Surface Area Of Carbon Materials Research Articles

Preparation of high porosity biochar materials by template method: a review.

Biochar plays an important role in soil improvement, pollutant removal, and nitrogen reduction. The excellent adsorption performance of biochar is closely related to its pore structure. Therefore, this paper combines a large amount of literatures to investigate the principle and method of preparing carbon materials by using the template method, and the idea of preparing high porosity biochar by template method was proposed. The results show that: (1) The specific surface area of the carbon materials prepared by the template method is more than 400m2g-1, and the total pore volume is more than 0.3cm3g-1, which is much higher than the biochar materials prepared under the traditional high temperature anoxic pyrolysis. (2) Compared with the hard template method, a soft template method with simple operation, low toxicity of the compound, and low cost is selected. (3) The lignin, which is also a hydrophilic carbon source similar to phenolic resin, can be used as an ideal carbon precursor. (4) In the selection of templating agents, the specific surface area and total pore volume of carbon materials prepared by using F127 as a template are relatively large, showing more excellent pore size performance. (5) Finally, the idea of using template method to prepare high porosity biochar is proposed: lignin extracted from straw material is used as precursor, block polymer F127 is used as template, an appropriate amount of a cross-linking agent and a solvent is added, and finally the target biochar material is prepared by pyrolysis carbonization.

Nanoarchitectonics of Nanoporous Carbon Materials in Supercapacitors Applications.

High surface area and large pore volume carbon materials having hierarchical nanoporous structure are required in high performance supercapacitors. Such nanoporous carbon materials can be fabricated from organic precursors with high carbon content, such as synthetic biomass or agricultural wastes containing cellulose, hemicellulose, and lignin. Using recently developed unique concept of materials nanoarchitectonics, high performance porous carbons with controllable surface area, pore size distribution, and hierarchy in nanoporous structure can be fabricated. In this review, we will overview the recent trends and advancements on the synthetic methods for the production of hierarchical porous carbons with one- to three-dimensional network structure with superior performance in supercapacitors applications. We highlight the promising scope of accessing nanoporous graphitic carbon materials from: (i) direct conversion of single crystalline self-assembled fullerene nanomaterials and metal organic frameworks, (ii) hard- and soft-templating routes, and (iii) the direct carbonization and/or activation of biomass or agricultural wastes as non-templating routes. We discuss the appealing points of the different synthetic carbon sources and natural precursor raw−materials derived nanoporous carbon materials in supercapacitors applications.

Non‐metallic printed circuit board waste derived carbon for the supercapacitor electrode material

Highly specific surface area carbon materials derived from the waste printed circuit board (WPCB) for supercapacitor electrode material are feasibly prepared via microwave carbonisation and KOH activation process with controlled activation temperature. The effect of activation temperature on the pore structure and the electrochemical performance of the products are studied. The results demonstrate that the appropriate pore structure plays an important role in the application of supercapacitor. The electrochemical performance tests show that the specific capacitance of WPCB-800 can reach 134.2 F g−1 at current density of 200 mA g−1, and the capacity retention rate is 96.2% after 2000 cycles.

On the Electrochemical Stability of PtRu Alloy Electrodes in Aqueous Acidic Baths: A Strategy for Recycling Pt and Ru

PtRu alloy nanoparticles supported on high surface area carbon material (PtRu/C) are common electrocatalysts used for the hydrogen oxidation reaction at polymer electrolyte membrane fuel cell (PEMFC) anodes. The recovery of these precious metals at the end of the lifetime of fuel cells is important for their further applications in a sustainable energy technology scenario. Here, new mechanisms for efficient recycling of the spent catalyst are proposed and examined based on the potentiodynamic dissolution of PtRu/C in chloride containing—and in chloride free dilute acidic baths, respectively, such as in 0.1 M HCl and 1 M H2SO4. During potential cycling, Ru exhibits a higher stability than Pt in 0.1 M HCl. This is in contrast to a relatively lower stability of Ru under potentiodynamic treatment in the absence of Cl−. For example, the % dissolutions of Pt and Ru are observed to be ∼72% and ∼33% during potential cycling between 0.2 and 1.6 V for 50 cycles at a scan rate of 100 mV s−1, in 0.1 M HCl. On the other hand, for similar initial Pt and Ru loadings, the corresponding dissolution values for Pt and Ru after potential cycling between 0.2 and 1.6 V for 10k cycles at a scan rate of 1 V s−1 in 1 M H2SO4 are observed to be ∼27% and ∼61%, respectively. This difference of behaviors is attributed to the formation and stability of soluble Pt and Ru species during potential cycling. The fast dissolution of Pt and higher stability of Ru found during potential cycling in dilute HCl may be explored towards separation of Pt and Ru and for separable recoveries from spent alloy catalysts. Finally, it is observed that the Pt and Ru dissolution rates during potential cycling may be enhanced through inhibition of redeposition of the dissolved species by using Cu as a surface switching species.

