Macroporous Carbon Research Articles

On the Importance of MPL Structural Characteristics for PEM Fuel Cell Performance

Gas diffusions layers (GDLs) constitute vital subcomponents of proton exchange membrane fuel cells (PEMFCs) since they participate in all relevant transport processes (gases, vapor, liquid water, electricity and heat).Meanwhile, state-of-the-art GDLs are produced on commercial scale using high volume reel-to-reel (R2R) processes. In almost any case, GDLs are designed as dual-layer structures with a macro-porous carbon fiber-based substrate (backing) and a micro-porous layer (MPL) consisting of carbon particulates bonded with polytetrafluoroethylene (PTFE) binder. A body of scientific work has verified that different aspects of the MPL microstructure and the MPL/macroporous substrate interface play a substantial role in the water management of PEMFCs [1-6].A systematic study was performed based on a singular backing using different MPL types and penetration levels.A simple method to estimate the micro-porous layer penetration in gas diffusion layers based on data obtained from force-deflection behavior of backings and MPL-coated GDLs is proposed. Comparison with SEM and previously published tomographic studies shows that a good estimate for the extent of MPL intrusion into the backing is obtained.MPL loading and penetration is shown to affect different ex-situ GDL properties (in-plane gas permeability, electrical and thermal conductivity) as well as the GDL single cell performance characteristics with respect to humification and high current density operation.Keywords: Gas diffusion layers, Microporous Layer, PEMFC fuel cells Weber, and J. Newman, “Effects of microporous layers in polymer electrolyte fuel cells”, J. Electrochem. Soc. 152, A677-A688 (2005).Lee, R. Yip, P. Antonacci, N. Ge, T. Kotaka, Y. Tabuchi, and A. Bazylak, Synchrotron investigation of microporous layer thickness on liquid water distribution in a PEM fuel cell, J. Electrochem. Soc. 162, F669-F676 (2015).Zhou, S. Shukla, A. Putz, and M. Secanell, “Analysis of the role of the microporous layer in improving polymer electrolyte fuel cell performance”, Electrochim. Acta. 268, 366-382 (2018).Cho, J. Park, H. Oh, K. Min, E. Lee, and J.Y. Jyoung, “Analysis of the transient response and durability characteristics of a proton exchange membrane fuel cell with different micro-porous layer penetration thicknesses”, Appl. Energy 111, 300-309 (2013).T. Gostick, M. A. Ioannidis, M. W. Fowler, and M. D. Pritzker, “On the role of the microporous layer in PEMFC operation.”, Electrochem. Comm. 11, 576-579 (2009).P. Ramasamy, E. C. Kumbur, M. M. Mench, W. Liu, D. Moore, and M. Murthy, “Investigation of macro- and micro-porous layer interaction in polymer electrolyte fuel cells”, Int. J. Hydrogen Energy 33, 3351-3367 (2008).

Hierarchical porous carbon fibers for broadband and tunable high-performance microwave absorption

Constructing multiple polarization losses and improving impedance matching in carbon materials is essential for improving electromagnetic wave absorption performance of carbon materials. Meanwhile, surface contamination of electromagnetic wave absorbers has a significant impact on their absorption performance. Herein, a pod-like macroporous carbon nanofibers with self-cleaning function are successfully prepared by Electrospinning-etching strategy. Through the adjustment of SiO2 and pore structure, conduction loss, dipole polarization loss, interface polarization loss, and impedance matching of carbon nanofibers are optimized simultaneously. The optimized a pod-like macroporous carbon nanofibers has strong absorption and wide effective absorption bandwidth. With a cavity content of 4 %, the minimum reflection loss at 2.29 mm is -49.36 dB, and the effective absorption bandwidth is 7.6 GHz and the matched thickness is 2.16 mm. This result indicates that cavity and pod-like structure can significantly improve dielectric properties and enhance interface polarization loss and conductivity loss. The simulation results verify that the pod structure has a greater impact on surface electric field distribution, which shows that interface polarization is caused by the cavity structure. In addition, the contact angle of absorber is 105 °, which proves its self-cleaning ability. This functional absorbing material has potential to meet future practical applications.

