Non-porous Carbon Research Articles

An oxygen-tolerant visible light induced free radical polymerization using mesoporous graphitic carbon nitride

A novel oxygen-tolerant visible light photoinitiating system based on in-situ generation of Fenton reagents using mesoporous graphitic carbon nitride (mpg-C3N4) in conjunction with FeCl3·6H2O, water and oxygen for free radical polymerization is described. A mpg-C3N4-catalysed photoinduced electron transfer reactions of water/oxygen and Fe3+ were demonstrated to enable generation of hydroxyl radicals that are capable of initiating the polymerization of mono and bifunctional monomers. The efficiency of the photoinitiation is controlled by specific surface area of the carbon nitride. Apparently, non-porous carbon nitrides did not yield polymers under the given conditions. Due to its heterogeneous nature, after the polymerization, although at lower rate, separated mpg-C3N4 could be used for further polymerizations.

Understanding catalytic hydrogenolysis of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) using carbon supported Ru catalysts

Herein, our study has demonstrated that microporous carbon supported Ru catalysts can selectively convert 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) in isopropanol through hydrogenolysis in a catalytic ratio of 2.47mol% under 5 bar of hydrogen at 125 °C for 1 h. DMF yield can reach 69.52% with complete HMF conversion. The effects of reaction temperature, hydrogen pressure, metal loading and reaction solvent for hydrogenolysis have been carefully investigated. In addition, to better understand the influence of the intrinsic nature of carbonaceous material, carbon materials possessing different surface texture including microporosity, mesoporosity and nonporous carbon black were used as catalyst supports, and structural properties have been comprehensively characterized by powder X-ray diffraction spectrometer (PXRD), transmission electron microscopy (TEM), nitrogen and CO2 sorption, thermogravimetric analysis (TGA), and X-ray absorption spectroscopy (XAS). We have concluded that the nature of the carbonaceous material affects the Ru nanoparticle formation upon thermal reduction. The atomic configuration of Ru nanoparticles on carbon support (i.e., metallic Ru or RuOx) would direct the catalytic pathway differently and could be attributed to the interaction between ruthenium and carbon surface.

Preparation and characterization of mesoporous activated carbons from nonporous hard carbon via enhanced steam activation strategy

Activated carbon materials have been extensively investigated as electrode materials for supercapacitors because of their low cost, high specific surface area, and high charge storage capacity. In this work, we developed activated carbon with a high specific surface area from a nonporous hard carbon (HC) material through an enhanced steam activation strategy. In general, steam activation is carried out under atmospheric pressure. The enhanced steam activation strategy introduced in this study involves controlling the pressure of the injected steam. The activated hard carbon (AHC) obtained via the proposed activation strategy exhibited enhanced textural properties compared with AHC prepared under atmospheric steam pressure. Furthermore, AHCs with a specific surface area greater than 2000 m2 g−1 were obtained in high yield within a short time. The specific capacitance of the AHCs increased by a factor of up to approximately 12.7 compared with that of the nonporous HC. Furthermore, the specific capacitance of AHCs with a higher mesopore volume was confirmed to be retained with increasing applied current, indicating high rate capability. Therefore, the proposed enhanced steam activation strategy not only improves the energy storage capacity but also is effective in forming mesopores, which is an effective approach to improving the power characteristics of activated carbon materials.

Rational design of MnO2-nanosheets-decroated hierarchical porous carbon nanofiber frameworks as high-performance supercapacitor electrode materials