Surface area measurements of graphene and graphene oxide samples: Dopamine adsorption as a complement or alternative to methylene blue?

The possible use of dopamine, monitored spectroscopically, as a probe molecule for surface area measurements is investigated. Using high surface area carbon materials, including both graphene and graphene oxide (GO), the method is established as a complement or alternative to methylene blue or conventional N2 (BET) adsorption. The molecular reorientation (flat to vertical) of dopamine on the graphene and GO surface provides a direct indication of the monolayer coverage and the rapid adsorption (within 10 min to saturation) offers high convenience. The smaller dopamine molecule size and less self-repulsion compared to methylene blue can be considered to yield a more closely-packed surface coverage on the materials of interest. Especially for materials with complex morphologies and internal structures, the dopamine adsorption will therefore lead to a more ‘correct’ measurement.

Synthesis of a high-temperature stable electrochemically exfoliated graphene

A new and facile electrochemical exfoliation approach is proposed to produce better quality electrochemically exfoliated graphene with excellent high-temperature stability. The method is based on graphene exfoliation in inorganic electrolytes (e.g. (NH4)2HPO4 and (NH4)2SO4 and different combinations of these salts) where the electrolyte composition was found to have a significant impact on the yield, morphology, structure, and high-temperature stability of the graphene sheets. The graphene prepared using (NH4)2HPO4 electrolyte showed the lowest level of defects in comparison to the other electrochemically exfoliated graphene and an exceptional high-temperature stability in air, at temperatures of up to 750 °C; much higher than typical high surface area carbon materials which are unstable around 400 °C–500 °C in air. The addition of (NH4)2SO4 to the (NH4)2HPO4 electrolyte improved the exfoliation process and increased the production of single layer graphene sheets from 19% to ∼50%. These hybrid electrolytes also led to nitrogen, phosphorus, and sulphur tri-doped graphene sheets with a fewer defects and high-temperature stability in air. This simple process offers a promising approach for large scale preparation of doped graphene with fewer defects and exceptional properties for various applications.

Surface energetics of carbon nanotubes–based nanocomposites fabricated by microwave-assisted approach

Abstract

Sub-Ångström-level engineering of ultramicroporous carbons for enhanced sulfur hexafluoride capture

Ultramicroporous carbon materials are realized by exploiting nitrogen-doping and alkali ions activation strategies on classical carboxylic phenolic resins. Through tuning the nitrogen-doped content as well as activation strength and size of the alkali ions, carbon materials present pore sizes that are controlled at the sub-Ångström level from 5.8 to 7.7 Å with precision between 0.1 and 0.4 Å. The fine-tuning of the ultramicropore size using melamine as the sacrificial templating agent improves the practicality of the carbon materials for the recovery of SF6 which are larger than conventional molecules such as CO2. Resultantly, the optimized carbon material at 1 bar and 25 °C saw a >16-fold increase in SF6 adsorption from 0.39 to 6.55 mmol g−1 while the SF6/N2 selectivity reached as high as 78.8. We attribute this to the fine-tuning of ultramicropores, leading to optimizable pore sizes that allow easy access to the large surface areas of carbon materials by the SF6 molecules. Furthermore, owing to its high adsorption performance, a 1.5-fold higher breakthrough SF6 adsorption capacity alongside a 2-fold increase in SF6/N2 selectivity were realized under dynamic breakthrough conditions. The stability and recyclability of the carbon materials were also demonstrated with a long-term performance evaluation of up to 10 consecutive adsorption-desorption cycles.

