Pore Size Of Carbon Research Articles

Tailored 3D Porous N-Doped Carbon Nanospheres for Bottom-up Electrode Design - Independent Pore and Particle Size Control for the Use in Model Electrodes

Design of porous carbon-based electrode materials and derived porous electrode structures is crucial for the performance of electrochemical energy storage and conversion devices. In that context carbon-based electrode material building blocks with well-defined properties are desired. Such properties include controlled morphology (preferably spherical), particle size, and intra-particle porosity along with controlled composition, surface chemistry, and processability. These factors influence the particle arrangement and electrode structure during processing, as well as electrolyte interaction, distribution, and mass transport phenomena within the electrode.In this work, we introduce a hard-templating method for producing highly uniform meso- and macroporous N-doped carbon nanospheres with independently tuneable pore and particle sizes, serving as a versatile material platform for the bottom-up design of 3D porous carbon electrodes. We could thereby customize the pore sizes between approximately 10 to 100 nm at a constant particle size, while particle sizes between 50 and 300 nm could be achieved for a constant pore size. Other physicochemical parameters such as chemical composition, graphitization, and surface functionalization remained constant across all samples, allowing for the exclusive investigation of pore and particle size effects independently from each other.We further used our different N-doped carbon nanospheres as building blocks for 3D porous electrodes and studied these in electrochemical double-layer capacitors with the aim to (i) showcase the versatility of our materials and (ii) examine pore and particle size effects on the performance. Indeed, electrochemical double-layer capacitors serve as an excellent model system for such investigations due to their sensitivity to carbon particle surface area, pore size, and mass transport phenomena within the 3D percolated structure of porous carbon electrodes.

Carbon-Based Adsorbents for Microplastic Removal from Wastewater.

Plastics are widely used across various industries due to their flexibility, cost-effectiveness, and durability. This extensive use has resulted in significant plastic pollution, with microplastics (MPs) becoming pervasive contaminants in water bodies worldwide, adversely affecting aquatic ecosystems and human health. This review explores the surface characteristics of carbon-based adsorbents, including biochar, activated carbon, carbon nanotubes (CNTs), and graphene, and their influence on MP removal efficiency. Key surface characteristics such as the carbon content, surface area, pore size, and particle size of adsorbents influenced adsorption efficiency. Additionally, hydrophobic interaction, van der Waals forces, π-π interactions and electrostatic interaction were found to be mechanisms by which microplastics are trapped onto adsorbents. Modified biochar and activated carbon demonstrated high adsorption efficiencies, while CNTs and graphene, with their high carbon contents and well-defined mesopores, showed outstanding performance in MP removal. Although a high surface area was generally associated with better adsorption performance, modifications significantly enhanced efficiency regardless of the initial surface area. This review emphasizes the importance of understanding the relationship between surface characteristics and adsorption efficiency to develop optimized adsorbents for MP removal from wastewater. However, challenges such as the lack of standardized testing methods, variability in biochar performance, and the high cost of regenerating carbon adsorbents remain. Future research should focus on developing cost-effective production methods, optimizing biochar production, and exploring advanced modifications to broaden the application of carbon adsorbents. Integrating advanced adsorbents into existing water treatment systems could further enhance MP removal efficiency. Addressing these challenges can improve the effectiveness and scalability of carbon-based adsorbents, significantly contributing to the mitigation of microplastic pollution in wastewater.

Characteristics of Activated Carbon Panels in Reducing CO, NO2, HC, Pb, and Noise

Increasing population growth has resulted in increased vehicle ownership and the need for parking facilities, including in basements. This study aimed to explore the efficacy of palm shell activated carbon panels in reducing CO, NO2, HC, Pb, and noise. The experiment was conducted in a 4 m x 3 m x 2.1 m room using three treatments: without installed activated carbon panels; with 1 cm x 20 cm x 20 cm activated carbon panels; and with 2 cm x 20 cm x 20 cm activated carbon panels. During the measurement, three motorcycles were turned on and kept in idle mode. The concentrations of CO, NO2, HC, ambient Pb, and noise were measured. The results showed that the activated carbon panels were able to reduce CO, NO2, Pb, HC, and noise. The highest performance was obtained for 2-cm thickness of activated carbon panels, with CO, NO2, HC, Pb, and noise decreasing to 824 µg/m3, 8.4 µg/m3, 4.4 µg/m3, 0.2 µg/m3, and 87.44 dB, respectively. Following the adsorption process, the carbon content and pore size of the activated carbon panels had changed from 68.32% to 90.95% and 0.17-3.652 µm to 0.34-5.56 µm respectively for testing with 2-cm thickness panels.