La-doped macroporous carbon fiber catalytic converter for tetracycline efficient removal

Metal-organic frameworks (MOFs) show substantial potential and impressive development prospects in persulfate-based advanced oxidation (SR-AOPs) due to their exceptional structural advantages. Nevertheless, the structural characteristics, catalytic performance, and catalytic mechanism of lanthanide metal-doped MOFs (La-MOFs) remain unclear. Therefore, we prepared lanthanum-nitrogen co-doped hollow carbon nanofibers (La-HCNFs) through electrospinning and pyrolysis to study the structure, catalytic activity, and mechanism of La-MOFs. Furthermore, we analyzed the physicochemical properties of La-HCNFs with a range of characterisation techniques, and examined the catalytic oxidation mechanism with quenching experiments. Finally, this study clarifies the role of SR-AOPs in La-MOFs and indicates pathways for future research on La-MOFs materials, in order to advance the use of MOFs materials in environmental chemistry and sustainable catalysis.

New insights into the performance analysis of flow-electrode capacitive deionization using ferri/ferrocyanide redox couples for continuous water desalination

Flow Electrode Capacitive Deionization (FCDI) is a promising technology that uses carbon materials as flow electrodes in aqueous conditions to enable continuous desalination. In this work, the parametric investigation of the FCDI cell was carried out for low and high surface area activated carbon. When 1 mM/1 mM ferri-/ferrocyanide redox couple in the 1 M NaCl supporting electrolyte containing the 5 wt% high surface area activated carbon and 0.5 wt% MWCNT is circulated as flow electrode at the flow rate of 8 mL/min in the electrode chamber and 0.1 mM NaCl feed water is circulated in single-pass mode at 8 mL/min, the FCDI system achieved a significant improvement in desalination performance up to 76.38 % of SRE, with a high average salt removal rate of 43.925 µg/cm2s @ 2 V, charge efficiency of 20.11 % and average energy consumption of 0.27 kWh/mol, through a thorough parametric investigation. When the FCDI cell was tested with tap water, the average salt removal rate, average energy consumption, and salt removal efficiency were calculated at 6.11 μg/cm2s, 2.46 kWh/mol, and 46.61 % respectively, resulting in the reduction of total dissolved solids of 600 mg/L at the inlet to 365 mg/L at the outlet. The combination of microporous high surface area carbon and ferro-ferri redox couple propelled the desalination performance in comparison with the macroporous low surface area carbon, maximizing the ion removal rate, which further reduced the energy consumption and operating voltage for the process.

γ-irradiation induced ultrafine Ni nanoparticles supported on biomass-derived macroporous carbon for enhanced microwave absorption in the X-band

A series of ultrafine Ni nanoparticles (NPs) supported on biomass-derived macroporous carbon composites are conducted by γ-irradiation induced reduction method. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) characterization show that the obtained materials have abundant macroporous structure and the Ni NPs are evenly decorated on the surface of macroporous carbon. Both high irradiation doses and increasing Ni2+ contents favor the production of smaller dots. When the irradiation dose is 220 kGy and the C/Ni2+ mole ratio is 1:6, the average diameter of Ni NPs can reach 7.7 nm. Electromagnetic analyses indicate that the ultrafine Ni NPs have a positive effect on the magnetic loss ability, due to their strong natural ferromagnetic resonances. The obtained sample (CSC–Ni-3) exhibits the best microwave absorption performances among these composites, with the strongest reflection loss (RL) value of −70.2 dB at 10.8 GHz for the thickness of 2.3 mm, and the effective absorption band (EAB) in the X-band (8.2–12.4 GHz) is up to 3.2 GHz. The advantages of CSC-Ni-3 can be clearly established in both matched impedance and high magnetic loss ability. The γ-irradiation strategy presents a promising way for the design of ultrafine Ni NPs for high-performance microwave absorption.