Preparation of Carbon Metal Oxide Composites for Hybrid Supercapacitor Applications

Hybrid supercapacitors made of carbon – metal oxide composites are devices which can combine the advantages of both electric double layer capacitors and pseudocapacitors e.g. high energy density, high power density and high cyclibilty. Although there are many ways to make carbon – metal oxide composites, carbon nanofibers (CNFs) as high surface area carbon materials were used as matrix to host the metal oxides. Covering the carbon with metal oxides will cause a decrease in conductivity of the carbon material, hence encapsulating the metal oxides with CNFs is a way for achieving high performance system. It has been shown that blending two immiscible polymers at certain ratios, electrospinning and carbonizing them will lead to formation of carbon, in which the metal oxides can be placed. Polyacrylonitrile (PAN) as the carbon source and polymethacrylic acid (PMAA) as both metal oxide precursor carrier and in-situ porogen were blended at 1:1 ratio and electrospun. Upon annealing PMAA degraded and left pores. Adding a metal precursor to the blend solution cause interaction of metal with PMAA, hence upon degradation of PMAA, metal oxides were left in the carbon fibers. The prepared carbon – metal oxide composites not only preserves the conductivity of carbon but also adds the pseudocapacitance of metal oxides to the system which leads to a material with enhanced performance. It is predicted to load higher amounts of metal oxides using PMAA compared to conventional metal oxide carriers such as polymethyl methacrylate (PMMA), due to carboxylic groups on PMAA backbone.

Highly microporous carbon with nitrogen-doping derived from natural biowaste for high-performance flexible solid-state supercapacitor

Highly microporous carbon material with nitrogen doping has been synthesized via a facile one-step approach by employing natural biowaste miscellaneous wood fibers derived hydrochar as precursor and melamine as nitrogen source respectively. The added melamine not only results in the incorporation of some nitrogen into the carbon framework but also increases the specific surface area of carbon material. Such resultant N-doped microporous carbon possesses the functionalized nitrogen doping (1.75 at. %), a large specific surface area (∼1807 m2 g−1) and abundant highly interconnected micropores. Benefiting from the synergistic effect of high specific surface area, well-developed pore size distribution and functionalized groups, this carbon material delivers a high specific capacitance of 345 F g−1 at 0.5 A g−1, an excellent capacitance retention with 270 F g−1 at up to 30 A g−1, and a remarkable cycle ability with 91.3% retention after 10,000 cycles at 5.0 A g−1. Based on it, the as-developed flexible symmetric solid-state supercapacitor delivers a high energy density of 7.92 W h kg−1 at the power density of 250 W kg−1. Evidently, this work provides a facile and cost-effective route for functionalized natural biowaste-based carbon materials and further opens up a way for highly value-added recycling of biowaste-like materials.

Simple synthesis of porous carbon sheet by reduction reaction of in-situ formed carbon dioxide for supercapacitor application

Abstract Porous carbon sheet (PCS) was prepared by reduction reaction between NaBH4 and the in-situ formed CO2 gas from the thermal-decomposition of NaHCO3 under inert atmosphere. During this preparation process, NaHCO3 also could be used as the activation agent and increases the specific surface area of carbon materials. The obtained PCS has a specific surface area of 828 m2/g. At a current density of 0.5 A/g, the specific capacitance of the PCS electrode is 201 F/g. Furthermore, the PCS electrode exhibits excellent rate capability (80% capacitance retention at 15 A/g) and superior cycling stability. These results suggest a facile and environmental benign method to prepare economical and high quality porous carbon sheet materials for energy storage applications.

Preparation of carbon supported catalyst from cattail leaves for biodiesel fuel upgrading application

Abstract Carbon supported catalyst have been successfully synthesised from cattail leaves via hydrothermal carbonization for biodiesel fuel upgrading. This research study the effect of hydrothermal temperature (160-200 °C), reaction time (4-12 h) and influence of co-solvent such as CH3OH, C2H5OH, H2SO4, and HCl treatment to porosity and surface area of carbon material. The sample have been characterized by scanning electron microscopy, nitrogen sorption, fourier transform infrared spectroscopy were employed to characterize morphology, specific area (SBET), and surface function, respectively. The results revealed that hydrothermal-carbonization process and co-solvent treatment have effect on the properties of supported carbon. The hydrothermal temperatures and time were increased resulted in the surface area and pore volume of supported carbon gradually increased leading to increasing metal distribution on the surface of supported carbon. It can be implied that the catalyst is good catalytic activity.

