3D Graphene Electrode Research Articles

Fabrication of three-dimensional graphene anode for augmenting performance in microbial fuel cells

In the present work, we have reported the synthesis of 3D graphene structures by simple chemical reduction method for application in microbial fuel cell (MFC) as an anode. The synthesis procedure includes synthesis of graphene oxide by modified Hummers method followed by simultaneous reduction of graphene oxide and the formation of hydrogels. The 3D graphene structures are characterized using X-ray diffraction and Raman spectroscopy techniques. Electrochemical characterization is carried out to study the capacitive properties and impedance studies of electrodes in conductive electrolyte. 3D graphene electrodes show remarkably high capacitive current, charge storage and lower charge transfer resistance as estimated through cyclic voltammetry and Nyquist plots. In order to evaluate the performance of 3D graphene electrodes in MFC, power density and polarization curves are recorded in three configurations by varying terminal electron acceptors (TEA) viz., dissolved oxygen (MFC-DO), potassium ferricyanide and MFC without TEA (MFC-NDO). 3D graphene electrodes exhibits maximum power density of 0.49 mW/m2 in potassium ferricyanide followed by MFC-DO (0.36 mW/m2) and MFC-NDO (0.34 mW/m2). Present work highlights the viability of chemically synthesized 3D graphene electrodes as an efficient anode material in MFC.

Metal-assisted-chemical-etching of silicon nanowires for templating 3D graphene growth towards energy storage in microsystems

Three-dimensional (3D) architectures of graphene derivatives have attracted intensive attention due to their outstanding electric conductance and unique interconnected huge surface area. It is expected to transfer these excellent properties of 3D graphene into microsystems for further development in the microelectronic industry. However, limited applications are reported due to the absence of suitable fabrication approaches of 3D graphene that are compatible with existing silicon-based microfabrication techniques. In this paper, a novel 3D hierarchical graphene was prepared using a plasma-enhanced chemical vapor deposition to synthesize graphene nanoflakes on silicon nanowires (SiNWs) scaffolds that are generated from metal-assisted chemical etching (MACE). In addition to the first growth mechanism study of graphene on different substrates, the application of 3D graphene derivatives was further explored towards energy storage through an electrochemical evaluation. The 3D graphene electrode, combined with pseudocapacitive polyaniline coating, showed a large specific capacitance of 185 mF cm−2, which outperforms its planar counterparts and is desirable for constructing micro-supercapacitors towards chip-scale power supplying. Above all, this microfabrication strategy of 3D graphene on high aspect ratio silicon nanostructures can also be extended as a platform toolkit towards the application of micro-batteries, solar cells and sensors in microsystems.

Laser-derived graphene: A three-dimensional printed graphene electrode and its emerging applications

Abstract Printing of binder-free graphene electrodes directly on substrates has the potential to enable a large number of applications. Though conventional processing techniques such as ink-jet, screen-printing, and roll coating methods offer reliable and scalable fabrication, device performance has often been limited by re-stacking of the graphene sheets and by presence of passive binders and or additives. Laser-based, direct-write technologies have shown promise as a reliable, maskless, and template-free patterning method. Thus, laser-derived graphene (LDG) electrode is emerging as a promising three-dimensional graphene electrode that can be simultaneously derived from precursor carbons or polymers and patterned upon laser exposure. The LDG can be obtained through irradiation by a variety of laser sources including CO2 infrared laser and femtosecond laser pulses, depending on the nature of the starting carbon precursors. Controlling the microstructure, amount and types of doping, and post-deposition methods enable a variety of applications including energy storage, catalysis, sensing and biomedicine. In this review article, we discuss recent progress in using laser-based fabrication of printed 3D graphene electrodes and its wide spectrum of applications. The review also discusses the material aspects of 3D graphene electrodes and provides an outlook for future potential.

A brief review on graphene applications in rechargeable lithium ion battery electrode materials

Graphene is a single atomic layer of carbon atoms, and has exceptional electrical, mechanical, and optical characteristics. It has been broadly utilized in the fields of material science, physics, chemistry, device fabrication, information, and biology. In this review paper, we briefly investigate the ideas, structure, characteristics, and fabrication techniques for graphene applications in lithium ion batteries (LIBs). In LIBs, a constant three-dimensional (3D) conductive system can adequately enhance the transportation of electrons and ions of the electrode material. The use of 3D graphene and graphene-expansion electrode materials can significantly upgrade LIBs characteristics to give higher electric conductivity, greater capacity, and good stability. This review demonstrates several recent advances in graphenecontaining LIB electrode materials, and addresses probable trends into the future.