A hierarchical structure is proved to be important for the improvement of electrochemical performances of MnO2-based electrode materials used in supercapacitors. However, the rational design of materials’ structure and its real performance served as electrode materials are still facing challenges. Herein, hierarchical porous carbon nanofibers using ZIF-8 nanoparticles as pore templates are designed to provide one-dimensional hollow frameworks for the growth of ultrathin MnO2 nanosheets (referred as HPCNF/MnO2). The as-prepared HPCNF/MnO2 samples have a hierarchical coaxial core-shell structure, with HPCNFs as the core and MnO2 sheets as the shell. The novel nanostructure of this hybrid provides abundant electrochemical active sites for Faradic reactions and short diffusion channels for ions/electron transport. The utilization of HPCNF/MnO2 active material with such a structure can be significantly enhanced, especially at the high current density. When evaluated as electrode materials, HPCNF/MnO2 exhibits a specific capacitance of 269 F g−1 at 0.5 A g−1 (308 F g−1 for MnO2), a high capacitive retention of 98% even after 5000 cycles at 50 mV s−1 by cyclic voltammetry (86.7% capacitance retention at 1 A g−1 after 2000 cycles) and a rate capability of 58% from 0.5 to 10 A g−1. Especially at the current density of 10 A g−1, the specific capacitance of HPCNF/MnO2 has increased by 133% compared with that of non-porous carbon fiber/MnO2 composites, demonstrating a great superiority of hierarchical porous carbon nanofibers as frameworks to support pseudocapacitive materials.

Study of Polymer-Coating on Various Types of Carbon Supports to Enhance Platinum Utilization Efficiency in Polymer Electrolyte Membrane Fuel Cell Electrocatalysts

Polymer electrolyte membrane fuel cells (PEMFCs) have been receiving ample attention as an efficient and clean power source for stationary and automotive applications.1 One of the challenges for commercialization of PEMFCs is to minimize the amount of Platinum (Pt) to lower the cost of PEMFC. Pt is the most stable and active catalyst for oxygen reduction reaction (ORR).2 Incorporation of non-precious metals and decreasing the catalyst particle size are common methods to reduce the amount of Pt used in PEMFC. However, these methods involve dissolution of non-precious metals in acidic condition3 and agglomeration of small sized Pt4, resulting in decreased Pt utilization. Therefore, improvement of Pt utilization efficiency is required. Optimizing catalyst structure by increasing number of reaction sites is a promising strategy to improve the Pt utilization efficiency. One approach is increasing mass diffusion (oxygen, proton) by selecting a non-porous carbon support like acetylene black (AB).5 However, Pt durability and utilization are limited due to lack of anchoring sites for Pt particles in AB.6 Another approach is optimizing ionomer/carbon ratio. However, recent high-resolution transmission electron microscopy studies suggest that the ionomer coverage in the electrode may be rather inhomogeneous.7 In this study, we demonstrate a novel approach to improve Pt utilization efficiency in PEMFC by preventing deposition of Pt particles into interior pores of carbon support and simultaneously providing homogeneous ionomer; Nafion coverage. This approach involves polymer coating onto carbon blacks (CBs). Polybenzimidazole (PBI) is used as the surface coating material of CB where PBI interacts with CB via π-π and acid-base interactions. It is reported that PBI coating works as the micropore capping agent of CB.8 Therefore, PBI coating can reduce number of Pt particles deposited into geometrically restricted areas of CB. Moreover, PBI coating may trigger a homogeneous Nafion coverage due to the acid-base interaction between Nafion and PBI concurrently. Three morphologically different CBs; Vulcan, Ketjen black (KB) and AB were used to investigate the Pt utilization efficiency in polymer coated CBs. The PBI coating onto CB was easily done by addition of CB into PBI dissolved N,N-dimethylacetamide and 1 hr sonication to the mixture to prepare Vulcan/PBI, KB/PBI and AB/PBI. Then Pt nano-particles were deposited via polyol reduction to prepare Vulcan/PBI/Pt, KB/PBI/Pt and AB/PBI/Pt and compared with their non-coated Vulcan/Pt, KB/Pt and AB/Pt. AB/PBI/Pt shows homogeneous Pt dispersion over AB/Pt due to the presence of binding sites through coordination of Pt with imidazole groups in PBI as an additional advantage. The micropore density of CBs is increasing in the order of AB < Vulcan < KB. Power density of CB/Pts was decreased in the following order; AB/Pt < Vulcan/Pt < KB/Pt, consistent with the order of increasing micropore density. The lower performance of KB/Pt is due to the decreased number of accessible Pts for the electrochemical reaction especially for ORR5. Interestingly, power densities of CB/PBI/Pts were higher than that of respective CB/Pts. The higher power density of CB/PBI/Pt can be attributed to the reduced inaccessible amount of Pt deposited into the micropores of CB and the reduced protonic resistance in the catalyst layer due to the homogeneous Nafion layer.9 Furthermore, power densities of CB/PBI/Pts were increasing in the order of KB/PBI/Pt < Vulcan/PBI/Pt < AB/PBI/Pt. The highest performance of AB/PBI/Pt is believed to be due to lower mass transfer limitation in the catalyst layer which is caused by the lower pore density of AB/PBI along with the uniform Nafion coverage. References Kibsgaard, J.; Gorlin, Y.; Chen, Z.; Jaramillo, T. F., J. Am. Chem. Soc. 2012, 134, 7758.Nørskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jónsson, H., J. Phys. Chem. B 2004, 108, 17886.Colón-Mercado, H. R.; Kim, H.; Popov, B. N., Electrochem. Commun. 2004, 6, 795.Tang, L.; Han, B.; Persson, K.; Friesen, C.; He, T.; Sieradzki, K.; Ceder, G., J. Am. Chem. Soc. 2010, 132, 596.Park, Y.-C.; Tokiwa, H.; Kakinuma, K.; Watanabe, M.; Uchida, M., J. Power Sources 2016, 315, 179.Badam, R.; Vedarajan, R.; Matsumi, N., Chem. Commun. 2015, 51, 9841.Lopez-Haro, M.; Guétaz, L.; Printemps, T.; Morin, A.; Escribano, S.; Jouneau, P. H.; Bayle-Guillemaud, P.; Chandezon, F.; Gebel, G., Nat. Commun. 2014, 5, 5229.Fujigaya, T.; Hirata, S.; Berber, M. R.; Nakashima, N., ACS Appl. Mater. Interfaces 2016, 8, 14494.Jayawickrama, S. M; Han, Z. et al., in review.

