nanoparticles (ca. 60wt.% Pt loading) with an average diameter of ca. 3.2nm are uniformly decorated on the homogeneously interconnected pores of 3D GA even after a heat treatment at 300°C. Such a Pt/GA catalyst exhibits significantly enhanced electrocatalytic activity and improved durability for the oxygen reduction reaction. The enhancement in both catalytic activity and durability may result from the unique 3-D architecture structure of GA, the uniform dispersion of Pt nanoparticles, and the interaction between the Pt nanoparticles and GA. The GA-supported Pt can serve as a highly active catalyst for fuel cell applications.

Cobalt carbonate/ and cobalt oxide/graphene aerogel composite anodes for high performance Li-ion batteries.

Nanocomposites consisting of ultrafine, cobalt carbonate nanoneedles and 3D porous graphene aerogel (CoCO3/GA) are in situ synthesized based on a one-step hydrothermal route followed by freeze-drying. A further heat treatment produces cobalt oxide nanoparticles embedded in the conductive GA matrix (Co(3)O(4)/GA). Both the composite anodes deliver excellent specific capacities depending on current density employed: the CoCO(3)/GA anode outperforms the Co(3)O(4)/GA anode at low current densities, and vice versa at current densities higher than 500 mA g(-1). Their electrochemical performances are considered among the best of similar composite anodes consisting of CoCO(3) or Co(3)O(4) active particles embedded in a graphene substrate. The stable multistep electrochemical reactions of the carbonate compound with a unique nanoneedle structure contribute to the excellent cyclic stability of the CoCO(3)/GA electrode, whereas the highly conductive networks along with low charge transfer resistance are responsible for the high rate performance of the Co(3)O(4)/GA electrode.

Enhanced photocatalytic activities of three-dimensional graphene-based aerogel embedding TiO2 nanoparticles and loading MoS2 nanosheets as Co-catalyst

A novel graphene-based three-dimensional (3D) aerogel embedded with two types of functional nanomaterials had been prepared by a facile one-pot hydrothermal process. During the hydrothermal reaction, graphene, TiO2 nanoparticles and MoS2 nanosheets were self-assembled into the 3D interconnected networks aerogel, where the uniformly dispersed TiO2 nanoparticles were densely anchored onto the graphene nanosheets and decorated with the ultrathin MoS2 nanosheets. The UV–vis DRS and PL spectra measurement shows that the MoS2/P25/graphene aerogel exhibits enhanced light absorption and efficient charge separation properties. As a new photocatalyst, the photocatalytic activity was evaluated by photoelectrochemical test and photodegradation methyl orange (MO) under UV irradiation, an improvement of photocurrent was observed, as 6 times higher for MoS2/P25/graphene aerogel (37.45 mA/cm2) than pure P25 at +0.6 V, and the fastest photodegradation of MoS2/P25/graphene aerogel was found within 15 min. The improved photocatalytic activity is attributed to the porous structure, good electrical conductivity and the maximization of accessible sites of the unique 3D graphene aerogel, the increasing active adsorption sites and photocatalytic reaction centers for the introduction of MoS2 nanosheets, and the positive synergetic effect between the three components in this hybrid. This work demonstrates that the as-prepared MoS2/P25/graphene aerogel may have a great potential application in photoelectrochemical hydrogen production and pollution removal.

Direct electrochemical analysis of glucose oxidase on a graphene aerogel/gold nanoparticle hybrid for glucose biosensing

Homogeneously distributed self-assembling graphene aerogel/gold nanoparticle (GA/GNs) hybrid materials with three-dimensional (3D) interconnected pores were fabricated through a simple hydrothermal route. A highly sensitive glucose oxidase (GOD) sensor is then developed based on the GA/GN hybrid materials. The obtained porous structure of the GA/GNs hybrid favored high-density immobilization of the enzyme and penetration of water-soluble molecules, which provided a biocompatible sensing platform for GOD immobilization. This GOD biosensor exhibits remarkable sensitivity (257.60 μA · mM−1 · cm−2), an approximate linear detection range of glucose concentration (50 μmol · L−1 to 450 μmol · L−1), and a detection limit of 0.597 μmol · L−1. These results indicate that the in situ encapsulation of different nanomaterials into a 3D graphene aerogel framework can enable the fabrication of a series of graphene-based 3D porous materials with promising applications.