Integration of Highly Graphitic Three-Dimensionally Ordered Macroporous Carbon Microspheres with Hollow Metal Oxide Nanospheres for Ultrafast and Durable Lithium-Ion Storage

Achieving excellent electrochemical performance at high charging rate has been a long-cherished dream in the field of lithium-ion batteries (LIBs). As a part of the efforts to meet the goal, an innovative strategy for the synthesis of 3D porous highly graphitic carbon microspheres, to which numerous hollow metal oxide nanospheres are anchored, for use as anode in LIBs is introduced. Hollow carbon nanosphere-aggregated microspheres prepared from the spray drying process are graphitized with the aid of metal catalysts, and subsequent oxidation selectively removed amorphous carbon, leading to the formation of highly conductive graphitic carbon matrix. Numerous hollow metal oxide nanospheres formed simultaneously during the oxidation process via nanoscale Kirkendall diffusion are anchored onto the carbonaceous matrix, effectively reinforcing the structural integrity by alleviating volume changes and reducing lithium-ion diffusion lengths. The synergistic effect of combining hollow metal oxide nanospheres with high theoretical capacity with conductive carbon matrix led to accelerated electrochemical kinetics, resulting in high capacity at high charging rate. In addition, trapping the hollow metal oxide nanospheres inside hollow carbon nanospheres could effectively alleviate the volume changes, which led to high structural stability. When applied as LIB anodes, the microspheres exhibit a capacity of 411 mA h g−1 after 2500 cycles at 10.0 A g−1, with ~80% capacity retention. The anode exhibits a high capacity of 274 mA h g−1 at an extremely high current density of 50.0 A g−1, thus demonstrating the structural merits of the microspheres.

Three-dimensional porous carbon materials as catalysts for upgrading coal pyrolysis volatiles to boost light tar

The large proportion of heavy components in volatiles from coal pyrolysis is liable to entrain dust and form coke, resulting in the difficulty of separating oil from dust, which thus causes the blocking of technical pipelines. Carbon-based catalysts (BC and BHC) and metal-modified carbon-based catalysts (Fe-BC, Ni-BC, Fe-BHC and Ni-BHC) were prepared for the upgrading of volatiles from coal pyrolysis. This three-dimensional interconnected macroporous carbon material is primarily derived from the pyrolysis of the blend of a biochar and a caking coal. The results show that the metal-modified carbon-based catalysts aid in activating small molecules, such as CH4, CO2, and H2O, increasing in-situ hydrogen donation while cracking polycyclic aromatics, macromolecular oxygen-containing compounds, and N, S-containing heterocyclic compounds. This thus increases the selective catalysis of benzene, naphthalene, biphenyl, and anthracene and improves tar quality. The unactivated Fe-BC and Ni-BC catalysts exhibit high selectivity for light oil with a boiling point below 170 °C. In contrast, the activated Fe-BHC and Ni-BHC catalysts have a stronger ability to crack heavy tar due to the synergistic effect of metal and carbon defect structures. However, the micropores within the catalysts prevent mass transfer of macromolecular compounds, drastically lowering the tar yield with coke formation. Overall, the unactivated metal modified catalyst with three-dimensional porous structure allows for the synergistic effect of dust removal and upgrading of volatiles while maintaining the tar yield, especially the Fe-BC catalyst with a lower price.

Hierarchically ordered microporous Ag2S QDs-CoOx/NC nanostructures for enhancing photocatalytic CO2 reduction to chemical fuels

Rational design of advanced architectural photocatalysts with efficient separation and transfer of photoinduced charge carriers, and well solar light absorption ability is of critical significance for solar energy utilization and CO2-to-fuel conversion. Herein, a novel three-dimensional (3D) ordered hollow-wall hybrid composite (3DOM Ag2S-CoOx/NC) has been developed by integrating ultrafine Ag2S quantum dots (QDs) on the surface of metal–organic frameworks (MOFs)-derived hierarchically ordered macroporous nitrogen-doped carbon skeletons with implanted CoOx nanoclusters (3DOM CoOx/NC). Compared with pristine 3DOM CoOx/NC and traditional ZIF-67-derived CoOx/NC, the constructed 3DOM Ag2S-CoOx/NC composite exhibits remarkable performances toward the photocatalytic conversion of CO2 and H2O vapor without any sacrifice reagents to fuels (CO-66.00 μmol g−1h−1, CH4-1.21 μmol g−1h−1 and C2H4-2.33 μmol g−1h−1) and a higher C2H4 selectivity (16.47%) in the gas–solid system under light irradiation (λ > 420 nm). Impressively, dual Z-scheme charge transfer pathways in the 3DOM Ag2S-CoOx/NC can provide good channels for boosting electron transfer and charge separation. Experimental characterizations combined with density functional theory (DFT) calculations further elucidate that the key role of Ag2S QDs is served as an auxiliary in the 3DOM Ag2S-CoOx/NC catalyst to improve the electronic structure and further facilitate adsorption/activation capacity of CO2 and H2O. Moreover, the multiple photocatalytic mechanisms including related key intermediates and conversion process of CO2 molecules are further identified by in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). This innovation provides a novel strategy to design well-designed hierarchically porous hybrid structures for photocatalytic CO2 reduction to high-value fuels.