Controlled synthesis of three dimensional mesoporous C3N4 with ordered porous structure for room temperature Suzuki coupling reaction

We report on the synthesis of mesoporous graphitic C3N4 (MGCN-6) with 3D porous structure and Ia3d symmetry and controllable surface properties through a simple polymerization of an environmentally benign and non-toxic guanidine hydrochloride as a C and N precursor using KIT-6 with variable pore sizes as templates for Suzuki coupling reaction. The pore diameters (3.1–4.2 nm), specific surface areas (207–303 m2 g−1), and the specific pore volumes (0.58–0.71 cm3 g−1) of the MGCN-6 materials are finely controlled by varying the pore size of the templates used. The nano cavities of MGCN-6 with the highest specific surface area and a free amine groups are effectively utilized to chelate with Pd(OAC)2 and applied the prepared catalysts for Suzuki coupling reaction between aryl halides with phenylboronic acid derivatives under very mild and sustainable reaction conditions. The Pd(OAC)2/MGCN-6 is found to be very active and stable and exhibits an excellent reactivity and selectivity for all of substrates regardless of aryl halides with electron-withdrawing and electron donating groups at room temperature. The activity of the Pd(OAC)2/MGCN-6 is much higher than that of non-porous bulk graphitic carbon nitride and 2D mesoporous carbon nitride.

ANALYSIS OF INTERMOLECULAR INTERACTIONS IN MIXED ADSORPTION LAYERS OF SURFACTANTS

The adsorption of the surfactants mixtures of different chemical nature such as Triton X-100 and sodium hexadecyl sulfate at the surface of graphitized carbon black was studied. Using the model of phase separation (the Rubi–Rosen approach), the composition of the mixed adsorption layers and parameters of interaction between the surfactant molecules in the adsorption layers were calculated. It was found that mixed adsorption layers are enriched with molecules of the non-ionic surfactant Triton X-100.&#x0D; The purpose of the work was to study the adsorption of binary mixtures of surfactants of various chemical nature on the surface of non-porous hydrophobic carbon sorbent at different SAS ratio in mixtures.&#x0D; The results of calculations show that the composition of the adsorption layer on the surface of the GC is significantly different from the ratio of surfactants in the solution. The value of the parameter χ indicates that the mixed adsorption layer on the surface of the GC is enriched with non-ionic surfactant molecules, even with a small its content in the solution (αTХ-100 = 0,2). With an increase in the ТХ-100 molar fraction in the binary solution from 0,2 to 0,8 its share in the adsorption layer increases in approximately 1.5 times. Negative values of the interaction parameters βs indicate excessive attraction of the molecules and ions of the mixture components in the mixed adsorption layers. An increase in the absolute value of the parameter βs with an increase in αTХ-100 in the solution characterizes the enhancement of the interactions between the components in the adsorption layer.&#x0D; Thus, in the course of experiments carried out for mixed systems of SHDS-ТХ-100, the existence of a synergistic effect in relation to an increase in the adsorption of surfactants on the GC surface was established. It is found that mixed adsorption layers are enriched with molecules of the non-ionic surface active substance of the triton X-100.