A Precursor-Derived Ultramicroporous Carbon for Printing Iontronic Logic Gates and Super-Varactors.

A liquid precursor for 3D printing ultramicroporous carbons (pore width <0.7nm) to create a novel in-plane capacitive-analog of semiconductor-based diodes (CAPodes) is presented. This proof-of-concept integrates functional EDLCs into microstructured iontronic devices. The working principle is based on selective ion-sieving, controlling the size of the electrolyte ions, and the nanoporous sieving carbon's pore size. By blocking bulky electrolyte ions from entering the sub-nanometer pores, a unidirectional charging characteristic with controllable ion flux is achieved, leading to diodic U-I characteristics with a high rectification ratio. The liquid precursor approach enables successful printing of miniaturized in-plane CAPodes. A combination of inkjet and extrusion printing techniques with suitable inks is explored to fabricate electrode materials with engineered porosity. Deliberate fine-tuning of the ultramicroporous carbon's porosity and surface area is achieved using a customized carbon precursor and CO2 etching techniques. Electrochemical evaluation of the printed CAPodes demonstrates successful miniaturization compared with macroscopic film assembly. 3D manufacturing and miniaturization allow for the integration of CAPodes into logic gate circuits (OR, AND). For the first time, these switchable devices are used as variable capacitors in a high-pass filter application, adjusting the cut-off frequency of applied alternating voltage analogous to an I-MOS varactor.

Molecular dynamic study on the transport properties of ionic liquids in ZTC porous carbon materials

The adsorption and diffusion behavior of ions within electrodes have a significant impact on the energy density and charging/discharging speed of supercapacitors. Zeolite-Templated Carbon (ZTC) material, a type of porous carbon material characterized by well-defined pore shape and spatial structure, is recognized as a promising electrode material owing to its numerous advantages. This study employs molecular dynamics simulations to investigate the diffusion and adsorption profiles of ionic liquids [EMI][BF4] in different types of ZTC materials as electrodes. Additionally, the effect of ion size, pore dimension, pore shape, and the properties of the adsorbed ions are discussed. The degree of confinement (DOC) and ion diffusivity are thoroughly analyzed to elucidate the transport behavior of ions within the ZTC pores. The results demonstrate that the diffusion coefficient and degree of confinement of ionic liquids predominantly depend on the anion size and the pore size of the porous carbon. Surprisingly, in certain cases, larger anions exhibit enhanced diffusion ability and adsorption effect. These findings unravel the underlying transport mechanism of ions in ZTC materials and provide valuable theoretical insights for the application of ZTC materials as electrodes in the field of supercapacitors.

A column screening study: Validation of a RP-LC method for determination of teriflunomide with pentafluorophenyl stationary phase

The research focuses on column screening in order to develop a novel validation method to separate Teriflunomide significantly using comparative and equivalent column selection studies. This gives stationary phase efficiency relative to height equivalent to a theoretical plate (HETP) (>16000) and symmetry factor (<2.0%). After extensive column chemistry and technique development, the advanced Pentafluorophenyl (PFP) column separates halogenated drugs better. Teriflunomide is fluorinated drug, hence PFP is optimal for analysis. For statistical data comparison, the same chromatographic method was developed and transferred to another YMC Pack Pro C18 column that gives almost the same results as PFP column in terms of carbon load, pore size, and surface area. The refined and validated method yielded equivalent results with two stationary phases using a single analysis procedure. Column screening, technique creation, transfer, and validation with comparison studies with correlation coefficients over 0.999 are unique. The statistical data from both columns meets ICH requirements. The sensitive, reliable, robust, and reproducible approach is easy to apply in regular laboratory analysis. Data analysis showed that the validation study with PFP is better (LoD - 0.0015 ppm) for column ageing due to smaller injection volume and amount loaded in the column, shorter run time, and cheaper analysis cost. This research helps with column selection and method transfer with diverse column specifications. With less than 2.0% of RSD, the column screening analytical method validation is linear, precise, accurate, rugged, and efficient.