Boosting the performance of enzyme-free biosensing system with Ni–Co bimetallic nanorod anchored on macroporous carbon composites for glucose monitoring

In this study, a nickel–cobalt bimetallic nanorod-codoped macroporous carbon nanocomposite (NiCo NR/MPC) was prepared and used for glucose detection. NiCo NR was uniformly embedded into MPC scaffolds. The synergistic effect between the excellent electrocatalytic activity of NiCo NR and the remarkable conductivity of MPC carriers increased the electron transfer and the formation of numerous usable active sites. For glucose detection, the NiCo NR/MPC-glassy carbon electrode (GCE) exhibited a good linear range (0.1–831.7 μM) and a low limit of detection (0.063 μM) (S/N = 3), with a high corresponding sensitivity of 206.8 μA mM−1 cm−2. Additionally, the GCE sensor was used to detect glucose under the same test conditions; the relative standard deviation (RSD) of the sensor was 4% after 10 repeated measurements. This indicated the reproducibility of the constructed NiCo NR/MPC-GCE sensor. Therefore, the constructed NiCo NR/MPC glucose electrochemical sensor has good application prospects.

Modulating the Reaction Configuration by Breaking the Structural Symmetry of Active Sites for Efficient Photocatalytic Reduction of Low-concentration CO2.

Photocatalytic conversion of low-concentration CO2 is considered as a promising way to simultaneously mitigate the environmental and energy issues. However, the weak CO2 adsorption and tough CO2 activation process seriously compromise the CO production, due to the chemical inertness of CO2 molecule and the formed fragile metal-C/O bond. Herein, we designed and fabricated oxygen vacancy contained Co3O4 hollow nanoparticles on ordered macroporous N-doped carbon framework (Vo-HCo3O4/OMNC) towards photoreduction of low-concentration CO2. In-situ spectra and ab initio molecular dynamics simulations reveal that the constructed oxygen vacancy is able to break the local structural symmetry of Co-O-Co sites. The formation of asymmetric active site switches the CO2 configuration from a single-site linear model to a multiple-sites bending one with a highly stable configuration, enhancing the binding and structural polarization of CO2 molecules. As a result, Vo-HCo3O4/OMNC shows unprecedent activity in the photocatalytic conversion of low-concentration CO2 (10% CO2/Ar) under laboratory light source or even natural sunlight, affording a syngas yield of 337.8 or 95.2 mmol g-1 h-1, respectively, with an apparent quantum yield up to 4.2%.

(General Student Award Winner - 3rd Place) Electropolymerized Poly(3,4-ethylenedioxythiophene) Coatings on Porous Carbon Electrodes for Electrochemical Separation of Metals

