Thin Carbon Sheet Research Articles

Resistive Heating Catalytic Micro-Reactor for Process Intensified Fuel Reforming to Hydrogen

Abstract Process intensification of fuel reforming using micro-reactors has become crucial for feed flexibility in H2 production for fuel cells. In the literature on microreactors, energy supply for these endothermic reactions has faced limitations, relying on external heating, or autothermal operation. This paper explores a novel approach using a thin-film catalytic heater to develop micro-reactors. The study focuses on dry methane reforming in a simplified micro-reactor where thermal energy is supplied through electric resistive heating of a thin carbon sheet with a catalyst applied to its surface. The thin catalytic heated layer inside the reactor minimizes energy losses and the reactor footprint. Power input was varied from 90-225 W to understand its impact on the reactor temperature, CH4 conversion, H2 and CO yields. Fast thermal response times were achieved using the carbon paper as thin film for heating. Ni/MgO impregnated onto carbon paper was utilized as the catalytic heating element which resulted in CH4 conversions greater than 60% at temperature above750 K. Influence of operating conditions such as the input molar ratio of CO2/CH4, and gas hourly space velocity (GHSV) were also investigated to understand the scope of the catalyst in this setup. High GHSVs (592,885 and 948,617 mL/(hr.gcatalyst)) were tested to understand the throughput achievable using this setup. This approach demonstrates improved scope and feasibility for further intensification compared to conventionally heated microreactors. The research paves the way for efficient and compact micro-reactors for fuel reforming processes.

Green preparation of flake nano porous carbon: For sulfur scaffolds in high-performance lithium sulfur batteries

In this report, we describe the creation of 2D porous nitrogen-doped carbon nanosheets using carbon precursors derived from silkworm cocoon biomass and CaCl2, a non-toxic and environmentally friendly material. The resulting carbon material exhibits a unique structure of nitrogen-doped nanosheets, extensive pore structure, and a significant specific surface area of 675 m2 g−1, which is attributed to the effect of Ca2+ on the structural conformation of silk glue protein. The high nitrogen doping, thin carbon sheets, and dense pore structure of the electrode material contribute to its excellent electrochemical performance. When used in a lithium‑sulfur composite electrode, it demonstrates exceptional electrochemical properties, including a very high initial capacity of 1403 mAh g−1, good multiplicity performance, and excellent cycling performance (700 mAh g−1 after 100 cycles at 0.1 C, 319 mAh g−1 after 1000 cycles at 1 C, and a capacity decay rate of 0.07 % per cycle). Importantly, the preparation strategy avoids the use of strong acid and alkaline structural restructuring agents, and provides an effective and green way to prepare advanced porous carbon electrode materials for lithium‑sulfur batteries.

Tuning the electrochemical capacitance of carbon nanosheets by optimizing its thickness through controlling the carbon precursor in salt‐template

AbstractHerein, two‐dimensional (2D) carbon nanosheets derived from biomass precursor is successfully synthesized via a cost‐effective salt‐templated process. Microstructural characterization and Raman spectral analysis of the sample derived from the salt template method reveals the formation of carbon nanosheets. The nanosheet thickness and its capacitance have been altered by varying the carbon precursor to salt‐template ratio. From the AFM data, the thickness of the as‐prepared thin carbon sheet was measured as ~5.16 nm, and the other thicker carbon sheet thickness was determined to be between 24 and 38 nm. The Brunauer Emmett Teller (BET) analysis shows that the thinner nanosheets possess a high specific surface area (SSA) of 485 m2 g−1, with slit‐pore geometry having a total pore volume of 0.29 cm3 g−1. Hence, compared to thicker carbon nanosheets (63.6 F g−1), the thinner carbon nanosheets exhibit superior electrochemical capacitance of 146 F g−1 in an aqueous 6 M KOH electrolyte, without employing any chemical activation. The electrochemical series resistance of as‐prepared carbon nanosheet samples was found to be <1 Ω with charge transfer resistances in the range of 0.29 Ω (thicker sheets) to 0.18 Ω (thinner sheets). The specific capacitance and electrochemical properties vary significantly when the nanosheet thickness has been tuned from thicker to thinner by altering the starch ratio in NaCl. The two‐electrode cell assembled using thinner carbon nanosheets exhibited the capacitance of 70.1 F g−1 with energy and power densities as 9.7 Wh kg−1 and 20 kW kg−1 respectively.

WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

KCl-assisted synthesis of hierarchically porous carbon materials from water-soluble 2-hydroxyethyl cellulose for high-performance green supercapacitors

Hierarchically porous carbon materials (HPCMs) with large specific surface area (SSA) and interconnected hierarchical pore structures were prepared from 2-hydroxyethyl cellulose (HEC) via eco-friendly ice-templating and KCl-assisted carbonization. Morphological assessments revealed that the HPCMs had sponge-like porous structures with thin carbon sheets and interconnected pores. With increasing amounts of KCl, the SSA and pore volume of the HPCMs increased to 1095.74 m2 g−1 and 1.23 cm3 g−1, respectively. In a three-electrode system, the HPCM-based electrode exhibited a high specific capacitance of 278.09 F g−1 at 1 A g−1 in a 6.0 M KOH electrolyte. In a two-electrode system, a symmetric capacitor device exhibited a high specific capacitance of 67.23 F g−1 at 1 A g−1 with a capacitance retention of ∼80% at 30 A g−1, and an excellent cycling ability of ∼100% after 10,000 cycles at 10 A g−1. Additionally, a symmetric device showed a high-power and high-energy density of 15,000 W kg−1 and 9.34 Wh kg−1, respectively. These results reveal that HPCMs prepared from HEC with KCl can be a potential electrode material for high-performance green supercapacitors.

Large-scale and low-cost synthesis of porous carbon on the surface of commercial chlorinated polymers under the action of an intense electron beam of microsecond duration

The formation of a layer of porous carbon on the surface of low-cost commercial chlorinated polyvinyl chloride (CPVC) with the addition of ferrocene under the action of an intense electron beam of microsecond duration was investigated. The polymer was irradiated using a pulsed fore-vacuum plasma source of a large-diameter electron beam (cross-sectional area ∼100 cm2), which allows minimizes polymer charging during irradiation. The methods of scanning and transmission electron microscopy, EDX spectroscopy, Raman and X-ray photoelectron spectroscopy were used to study the carbon layers. We found that the carbon layer consists mainly of thin (∼10 nm) sheets of amorphous carbon containing curved graphene layers up to 4 nm in length. According to the XPS data analysis, the relative fraction of graphitized carbon (sp2-hybridized carbon) reaches 80% in the surface layer with a thickness of up to 3 nm. Possible mechanisms for the formation of a porous carbon layer on the CPVC surface were discussed. The porous carbon layer has a specific capacitance of 14 mF/cm2 at a scan rate of 5 mV/s. In many applications, it can be an alternative to the laser-induced graphene formed on the surface of expensive high-temperature polyimide.

High-performance discarded separator-based activated carbon for the application of supercapacitors

The high-performance activated carbon prepared from low-cost precursors is urgently needed for supercapacitors. In this paper, a novel activated carbon that has excellent electrochemical performance and uses the discarded separators of end-of-life supercapacitors as precursors is proposed. Through high-temperature carbonization and subsequent activation treatments, the obtained separator-based activated carbon had a high specific surface area of 2187.36 m2/g. In addition, it had a thin carbon sheet structure and a small amount of microcrystalline structures, which shorten ion transport distance and improve electrical conductivity. These characteristics endowed a high specific capacitance of 208 F/g at 1 A/g in an aqueous electrolyte, which remained at 82.2% even at a high current density of 10 A/g. In addition, after 10,000 cycles, the capacitance still remained at 93.42%, indicating great cycle stability. Furthermore, when a high-voltage organic electrolyte was used, the supercapacitor assembled by the separator-based activated carbon delivered a high energy density of 41.82 Wh/kg at a power density of 1349.2 W/kg, suggesting great application potential. Overall, this work provides an alternative method for recycling discarded cellulose separators from end-of-life commercial supercapacitors, which would be feasible for waste secondary battery recycling.