Aqueous Preparation of Platinum Nanoflowers on Three-Dimensional Graphene for Efficient Methanol Oxidation

A facile aqueous method to construct a platinum nanoflowers (PtNFs)/three-dimensional (3D) graphene electrode for electrochemical catalysis was demonstrated. PtNFs composed of thin Pt nanowires with the length of 6–16 nm and the diameter of 2–3 nm were prepared on 3D graphene foam as a growth template in the aqueous solution without any surfactant. The 3D graphene foam was used for patterning PtNFs and controlling their morphology. The fabricated PtNF/3D graphene electrode was applied for electrocatalytic methanol oxidation. Electrochemical measurements show that the PtNF/3D graphene electrode has higher electrocatalytic activity and better stability than commercial Pt-C modified glassy carbon electrode. It displays promising potential for applications in fuel cells.

Synthesis of molecularly imprinted polymers/NiCo2O4 nanoneedle arrays on 3D graphene electrode for determination of sulfadimidine residue in food

Three-dimensional (3D) molecularly imprinted polymer (MIP) arrays were used for electrochemical sensor to detect sulfadimidine (SM2) residue in food. NiCo2O4 nanoneedle arrays were decorated on the free-standing and highly conductive 3D graphene by a hydrothermal process. Polypyrrole (PPy) was coated onto NiCo2O4 nanoneedle arrays via electropolymerization in the presence of template molecule SM2 to obtain MIP/NiCo2O4 nanoneedle/3D graphene electrode. The desirable detectability of the composite electrode can be ascribed to the unique structure and the synergistic effects of the components: Nanoneedle arrays on 3D graphene offered the matrix to MIP and each nanoneedle as sensing unit was accessible to analyte, resulting in high specific surface area, desirable conductivity, short ion diffusion path and excellent adsorption capacity, which could powerfully boost the electrochemical property for the detection of SM2. Under optimized conditions, a wide linear range over SM2 of 0.2–1000 ng/mL with a detection limit of 0.169 ng/mL (S/N = 3) was obtained. The developed sensor also had favorable recovery of 92.3–102.23% and the relative standard deviation of 2.27–4.10%. The MIP array sensor provided an efficient tool for the selective and rapid detection of SM2 in food.

Lignin Laser Lithography: A Direct‐Write Method for Fabricating 3D Graphene Electrodes for Microsupercapacitors

AbstractIn this work, a simple lignin‐based laser lithography technique is developed and used to fabricate on‐chip microsupercapacitors (MSCs) using 3D graphene electrodes. Specifically, lignin films are transformed directly into 3D laser‐scribed graphene (LSG) electrodes by a simple one‐step CO2 laser irradiation. This step is followed by a water lift‐off process to remove unexposed lignin, resulting in 3D graphene with the designed electrode patterns. The resulting LSG electrodes are hierarchically porous, electrically conductive (conductivity is up to 66.2 S cm−1), and have a high specific surface area (338.3 m2 g−1). These characteristics mean that such electrodes can be used directly as MSC electrodes without the need for binders and current collectors. The MSCs fabricated using lignin laser lithography exhibit good electrochemical performances, namely, high areal capacitance (25.1 mF cm−2), high volumetric energy density (≈1 mWh cm−3), and high volumetric power density (≈2 W cm−3). The versatility of lignin laser lithography opens up the opportunity in applications such as on‐chip microsupercapacitors, sensors, and flexible electronics at large‐scale production.

Novel 3D porous graphene/Ni3S2 nanostructures for high-performance supercapacitor electrodes

A three-dimensional (3D) graphene/Ni3S2 nanostructure grown on nickel foam using a one-step chemical vapor deposition process is an excellent template for the synthesis of graphene-based composite electrodes for use in supercapacitors. The as-grown graphene/Ni3S2 nano-structures have high crystalline quality and surface area. Electrochemical characterization shows that the 3D porous graphene/Ni3S2 electrode exhibits a high specific capacitance of 741 F/g at 1 mV/s, with 92.3% of the specific capacitance retained after 5000 charging-discharging cycles. Such high performance of a 3D graphene electrode can enrich the prospects for future practical applications in energy storage.