Design and Development of Advanced Air-Cathodes for Li-Air Battery

NASA’s future missions demand high energy density batteries. Current state-of-the-art lithium-ion batteries (LIBs) reach the specific energy capacity limits (<250 Wh/kg), thus new electrochemical storage technologies are needed to meet NASA’s future mission requirement of >400 Wh/kg. Battery chemistries with higher theoretical energy densities in particular, Li-metal based battery chemistries such as Li-air, are being actively pursued, but there remains a number of issues to be solved. Development of advanced and optimized air cathodes will be crucial for improving capacity retention and cycle life of Li-air battery. The microstructure of carbon substrates and the catalytic oxygen reduction of the air-cathode play critical roles in the electrochemical performance in Li-air batteries. With the development and proper design of air cathodes, the energy efficiency and energy density can be enhanced significantly. In this presentation, the results of advanced permeable air cathodes design with different substrates such as 2D carbon paper or carbon cloth, vs. 3D graphene or metal foam, different high surface area carbon materials and incorporation with catalysts on oxygen reduction reactions, different porosity controlling of air cathode as well the additives in electrolyte will be presented. The cycling and rate capability performance of these air-cathodes in the Li-air cells will be discussed as well.

High surface area carbon materials derived from corn stalk core as electrode for supercapacitor

The activated carbon materials from the corn stalk core raw materials were prepared through the carbonization and activation process and applied as electrode in supercapacitor. The biomass carbon materials activated under different temperatures were tested by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge cycling method. The corn stalk core-derived material activated at 700 °C with the highest specific surface area (2349.89 m2 g−1) has exhibited the maximum specific capacitance of 140 F g−1. Further detailed characterization and theoretical analysis have demonstrated that the corn stalk core derived activated carbon anode material can not only enhance the capacity of supercapacitor but also realize the comprehensive utilization of corn stalks.

Microstructure effect of carbon materials on the low-concentration methane adsorption separation from its mixture with nitrogen

Due to the weak polarities of CH4 and N2 and their similar physicochemical properties, the microporous adsorbents have a little amount of adsorption capacity for the low-concentration methane, and the separation of CH4/N2 is also very difficult to accomplish by the adsorption-based process. Microstructure of carbon materials plays a decisive role for CH4/N2 effective separation and CH4 enrichment from the low-concentration methane gas mixed with nitrogen. This work focuses on the research of carbon material microstructure, including the selection of raw material or precursor for the carbon skeleton formation, effect of the specific surface area of carbon material on the low-concentration methane adsorption amount, the relationship between micropore size distribution of carbon material and CH4/N2 adsorption separation mechanism, and effect of different activator on the weak polar methane adsorption capacity. According to the microstructure analysis, the granular activated carbons (GACs) are prepared in lab-scale with the optimal preparation conditions, raw coconut shell carbonization for 2 h at 1073 K under N2 atmosphere and KOH activation for 1 h at 1073 K under N2 atmosphere with the KOH to carbonized material ratio of 3:1. And then, the home-made GACs (about 200 g) were packed in a column. A four-step one-bed vacuum pressure swing adsorption (VPSA) process was adopted to evaluate the low-concentration methane adsorption separation performance from its mixture with nitrogen.

Determining the Specific Surface Area of Carbon Electrode Materials for Electrodes of Supercapacitors via the Adsorption of Methylene Blue Dye

An improved way of measuring the specific surface area of carbon materials that is based on the adsorption of methylene blue is proposed. It is found that the proposed method is more accurate for microand mesoporous carbon materials than the one described in GOST (State Standard) 13144-79. It is shown that the method ensures good correlation with the measured specific electric capacitances of the materials and allows us to assess the geometric shape and average size of mesopores in an investigated carbon material.

Three-dimensional interconnected porous graphitic carbon derived from rice straw for high performance supercapacitors

Three-dimensional interconnected porous graphitic carbon materials are synthesized via a combination of graphitization and activation process with rice straw as the carbon source. The physicochemical properties of the three-dimensional interconnected porous graphitic carbon materials are characterized by Nitrogen adsorption/desorption, Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, Scanning electron microscopy and Transmission electron microscopy. The results demonstrate that the as-prepared carbon is a high surface area carbon material (a specific surface area of 3333 m2 g−1 with abundant mesoporous and microporous structures). And it exhibits superb performance in symmetric double layer capacitors with a high specific capacitance of 400 F g−1 at a current density of 0.1 A g−1, good rate performance with 312 F g−1 under a current density of 5 A g−1 and favorable cycle stability with 6.4% loss after 10000 cycles at a current density of 5 A g−1 in the aqueous electrolyte of 6M KOH. Thus, rice straw is a promising carbon source for fabricating inexpensive, sustainable and high performance supercapacitors' electrode materials.

