Mesoporous Carbon Powders Research Articles

Alleviating anode flooding by mesoporous carbon supports for alkaline polymer electrolyte fuel cells

Water management is one of the critical issues affecting the performance and stability of alkaline polymer electrolyte fuel cells (APEFCs). This study focuses on the effect of carbon supports on the water management of APEFCs. A series of carbon-supported Ru catalysts (Ru/MCP-x) were prepared using mesoporous carbon powder (MCP-x) with three-dimensional through-nanopore structures as supports and compared with Ru/XC72. The results show that although the catalysts’ hydrogen oxidation reaction (HOR) catalytic activities are similar in KOH solutions, the APEFCs performance can be severely different. APEFCs assembled with Ru/MCP-x and Ru/XC72 (noted as Ru/MCP-x cell and Ru/XC72 cell) have little performance difference at high inlet H2 flow (1000 mL/min), but have a noticeable difference at low inlet H2 flow (200 mL/min). By combining the electrochemical AC impedance and distribution of relaxation time (DRT) method, we quantitatively identify that severe gas transfer resistance occurred in the anode catalyst layer of the Ru/XC72 cell under low inlet H2 flow, which is more in line with the actual APEFCs operating conditions, led to considerable degradation of the Ru/XC72 cell performance. The high gas transfer resistance is later ascribed to the anode flooding by combining the voltammetry curves and DRT plots. In contrast, for Ru/MCP-x cells, increasing the carbon supports’ mesopore diameter dramatically reduced the gas transfer resistance and mitigated the anode flooding. This study shows a quantitative comparison of the impacts of different carbon supports on APEFCs performance and gas transfer resistance, indicating that mesoporous carbon materials have the potential to be supports for APEFCs anode catalysts to alleviate the anode flooding.

"Carbon in Metal" Anode with High Processability for Sodium Metal Batteries.

Sodium metal batteries are ideal candidates for next-generation grid-level energy storage systems. However, severe obstacles pertain with regard to the usage of metallic Na, including poor processability, dendrite growth, and violent side reactions. Herein, we design a "carbon in metal" anode (denoted as CiM) via a facile method by rolling a controllable amount of mesoporous carbon powder into the Na metal. The as-designed composite anode is endowed with dramatically lowered stickiness and increased hardness (3 times higher than that of pure Na metal) and strength along with improved processability, which can be fabricated into foils with varied patterns and limited thickness (down to 100 μm). Besides, nitrogen-doped mesoporous carbon, which can increase the sodiophilicity, is applied to fabricate N-doped carbon in the metal anode (denoted as N-CiM), which can effectively facilitate the diffusion of Na+ ions and decrease the depositing overpotential, consequently homogenizing the Na+-ion flow and rendering a dense and flat Na deposition. Therefore, the N-CiM anode offers enhanced cycling stability for 800 h at 1 mAh cm-2 in symmetric cells and 1000 cycles with a high average Coulomb efficiency (CE) (99.8%) in full cells based on the conventional carbonate electrolyte.

The effect of porosity of activated carbon cloth cathodes on the cyclic performance of Li–S cells

Binder-free carbon cloth (CC) cathodes with tunable porosity prepared from Kynol 1500 by CO2 activation at 900 °C with the specific surface area up to 3170 m2g-1 and pore volume up to 2.05 cc g−1 have been tested in Li–S battery prototypes with catholyte solutions containing Li2S8. The capacity of CCs normalized to carbon mass is linearly proportional to the surface area and pore volume values. Capacities of CC cathodes were compared to the capacity of a composite mesoporous carbon (MPC) cathode prepared from MPC powder with PVdF binder and tested in identical conditions as sulfur host. The results indicate that pore volume of the carbon hosts is a key factor which determines the capacity of Li–S cells with lithium polysulfide catholyte solution. The effect of the surface area and pore volume of carbon cathodes on capacity and cycling performance is discussed. The possibility of attaining of a practical level of the areal capacity of 3.4 mAh cm−2 is demonstrated for the activated CC with maximal pore volume. SEM analysis of CC cathodes after prolonged cycling reveals signs of degradation of the carbon fibers' structure. The results of XPS analysis of the surface of the cycled Li anodes is discussed.