Complex viscosity of graphene suspensions

Atomically thin flat sheets of carbon, called graphene, afford interesting opportunities to study the role of orientation in suspensions. In this work, we use general rigid bead-rod theory to arrive at general expressions from first principles for the complex viscosity of graphene suspensions. General rigid bead-rod theory relies entirely on suspension orientation to explain the elasticity of the liquid. We obtain analytical expressions for the complex viscosity of triangular and hexagonal graphene sheets of arbitrary size. We find good agreement with new complex viscosity measurements.

Synthesis of MnO anchored on carbon sheet networks using NaCl as template and its improved lithium-storage properties

MnO is considered as an attractive anode material for lithium ion batteries. However, the drastic volume changes during lithiation, and the low intrinsic conductivity will restrict the application of MnO anode. In this work, the MnO@carbon network hybrid is fabricated through template-based synthesis combing with vacuum freeze-drying, followed by a thermal reduction process. The resulting composite (MnO@carbon networks hybrid) is made up of thin carbon sheet networks and MnO particles anchored on carbon networks. The thin carbon sheet networks with high electrical conductivity can efficiently improve the conductivity of the hybrid, shorten the transport path of Li+, and buffer the drastic volume changes of nanosized MnO particles. As a consequence, the MnO@carbon network hybrid shows improved lithium-storages properties, which exhibits a highly reversible capacity of 1027 mA h g-1 at 0.2 A g-1 after 100 cycles and outstanding rate capacity of 321 mA h g-1 at 5 A g-1.

Construction of three-dimensional graphene like carbon on carbon fibers and loading of polyaniline for high performance asymmetric supercapacitor

Integrated three-dimensional (3D) hierarchical carbons are of particular interest to supercapacitors since they are good matrix for supporting active materials. Hereby, we have developed a simple strategy to construct 3D graphene like thin carbon sheets on carbon fiber paper (3DGC-CFP) using a template method according to the presence of glucose at high temperature. The 3DGC-CFP exhibits high surface area, good conductivity and good mechanical property, and could bear compression, which could enhance the performance of active materials. After coating of polyaniline (PANI), 3DGC/PANI-CFP has been fabricated, which shows a high specific capacitance of 1013 F g−1 at 1 A g−1 and good cycling stability. Furthermore, an asymmetric supercapacitor has been assembled using 3DGC/PANI-CFP and activated carbons (AC). It exhibits a high cell specific capacitance of 151.8 F g−1 within 1.6 V according to a specific energy of 54 Wh kg−1. A simple model has been developed to reveal the influence of mass ratio between negatvie and positive electrodes on the cell performance. In addition, the temperature effect on the cell performance has also been evaluated in view of practical applications. This work sheds light on constructing integrated 3DGC-CFP and loading of PANI for supercapacitor applications.

Unraveling the Polymer Chain-Adsorbed Constrained Interfacial Region on an Atomistically Thin Carbon Sheet.

Confinement of graphene and its functional derivatives in synthetic and biomacromolecules has been widely demonstrated recently to manifest in several multiscale phenomena in their mixtures. However, the intricate adsorbed interfacial region formed between polymer chains and a single layer of atomistically thin carbon sheet hitherto evaded an understanding of its nature and characteristics. Here, we reveal the structure of this constrained region and estimate the thickness of the adsorbed polymer layer on a single layer of an atomistically thin graphene oxide sheet using both direct experiments and molecular dynamics simulations. We use small-angle neutron scattering on a model multicomponent mixture formed by an adsorbing polymer, graphene oxide, and solvent for revealing the structure of the constrained interfacial region. We quantify the intricate adsorbed polymer layer thickness on a single layer of atomistically thin graphene oxide sheet by Euclidean approximation of the experimentally observed self-similar interfacial structure. The state of polymer chain random walk and influence of unadsorbed chains under experimental conditions are investigated and juxtaposed against the accuracy of this quantification. For long-chain polymers, the adsorbed layer thickness increases with increasing polymer molecular weight and shows a scaling relationship δ ∼ Rg0.22 with the polymer radius of gyration. For short-chain polymers, the thickness is nearly independent of molecular weight and shows a scaling relationship δ ∼ 0.6 Rg0.22. Coarse-grained molecular dynamics simulations performed on a model system similar to experiments qualitatively ratify the experimentally observed molecular weight-thickness relationship. Simulations show no discernible scaling relationship between radius of gyration and adsorbed layer thickness for low-molecular-weight polymers but show a consistent scaling δ ∼ Rg for high-molecular-weight polymers. A comparison between results from experiments and simulations indicates a discerning pathway in deciphering interface-governed multiscale phenomena in mixtures of adsorbing macromolecules with graphene and its functional derivatives.