Structural engineering of porous biochar loaded with ferromagnetic/anti-ferromagnetic NiCo2O4/CoO for excellent electromagnetic dissipation with flexible and self-cleaning properties

Design of multi-functional microwave absorption materials with strong dissipation ability is a practical approach to address the current issue of electromagnetic radiation pollution. Herein, based on the exchange bias interaction between ferromagnetic and anti-ferromagnetic interfaces, a series of absorbers composed of the porous biochar loaded with ferromagnetic/anti-ferromagnetic NiCo2O4/CoO were successfully prepared via a fairly simple process of one-step calcination. By regulating the calcination temperature, the pore size and porosity of porous carbon, morphology of loaded NPs as well as the electromagnetic response property and impedance matching characteristic in such composites can be modulated. The porous biochar/NiCo2O4/CoO composite prepared under 350 °C possesses a remarkable electromagnetic absorption reflection loss (RL) of –48.41 dB at 9.12 GHz with 2.5 mm thickness, and the effective absorption bandwidth (EAB) of 4.32 GHz with 2.2 mm thickness is located at X band, this is owing to the strong coupling effect of multiple dielectric polarizations, magnetic resonances, and eddy current consumption under matched impedance. In addition, the microwave absorbing patch prepared with this composite exhibits a well-hydrophobic property for self-cleaning function, and the large extensibility with substantial breaking strength endows its practical usage as a flexible absorber.

Sub-nm Pore Size of Phenylethynyl End-Capped Imide Oligomer-Derived Carbon for Molecular Sorption and Separation

Sub-nm Pore Size of Phenylethynyl End-Capped Imide Oligomer-Derived Carbon for Molecular Sorption and Separation

Understanding Ion Charging Dynamics in Nanoporous Carbons for Electrochemical Double Layer Capacitor Applications

The electric double layer (EDL) is one of the key concepts in electrochemistry, and understanding its charging kinetics is of key importance. Significant progress has been made via theoretical methods; however, it is challenging to study the ion dynamics experimentally in porous carbon electrodes under realistic conditions because of fast charge relaxation. In this work, the charging kinetics of porous carbon electrodes with different pore sizes in an aqueous electrolyte was experimentally investigated in electrolytes with various concentrations by using a cavity microelectrode. We were able to observe electrolyte depletion, and we systematically studied the key parameters that will affect the electrolyte depletion, resulting in major changes in the charging kinetics. Results showed that low concentration, high overpotential, and small carbon pore size triggered the electrolyte depletion, decreasing the charging kinetics. These findings further push our understanding of the ion dynamics of the EDL at the charged porous carbon/electrolyte interface.

Analysis of Fe metal adsorption in industrial wastewater using adsorbents from betel nut skin

This study aims to determine the adsorption ability of betel nut skin-activated carbon on Fe metal in industrial wastewater. Betel nut skin carbon is activated using H2SO4 and HNO3. To identify the quality of adsorption using betel nut skin adsorbents, carbon and activated carbon are characterized using XRD and BET analysis. To determine the concentration of Fe metal adsorbed in the adsorption process, it was analyzed using AAS by determining the optimum conditions for the adsorption of Fe metal from the adsorbent using mass and contact time variations. The XRD characterization results show that betel nut skin carbon activated with sulfuric acid has a higher degree of crystallinity (41.03%) than that activated with nitric acid (20.61%). Betel nut skin activated carbon has a larger pore size of 3.2110 nm than the pore size of betel nut skin carbon of 2.2644 nm. The optimum condition of activated carbon on the adsorption of Fe metal was obtained at a mass of 1 gram with an optimum contact time of 45 minutes. The adsorption capacity of betel nut skin-activated carbon obtained was 1.4174 mg/g and the adsorption efficiency of betel nut skin-activated carbon was 99.84%. The initial concentration of Fe metal obtained was 25.86 ppm, after adding activated carbon from betel nut skin is decreased the concentration of Fe metal obtained was 3.72 ppm. So, the ability of betel nut skin adsorbent to adsorb Fe metal in industrial wastewater was 22.14 ppm. Keywords: Activated carbon; Adsorption; Amorphous; Betel nut skin; Wastewater