All‐Cellulose‐Based Quasi‐Solid‐State Sodium‐Ion Hybrid Capacitors Enabled by Structural Hierarchy

AbstractNa‐ion hybrid capacitors consisting of battery‐type anodes and capacitor‐style cathodes are attracting increasing attention on account of the abundance of sodium‐based resources as well as the potential to bridge the gap between batteries (high energy) and supercapacitors (high power). Herein, hierarchically structured carbon materials inspired by multiscale building units of cellulose from nature are assembled with cellulose‐based gel electrolytes into Na‐ion capacitors. Nonporous hard carbon anodes are obtained through the direct thermal pyrolysis of cellulose nanocrystals. Nitrogen‐doped carbon cathodes with a coral‐like hierarchically porous architecture are prepared via hydrothermal carbonization and activation of cellulose microfibrils. The reversible charge capacity of the anode is 256.9 mAh g−1 when operating at 0.1 A g−1 from 0 to 1.5 V versus Na+/Na, and the discharge capacitance of cathodes tested within 1.5 to 4.2 V versus Na+/Na is 212.4 F g−1 at 0.1 A g−1. Utilizing Na+ and ClO4− as charge carriers, the energy density of the full Na‐ion capacitor with two asymmetric carbon electrodes can reach 181 Wh kg−1 at 250 W kg−1, which is one of the highest energy devices reported until now. Combined with macrocellulose‐based gel electrolytes, all‐cellulose‐based quasi‐solid‐state devices are demonstrated possessing additional advantages in terms of overall sustainability.

Modeling Water Uptake and Pt Utilization in High Surface Area Carbon

Local transport losses limit high-current density performance of fuel-cells, especially at low Pt-loadings. Optimizing catalyst-layer structure and material properties to mitigate these losses is critical for wide-scale fuel-cell commercialization. Carbon supports form the primary porous structure of catalyst layers in which Pt particles are deposited and ionomer films are distributed. Unlike non-porous carbon supports, high surface area carbon support is unique in its relative humidity dependent Pt utilization and performance due to presence of Pt particles in the micropores interior of carbon particles. We model water uptake and Pt utilization in catalyst layers with high-surface-area carbon support. Interactions between functional groups on the carbon pore walls and water play a vital role in controlling water uptake from water vapor by catalyst layers. Ionomer is shown to influence proton access in micropores, even though it may not deposit into the micropores.

Chitin and Chitosan—Structurally Related Precursors of Dissimilar Hard Carbons for Na-Ion Battery

Hard carbons (HCs) prepared from renewable precursors are promising cost-effective electrode-material candidates for the application in Na-ion battery. Usually these materials are derived from cellulose. Here, however, we demonstrate that other polysaccharides, such as chitin and chitosan, can be as well up-and-coming parent materials of HCs. Despite structural similarities, thermal decomposition of these two biopolymers proceeds differently, contributing to the discrepancies in physicochemical properties of resulting HCs. Although chitin- and chitosan-derived HCs have comparable d-spacings and crystallite sizes, solid-state pyrolysis of the former biopolymer leads to micromesoporous material with significant specific surface area, while that of chitosan yields nonporous carbon. Despite that, both materials deliver similar initial specific charge of 280 mAh g–1 (at C/10 rate), and their electrochemical performance starts to diverge only upon longer cycling at higher rate. With time, inorganic contaminants present in chitosan-derived HC presumably delay the diffusion of Na ions to and within the electrode and slow the rate of electrochemical reactions, eventually triggering polarization buildup. Further optimization of the chitosan-derived HC through acid treatment enables unblocking some of the micropores and increasing the carbon content in this material, therefore enhancing its active surface area and suppressing continuous fading of the specific charge.