N-Doped 3D Porous Ni/C Bifunctional Electrocatalysts for Alkaline Water Electrolysis

Water electrolysis offers a promising approach toward future sustainable energy mix utilizing hydrogen as energy carrier. Bifunctional catalyst which is active in both oxygen and hydrogen evolution reactions can significantly enhance total electrochemical water splitting efficiency and simplify electrolysis systems. In this study, nitrogen doped nickel-containing porous carbon networks were prepared to fulfill this role. Peptone was used as carbon and nitrogen source during the synthesis and NaCl presence as a template resulted in the formation of open mesopores interconnected by thin carbon sheets with nanosized Ni particles encapsulated in the carbon matrix. A low onset potential of 53 mV and a charge transfer resistance of 3.8 Ω with excellent cycling stability were demonstrated when the optimized catalyst Ni-2 was applied in HER. It was also shown that Ni-2 onset potential, charge transfer resistance, and durability in OER were comparable to those of a commercial RuO2 catalyst. During the electrolysis...

Electrochemically assisted photocatalytic removal of m-cresol using TiO2 thin film-modified carbon sheet photoelectrode

In this study, removal of m-cresol has been performed using photoeletrocatalysis technique at the surface of titanium dioxide (TiO2) thin film-modified carbon sheet photoelectrode. A biased potential was applied across this photoelectrode illuminated by UV light to investigate the feasibility of an electrochemically assisted photocatalytic process in this degradation. For preparation of this photoelectrode, the photocatalytically active TiO2 thin film was covered on the carbon sheet by dip coating technique using economically accessible TiO2 powder (Degussa P25). It was found that the m-cresol could be degraded more efficiently by this photoelectrocatalytic process than the degradation obtained by photocatalytic oxidation or by electrochemical oxidation or alone. The effect of various parameters, such as m-cresol concentration, pH and applied potential on the photoelectrocatalytic degradation of m-cresol was studied and discussed.

Nanostructured Graphene: An Active Component in Optoelectronic Devices

Nanostructured and chemically modified graphene-based nanomaterials possess intriguing properties for their incorporation as an active component in a wide spectrum of optoelectronic architectures. From a technological point of view, this aspect brings many new opportunities to the now well-known atomically thin carbon sheet, multiplying its application areas beyond transparent electrodes. This article gives an overview of fundamental concepts, theoretical backgrounds, design principles, technological implications, and recent advances in semiconductor devices that integrate nanostructured graphene materials into their active region. Starting from the unique electronic nature of graphene, a physical understanding of finite-size effects, non-idealities, and functionalizing mechanisms is established. This is followed by the conceptualization of hybridized films, addressing how the insertion of graphene can modulate or improve material properties. Importantly, it provides general guidelines for designing new materials and devices with specific characteristics. Next, a number of notable devices found in the literature are highlighted. It provides practical information on material preparation, device fabrication, and optimization for high-performance optoelectronics with a graphene hybrid channel. Finally, concluding remarks are made with the summary of the current status, scientific issues, and meaningful approaches to realizing next-generation technologies.