(Invited) Effects of Support Mesoporosity on Pt Dissolution in PEM Fuel Cells

Interest in hydrogen as an energy carrier continues to grow due to the high demand for clean and sustainable, energy sources in the global energy market. Polymer exchange membrane fuel cells (PEMFCs) convert the chemical energy of hydrogen to electricity and have great potential as power sources for automotive applications. A key challenge in the development of cost-efficient and reliable PEMFC electrodes is catalyst layer durability. Typically, PEMFC cathodes comprise Pt-based electrocatalysts supported on high-surface-area carbons. It has been previously shown that the morphology and surface chemistry of carbon supports play significant roles in modulating both the activity and stability of Pt-based catalysts.Here, we will present our recent efforts to investigate the effects of the porous structures and surface properties of different mesoporous carbon powders on Pt dissolution in PEMFC cathodes. Using atomic layer deposition (ALD), we fabricate cathodes by depositing Pt nanoparticles of uniform sizes and mass loadings onto mesoporous carbon supports with varying pore sizes and surface areas. We then evaluate the beginning-of-life and end-of-life performance of these cathodes after accelerated Pt dissolution tests under single cell conditions, while comparing them to a microporous Ketjenblack-based cathode as a benchmark. Based on our findings, we discuss new insights into the underlying mechanisms for Pt dissolution within the porous structures of mesoporous carbon supports.

Mesoporous carbon decorated with MIL-100(Fe) as an electrochemical platform for ultrasensitive determination of trace cadmium and lead ions in surface water

In this work, MIL-100(Fe)-decorated mesoporous carbon powders (MC@MIL-100(Fe)) were prepared by in situ growth of MIL-100(Fe) on the surface of ZIF-8 framework-based mesoporous carbons (MC). The hybrid material was characterized using SEM equipped with EDS mapping for morphology investigation, X-ray photoelectron spectroscopy for chemical valence analysis, and X-ray diffraction for crystal structure determination. The developed sensor separated from the traditional bismuth film decoration, and simultaneously, MC@MIL-100(Fe) was applied for the first time to electrochemically detect trace amounts of Pb(II) and Cd(II). The fabricated MC@MIL-100(Fe)-based electrochemical sensor showed excellent response to the target analytes at –0.55 and − 0.75 V for lead and cadmium ions, respectively. By adjusting some measurement parameters, that is, the loading concentration of MC@MIL-100(Fe), acidity of the HAc-NaAc buffer (ABS), deposition potential, and deposition time, the analytical performance of the proposed electrochemical sensor was examined by exploring the calibration curve, repeatability, reproducibility, stability, and anti-interference under optimized conditions. The response current of the proposed MC@MIL-100(Fe) electrochemical sensor showed a well-defined linear relationship in the concentration ranges of 2–250 and 2–270 μg·L−1 for Cd(II) and Pb(II), respectively. In addition, the detection limits of the sensor for Cd(II) and Pb(II) were 0.18 and 0.15 μg L−1, respectively, which are well below the World Health Organization (WHO) drinking water guideline value. The MC@MIL-100(Fe) can be potentially used as an electrochemical platform for monitoring heavy metals in surface water, with satisfactory results.

Oxygen and nitrogen enriched pectin-derived micro-meso porous carbon for CO2 uptake.

Oxygen and nitrogen enriched micro–meso porous carbon powders have been prepared from pectin and melamine as oxygen and nitrogen containing organic precursors, respectively. The synthesis process has been performed following a solvothermal approach in an alkaline solution during which Pluronic F127 was added to the solution as the soft template. Following the solvothermal treatment, the carbonization process has been performed at 700, 850 and 950 °C. The synthesized porous carbons have been characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and Fourier transform infrared spectroscopy (FTIR). The surface area of 499.5 m2 g−1, total pore volume of 0.35 cm3 g−1, and a high nitrogen and oxygen content of 9.3 and 29.1 wt% are displayed for the fine sample. The optimal porous carbon had CO2 adsorption of up to 3.1 mmol g−1 at 273 K at 1 bar owing to abundant basic nitrogen-containing functionalities and the valuable micro–meso porous structure. Despite the absence of any reagent and also having a relatively moderate specific surface area, compared to similar materials, a very high ratio of adsorption capacity to specific surface area (6.2 μmol m−2) was observed. The Elovich kinetic model was found to be the best and the physisorption process was reported.