Theory-guided preparation of pore size tunable porous carbon for efficient adsorption and separation of the light hydrocarbons

The efficient adsorption and separation of light hydrocarbons is considered to be the vital processes in petrochemicals. Therefore, it is important to design and develop efficient adsorbents. Herein, we investigated the detailed mechanistic effects of the pore size of porous carbon on the adsorption and separation performance of three light hydrocarbons based on GCMC simulations. The optimum pore size range for their adsorption and separation was determined. Accordingly, bamboo fibres-based porous carbons (BPCs) with tunable pore size distribution were prepared using bamboo fibres mixed with different ratios of KOH. The results display that C3H8 (0.7–1.6 nm) exhibits the wider optimal pore size range for adsorption compared to CH4 (0.7–0.8 nm) and C2H4 (0.7–1.2 nm). Meanwhile, the selectivity of C3H8/CH4 (C3H8/C2H4) depends primarily on the 1.0–1.6 nm (1.2–1.6 nm) pore size. Furthermore, BPCs with these optimal pore sizes exhibited excellent adsorption performance for CH4 (2.07 mmol/g), C2H4 (6.29 mmol/g) and C3H8 (12.23 mmol/g). Among them, BPC-4 possessed the greatest selective separation for C3H8/CH4 (11.1) and C3H8/C2H4 (2.3). This study achieved effective adsorption separation of light hydrocarbons, which would further guide the design direction regarding the pore size of light hydrocarbon adsorbents and provide new ideas for preparation of porous carbon materials.

Carbon coated cobalt catalysts for direct synthesis of middle n-alkanes from syngas

Core-shell structure catalysts with adjustable carbon shell thickness and pore size were obtained by dissociating acetylene, leading to new product distribution characteristics: (1) the core–shell catalyst without reduction still showed high activity, and showed high selectivity of C 5 ∼C 12 (48.5%); (2) after reduction, it had the same activity as the uncoated catalyst, and showed high selectivity of C 13 ∼C 20 (41.7%), and high selectivity of C 5 ∼C 20 (66.9%); (3) more than 90% of the products are n-alkanes. • Carbon coated catalysts were obtained at a low acetylene dissociation temperature. • The thickness of carbon coating can be regulated based on the dissociation temperature. • The carbon coating can determine the FTS products distribution. • More than 90% of the FTS products are n-alkanes. A series of carbon coated core–shell cobalt catalysts with different thickness of shell were easily prepared by C 2 H 2 dissociation. The characterization results showed that dissociation temperature plays an important role in determining the thickness of carbon shell. There were two kinds of carbon species on the surface of coated catalysts: deposited carbon and graphitic carbon. Only deposited carbon could be obtained during lower temperature coating, while both deposited carbon and graphitic carbon were found during higher temperature coating. Deposited carbon blocked the active sites, while graphitic carbon didn’t block the active sites but only limited the diffusion of the products. The coated catalyst possessed better dispersion and reduction, and retains more elemental Co after surface passivation. The performance test results of Fischer-Tropsch synthesis (T = 220 °C) indicated that: (1) the core–shell catalyst without reduction still showed high activity, and showed high selectivity of C 5 ∼ C 12 (48.5%); (2) after reduction, it had the same activity as the uncoated catalyst, and showed high selectivity of C 13 ∼ C 20 (41.7%), and high selectivity of C 5 ∼ C 20 (66.9%); (3) more than 90% of the products were n-alkanes.