Biomass derived nitrogen-doped hierarchical porous carbon sheets for supercapacitors with high performance

A facile potassium chloride salt-locking technique combined with hydrothermal treatment on precursors was explored to prepare nitrogen-doped hierarchical porous carbon sheets in air from biomass. Benefiting from the effective synthesis strategy, the as-obtained carbon possesses a unique nitrogen-doped thin carbon sheet structure with abundant hierarchical pores and large specific surface areas of 1459 m2 g−1. The doped nitrogen in carbon framework has a positive effect on the electrochemical properties of the electrode material, the thin carbon sheet structure benefits for fast ion transfer, the abundant meso-pores provide convenient channels for rapid charge transportation, large specific surface area and lots of micro-pores guarantee sufficient ion-storage sites. Therefore, applied for supercapacitors, the carbon electrode material exhibits an outstanding specific capacitance of 451 F g−1 at 0.5 A g−1 in a three-electrode system. Moreover, the assembled symmetric supercapacitor based on two identical carbon electrodes also displays high specific capacitance of 309 F g−1 at 0.5 A g−1, excellent rate capacity and remarkable cycling stability with 99.3% of the initial capacitance retention after 10,000 cycles at 5 A−1. The synthesis strategy avoids expensive inert gas protection and the use of corrosive KOH and toxic ZnCl2 activated reagents, representing a promising green route to design advanced carbon electrode materials from biomass for high-capacity supercapacitors.

Synthesis, Characterization, and Light-Induced Spatial Charge Separation in Janus Graphene Oxide

Janus graphene oxides and Janus graphenes are materials with different functionalization on opposite faces of atomically thin carbon sheets. Owing to their monolayer nature, these Janus sheets show unique properties where the functionalization on one face can modulate the properties on the opposite face. However, few general procedures to create and characterize Janus graphene oxides or Janus graphenes have been reported, and as a consequence these intriguing materials remain largely unexplored. Here we report a general synthesis of Janus graphene oxide, where particles are deposited in situ from molecular precursors on opposite faces of monolayer graphene oxide (GO). We used a silicon wafer and a polymer film to successively expose and protect alternate graphene oxide faces for asymmetric deposition of Pt and TiO2 nanocrystals, thus producing Janus graphene oxide composites (Pt|GO|TiO2). We used electron microscopy of Janus graphene oxide cross-sections to conclusively show that Pt and TiO2 particles are...

Nanostructured thin lignin-derived carbon sheets as excellent reinforcement fillers in polypropylene.

In this article, natural alkali lignin was freeze-dried and then annealed at different temperatures to achieve lignin-derived carbons (LCs) with mesh-shape or sheet-like morphology, which were incorporated into polypropylene (PP) matrix by melt compounding. Owing to the significantly increased interfacial area and improved dispersion of the carbons in the polymer matrices, with the addition of only 2 wt% relatively low temperature annealed freeze-dried lignin-derived carbon (FD-LC), the obtained PP/LC composites show notably enhanced tensile mechanical properties, including markedly improved Young's modulus and remarkably increased elongation at break compared with those of neat PP. The enhancements brought by the nano-structured thin FD-LC sheets are far more impressive than that with the same loading of particulate as-received lignin-derived carbon (AR-LC). The FD-LC filled PP composites also have rough fractured surfaces with fiber pull-out near the interface, revealing the non-negligible toughening effect of the LC. In addition, the higher temperature annealed FD-LC filler induces the further reinforcement of the composites. For the FD-LC annealed at 900 °C, the corresponding composite possesses the highest Young's modulus of 668 MPa.