Advances in decarbonization technologies such as batteries, photovoltaics, and wind turbines are accelerating the energy transition from fossil fuels to renewables. However, these technologies drive the demand for so called “critical metals” (e.g., Co, Ni, Li) that are unequally distributed over the planet and their mining has a significant environmental impact1. Electroplating and mining effluents can be utilized as a secondary source for these metals, but the low concentration of metals in their ionic form is a challenging medium for conventional separation methods2. Electrode-assisted separation methods where ions are immobilized on the electrode surface are well-suited for ionic separations as they can offer selectivity for the target metal ion with low energy consumption, minimal chemical input, and direct integration with the electrical grid3. These technologies can greatly benefit from the infrastructure of flow electrochemical platforms, including the use of porous carbonaceous electrodes to boost convective transport and minimize reactor resistances4. Imparting ion-selectivity on carbon electrodes is possible by immobilizing redox-active layers on their surface3. However, traditional coating techniques used to deposit functional materials (i.e., dip coating, spraying, doctor blading) cannot be realized on macroporous supports without compromising their microstructure. The use of conductive polymers can overcome this challenge as they can be coated on complex morphologies with controllable thickness through electropolymerization reactions, and they can provide a conductive and switchable matrix for ion-exchange. We hypothesize that the electrochemically switchable ion exchange (ESIX) property of conductive polymers, combined with the utility of macroporous carbon scaffolds can unlock convection enhanced and zero-gap reactor architectures for ionic separations.In this work, we investigate the electropolymerization of an industrially relevant polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on commercial carbon fiber-based paper electrodes in terms of its synthetic parameters, morphology and ESIX-activity5. When coordinated to poly(4-styrenesulfonate) anions, PEDOT/PSS blend forms smooth and conformal layers on the carbon fibers with a controllable thickness down to 0.1 µm. We show that the PEDOT/PSS system acts as potential-controlled cation exchange material that can ingress Ni2+ at a low potential of -0.25 V (vs Ag/AgCl) and demonstrates higher affinity towards Ni2+ than Zn2+. The advantage of ESIX is that both adsorption and desorption are potential controlled. To verify this, we performed a complete ESIX-swing on PEDOT/PSS coatings with increasing coating weights and analyzed the desorbate for ion content (Figure 1). We find that by increasing the PEDOT/PSS coating weight, more Ni2+ can be separated from binary Ni2+:Na+ solutions, but the adsorption capacity decreases. The highest adsorption capacity of 227 mg g-1 is reached for the lowest coating weight, which suggests that thicker coatings are not well utilized within the time frame of the ESIX experiments. Although this work focuses on conductive polymers for electrochemical separation of metals, it can inform researchers on electropolymerization-based coatings for various electrochemical technologies (e.g., fuel cells, electrolyzers, redox flow batteries) that utilize porous electrodes. References T. Watari, K. Nansai, and K. Nakajima, Resources, Conservation and Recycling, 155, 104669 (2020).K. Kim et al., iScience, 24, 102374 (2021).X. Su, Current Opinion in Colloid & Interface Science, 46, 77–93 (2020).W. Tang et al., Water Research, 150, 225–251 (2019).E. B. Boz, M. Fritz, and A. Forner-Cuenca, submitted (2022). Figure 1

Three-Dimensional (3D) Ordered Macroporous Bimetallic (Mn,Fe) Selenide/Carbon Composite with Heterojunction Interface for High-Performance Sodium Ion Batteries.

Transition-metal selenides have captured significant research attention as anode materials for sodium ion batteries (SIBs) due to their high theoretical specific capacities and excellent electronic conductivity. However, volumetric expansion and inferior cycle life still hinder their practical application. Herein, a three-dimensional (3D) ordered macroporous bimetallic (Mn,Fe) selenide modified by a carbon layer (denoted as 3DOM-MnFeSex@C) composite containing a heterojunction interface is fabricated through selenizing a 3D ordered macroporous Mn-based Prussian Blue analogue single crystal. The 3DOM-MnFeSex@C exhibits hierarchically porous architecture with enhanced mass-transfer efficiency; MnSe and FeSe2 particles are encapsulated into macroporous carbon framework, which can significantly promote the electronic conductivity and maintain the structural integrity. The density functional theory calculation indicates that the heterojunction interface between MnSe and FeSe2 has been successfully engineered so that Na+ can be readily adsorbed and rapidly converted, thus promoting the reaction kinetics and extending the cyclic life. As expected, the 3DOM-MnFeSex@C composite delivers excellent rate performance (277.6 mA h g-1 at 10 A g-1), and prolonged cycling life (191.6 mA h g-1 even after 1000 cycles at 2 A g-1) as a sodium storage anode. The sodium storage mechanism of the composite was further investigated by in situ X-ray diffraction and ex situ high-resolution transmission electron microscopy characterization techniques.