Synthesis of Carbon from Yellowfin Tuna Fishbone to Remove Iron (Fe) Metal in Well Water from Bandar Setia

The performance of tuna fishbone waste as carbon to remove iron (Fe) metal from well water was studied. The parameters of carbon synthesis were set by varying the carbonization temperature of 300, 400, and 500°C. Fishbone carbon was characterized using Scanning Electron Microscopy (SEM-EDX), X-ray Diffraction (XRD), and SSA (nitrogen adsorption). The BET and (BJH) analysis showed that the increase in carbon surface area and pore size was proportional to the increase in carbonization temperature. Fishbone carbon was used as a filtration medium to reduce high levels of iron metal in well water. Samples were taken from wells belonging to residents in Bandar Setia, Medan Tembung. Fishbone carbon was effective as an adsorbent for removing iron metal from well water by the filtration method. The rate of iron removal was 99% for fishbone carbon, carbonized at 400°C.

Ionic Liquid Mixture Electrolyte Matching Porous Carbon Electrodes for Supercapacitors.

Ionic liquids (ILs), with their wide electrochemical stable potential window, are promising electrolytes for supercapacitors (SCs). The suitable matching of the ion size and shape of the ILs to the pore size and structure of porous carbon (PC) electrode materials can realize the enhanced capacitive performance of the SCs. Here we report an interesting result: The capacitance of PC-based SCs shows a quasi-sinusoidal relationship with the composition (mass fraction) of the binary IL mixture as the electrolyte. This relationship is also interpreted based on the matching between the pore sizes of the PC materials and the size/shape of various ions of the IL mixture electrolyte. This can provide a new strategy to improve the performance of SCs by formulating a suitable mixture of different ILs to match the carbon-based electrode materials with a special pore size distribution.

High-performance carbon molecular sieve membrane for C2H4/C2H6 separation: Molecular insight into the structure-property relationships

Carbon molecular sieve (CMS) membranes show attractive potential for energy-efficient separation of C2H4/C2H6 due to their unique slit-like pore structure. In this work, a novel precursor polymer of phenolphthalein-based poly(arylene ether ketone) (PEK-C) was introduced to prepare high-performance CMS membranes for C2H4/C2H6 separation. Molecular insight into the effect of the sp3/sp2 hybridized carbon ratio on the packing morphology of carbon layers, pore size and configuration, and C2H4/C2H6 diffusion and separation properties of CMS membranes was investigated via using in-depth characterization techniques combined with molecular simulations. Results show that the carbon layers with more sp3 hybridized carbons lead to forming a loose and disordered carbon structure and pore structure with large pore volume and micropore size (steric voids), resulting in low C2H4/C2H6 permselectivity of CMS membrane. With the reduction of the sp3/sp2 hybridized carbon ratio, a compact and graphite-like carbon structure with the two-dimensional slit-like ultramicropore structure is formed, and the C2H4/C2H6 permselectivity is obviously enhanced. The CMS membranes derived from the novel precursor of PEK-C exhibit high C2H4 permeability with superior C2H4/C2H6 selectivity, which have surpassed the trade-off bounds of both polymeric membrane and CMS membrane, and reveal a great potential in the industrial applications of C2H4/C2H6 separation.

Capacitive dominated charge storage in supermicropores of self-activated carbon electrodes for symmetric supercapacitors

The present work demonstrates a systematic study of pore size and specific surface area (SSA) of biomass-derived carbon and the choice of electrolyte concentrations affecting charge-storage mechanism (surface controlled and diffusion controlled) and electrochemical behaviour. Porous nanocarbons derived from Caesalpinia Sappan pods were synthesized by pyrolysis at 400, 600, and 800 °C. Pyrolysis at 800 °C was found suitable for the self-activation mechanism which formed bimodal porous nanocarbons with a high SSA of 675 m2/g. A maximum specific capacitance of 261.8 F/g at 0.5 A/g in 5.0 M KOH was observed for electrode materials synthesized at 800 °C. The highlight of the study is the porous nanocarbon synthesized at 800 °C which was found to possess micropores of size 0.7–1.0 nm playing a pivotal role in enhancing capacitance. The effect of electrolyte concentration on capacitance and charge storage mechanisms was also analyzed. A diffusion-controlled self-discharge model is established for supercapacitor devices. The single cell can power a red LED for 15 min; exemplifying the sustainable strategy of the utilization of abundant bio-waste to efficient energy storage devices.