Synthesis of mesoporous carbon powder from gold beard grass pollen for use as an anode for lithium-ion batteries

There is a large amount of energy used in everyday life. Whether it is inside a residence, transportation, or even the production process of consumer goods, these activities require a tremendous energy amount. Currently, there is a need for more energy. Lithium-ion batteries are of particular interest due to their small size, low weight, high electrical Capacity, safety, and long life. Carbonaceous anode materials are commonly utilized in energy storage systems. This study synthesized mesoporous carbon powder from bee-collected pollens through carbonization and KOH activation as an anode in lithium-ion batteries. An X-ray diffractometer (XRD) was used to characterize phase formation. Raman Spectrometer analyzed the relation between the strain components and the change of the Raman peak's wavenumber. Also, a Scanning electron microscope (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) were used to characterize the microstructure and chemical composition. In addition, the electrical properties of the sample were also tested. These outstanding results open new paths towards the development of novel Li-ion batteries.

Enhanced thermoelectric composite performance from mesoporous carbon additives in a commercial Bi0.5Sb1.5Te3 matrix

Composites were prepared, through hot pressing, using carbon materials with different pore size distributions as additives for commercial Bi0.5Sb1.5Te3 thermoelectric material (BST, p-type). Thermoelectric properties of the composites were measured in a temperature range of 298‒473 K. Thermal conductivity of the composites, especially lattice thermal conductivity, was effectively decreased due to the mesoporous properties of the incorporated carbon additives. The electrical conductivity of the composites slightly decreased due to the electron scattering at the interface between the carbon material and the commercial BST matrix. The composite with 0.2 vol.% mesoporous carbon powder (36% mesoporosity) exhibited a figure of merit value approximately 10.7% higher than that of commercial BST without additives. This behavior resulted in 116% improved output power in the composite block-based single element compared with a bare BST thermoelectric block. The enhanced figure of merit was attributed to the effective reduction of lattice thermal conductivity by acoustic phonons scattering at the interface between the BST matrix and the mesoporous carbon as well as at the pore surfaces within the mesoporous carbon. By utilizing mesoporous carbon materials used in this study, the shortcomings and economic difficulties of the composite process with low dimensional carbon additives (carbon nanotubes, graphene, and nanodiamond) can be overcome for extensive practical applications. Mesoporous carbon powder with a tailored porosity distribution revealed the validity of bulk-type carbon additives to enhance the figure of merit of commercial thermoelectric materials.

A novel approach for development of graphene structure in mesoporous carbon of high specific surface area

The challenge of developing highly graphitized regions in mesoporous carbon powders via non-catalytic approach has been the focus of many researchers worldwide without much noticeable achievements. Here, in this work, for the first time, we report the profound effect of the addition of water soluble planar polyaromatic hydrocarbon molecules (PAH) on the development of graphene structure within amorphous carbon matrix, as confirmed by our detailed analytical experiments. The formation of rather long-range ordered graphene layers for the prepared samples is believed to be mainly governed by the initial spatial planar alignments of benzene rings of phenolic resin monomers and those of PAHs molecules. Amongst the synthesized samples, the highest specific surface area (∼620 m2/g) and electrical conductivity (∼6.25 S/cm) were obtained for Emodin added sample as a non-metallic graphitizing agent. Such rather high specific surface areas and electrical conductivity potentially promises wide range of interesting applications for mesoporous carbon materials.