An Ideal Electrode Material, 3D Surface-Microporous Graphene for Supercapacitors with Ultrahigh Areal Capacitance.

The efficient charge accumulation of an ideal supercapacitor electrode requires abundant micropores and its fast electrolyte-ions transport prefers meso/macropores. However, current electrode materials cannot meet both requirements, resulting in poor performance. Herein, we creatively constructed three-dimensional cabbage-coral-like graphene as an ideal electrode material, in which meso/macro channels are formed by graphene walls and rich micropores are incorporated in the surface layer of the graphene walls. The unique 3D graphene material can achieve a high gravimetric capacitance of 200 F/g with aqueous electrolyte, 3 times larger than that of commercially used activated carbon (70.8 F/g). Furthermore, it can reach an ultrahigh areal capacitance of 1.28 F/cm2 and excellent rate capability (83.5% from 0.5 to 10 A/g) as well as high cycling stability (86.2% retention after 5000 cycles). The excellent electric double-layer performance of the 3D graphene electrode can be attributed to the fast electrolyte ion transport in the meso/macro channels and the rapid and reversible charge adsorption with negligible transport distance in the surface micropores.

Vertical few-layer graphene/metalized Si-nanocone arrays as 3D electrodes for solid-state supercapacitors with large areal capacitance and superior rate capability

A strategy to promote the energy density of graphene-based supercapacitors by a combination of dry etching and chemical vapor deposition (CVD) techniques is demonstrated. A three dimensional (3D) electrode is composed of vertically oriented graphene that is deposited on metalized silicon nanocones. The design of the 3D electrodes improves specific surface area, electrolyte ion migration and electrical contact, resulting in an enhancement of areal capacitance and rate capability. Furthermore, a solid-state supercapacitor was prepared based on the 3D graphene electrodes and gel polymer electrolyte. The 3D electrode with 10min of CVD growth of graphene endows the electrical double layer capacitor with the highest areal capacitance of 667.2μFcm−2, which is larger than that of supercapacitors with flat electrodes.

Controlled multimodal hierarchically porous electrode self-assembly of electrochemically exfoliated graphene for fully solid-state flexible supercapacitor.

Supercapacitors constructed from three-dimensional (3D) graphene electrodes with high ion-accessible surface area and durable mechanical flexibility have great potential for wearable devices. For the development of a highly efficient graphene electrode for electrical double layer capacitors (EDLCs), proper control over not only the specific surface area but also the type of pore (macro-, meso- and micro-porous networks) adapted for an appropriate type of electrolyte is crucial to ensure an ideal performance in terms of both energy density and power delivery rate. However, there is still a lack of technology to create graphene structures that combine macro-, meso- and micro-pores by a one-step and facile method. In addition, the ion/electron transport of a solid state electrolyte among such multimodal pore structures is not fully investigated. Here, we report a novel cost-effective technique of concentration dependent self-assembly of electrochemically exfoliated graphene (EC-graphene) to obtain a 3D architecture with controllable macropores (0.39-4.99 μm) and multimodal hierarchical meso- and micro-pores. The better performance of the 3D architecture is obtained due to its optimum micron-sized macropore diameter (∼5 μm) that serves as an ion buffering reservoir, followed by facile ion diffusion kinetics through the well-modulated combination of macro-, meso- and micro-pores. The binder and conductive carbon additive free supercapacitor constructed from the 3D graphene electrode exhibited a specific capacitance of 45.40 F g-1 (6 M KOH) and 23.89 F g-1 (1 M H2SO4 gel electrolyte). A capacitance retention of above 90% (up to 180° folding angle) after 50 bending-relaxing cycles is obtained, implying the superior durability of the device and the worthiness of the synthesis procedure. The method reported here may pave the way for the development of an environment friendly, large scale producible and controlled porous graphene-based architecture for the high performance next generation flexible, all-solid-state and binder-free energy storage devices.