Pyrolysis regulation of ZIF-8 to construct a robust multifunctional N-doped macroporous carbon for lipase immobilization

Pyrolyzing ZIF-8 into N-doped carbon is now inspiring new potential of ZIF-8 for extensive applications. However, the exploration of such ZIF-8-derived carbon for biotechnological applications has been rarely investigated, especially in this context that imidazole derivatives are of rich functionality in life science. Herein, we reported a facile temperature-dependent pyrolysis method to achieve the effective N-doping in ZIF-8-derived macroporous carbon, which was systematically investigated for the immobilization of lipase from Thermomyces lanuginosus (TLL) in biodiesel production. MNC-600 (macroporous N-doped carbon derived at 600 °C) exhibited the best immobilization performance, with the highest specific activity of 190.6 U mg−1, a 36.9% increase than free TLL. Moreover, MNC-600@TLL showed superior effectiveness and robustness in biodiesel production. A much faster rate of conversion and the highest biodiesel yield of 87.4% were observed. After eight successive batches of recycling, MNC-600@TLL retained 93.4% of its initial activity. XPS analysis revealed the evolution of N species during the pyrolysis of ZIF-8. It was proposed that the abundant doping of pyrrolic N species played a major role in the surprising performance of MNC-600, mainly through hydrogen bonding interactions, which simultaneously realized the activation of reactants as well as the in-situ hydrophobization of biocatalyst. This report is anticipated to pave a way for the exploration of ZIF-8-derived N-doped carbon for extensive biotechnological applications.

Extraction of organic pollutants from wastewater to improve the sanitary reliability of water bodies

. The purpose of this study was to evaluate the principal possibility of increasing the adsorption of hydroxybenzene by the carbon sorbent Purolate-standard by a combination of reactive and thermal oxidative modification. The control of the hydroxybenzene concentration from the solution was determined by spectrophotometry. The possibility of increasing the adsorption capacity by means of combined oxidative modification (reagent oxidation followed by heat treatment) of carbon material was considered. The characteristics of the extraction process were established on the basis of Langmuir and Dubinin-Radushkevich models. Analysis of the porous structure and functional groups of the surface of anthracite and its modified samples showed changes in the above parameters. The processing of experimental data in the coordinates of the Langmuir and Dubinin-Radushkevich equations showed a satisfactory correlation, which allows us to calculate the values: Gibbs energy, the maximum adsorption capacity of the monolayer, the adsorption equilibrium constant, the maximum volume of the adsorption space. The obtained values allow us to establish the adsorption mechanism, both on the feedstock and on the processed samples. It was found that the oxidation of 2 % ammonium salt of peroxodiseric acid with subsequent heating at 200°C reduced the adsorption of phenol. Treatment of the adsorbent with 5 % ammonium salt of peroxodiseric acid with heating at 250°C slightly increased the adsorption of phenol. The use of the studied oxidants to increase the adsorption capacity of anthracite did not give the expected result with respect to hydroxybenzene. Sorption on macroporous carbon materials with preliminary modification can be recommended as a promising direction in relation to organic pollutants. The study of the adsorption of hydroxybenzene on anthracite of the Purolate-standard brand was carried out under static conditions. The authors have proved that reducing the sanitary reliability of reservoirs is possible by means of reducing the level of contamination of wastewater. The mechanism of adsorption of hydroxybenzene on sorbents modified by a combined method under different regimes has been studied for the first time, which is a scientific novelty of the study.

Fluoride removal from water using Zr-modified meso- and macroporous carbons: Effect of pore structure and adsorption conditions

We investigated the effects of the pore structure and adsorption conditions (pH and coexisting anions) on the fluoride (F–) removal capacity of Zr-modified porous carbons. The porous carbons used in this study possessed well-defined pore structures created by the template technique with pore diameters of 10, 30, and 150 nm. These porous carbons were oxidized to functionalize them with oxygen-containing groups before being modified with Zr4+. Zr4+ modification improved the F– removal capacity of porous carbons. The maximum amount of F– adsorbed increased by approximately 3–10 times by Zr4+ modification. The F– adsorption capacity depends on the pore size. The samples with larger pore diameters (smaller specific surface areas) exhibited higher F– adsorption capacities than the samples with smaller pore diameters. This tendency can be explained using the theory of liquid imbibition in porous media. The adsorption capacities at pH 7.0 and 11.1 were lower than those at pH 3.1. This tendency can be interpreted based on competition between F– and OH– on adsorption sites and attractive/repulsive interactions between F– and protonated/deprotonated adsorbent surfaces. The coexisting carbonate anions notably suppress the F– adsorption. This suppressive effect can be explained by the competitive bonding of F– and CO32– to the adsorption sites.