Influence of carbon characteristics on Sb/carbon nanocomposites formation and performances in Na-ion batteries

The impact of carbon characteristics (structure, porosity and surface chemistry) on the Sb/Carbon composites formation and electrochemical performances in Na-ion batteries is investigated herein. Mesoporous and non-porous hard carbon heated at different temperatures were used to support Sb nanoparticles prepared via a ball-milling/thermal reduction synthesis approach. The mesoporous carbon presenting higher surface area and oxygen functional groups induce the formation of small Sb nanoparticles (<5 nm) well dispersed in the carbon network. For the hard carbon, the increase in the annealing temperature from 1100 to 1500 °C leads to more organized structure but lower porosity and surface functionalities having as consequence the increase of Sb nanoparticle size and the particle agglomeration. The best electrochemical performances vs. Na were achieved for hard carbon/Sb composite treated at 1100 °C which combines several advantages like dispersed Sb nanoparticle, low surface area and good conductivity (360 mAh g−1 after 200 cycles). Regarding the long-term capacity retention, for all materials a drastic decay was observed starting to 300 cycles and associated to the Sb particle size agglomeration and growth during repeated charge/discharge cycles and amorphization of Sb particles as demonstrated by post-mortem analyses.

Activated carbons prepared by the KOH activation of a hydrochar from garlic peel and their CO2 adsorption performance

Biomass is regarded as a promising low-cost precursor for the preparation of activated carbons. However, direct carbonization of biomass usually produces a low-surface-area or even non-porous carbons that are useless for CO2 capture. In this work, garlic peel was first transformed to a hydrochar by hydrothermal carbonization and then chemically activated by KOH to obtain activated carbons with high-surface-areas and large pore volumes. The microstructure and morphology of the activated carbons were characterized by N2 adsorption, SEM and XRD. Results indicate that their surface area and pore volume are mainly determined by the activation temperature and KOH/hydrochar mass ratio. Activated carbon (AC-28) obtained by KOH activation with a KOH/hydrochar ratio of 2 at 800 °C has a well-developed porosity with a surface area and pore volume of 1 262 m2/g and 0.70 cm3/g, respectively, while a reduction of the activation temperature to 600 °C (AC-26) results in a material whose corresponding values are 947 m2/g and 0.51 cm3/g. Although AC-26 exhibits a much lower surface area and pore volume compared with AC-28, it has the larger CO2 uptake of up to 4.22 mmol/g at 25 °C and 1 bar due to its higher microporosity of up to 98% and abundant narrow micropores, implying that the microporosity is one of the main factors for CO2 capture besides the traditionally-believed surface area and pore volume. The isosteric heat of CO2 adsorption indicates that the affinity between the activated carbon and CO2 molecules increases with the volume of narrow micropores less than 0.8 nm and the number of surface oxygen-containing functional groups.

Unraveling the Li2S Deposition Process on a Polished Graphite Cathode for Enhancing Discharge Capacity of Lithium–Sulfur Batteries

Solid deposition accounts for three-quarters of the theoretical capacity in lithium–sulfur (Li–S) batteries with liquid electrolyte. Despite extensive research efforts on cathode material synthesis, little knowledge has been gained so far in understanding and controlling the growth of solid discharge product in Li–S batteries. In this work, a polished graphite was used as a cathode to understand the growth mechanism of Li2S. The SEM/EDS analysis of the discharged cathodes indicates that the Li2S precipitate can grow over a micrometer in size and its morphology strongly depends on the depth of discharge (DODs) and discharge rate of the cell. In addition, the morphology evolution and the in situ electrochemical impedance spectra (EIS) show that the Li2S follows a dissolution–precipitation mechanism during its deposition on the graphite surface. Finally, a mathematical model based on the multicomponent transport theory is developed and used to describe the nucleation and precipitation phenomena on the 2D surface and the EIS spectra at different DODs. The model confirms that the surface passivation of the cathode plays a major role during the discharge of the battery and offers a simple way to measure experimentally the surface coverage as a function of the DOD in Li–S batteries. This work highlights the importance of deferring cathode surface passivation in Li–S batteries and indicates the potential utilization of nonporous carbons as alternative sulfur hosts.