Synthesis of NiCo2O4 nanoneedle@polypyrrole arrays supported on 3D graphene electrode for high-performance detection of trace Pb2+

In this work, we reported the highly ordered NiCo2O4 nanoneedle@polypyrrole arrays anchored on three-dimensional graphene (NiCo2O4@PPy/3D graphene) for high-sensitivity detection of trace lead ions (Pb2+). The 3D graphene was prepared by a hydrothermal process and then decorated with NiCo2O4 nanoneedle arrays by another hydrothermal process. This two-step hydrothermal method is simple and mild. Furthermore, the highly conductive PPy was coated on NiCo2O4 via a chemical vapor-phase polymerization to prepare NiCo2O4@PPy/3D graphene. The free-standing NiCo2O4@PPy/3D graphene can be directly utilized as 3D electrochemical working electrode without being decorated onto working electrode like Au and glassy carbon electrode. High conductivity, large specific surface area, short ion diffusion path and excellent adsorption capacity of NiCo2O4@PPy/3D graphene efficiently improved electrochemical property for the detection of Pb2+. Using square-wave anodic stripping voltammetry (SWASV), a linear range between the currents and the concentrations of Pb2+ of 0.0125–0.709 μM with a high sensitivity of 115.621 μA μM−1 was obtained. The limit of detection can reach to 0.2 nM. In addition, the fabricated sensor of Pb2+ also had good selectivity, reproducibility and long-term stability. Finally, NiCo2O4@PPy/3D graphene electrode was utilized for determining Pb2+ in tap water sample using the standard addition method, revealing a promising application for the quantitative detection of certain concentration ranges of Pb2+ in real sample.

Robust Electrografting on Self-Organized 3D Graphene Electrodes.

Improving graphene-based electrode fabrication processes and developing robust methods for its functionalization are two key research routes to develop new high-performance electrodes for electrochemical applications. Here, a self-organized three-dimensional (3D) graphene electrode processed by pulsed laser deposition with thermal annealing is reported. This substrate shows great performance in electron transfer kinetics regarding ferrocene redox probes in solution. A robust electrografting strategy for covalently attaching a redox probe onto these graphene electrodes is also reported. The modification protocol consists of a combination of diazonium salt electrografting and click chemistry. An alkyne-terminated phenyl ring is first electrografted onto the self-organized 3D graphene electrode by in situ electrochemical reduction of 4-ethynylphenyl diazonium. Then the ethynylphenyl-modified surface efficiently reacts with the redox probe bearing a terminal azide moiety (2-azidoethyl ferrocene) by means of Cu(I)-catalyzed alkyne-azide cycloaddition. Our modification strategy applied to 3D graphene electrodes was analyzed by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy (XPS). For XPS chemical surface analysis, special attention was paid to the distribution and chemical state of iron and nitrogen in order to highlight the functionalization of the graphene-based substrate by electrochemically grafting a ferrocene derivative. Dense grafting was observed, offering 4.9 × 10(-10) mol cm(-2) surface coverage and showing a stable signal over 22 days. The electrografting was performed in the form of multilayers, which offers higher ferrocene loading than a dense monolayer on a flat surface. This work opens highly promising perspectives for the development of self-organized 3D graphene electrodes with various sensing functionalities.

The hierarchical porosity of a three-dimensional graphene electrode for binder-free and high performance supercapacitors

We report the hierarchical porosity of a 3D graphene electrode for binder-free supercapacitors composed of the submicrometer porosity of graphene self-assembled by nanopores of graphene flakes, which shows superior high electrochemical performance.

Grafting sulfonic and amine functional groups on 3D graphene for improved capacitive deionization

A novel ion-selective 3D graphene electrode was designed to overcome the co-ions expulsion effect and improve the CDI performance.

Synthesis of Three-dimensional Graphene Electrodes and Their Applications in Capacitive Deionization†

In this paper, three-dimensional( 3D) graphene hydrogel/aerogel were synthesized by wet chemistry methods,and then used as electrode materials in capacitive deionization( CDI) to separate Na Cl from aqueous solution. Besides,the structure and character of the electrodes were analyzed by scanning electron microscopy,cyclic voltammetry,X-ray photoelectron spectroscopy and other methods. The results show that 3D graphene hydrogel has larger adsorption capacity than graphene aerogel. Then the graphene hydrogel electrode was optimized by pressing graphene hydrogel( pressing hydrogel). 3D graphene electrodes achieve good results in capacitive deionization. And the adsorption capacity ranking from big to small is pressing hydrogel,graphene hydrogel,graphene aerogel.

Three-Dimensional Macroporous Polypyrrole-Derived Graphene Electrode Prepared by the Hydrogen Bubble Dynamic Template for Supercapacitors and Metal-Free Catalysts.