Synthesis of ordered mesoporous carbon films with a 3D pore structure and the electrochemical performance of electrochemical double layer capacitors

Ordered mesoporous carbon films with a 3D pore structure (COU-3) were synthesized by a soft-templating method using resorcinol (R)/formaldehyde (F) as a carbon source and Pluronic F127 as a template agent. The carbon films were prepared by a spin-coating technique. From the results of X-ray diffraction pattern, field emission scanning electron microscope and transmission electron microscope observation, the structure of the COU-3 film was determined to be an Im3m structure whose c-axis is oriented perpendicular to the film surface. The pores run in the directions both perpendicular and parallel to the film surface. The porous structure of the film is different from the ordered mesoporous carbon powders and thick films (COU-1 and COU-2) which were synthesized using the same precursor solution. In the preparation of the COU-3 films, the self-assembly and condensation of a RF-F127 composite immediately occurred during the spin-coating. In this process, the RF-F127 composites are arranged on a substrate surface and an ordered structure spreads from the substrate surface to an upper region. The electrochemical performance of electrochemical double layer capacitor was examined. The CV curves are flat and rectangular in shape, and did not change even at a high scan rate, indicating that the internal resistance in grain boundary and the contact resistance with the substrate can be ignored in the COU-3 film. Additionally, the COU-3 film shows good cycle stability after 250 cycles.

Synthesis of mesoporous carbons using a triblock copolymer containing sulfonic acid groups and their capacitance property

Mesoporous carbon films and powders were synthesized by a soft-templating method using a triblock (poly(α-methylstyrene)-hydrogenated polybutadiene-poly(α-methylstyrene), PS-PB-PS) copolymer (S-BCP) as a template. In the triblock copolymer, the polystyrene blocks are functionalized with hydrophilic sulfonic groups. Therefore, they not only interact with hydrophilic carbon sources (resorcinol) but also act as an acid catalyst for polymerization of a resorcinol–formaldehyde composite. Spherical pores with 20 nm in size which are connected to each other were found in both the carbon film and powder products of the carbon (COU-4). The spherical pore structure of the mesoporous carbon can be explained by a surfactant packing parameter (g value). The hydrophilic tails of the triblock copolymer contain bulky phenyl groups and sulfonic acid groups in the PS blocks. Therefore, the structure of the RF–S-BCP composite becomes conic. After the KOH activation, the BET surface area of the mesoporous carbon powders was largely increased from 261 m2 g−1 to 1862 m2 g−1 and the micropore volume was increased from 0.04 cm3 g−1 to 0.31 cm3 g−1. The KOH activated carbon powder (K-COU-4) shows superior capacitance performance in aqueous electrolyte solutions over microporous carbon (K-AC) and the previously reported ordered mesoporous carbon (K-COU-2).

Mesoporous carbon amperometric glucose sensors using inexpensive, commercial methacrylate-based binders

Two ordered, soft-templated mesoporous carbon powders with cubic and hexagonal framework structure and four different commercial, low cost methacrylate-based polymer binders with widely varying physical properties are investigated as screen printed electrodes for glucose sensors using glucose oxidase and ferricyanide as the mediator. Both the chemistry and concentration of the binder in the electrode formulation can significantly impact the performance. Poly(hydroxybutyl methacrylate) as the binder provides hydrophilicity to enable transport of species in the aqueous phase to the carbon surface, but yet is sufficiently hydrophobic to provide mechanical robustness to the sensor. The current from the mesoporous carbon electrodes can be more than an order of magnitude greater than for a commercial printed carbon electrode (Zensor) with improved sensitivity for model glucose solutions. Even when applying these sensors to rabbit whole blood, the performance of these glucose sensors compares favorably to a standard commercial glucose meter with the lower detection limit of the mesoporous electrode being approximately 20mgdL−1 despite the lack of a separation membrane to prevent non-specific events; these results suggest that the small pore sizes and high surface areas associated with ordered mesoporous carbons may effectively decrease some non-specific inferences for electrochemical sensing.