Three dimensional graphene aerogels and their electrically conductive composites

Three dimensional (3D) graphene aerogel was prepared by in situ reduction-assembly method. Paraphenylene diamine (PPD) was used as reducing and functionalizing agent of graphene oxide in an aqueous medium with ammonia. The synthesized 3D graphene-PPD aerogel has highly porous structure, low density, high electrical conductivity and good mechanical properties. Further, epoxy/aerogel composites were prepared by vacuum-assisted impregnation process, which exhibited good electrical conductivity and compressive properties.

Mesoporous TiO2 Nanocrystals Grown in Situ on Graphene Aerogels for High Photocatalysis and Lithium-Ion Batteries

TiO2/graphene composites have been well studied as a solar light photocatalysts and electrode materials for lithium-ion batteries (LIBs). Recent reports have shown that ultralight 3D-graphene aerogels (GAs) can better adsorb organic pollutants and can provide multidimensional electron transport pathways, implying a significant potential application for photocatalysis and LIBs. Here, we report a simple one-step hydrothermal method toward in situ growth of ultradispersed mesoporous TiO2 nanocrystals with (001) facets on GAs. This method uses glucose as the dispersant and linker owing to its hierarchically porous structure and a high surface area. The TiO2/GAs reported here exhibit a highly recyclable photocatalytic activity for methyl orange pollutant and a high specific capacity in LIBs. The strong interaction between TiO2 and GAs, the facet characteristics, the high electrical conductivity, and the three-dimensional hierarchically porous structure of these composites results in highly active photocatalysis, a high rate capability, and stable cycling.

Three-Dimensional Graphene-Based Macro- and Mesoporous Frameworks for High-Performance Electrochemical Capacitive Energy Storage

Three-dimensional graphene-based frameworks (3D-GFs) with hierarchical macro- and meso-porous structures are presented. The interconnected macropores are derived from hydrothermally assembled 3D graphene aerogels (GAs), while the mesopores are generated by the silica networks uniformly grown on the surface of graphene. The resulting 3D-GFs exhibit narrow mesopore size distribution (2-3.5 nm), high surface area, and low mass density. These intriguing features render 3D-GFs a promising template for creating various 3D porous materials. Specifically, 3D GA-based mesoporous carbons (GA-MC) and metal oxide hybrids (GA-Co(3)O(4), GA-RuO(2)) can be successfully constructed via a nanocasting technology. Benefiting from the integration of meso- and macroporous structures, 3D GA-MC manifests outstanding specific capacitance (226 F g(-1)), high rate capability, and excellent cycling stability (no capacitance loss after 5000 cycles) when it is applied in electrochemical capacitors.

3D porous and redox-active prussian blue-in-graphene aerogels for highly efficient electrochemical detection of H2O2

3D porous and redox-active prussian blue-in-graphene (PB@G) aerogels with mass ratios of graphene to PB from 2.5 : 1 to 1 : 2.5 have been fabricated for the first time by supercritical fluid drying of its hydrogel precursors, which have been synthesized by co-reduction of graphene oxide and FeCl3 with L-ascorbic acid as the reducing agent in the presence of ferricyanide. The chemical composition and crystalline structure of the resulting PB@G aerogels, as well as the strong interaction between graphene sheets and PB nanoparticles, have been disclosed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and X-ray powder diffraction (XRD). The morphology and hierarchically porous attributes of the resulting PB@G aerogels have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption tests. The electrical conductivity and electrochemical performance of the resulting PB@G aerogels have also been revealed in this study. The as-synthesized PB@G aerogel monoliths possess large surface area (601 m2 g−1), abundant pore volume (3.8 cm3 g−1) and high conductivity (38.4 S m−1), and the electrodes modified with the as-synthesized PB@G aerogels have performed very well in the electrocatalytic reduction of H2O2 with a very low limit of detection (5 × 10−9 M) and a wide linear range (0.005–4 mM). These results imply that in situ encapsulation of different nanoscale materials into 3D graphene aerogel framework may open up a significant avenue to fabricate a series of graphene-based 3D porous materials with promising applications.