Competitive adsorption in CO2 enhancing shale gas: Low-field NMR measurement combined with molecular simulation for selectivity and displacement efficiency model

CO2 enhanced shale gas recovery is considered to be a potential method of shale gas development and CO2 reduction. However, core experiments cannot independently analysis competitive adsorption when the partial pressure of CH4 in the core sample keeps changing during displacement. In this study, an experimental method based on low-field nuclear magnetic resonance (NMR) and in situ gas chromatography is developed to quantitatively analyze the competitive adsorption of shale particles. As was demonstrated in our previous study, the adsorption capacity of the nanopores at various pressures can be obtained from the transverse relaxation spectrum of NMR and the change in pressure in a reference cavity. By NMR experiment combined with gas chromatography, the competitive adsorption selectivity of CH4 and CO2 in nanopores is investigated. In addition, molecular simulations are used to simulate the competitive adsorption and selectivity of CO2 and CH4 in shale nanopores with different pore structures, sizes, and shapes. The results reveal that as the pressure, carbon dioxide mole fraction, temperature, and pore size increases, the competitive adsorption selectivity S decreases. However, it remains greater than one, which demonstrates that CO2 has a stronger adsorption ability than CH4. For shale gas development, as the total pressure decreases, the contribution of the competitive adsorption effect becomes significant. A competitive adsorption model for CO2 and CH4 is established, and it is shown to fit the experimental data and simulation data well at different pressures. Finally, based on single-component adsorption results, we can separate the different effects and predict the displacement efficiency, which may provide a criterion in field scale simulations.

Pd@Pt Core-Shell Structured Catalyst Supported on Mesoporous Carbon for Achieving a High Cell Performance

1. Introduction An extremely high performance is required for polymer electrolyte fuel cells (PEFCs) installed in fuel cell electric vehicles after 2030 as shown in Figure 1 [1] and a high oxygen accessibility [2] in addition to a high ORR activity and a durability is crucial for Pt-based cathode catalysts in PEFCs. In order to achieve the cell performance, it is of great importance to suppress cell voltage drop especially in a high current density (HCD) region and we consider that carbon support for the Pt-based catalysts would play an important role. In this study, mesoporous carbon (MPC) with a large specific surface area was selected for the support of Pd@Pt core-shell structured catalyst and cell performance of the catalyst supported on the MPC was compared with the catalyst supported on a conventional carbon support of Ketjen Black (KB). 2. Experimental KB-600JD (SBET: 1,335 m2/g) and MPC (CNovel MH-18, SBET 1,278 m2/g, TOYO TANSO [3]) were used as carbon supports for synthesis of Pd@Pt core-shell structured catalyst. The Pd@Pt core-shell structured catalyst was synthesized by a direct displacement reaction method [4]. The metal loadings of the catalyst were 20 wt.% for Pt and 30 wt.% for Pd. CV was recorded at 25oC in Ar-saturated 0.1 M HClO4 and ORR activity was evaluated by RDE method performed in O2-saturated 0.1 M HClO4 at 25oC with a rotation speed of 1,600 rpm and a positive potential scan rate of 10 mV/s. Fuel cell performance was evaluated by using a single cell with an active area of 1 cm2 (5 serpentine flow paths). Nafion® DE2020 was used as an ionomer for the catalyst ink preparation (I/C was set to 0.83) and Nafion® NRE 211 (25 µm in thickness) was used as a membrane. The Pt loading in cathode catalyst layer was set to 0.1 mg/cm2, and H2 and air were supplied to anode and cathode by 418 NmL/min. and 988 NmL/min., respectively (utilization was 5% at current density of 3.0 A/cm2). The cell temperature was set to 80oC and humidified by 95% RH. 3. Results and Discussion Figure 1 shows cell performances of a reference Pt catalyst supported on KB-300J (TEC10E50E, mean diameter: 2.8 nm, metal loading: 48 wt.%, TKK) and Pd@Pt core-shell structured catalyst supported on KB-600JD evaluated with 1.0 atm at gas outlet. Although the cell performance of the Pt/Pd/KB-600JD catalyst overcame the performance of the reference Pt/KB-300J catalyst, cell voltage significantly dropped in HCD region (> 2.0 A/cm2) compared to cell voltage required in 2030. In order to suppress the voltage drop, gas diffusion layer (GDL) was altered to a high current use (22BB, SGL Carbon Inc.) from a stational use (28BC, SGL Carbon Inc.) and the cell performances are overwritten on Figure 1. It is clear that the voltage drop in HCD region was well suppressed by using the GDL 22BB, which arose from a three-fold higher gas permeability of the GDL 22BB compared to the GDL BC28.Next, CNovel MH-18 was used as a carbon support and pore size distribution is demonstrated in Figure 2. The KB-600JD possesses mesopores broadly ranging from 2 to 20 nm in diameter, while the CNovel MH-18 has mesopores with a narrower size distribution centered at 4 nm in diameter. Figures 3 and 4 summarize cell performances using the Pt/KB-300J, the Pt/Pd/KB-600JD and the Pt/Pd/CNovel MH-18 cathode catalysts. When the cell performance was evaluated with 1.0 atm at gas outlet, the Pt/Pd/KB-600JD catalyst exhibited a superior cell performance to that of the Pt/Pd/CNovel MH-18 catalyst. On the contrary, when the cell performance was evaluated with 1.5 atm at gas outlet, the performance using the Pt/Pd/CNovel MH-18 catalyst was much improved and exhibited a higher cell voltage in a low current density region (0.01-1.0 A/cm2) as shown in Figure 5. Since more than 60% of the Pd@Pd NPs were deposited at interior part of the CNovel MH-18 MPC support, it is considered that the cell performance using the Pt/Pd/CNovel MH-18 catalyst exhibited the significant improvement under the pressurized condition at 1.5 atm and the higher cell voltage in the low current density region due to suppression of a direct ionomer adsorption onto the catalyst surface.This study was partly supported by NEDO, Japan.