We report a general method for the fabrication of three-dimensional (3D) macroporous graphene/conducting polymer modified electrode and nitrogen-doped graphene modified electrode. This method involves three consecutive steps. First, the 3D macroporous graphene (3D MG) electrode was fabricated electrochemically by reducing graphene oxide dispersion on different conducting substrates and used hydrogen bubbles as the dynamic template. The morphology and pore size of 3D MG could be governed by the use of surfactants and the dynamics of bubble generation and departure. Second, 3D macroporous graphene/polypyrrole (MGPPy) composites were constructed via directly electropolymerizing pyrrole monomer onto the networks of 3D MG. Due to the benefit of the good conductivity of 3D MG and pseudocapacitance of PPy, the composites manifest outstanding area specific capacitance of 196 mF cm(-2) at a current density of 1 mA cm(-2). The symmetric supercapacitor device assembled by the composite materials had a good capacity property. Finally, the nitrogen-doped MGPPy (N-MGPPy or MGPPy-X) with 3D macroporous nanostructure and well-regulated nitrogen doping was prepared via thermal treatment of the composites. The resultant N-MGPPy electrode was explored as a good electrocatalyst for the oxygen reduction reaction (ORR) with the current density value of 5.56 mA cm(-2) (-0.132 V vs Ag/AgCl). Moreover, the fuel tolerance and durability under the electrochemical environment of the N-MGPPy catalyst were found to be superior to the Pt/C catalyst.

Ultra‐light Hierarchical Graphene Electrode for Binder‐Free Supercapacitors and Lithium‐Ion Battery Anodes

A mild and environmental-friendly method is developed for fabricating a 3D interconnected graphene electrode with large-scale continuity. Such material has interlayer pores between reduced graphene oxide nanosheets and in-plane pores. Hence, a specific surface area up to 835 m(2) g(-1) and a high powder conductivity up to 400 S m(-1) are achieved. For electrochemical applications, the interlayer pores can serve as "ion-buffering reservoirs" while in-plane ones act as "channels" for shortening the mass cross-plane diffusion length, reducing the ion response time, and prevent the interlayer restacking. As binder-free supercapacitor electrode, it delivers a specific capacitance up to 169 F g(-1) with surface-normalized capacitance close to 21 μF cm(-2) (intrinsic capacitance) and power density up to 7.5 kW kg(-1), in 6 m KOH aqueous electrolyte. In the case of lithium-ion battery anode, it shows remarkable advantages in terms of the initiate reversible Coulombic efficiency (61.3%), high specific capacity (932 mAh g(-1) at 100 mA g(-1)), and robust long-term retention (93.5% after 600 cycles at 2000 mAh g(-1)).

Novel 3D Nanocarbon Electrodes for High-Rate Li-Ion Batteries

Portable electronic devices are negatively impacted by power density limitations of current Li-ion batteries (LIBs). Architectures or materials for faster ion and electron transport are required. Graphene-based electrodes with a 3D hierarchical structure have shown promise in LIBs due to their short ion diffusion distance, excellent electrical conductivity and high surface area. However, techniques for fabricating such hierarchical nanostructures with textural properties that can be easily tailored are still complicated and not fully developed. In this work, a low cost, green, facile, controllable and scalable approach for the fabrication of 3D hierarchical graphene-based electrodes is proposed. The 3D hierarchical structures with adjustable pores and nanowrinkles are prepared from graphene oxide or chemically functionalized graphene sheets via a wet chemical method using polymeric micro-gels as the template. The resulting 3D graphene electrodes have been used as a model 3D electrode system to establish correlations between the 3D properties (surface chemistry, defect density and textural properties) and the LIB performance (rate capability, energy capacity and durability).

Fabrication of MnO2/nanoporous 3D graphene for supercapacitor electrodes

Nanoporous 3D graphene was fabricated using NH2–SiO2 particles as a sacrificial template. For further capacitance boost, MnO2 was firstly deposited onto the nanoporous 3D graphene through the reaction between KMnO4 and graphene via the hydrothermal method. Owing to the synergistic effect between the unique nanoporous 3D graphene and the high specific capacitance of MnO2, the MnO2/nanoporous 3D graphene electrode demonstrated excellent electrochemical performance, including a high specific capacitance and an extended long cycle life. This work showed that the MnO2/nanoporous 3D graphene could present significant potential for energy storage applications.