Oxygen-Functionalized Mesoporous Activated Carbons Derived from Casein and Their Superior CO2 Adsorption Capacity at Both Low- and High-Pressure Regimes

We report on a simple approach for converting casein into oxygen-functionalized mesoporous carbons (MPCs) with extremely high surface areas and carbon contents (∼94%). The materials synthesized by KOH activation of a casein-based nonporous carbon precursor at a carbonization temperature of 800 °C displayed mixed micro- and mesoporosity, which can be easily controlled by simple adjustment of the amount of KOH. The optimized material MPC3, which was prepared with a KOH/carbon source ratio of 3, exhibited a highest specific surface area of 3617 m2 g–1, a pore volume of 2.16 cm3 g–1, and a pore diameter of 2.7–3.1 nm. Because of these excellent textural features, MPC3 achieved excellent CO2 uptake at 1 bar/0 °C (4.12 mmol g–1) and 30 bar/0 °C (39.1 mmol g–1), which are higher than those of mesoporous carbons and silica, activated carbon, carbon nitrides, and carbon nanotubes. The high performance is linked with the combination of excellent textural parameters and unique oxygen functionalities on the surface. ...

Composite functioning as trap of photoproducts: TiO2 nanobelts anchored to carbon particles

Abstract A composite material (TNB/SC) based on TiO2 nanobelts anchored to carbon particles (SC), and made from soybean husk, was prepared by an alkaline hydrothermal method. Microscopy analysis confirmed the nanobelt morphology of TiO2 and the incorporation of nanobelts onto carbonized soybean husks in the effective formation of a TNB/SC composite. XRD analysis ascertained the formation of the anatase phase in the TNB/SC composite. X-ray fluorescence spectroscopy and elemental analysis defined the 1.2:1 TiO2:carbon ratio. UV–Vis diffuse reflectance spectroscopy assessed lower band-gap energy in the composite than in the similarly prepared TiO2 nanobelts. Fourier transform infrared spectroscopy showed that the functional groups of the carbon are retained in the composite. Nitrogen adsorption isotherms revealed that the hydrothermal conditions served for the activation of the non-porous carbon obtained from soybean husk, thus creating micro and mesopores and increasing the specific surface area value. The photocatalytic activity of the TNB/SC composite was studied by the degradation of an aqueous solution of the dye Basic Yellow 28 (BY28). The photoproducts were monitored and identified using HPLC-DAD and HPLC-ESI-QToF-MS chromatography. The degradation capacity of the TNB is preserved in the TNB/SC composite. Photodegradation and adsorption go hand in hand during the decolorization of the solution since the hydroxylated hydrazono-indolium species, and small molecules formed photocatalytically by the TNB, get adsorbed on the carbonaceous portions of the composite. Thus, we reliably disaffirm synergism reflected as an increase in the composite's photoactivity, but rather as the combination of two phenomena for elimination effectiveness. It was demonstrated that the observed total decoloration does not necessarily lead to the mineralization of the dye solution.

Progress, status and prospects of non-porous, heteroatom-doped carbons for supercapacitors and other electrochemical applications

A remarkable amount of work on non-porous carbons has been done by few research groups and some important and very interesting features have been described. The conceptual idea of pseudo effect due to heteroatoms in the carbon framework has been expected to give rise to huge specific capacitance from high-density non-porous carbon that will result in high volumetric capacitance. The focus was on their redox activity in electron transfer from electrolyte ion to heteroatoms in carbon electrodes with negligible contribution from the electrical double layer. Various types of interesting structures like nanofibers, and microspheres have been described. The presence of heteroatoms increases the electroactivity of nanofibers and microspheres of carbon and significantly affects their faradaic reactions at electrode–electrolyte interface, which gives surplus pseudocapacitance. As a result of these investigations, non-porous nanostructured carbons decorated with P-, F-, B-, N- and O-heteroatoms in different structural positions have been described. These materials have been provided with excellent pseudocapacitive performance. Many experimental results are being reported here with various electrolytes, for a supercapacitor device and other electrochemical applications.