Carbon microspheres with gigapores for application as electrode-active material of sodium-ion batteries

Micro- and mesoporous carbons are known to be effective anode materials for sodium-ion (Na+) batteries (SIBs). In contrast, macroporous and gigaporous carbons have rarely been studied for this purpose, even though their porous structure may facilitate electrolyte infiltration to enhance cell performance. Here, a series of gigaporous carbon microspheres (GCS) was synthesized by carbonizing gigaporous polymeric microspheres at different temperatures (700–2500 °C) and adopted as anode-active material of SIBs. All GCS samples exhibited a particle size of 10–15 μm and an average pore size of 0.3–0.5 μm. Nevertheless, their specific surface areas decreased over a large range with increasing carbonization temperature from >400 m2 g−1 to <30 m2 g−1. The GCS samples fabricated at higher temperatures demonstrated better electronic conductivity and a larger contribution from Na + insertion/extraction instead of adsorption/desorption to the capacity of constructed cells during charge/discharge. GCS carbonized at 850–1000 °C resulted in cells with the best capacity performance (>300 mAh g−1). The reason is that GCS produced at lower temperatures had insufficient conductivity and underwent limited electrochemical reactions with Na+, leading to a low capacity. On the other hand, an excessively high carbonization temperature produced carbons having a small d-spacing and lacking the beneficial carbonyl groups, which hindered both Na+ insertion/extraction and adsorption/desorption and therefore also reduced the cell capacity.

Study of the influence of the type of pores present in the electrodes on the behaviour of a SWAGELOK-type supercapacitor

The sharp increase in energy consumption in recent years has increased the demand for new energy storage systems or the improvement of existing ones. Supercapacitors are the answer to this great challenge needed by any industrialized society. In this work, to improve the storage system of these supercapacitors, the composition of carbon-based electrodes has been modified by adding carbon carbonaceous materials and the influence of porous texture (porosity and porosity distribution) on carbonaceous electrodes. Thus, a commercial activated carbon-based electrode PCO-1000 was modified by adding structured carbons TEG, TEG-B92, and carbon black V3. For this purpose, three PCO-1000 (commercial activated carbon) base electrodes were prepared, to which 5 % Teflon was added as a binder and 5 % TEG (structured carbon), TEG-B92 (92 h heat-treated structured carbon) and V3 (carbon black), to provide the electrodes with carbon porous structures, as well as graphitic structures with carbon separation between lamellar layers. The structured carbons (TEG and TEG-B92) have carbon structures formed by interlamellar layers at carbon spacing distances and micro, macroporous pore distributions versus V3 carbon black with meso-macroporous distributions. Furthermore, carbon black V3 was selected as it has a pore distribution (meso-macroporous) greater than 50 Å which is electrochemically accessible by aqueous solutions of H2SO4, in an organic medium large solvated ions are not accessible to small pores. The supercapacitor prepared on the PCO-1000 basis with V3 (E-V3), is the best performing, with capacity, power, and energy parameters far superior to the other samples. This seems to indicate that E-V3 supercapacitors with a varied pore structure perform better than those with a predominantly micropore distribution. It seems to be deduced that it is the wide mesopores present in V3 that favour the diffusion of ions inside the carbons.In conclusion, the resistance of the supercapacitor cell is strongly dependent on the resistance of the electrolyte used, the size of the electrolyte ions in which it diffuses, and the size of the electrode pores, so the characteristics of the electrode material and the electrolyte must be considered together and not separately.Finally, this study could be of great importance in the fabrication of electrodes with a certain porosity distribution and predominance of wide mesopores and macropores to achieve important energy storage capacities in this type of supercapacitors and their application to hybrid electric vehicles, computers, uninterruptible power supply systems (UPS), motor starters, etc.