Graphene-Directed Formation of a Nitrogen-Doped Porous Carbon Sheet with High Catalytic Performance for the Oxygen Reduction Reaction

A nitrogen (N)-doped porous carbon sheet is prepared by in situ polymerization of pyrrole on both sides of graphene oxide, following which the polypyrrole layers are then transformed to the N-doped porous carbon layers during the following carbonization, and a sandwich structure is formed. Such a sheet-like structure possesses a high specific surface area and, more importantly, guarantees the sufficient utilization of the N-doping active porous sites. The internal graphene layer acts as an excellent electron pathway, and meanwhile, the external thin and porous carbon layer helps to decrease the ion diffusion resistance during electrochemical reactions. As a result, this sandwich structure exhibits prominent catalytic activity toward the oxygen reduction reaction in alkaline media, as evidenced by a more positive onset potential, a larger diffusion-limited current, better durability and poison-tolerance than commercial Pt/C. This study shows a novel method of using graphene to template the traditional porous carbon into a two-dimensional, thin, and porous carbon sheet, which greatly increases the specific surface area and boosts the utilization of inner active sites with suppressed mass diffusion resistance.

GO-induced assembly of gelatin toward stacked layer-like porous carbon for advanced supercapacitors.

Layer-like nanocarbons with high surface area and good conductivity are promising materials for supercapacitors due to their good ability for effective charge-transfer and mass-transfer. In this paper, stacked layer-like porous carbon containing RGO (reduced graphene oxides) (LPCG) was constructed via the GO-induced assembly of gelatin followed by carbonization and activation processes. Under suitable conditions, LPCG-based materials with a thickness of about 100 nm and a high specific surface area (up to 1476 m(2) g(-1)) could be obtained. In the materials, the closed combination of RGO and porous carbon can be observed, which is favourable for the development of the synergistic effects of both components. The presence of GO can not only enhance the conductivity of LPCG-based materials, but also is essential for the formation of a thin carbon sheet with a stacked structure. Otherwise, the plate-like, non-stacked carbon with a thickness of about 500 nm could be formed in the absence of RGO. The porous structure along with the presence of RGO allows rapid charge-transfer and easy access and diffusion of electrolyte ions. As a result, the materials exhibited a high discharge specific capacitance (455 F g(-1) at 0.5 A g(-1), 366 F g(-1) at 1 A g(-1)), good rate capability (221 F g(-1) at density 30 A g(-1)) and good cycling stability. In aqueous electrolytes, the energy density could be up to 9.32 W h kg(-1) at a relatively low power density of 500 W kg(-1) with a good cycling stability (>96% over 5000 cycles). It was found that (1) the rational combination of RGO and porous carbon is essential for enhancing the capacitance performance and improving the cycling stability and (2) the high conductivity is favorable for improving the rate performance of the materials. The LPCG-based materials have extensive potential for practical applications in energy storage and conversion devices.

Facile synthesis of nitrogen and sulfur co-doped graphene-like carbon materials using methyl blue/montmorillonite composites

Heteroatom-doped carbon materials are currently drawing increasing interest because they show remarkable performance when applied in lithium-ion batteries, supercapacitors, and fuel cells. In this work, a facile method was developed to synthesize N and S co-doped graphene-like carbon materials using montmorillonite (Mt) after the adsorption of methyl blue (MB). The MB–Mt composites were pyrolyzed in a N2 atmosphere to carbonize the adsorbed MB within the interspace of Mt. The resulting pyrolyzed carbon/Mt composite showed a basal spacing value of approximately 0.44 nm, close to the thickness of a single graphene sheet, suggesting the formation of graphene-like carbon materials within the interspace of Mt. Then, the carbon/Mt composite was demineralized by acid washing to liberate the carbon materials. Transmission electron microscopy and atomic force microscopy results directly showed the morphology of the resulting carbon material, i.e., the stacking of thin carbon sheets. Raman spectra showed the simultaneous presence of both a D-band and G-band for the obtained carbon materials, and their intensity ratio decreased with increasing pyrolysis temperature. X-ray photoelectron spectroscopy results indicated the presence of C, S, and N atoms in the carbon materials, and the doping sites of the S and N atoms were proposed. Finally, the obtained carbon materials showed interesting electrocatalytic activity for the oxygen reduction reaction, suggesting their potential application as efficient metal-free electrocatalysts in fuel cells. Our work synthesized N and S co-doped graphene-like materials with interesting electrocatalytic activity, which proved that the templated synthesis method could be a facile approach to synthesize various heteroatom-doped graphene-like carbon materials.