Nitrogen-doped hierarchical porous carbon from polyaniline/silica self-aggregates for supercapacitor

Abstract In this paper, nitrogen-doped hierarchical porous carbon (N-HPC) was prepared from polyaniline (PANI)/silica self-aggregates. H-bonding between N H groups in aniline/PANI and OH groups in nano silica template led to a self-assembly type, which enabled the formation of uniform N-HPC nanoparticles. Silica self-aggregates provided macroporous channels resulted in a decreased diffusion distance. After removing the hard template, the N-HPC had a high surface area (899 m2·g−1). Owing to two co-existed synergetic energy-storage mechanisms and the hierarchical porous structure, the obtained N-HPC exhibited a high specific capacitance of 218.75 F·g−1 at 0.5 A·g−1, compared with the nonporous nitrogen-doped carbon (N-C) derived from pure PANI. Moreover, the N-HPC electrode demonstrated excellent cycle life, retaining 99% of its initial specific capacitance after 1000 cycles.

Controlled synthesis of cobalt nanocrystals on the carbon spheres for enhancing Fischer–Tropsch synthesis performance

Abstract Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine cobalt nano-particles was studied. Thermal decomposition synthesis method was applied to obtain cobalt catalysts with high dispersion and narrow particle size distribution. Furthermore the cobalt size can be controlled by the molar ratio of o-dichlorobenzene/ benzylamine. Compared with supported cobalt catalysts prepared by incipient wetness impregnation method and ultrasonic impregnation method, the catalyst prepared by thermal decomposition method showed higher catalytic activity, higher long chain hydrocarbons selectivity and lower methane selectivity.

Immense Microporous Carbon@Hydroquinone Metamorphosed from Nonporous Carbon As a Supercapacitor with Remarkable Energy Density and Cyclic Stability

We report transformation of a cost-effective nonporous carbon (NC) to an immense microporous carbon (IMC) employing a simple chemical activation route at 750 °C. N2 adsorption/desorption experiments revealed a remarkable increase in BET surface area (80–3030 m2 g–1) for successor nanomaterial (IMC) in comparison to precursor nanomaterial (NC) presumably due to enhanced accessibility of reaction surface area on carbon material for oxidants to react. In consequence, 250 times specific capacitance enhancement (2.5–605 F g–1 at 0.5 A g–1 current density) was observed in 2 M H2SO4 using a three-electrode configuration. Further, a massive specific capacitance of 1177 F g–1 with a remarkable energy density of 163 Wh kg–1 has been achieved by addition of hydroquinone in electrolyte with IMC (IMC@H2Q) employing a two-electrode configuration. Notably, a simple electrode potential dependent chemical reversibility for hydroquinone redox chemistry in the long term cyclic experiment (95% capacitance retention after 500...

Model electrode study of Ru@Pt core-shell nanosheet catalysts: Pure two-dimensional growth via surface limited redox replacement

Bimetallic nanostructures utilizing Pt and other metals have garnered much interest particularly in the form of non-Pt core@Pt shell structures. The use of two-dimensional nanosheets as the catalyst core is a promising approach since the nanosheets offer high utilization and stability owing to their atomic scale thickness and extended surface. In this work, we demonstrate the pure two-dimensional growth of Pt overlayers on a Ru nanosheet core supported on a flat, non-porous glassy carbon surface. The atomically-controlled deposition of the Pt shell was carried out by Surface Limited Redox Replacement (SLRR) in a one-cell configuration, using adsorbed Cu as a mediator prepared by underpotential deposition. The catalyst surface coverage determined by Cu stripping voltammetry showed that the surface of the nanosheet catalysts was completely covered by Pt after 2 SLRR cycles and maintained the original atomic flatness of the Ru nanosheet core. Consecutive SLRR cycles resulted in the two-dimensional growth of Pt multi-layers without significant increase in roughness, in contrast to the case where a porous carbon black support was used. The catalysts performance was investigated by hydrogen oxidation reaction and oxygen reduction reaction measurements.