Ordered Mesoporous Carbons with High Micropore Content and Tunable Structure Prepared by Combined Hard and Salt Templating as Electrode Materials in Electric Double‐Layer Capacitors

AbstractSynthesis of high surface area carbon materials with hierarchical pore structure is reported. Combined salt templating with ZnCl2 and hard templating with SBA‐15 is used to produce ordered mesoporous and microporous hard–salt‐templated carbons (OM‐HSTCs) from simple sucrose as carbon precursor. OM‐HSTCs achieve specific surface areas of more than 2600 m2 g−1 and total pore volumes up to 2.2 cm3 g−1. In comparison to purely hard‐templated ordered mesoporous carbons, the additional salt template leads to high micropore volume and provides control over the size/distribution of micro‐ and mesopores and over the carbon microstructure. This method combines carbonization and the formation of well‐defined micropores in one step and is more versatile in terms of resulting pore structure than previously reported routes toward ordered mesoporous/microporous carbons. When applied as electrode materials in electric double‐layer capacitors with 1 m tetraethylammonium tetrafluoroborate in acetonitrile organic electrolyte, OM‐HSTCs combine high gravimetric capacitance (133 F g−1 at 0.1 A g−1) resulting from high micropore volume with high capacitance retention under high‐power conditions (126 F g−1 at 40 A g−1), exceeding the purely microporous or purely ordered mesoporous reference materials.

Durabilty of Pt-Based Alloy Nanoparticles Supported on Functionalized Carbon Materials for the ORR – Tuning the Interaction between Particles and Support Material

In the last decades, proton exchange membrane fuel cells (PEMFC) have attracted large attention as promising renewable and clean technology for energy conversion. Designing nanomaterials with the aim to improve their electrocatalytic performance and long-term durability is still a critical challenge. Today´s PEMFC research has focused on Pt-based alloy nanoparticles combined with high surface area carbon materials due to its improved activity and stability for the ORR compared to pure Pt/C.[1,2,3] Although many studies have focused on the relations between the structural and chemical properties of the catalytically active metal nanoparticles and their catalytic ORR performance, the interactions of these nanoparticles with the carbon substrate have been rarely investigated up to date. In particular, the immobilization and stabilization of the nanoparticles on the support material have a strong influence on the long-term durability of the ORR catalysts. Therefore, one crucial point is the functionalization of the carbon support with hydroxide and carboxylate groups which seems to improve nucleation and dispersion of the Pt alloy nanoparticles; on the other hand, these oxygen-containing surface groups can accelerate the carbon corrosion associated with particle detachment during the potential cycling. Therefore, another strategy is the introduction of hetero-atoms as N-C-, C-B, C-F and C-S-bonds into the carbon framework improving their electrochemical oxidation resistance.[4,5,6,7]One target of this work is the stabilization of the carbon support material by functionalization to prevent carbon corrosion under the operating fuel cell conditions. We modified the morphology, structure and chemical properties of the porous carbon materials by using different methods such as acid treatment or thermal treatment in a reactive gas atmosphere. On the other hand, we optimized the design of Pt-based alloy (Pt-Ni, Pt-Co) nanoparticles supported on these functionalized porous carbon support materials. The properties and behavior of these materials are monitored by using high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and X-ray absorption spectroscopy (XAS). The electrochemical stability and durability of the catalysts were also investigated by applying various accelerated test protocols such as potential cycling between 0.5 - 1.0 (10.000 cycles), 0.5 - 1.5 (2000 cycles) and 1.0 - 1.5 V vs. RHE (2000 cycles). We monitored the electrochemically active surface area (ECSA) of the Pt and Pt alloy nanoparticles supported on these functionalized carbon materials during the runs to correlate its loss to the number of cycles, scan rate and potential range. Based on these results we evaluate the relationship between the carbon modification, size and chemical composition of the bimetallic nanoparticles, electrocatalytic properties and durability.Based on this study, we developed a model, describing the critical parameters to improve the interaction between the particles and the support material. This approach serves to enhance the catalytic properties and long-term durability of the ORR electrocatalysts for PEMFC applications.

Morphological features of porous silicon carbide obtained via a carbothermal method

AbstractSamples of porous silicon carbide were obtained using sucrose or carbon and aerosil or silica mesoporous molecular sieves (SBA‐3, SBA‐15, KIT‐6 and MCF). Fibers content in silicon carbide samples is higher when the mesopore surface area of carbon materials derived from carbon‐silica composites is lower. Based on the found correlation between the morphology and porosity of SiC and mesopore surface area of the carbon component in the composites, a templating action of carbon in carbothermal reduction was suggested.