Preparation and characterization of hydrochar-derived activated carbon from glucose by hydrothermal carbonization

Activated carbon (AC) was produced from glucose using hydrothermal carbonization (HTC) and KOH activation. The HTC temperature was 170–280 °C over 30min–12h of holding time and the KOH activation temperature was 500–700 °C at 1 h. The results show that there are several carbon spheres of 0.6 to 7 μm in the hydrochar. The hydrochar contained many aromatic rings and oxygen-containing functional groups. The hydrochar obtained from glucose was used as precursor, whereas KOH was used as activating agent. The pore characteristic of activated carbon changes significantly with the impregnation ratio and activated temperature. The dry-basis AC yield was in the range of 42.23–55.8wt.%. The maximum Brunauer–Emmett–Teller (BET) surface area of the product was 1413.62 m2/g. The average pore size of the AC was 2.2 to 2.5 nm with total pore volume of 0.2–0.47 cm3/g. The maximum surface area and pore volume were reached at a 1:4 impregnation ratio (hydrochar:KOH) and 700 °C temperature. The pore size of glucose-activated carbon is less than 10 nm, and most of the pores are micropores and mesopores. The existence of mesopores and micropores in activated carbon can enhance their adsorption capacity, especially for macromolecular adsorbent.

Rational regulation ultra-microporous structure size for enhanced potassium ion storage performance

The traditional views consider that the interlayer spacing is the major factor controlling battery performance due to the intercalation mechanism, but we find that the pore size of porous carbon in potassium ion storage is the most important factor determining battery electrochemical performance, because the adsorption mechanism occupies the leading position in the process of contributing energy. Herein, we prepare the short-range order ultra-microporous carbon (SROM) through physical grinding following a pyrolysis method. The optimized SROM-15 as anodes in the potassium-ion batteries delivers a remarkable reversible capacity of 264.2 mA h g − 1 at 100 mA g − 1 after 100 cycles, superior rate capacity (149.1 mA h g − 1 at 5 A g − 1), and excellent cycling life. The electrochemical properties of SROM-15 are better than most reported carbon materials. This experiment has demonstrated that when the pore size is adjusted to 0.84 nm, the specific capacity and K+ diffusion coefficient of SROM are the largest. In addition, the potassium-ion hybrid capacitors fabricated using SROM-15 anodes and corn stalk-derived activated carbons cathodes display outstanding specific energy of 50.6 W h kg−1 at specific power of 4500 W kg−1.