Pd NPs encapsulated by COF in nitrogen-doped macroporous chitosan carbon microspheres act as an efficient and recyclable multifunctional catalyst

Developing efficient, recoverable, and versatile palladium catalysts is of great significance. In this paper, nitrogen-doped macroporous chitosan carbon microspheres (MCM) were prepared by emulsion polymerization method with polystyrene microspheres as a template. The core-shell structured MCM@Pd@COF catalysts were then prepared using a coral-structured COF shell layer to seal the Pd NPs in the channels of the MCM. The introduction of COF with good photocatalytic properties improved the stability of the material while imparting its photocatalytic properties without affecting its catalytic activity. MCM@Pd@COF efficiently catalyzed the Suzuki coupling reaction (Iodobenzene and phenylboronic acid, 98 % yield, TON = 6.7 × 105, TOF = 3.4 × 105 h−1), and the reduction of 4-nitrophenol (4-NP, reaction rate constant Kapp = 9.48 × 10−1 min−1). The kinetic study revealed that the reduction reaction of 4-NP by MCM@Pd@COF was compliant with the quasi-first-order kinetic model. Furthermore, MCM@Pd@COF removed up to 96.3 % of high concentrations of rhodamine B (RhB) within 30 min under visible light irradiation. Mechanistic investigation showed that MCM@Pd@COF efficiently promotes the production of O2– and OH radicals under visible light irradiation, which drives the photocatalytic degradation of organic dyes. There was no significant decrease in the catalytic activity of MCM@Pd@COF over the eight uses.

3D ordered macroporous sulfur-doped g-C3N4/TiO2 S-scheme photocatalysts for efficient H2O2 production in pure water

Photocatalytic hydrogen peroxide (H2O2) production offers a clean and cost-efficient alternative to the traditional anthraquinone oxidation approach. Herein, a step-scheme (S-scheme) heterojunction photocatalyst is fabricated by coupling TiO2 with three dimensionally ordered macroporous sulfur-doped graphitic carbon nitride (3DOM SCN/T) by electrostatic self-assembly. The optimized photocatalyst achieved a high photocatalytic H2O2 production activity with a yield of 2128 μmol h−1g−1 without the addition of hole scavengers. The remarkable performance was attributed to the synergy between the 3DOM framework and the S-scheme heterojunction. The former enhances light harvesting and provides abundant active sites for surface reactions, while the latter promotes the spatial separation of photogenerated carriers and enhances the redox power. Finally, the mechanism of photocatalytic H2O2 production over the 3DOM SCN/T S-scheme composite is proposed. This work provides novel insights into the development of efficient photocatalysts for H2O2 production from water and O2.

Fabrication of ordered macro-mesoporous single-crystalline Prussian blue and their derivatives for rechargeable sodium ion batteries

Benefiting from their improved accessibility of active sites and accelerated ion diffusion processes, ordered macro-mesoporous materials have received substantial attention in energy storage fields. However, preparing ordered hierarchical porous materials with single-crystal nature remains a huge challenge. Herein, we successfully prepare ordered macro-mesoporous single-crystalline Fe-based Prussian blue (denoted as OMMS-Fe-HCF) by chelating-agent-assisted in-situ crystallization strategy within a three-dimensional (3D) ordered polystyrene spheres (PS) template interstice. Subsequently, 3D ordered macroporous iron diselenide@carbon hybrid tetradecahedron (denoted as 3DOM-FeSe2@C) is favorably prepared by in-situ selenization of the OMMS-Fe-HCF template. The resulting composite can commendably inherit and reserve the macroporous architecture and cubo-octahedron morphology of the precursor. In particular, FeSe2 nanoparticles are homogeneously encapsulated into the macroporous carbon matrix, significantly improving the mass transfer performance while maintaining the structural integrity. By virtue of hierarchical structure advantages and excellent conductivity, the 3DOM-FeSe2@C exhibits high-rate capability (361.6 mAh g−1 at 20 A g−1) and excellent cycling durability (306.4 mAh g−1 after 900 cycles at 2 A g−1) for sodium-ion batteries. Considering the rational design and accurate construction of OMMS-Fe-HCF, our work provides a new perspective on the preparation of such highly ordered macro-mesoporous composite for application in the energy storage fields.