MESOPOROUS CARBON POWDER GAS SENSORS FOR DETECTION OF CARBON MONOXIDE

This article reports a new class of silicon-based microgas sensors utilizing hexagonally-ordered mesoporous carbon powders (MCPs) as the sensitive film. The mesoporous carbon powders featuring high-specific surface area are replicated by the SBA-15 silica template and immobilized between Cr electrodes on a 9 × 9 cm silicon chip by using a.c. dielectrophoresis (DEP) process at room temperature. The silicon sensor platform comprises Cr microheaters embedded in a dielectric thin membrane manufactured by microelectromechanical systems back-etching techniques. It is shown that MCPs can be satisfactorily aligned along electric fields and accumulated to the electrode area. Investigations into CO detection are carried out to verify gas-sensitive characteristics of the MCP nanofilm. Our experimental results disclose the mesoporous carbon powders are successfully chemoresistive to CO , and demonstrate distinct resistance change with respect to ppm-level variation. In addition, response time, recovery time, and reproducible sensing behavior are experimentally obtained.

Microfabrication and chemoresistive characteristics of SBA-15-templated mesoporous carbon gas sensors with CMOS compatibility

We describe a new class of silicon-based gas sensors that employ gas-sensitive films made of hexagonally ordered mesoporous carbon nanopowders. The mesoporous carbon powders (MCPs) are replicated by the SBA-15 silica template and immobilized between interdigitated Cr electrodes on a 300 μm × 300 μm active area using an alternating current dielectrophoresis (DEP) process at room temperature. The silicon sensor platform comprises Cr microheaters embedded in a dielectric thin membrane formed by conventional back-etching techniques with microelectromechanical systems (MEMS) manufacturability and complementary metal oxide semiconductor (CMOS) compatibility. It is observed that MCPs can be satisfactorily aligned along electric fields and accumulated to the electrode region. Comprehensive investigations are carried out to evaluate the gas-sensitive characteristics of MCP nanoparticles to gases such as O 2 and NH 3 for the first time. Experimental results disclose that the amorphous carbon powders are chemoresistively sensitive to oxidising and reducing gas species, and demonstrate distinct resistance change with gas concentrations in ppm-level. Fast response times estimated as ∼100 s for O 2 and ∼90 s for NH 3 and reproducible response behaviour are observed. The measured characteristics reported in this paper make MCPs a competitive alternative to carbon nanotubes (CNTs) because of their superior porosity, high specific surface area and cost-effective immobilization process.

Synthesis of ordered mesoporous carbon films, powders, and fibers by direct triblock-copolymer-templating method using an ethanol/water system

Morphology control of ordered mesoporous carbon was performed using an organic–organic interaction approach. Mesoporous carbons were synthesized from a resorcinol–phloroglucinol/formaldehyde polymer and triblock copolymer Pluronic F127 in ethanol–water solutions of different molar ratios. A face-centered orthorhombic Fmmm structure was formed in the film prepared by dip-coating method. A three-dimensional wormhole-like mesostructure was formed during powder preparation at EtOH/water molar ratios ranging from 0.5 to 1.25. When the molar ratio was further increased to 2.5, a hexagonal p6 mm structure was obtained. The pore size of the mesoporous carbon powders increases with increasing EtOH/water molar ratio. A dual-templating approach was demonstrated to prepare mesoporous carbon nanofibers. Anodic aluminum oxide membranes were used as a hard template. A mesostructure with a short-range order was formed and oriented along the surface in different directions. The structural order became distorted in the interior region.

Micro- and Mesoporous Carbide-Derived Carbon Materials and Polymer Membranes for Supercapacitors

Several nanoscale fine-tuned micro- and mesoporous carbon powders C(Mo2C) produced by reacting Mo2C with Cl2 at various temperatures were studied and characterized using XRD and Raman spectroscopy methods and compared with low temperature N2 adsorption/desorption measurements data. Supercapacitors based on two ideally polarizable nanoporous carbon electrodes and different mesoporous commercially available separators in acetonitrile (AN) as the solvent for the 1.0 M (C2H5)3CH3NBF4 electrolyte have been completed and tested by cyclic voltammetry and electrochemical impedance methods.

Platinum and platinum–ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum–ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt–Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation.