Well-defined Mesoporous Structure Research Articles

Hierarchically porous architecture of metal–organic framework-derived and S induced electron localization of Fe single atom sites for boosted ORR

Metal-organic frameworks (MOFs), with their high specific surface area, excellent stability and high electron transfer ability, are ideal supports for accommodating single metal atoms. However, the low utilisation of single-atom active sites limits the improvement of oxygen reduction reaction (ORR) performance.In this work, NH2-MIL-53(Al), a MOF possessing a mesoporous cage architecture, is used as the precursor to prepare N-doped carbon supports (denoted herein as N-HPC) with a well-defined mesoporous structure through pyrolysis. Thiourea was further employed for S doping and impregnated with a FePc, and heated again to yield Fe@S/N-HPC catalysts rich in accessible FeNx single atom sites. The porous structure is more accessible to Fe center atoms by exposing the active sites, provide easy electron conductivity and facilitate mass transport of ORR-intermediates. The prepared hierarchically porous architecture of NH2-MIL-53(Al)-derived and S induced electron localization of Fe SAs sites exhibit excellent ORR performance in alkaline (E1/2 = 0.88 V) medium.

Reparation of nano-FeS by ultrasonic precipitation for treatment of acidic chromium-containing wastewater

Nano-FeS is prone to agglomeration in the treatment of chromium-containing wastewater, and ultrasonic precipitation was used to synthesize nano-FeS to increase its dispersion. The optimization of the preparation method was carried out by single factor method (reaction temperature, Fe/S molar ratio and FeSO4 dropping flow rate) and response surface methodology. Dynamic experiments were constructed to investigate the long-term remediation effect and water column changes of nano-FeS and its solid particles. The changes of the remediation materials before and after the reaction were observed by SEM, and the mechanism of the remediation of chromium-containing wastewater by nano-FeS prepared by ultrasonication was revealed by XRD. The results showed that the reaction temperature of 12 °C, Fe/S molar ratio of 3.5 and FeSO4 dropping flow rate of 0.5 mL/s were the best parameters for the preparation of nano-FeS. The nano-FeS has efficient dispersion and well-defined mesoporous structure in the form of needles and whiskers of 40–80 nm. The dynamic experiments showed that the average removal of Cr(VI) and total chromium by nano-FeS and its immobilized particles were 94.97% and 63.51%, 94.93% and 45.76%, respectively. Fe2+ and S2− ionized by the FeS nanoparticles rapidly reduced Cr(VI) to Cr(III). Part of S2− may reduce Fe3+ to Fe2+, forming a small iron cycle that gradually decreases with the ion concentration. Cr(III) and Fe2+ form Cr(OH)3 and FeOOH, respectively, with the change of aqueous environment. Another part of S2− reacts with Cr(III) to form Cr2S3 precipitate or is oxidized to singlet sulfur. The FeS nanoparticles change from short rod-shaped to spherical shape. Compared with the conventional chemical precipitation method, the method used in this study is simple, low cost, small particle size and high removal rate per unit.

The fabrication of mesoporous η-Al2O3 nanofiber with tunable pore size by template-induced strategy

In this work, we prepared mesoporous η-Al2O3 nanofiber with tunable pore size using diverse surfactants. The as-prepared mesoporous η-Al2O3 nanofiber was characterized by a combination of various physicochemical techniques. The influence of surfactants types and polymerization degree on surface morphology and adsorption performance of mesoporous η-Al2O3 nanofiber was compared. The results of transmission electron microscopy (TEM), low-angle X-ray diffraction (XRD) and N2 adsorption–desorption isotherm prove the existence of mesoporous structure in η-Al2O3 nanofiber. Polyethylene glycol (PEG) is favored over polyether (PPG) in the preparation of mesoporous η-Al2O3 nanofiber, and PEG with a lower degree of polymerization is beneficial to form well-defined mesoporous structure. The η-Al2O3 nanofiber (PEG600) has the highest specific surface area and the best adsorption performance, followed by the η-Al2O3 nanofiber (PEG2000), and then the η-Al2O3 nanofiber (PPG). Both the adsorption isotherm and the adsorption kinetics equation prove that the adsorption mechanism of methylene blue on mesoporous η-Al2O3 nanofiber is the combination of chemical and multilayer adsorption. This work provides a new avenue to prepare mesoporous η-Al2O3 nanofiber with tunable pore size for the application of mesoporous material in battery, adsorbent, catalytic and biomedical carrier.

Ethylene oligomerization over mesoporous FeNi-BTC catalysts: Effect of the textural properties of the catalyst on the reaction performance

Mesoporous FeNi-1,3,5-benzenetricarboxylates (FeNi-BTCs) with different Fe/Ni ratios were prepared, and their catalytic activities in ethylene oligomerization were evaluated. The textural properties of the bimetallic FeNi-BTC were considerably affected by the Fe/Ni ratio, exhibiting a volcano relationship, with the maximum specific surface area, pore volume, and diameter observed at Fe/Ni = 10/90. The enhanced textural properties of the FeNi-BTC catalyst resulted in accelerated ethylene oligomerization and an increased C6–C8 oligomer selectivity. Using the Fe10Ni90-BTC catalyst, the rate of ethylene consumption and C6–C8 oligomer selectivity reached as high as 2823 g C2H4/g Ni h and 49%, which were approximately four- and two-fold higher than those of Ni-BTC, respectively. The remarkable reaction performance of the Fe10Ni90-BTC catalyst could be rationalized in terms of its well-defined mesoporous structure, which could decrease the mass transfer resistance and thereby facilitate intrapore ethylene diffusion during ethylene oligomerization. These results clearly demonstrate the potential of the FeNi-BTC catalyst in promoting ethylene oligomerization with a high activity and selectivity towards C6∼C8 oligomers. In the catalyst recycling study, whereas the catalytic activity decreased due to the partial deformation of the FeNi-BTC catalyst with repeated recycling, the selectivity towards C6+ oligomers gradually increased.

Optimization of hierarchical ZSM-5 structure from kaolin as catalysts for biofuel production.

Optimization of hierarchical ZSM-5 structure by variation of the first hydrothermal step at different times provides insight into the evolution of micro/mesopores and its effect as a catalyst for deoxygenation reaction. The degree of tetrapropylammonium hydroxide (TPAOH) incorporation as an MFI structure directing agent and N-cetyl-N,N,N-trimethylammonium bromide (CTAB) as a mesoporogen was monitored to understand the effect towards pore formation. Amorphous aluminosilicate without the framework-bound TPAOH achieved within 1.5 h of hydrothermal treatment provides flexibility to incorporate CTAB for forming well-defined mesoporous structures. Further incorporation of TPAOH within the restrained ZSM-5 framework reduces the flexibility of aluminosilicate gel to interact with CTAB to form mesopores. The optimized hierarchical ZSM-5 was obtained by allowing hydrothermal condensation at 3 h, in which the synergy between the readily formed ZSM-5 crystallites and the amorphous aluminosilicate generates the proximity between micropores and mesopores. A high acidity and micro/mesoporous synergy obtained after 3 h exhibit 71.6% diesel hydrocarbon selectivity because of the improved diffusion of reactant within the hierarchical structures.

Dihydropyrano quinoline derivatives functionalized nanoporous silica as novel fluorescence sensor for Fe3+ in aqueous solutions(aq)

A novel nanoporous silica-based fluorescence sensor with high selectivity and sensitivity was successfully prepared via grafting of 3-isocyanatopropyltriethoxysilane and dihydropyrano [3, 2-c] quinoline derivatives (DPQ) onto the pore walls of mesoporous silica. The attachment of fluorophore groups onto the surface of the SBA-15 was approved via TGA and FT‐IR spectroscopy. TGA analysis indicates a large weight loss about 49%, which is attributed to the binding of a large number of organic groups on the pores surface, which functional groups appeared in the FT-IR spectra. Structural characterization techniques have proved the type IV for N2 adsorption-desorption isotherm, which revealed the preservation of the mesoporous structure. Also, low-angle XRD, FESEM and TEM analyses demonstrate the formation of ordered and well-defined 2D hexagonal mesoporous structure (space group p6mm). Whereas, Fe3+ ions caused discernible fluorescence quenching of the fluorescence sensor, the other cations used did not significantly changed fluorescence emission of SBA-Si-DPQ. The fluorescence quenching of the sensor is attributed to the paramagnetic properties of Fe3+ ions that appear by complex formation between the urea group of the probe and Fe3+ ions. It is noteworthy that, the excitation at 310 nm caused an emission with a maximum at 478 nm wavelength. By the increasing concentration of the analytes, the emission intensity was decreased dramatically and good linearity observed between analytes concentrations and the fluorescence intensity quenching of the sensor. The measured detection limits for Fe3+ ions was 2.0 × 10−6 M.

A two-dimensional nanocontainer based on mesoporous polydopamine coated lamellar hydroxyapatite towards anticorrosion reinforcement of waterborne epoxy coatings

Two-dimensional (2D) nanocontainers provide exciting opportunities in anticorrosion application through a skillful combination of delivery functionality for corrosion inhibitors and barrier property of lamellar materials. Herein, we used a versatile emulsion-induced approach to synthesis sandwich-like 2D nanocontainers based on mesoporous polydopamine (PDA) heterostructures on ultrathin bio-ceramic hydroxyapatite (HA) nanosheets. Triblock copolymer and 1,3,5-trimethyl benzene (TMB) synergistically promote the formation of well-defined mesoporous structure. The porous PDA not only provides large amount of contact interface for embedding benzotriazole (BTA), but also serves as another important corrosion inhibitor to achieve active protection effect. In addition, rich functional groups in PDA structure ensure the fine interface compatibility between lamellar HA and waterborne resin, leading to the improvement in terms of coating barrier performance. In comparative evaluation, the composite coatings containing BTA-loaded nanocontainers (1 wt%) exhibit high impedance value (Zf=0.01 Hz) in 3.5 wt% NaCl solutions for 60 days, indicating the long-term anticorrosion properties. Meanwhile, local electrochemical impedance technology proves nanocontainers with BTA loaded obviously inhibited the corrosion reactivity in corrosive microregions. This work puts new insights into designing functional anticorrosion coatings based on the surface construction on 2D materials, which has potential application for improving coating service life in marine environment.

Collaborative fabrication of poly(L-proline)s with well-defined mesopores and hydrophobicity: Synergistic effect of mesoporous confinement and hydrophobic micro-environment on organic transformations

The preparation of materials with a well-defined mesoporous structure and hydrophobicity is of great significance for heterogeneous catalyst development, yet there still remains a challenge for fabricating the above materials without using templates. Herein, the polymerization of L-proline-functionalized monomer with crosslinkers containing variable alkyl-bridged length (n = 2,4,6,8) and vinyl-modified Fe3O4 nanoparticles to construct mesoporous poly(L-proline)s (MPLPs) has been reported for the first time. The resultant MPLPs were analyzed by characterization methods, suggesting that MPLPs with a well-defined mesoporous structure and unique hydrophobicity were successfully constructed by synergistic regulation of vinyl-modified Fe3O4 nanoparticles and crosslinkers with alkyl-bridged length of 6 carbon atoms, in which vinyl-modified Fe3O4 nanoparticles as structural reinforcer plays a vital role for the mesoporous formation. Moreover, the resultant MPLPs were found to be efficient catalysts for one-pot synthesis of functionalized spiroindolones and olefins. The kinetic study and the water contact angle indicate the mesoporous confinement and hydrophobic micro-environment in organic transformations. Hence, the high activity of MPLPs is ascribed to synergistic effect of mesoporous confinement and hydrophobic micro-environment, and the adsorption experiment results further confirm this synergistic catalysis. This work promotes a textural engineering approach to the development of multifunctional materials with well-defined mesopores and hydrophobicity.

MIL-101-Derived Mesoporous Carbon Supporting Highly Exposed Fe Single-Atom Sites as Efficient Oxygen Reduction Reaction Catalysts.

Fe single-atom catalysts (Fe SACs) with atomic FeNx active sites are very promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR). The pyrolysis of metal-organic frameworks (MOFs) is a common approach for preparing Fe SACs, though most MOF-derived catalysts reported to date are microporous and thus suffer from poor mass transfer and a high proportion of catalytically inaccessible FeNx active sites. Herein, NH2 -MIL-101(Al), a MOF possessing a mesoporous cage architecture, is used as the precursor to prepare a series of N-doped carbon supports (denoted herein as NC-MIL101-T) with a well-defined mesoporous structure at different pyrolysis temperatures. The NC-MIL101-T supports are then impregnated with a Fe(II)-phenanthroline complex, and heated again to yield Fe SAC-MIL101-T catalysts rich in accessible FeNx single atom sites. The best performing Fe SAC-MIL101-1000 catalyst offers outstanding ORR activity in alkaline media, evidenced by an ORR half-wave potential of 0.94V (vs RHE) in 0.1 m KOH, as well as excellent performance in both aqueous primary zinc-air batteries (a near maximum theoretical energy density of 984.2Wh kgZn -1 ) and solid-state zinc-air batteries (a peak power density of 50.6mW cm-2 and a specific capacity of 724.0 mAh kgZn -1 ).

Flower-like Pt/Fe2O3–CeO2 Catalysts for Highly Efficient Low-Temperature Catalytic Oxidation of Toluene

A series of porous Pt/FeₓCey microflowers have been synthesized through a solvothermal method. The well-defined mesoporous structure promotes gas distribution as well as even dispersion of active species, thus exposing more active sites and improving the catalytic efficiency for low-temperature toluene removal. The catalyst composition can be regulated by changing the Fe/Ce molar ratio and Pt loading content. Among the samples, 1 wt % Pt/Fe₃Ce₁ performed the best, with a reaction temperature for 90% toluene conversion of 192 °C at a WHSV of 36,000 mL/(h·g). The synergistic effect of Fe₂O₃ and CeO₂ promotes electron transfer and migration of oxygen species. Addition of Pt enhances the mobility of lattice oxygen, generating a high concentration of active surface lattice oxygen, which facilitates toluene removal. The Mars–van Krevelen model could be applied to explain the mechanism of toluene oxidation over these Fe-based catalysts.

Alkene-modified Fe3O4 nanoparticle-mediated construction of functionalized mesoporous poly(ionic liquid)s: Synergistic catalysis of mesoporous confinement effect and hydrogen proton for organic transformations

Abstract The preparation of mesoporous poly(ionic liquid)s (MPILs) is critically fundamental for the design of heterogeneous catalysts, whereas traditional methods are difficult to obtain these materials with both well-defined mesoporous structure and unique functionality. Here, HClO4-functionalized MPILs with well-defined mesoporous structure were successfully fabricated, in which the alkene-modified Fe3O4 nanoparticles as structural reinforcer play a vital role for mesoporous structure formation. The MPILs were characterized by N2 adsorption/desorption, scanning electron microscope (SEM), transmission Electron Microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and vibration sample magnetometry (VSM), and the results confirm that MPILs possess moderate surface area, well-defined mesoporosity, abundant active ionic centers, as well as efficient magnetic recovery. The resulting MPILs show excellent catalytic activity for condensation reaction and Knoevenagel condensation. The kinetic study reveals that the excellent catalytic activity of MPILs is attributed to the synergistic catalysis of mesoporous confinement effect and hydrogen proton from MPILs, albeit with mass transfer resistance produced by mesoporous channels. Further, the catalyst can be recovered using an external magnetic field and reused at least 10 times without a considerable decrease in its catalytic activity. Finally, alkene-modified Fe3O4 nanoparticle-mediated mesoporous construction promotes a textural engineering approach to the development of novel mesoporous materials for other applications.

Honeycomb-like mesoporous all-carbon graphene-based fiber for flexible supercapacitor application: Effect of spacers

Graphene-based fiber electrodes have attracted more interests for portable/wearable electronics. Here, the porous structure of the graphene-based fibers was investigated with nanoscale carbon powder (NC) and micrometer carbon black (CB) as spacer, respectively. The well-defined honeycomb-like mesoporous reduced expandable graphene oxide (rEGO)/NC fiber was fabricated by the wet spinning of the expandable graphene oxide (EGO) with 30% of NC as spacer, possessing a unique mesoporous structure with pore size of ∼4 nm and BET specific surface area of 142.0 m2 g−1. Owing to the unique mesopores and larger specific surface area, the rEGO/NC fiber delivered a higher specific capacitance up to 113.0 F cm−3, in comparison with the rEGO/CB fiber (73.7 m2 g−1 and 75.7 F cm−3). After the in-situ electropolymerization of aniline adsorbed in the honeycomb-like fiber, the polyaniline (PANI)@rEGO/NC composite fiber was obtained with specific capacitance of 177.5 F cm−3. The symmetrical solid-state supercapacitors based on the proposed PANI@rEGO/NC composite fibers exhibited better electrochemical, bending and cyclic performance than the PANI@rEGO/CB ones, owing to the well-defined honeycomb-like mesoporous structure.

Preparation, characterization and catalytic performance of ordered macroporous-mesoporous SiO2-supported MnMOx catalysts for soot combustion

In this work, three-dimensionally ordered macroporous-mesoporous SiO2 (3DOM-m SiO2) materials were synthesized by the mesoporous template (P123)-assisted colloidal crystal template (CCT) method and the preparation conditions of 3DOM-m SiO2 were investigated. A series of novel MnMOx/3DOM-m SiO2 (M: Fe, Co, Ni, Cu, Zn, La, Ce) catalysts were successfully prepared by a facile incipient-wetness impregnation method. The as-prepared catalysts were characterized by means of N2-adsorption-desorption isotherms, XRD, SEM, TEM, H2-TPR and O2-TPD and so on. For the synthesis of 3DOM-m SiO2, the suitable conditions, whose reaction temperature is 45 °C, the ratio of P123 to TEOS is 0.533 and ratio of water to ethanol is 0.5, were obtained by modifying reaction conditions. The as-prepared MnMOx/3DOM-m SiO2 catalysts also maintain well-defined macroporous and mesoporous structures after the loading process. Meanwhile, they exhibit good catalytic performance for soot combustion. Among the studied catalysts, MnCeOx/3DOM-m SiO2 catalyst give the best catalytic performance and its T10, T50, T90 and SmCO2 are 285, 355, 393 °C and 98.8 %, respectively.

Synthesis of ZSM-5 Microspheres Made of Nanocrystals from Iron Ore Tailings by the Solid-Phase Conversion Method.

ZSM-5 microspheres made of nanocrystals are successfully synthesized from iron ore tailings (IOTs) using a novel and environmentally friendly method, which have a well-defined microporous and mesoporous structure with a large surface area and high acidic strength. In the absence of the liquid water phase during the solid-phase conversion, the phase separation between the surfactant and the solid silica phase is able to be bypassed. Compared to conventional methods, such as hydrothermal and steam-assisted conversion methods, this approach enhances the utilization of autoclaves, considerably reduces pollutants, and simplifies the synthetic process, which saves both energy and time. Furthermore, the crystallization of ZSM-5 microspheres via the solid-phase conversion was examined at 413, 433, and 453 K. The results of the kinetic study suggest that the experimental values obtained conform to those of the nonlinear regression model of Kolmogorov-Johnson-Mehl-Avrami for crystallization and nucleation. For the induction, transition, and crystallization stages, the activation energies are 70.96, 39.76, and 36.23 kJ·mol-1, respectively. The new method is economical and offers a valuable industrially applicable route for the reuse of IOTs to synthesize ZSM-5 microspheres. This synthetic concept could also be expanded to obtain other types of mesoporous zeolites.

Effects of synthetic routes on the compositional and structural properties of dendritic mesoporous organosilica nanoparticles: The unexpected reversed “double-edged sword” role of reaction time

ABSTRUCT Dendritic mesoporous organosilica nanoparticles (DMONs) have attracted increasing attention owing to the variety of appealing properties offered by the hybrid organic-inorganic framework and the central-radial pore structure. To date, two synthetic routes have been developed for the preparation of DMONs, including aqueous phase and water/oil bi-phasic systems. However, the impact of synthetic routes on the compositional and structural properties of the resultant nanomaterials remains largely unexplored. In the present work, we aim to gain insight on these two synthetic routes and have observed an unexpected reversed “double-edged sword” effect of reaction time on the compositional and structural properties of DMONs for two synthetic routes. For the aqueous phase route, prolonged reaction time is beneficial for improving the organosilica content, but leads to the loss of porous structure. In contrast, for the water/oil biphasic route, prolonging the reaction time causes the reduction of organic content in the products, but facilitates the formation of well-defined dendritic mesoporous structure. A “rate determine step” based mechanism has been proposed to explain these observations. Moreover, DMONs prepared from aqueous route possess higher organic content than those prepared from the biphasic route, which has resulted in a significantly higher hydro-stability. Our work unravels that synthetic routes largely determine the compositional and structural properties of DMONs, for which the reaction time needs to pay particular attention to achieve maximized organic content and well-preserved pore structure for optimal performance in desired applications.

(Invited) Development of Porous Structures for Electrochemical Energy Storage

We discuss the development of porous structures for the storage of electrochemical energy. Challenges in designing gas-diffusion electrodes for aqueous fuel cells are well known. Extending the use of oxygen electrode to a reversible metal-oxygen battery operating in aprotic media faces further difficulties. They include sluggish kinetics, components degradation, and formation of insulating solid oxide with irreversible structural changes. We synthesize carbon electrodes with controlled hierarchical porosity to investigate the impact of pore structure on performance. Using hierarchical porous carbon electrodes, investigations are carried out for electrocapacitance [1], the oxygen reduction reaction(ORR) in aqueous fuel cells,[2] and the cathode of an aprotic Li-O2 battery[3]. Results observed for Li-O2 has a capacity reaching 1/3 the theoretical energy density. The good performance of a Fe-N-doped hierarchical mesoporous carbon electrode are attributed to: i) A well-defined core-shell mesoporous structure for mass transport and dispersion of Li2O solid; ii) the Fe-N doping of carbon for corrosion resistance and improved conductivity; and iii) small and amorphous RuO2 for effective decomposition of Li2O. Challenges in electrodes for the sodium-oxygen battery technology are different and also discussed. The economic production of mesoporous materials is important for deployment of energy storage technologies in large scale. We also discuss the use of combustion techniques for the synthesis of porous metal oxides.[4,5] Li, M. Morris and K.Y. Chan, J. Mater. Chem. 21 (2011) 8880-8886.M. Zhou, C. Yang, K.Y Chan, Adv. Energy Mater., 4 (18), (2014) 1400840.M. Zhou, C.Y.V. Li, and K.Y. Chan, Energy Technology, 5 (2017) 732-739.A. Voskanyan, K.Y. Chan, and C.Y.V. Li, Chem. Mater. 28(8), (2016) 2768-2775.A.A. Voskanyan and K.Y. Chan, ACS Applied Nano Materials 1(2) (2018) 556-563.

Two-dimensional mesoporous sensing materials

Two-dimensional mesoporous materials combing ultrathin nanosheet morphology with well-defined mesoporous structures, are now emerging and becoming increasingly important for their promising applications in energy storage, electronic devices, electrocatalysts and so on. Here, we synthesized a kind of polypyrrole-based two-dimensional mesoporous materials with uniform pore size, ultrathin thickness and high surface area. Serving for electrochemical NH3 sensor, they exhibited a fast response and high sensitivity. Therefore, our study would promote much interest in design of new materials for gas sensor applications.

UIO-66-NH2 -Derived Mesoporous Carbon Catalyst Co-Doped with Fe/N/S as Highly Efficient Cathode Catalyst for PEMFCs.

Efficient, low-cost catalysts are desirable for the sluggish oxygen reduction reaction (ORR). Herein, UIO-66-NH2 -derived multi-element (Fe, S, N) co-doped porous carbon catalyst is reported, Fe/N/S-PC, with an octahedral morphology, a well-defined mesoporous structure, and highly dispersed doping elements, synthesized by a double-solvent diffusion-pyrolysis method (DSDPM). The morphology of the UIO-66-NH2 precursor is perfectly inherited by the derived carbon material, resulting in a high surface area, a well-defined mesoporous structure, and atomic-level dispersion of the doping elements. Fe/N/S-PC demonstrates outstanding catalytic activity and durability for the ORR in both alkaline and acidic solutions. In 0.1 m KOH, its half-potential reaches 0.87 V (vs reversible hydrogen electrode (RHE)), 30 mV more positive than that of a 20 wt% Pt/C catalyst. In 0.1 m HClO4 , it reaches 0.785 V (vs RHE), only 65 mV less than that of Pt/C. The catalyst also exhibits excellent performance in acidic hydrogen/oxygen proton exchange membrane fuel cells. A membrane electrode assembly (MEA) with the catalyst as the cathode reaches 700 mA·cm-2 at 0.6 V and a maximum power density of 553 mW·cm-2 , ranking it among the best MEAs with a nonprecious metal catalyst as the cathode.

Nanostructured porous carbons with high rate cycling and floating performance for supercapacitor application

Biomass-derived activated carbon from cork (Quercus Suber) (ACQS) was prepared via a two-step environment-friendly route using mild KHCO3 as the activating agent. This synthesis route makes the material produced less toxic for usage as electrode material for energy storage application. The ACQS has well-defined microporous and mesoporous structures and a specific surface area of 1056.52 m2 g-1 and pore volume of 0.64 cm3 g-1. Three-electrode tests were performed in 6 M KOH, 1 M H2SO4 and 3 M KNO3 aqueous electrolytes, to analyse the material performance in acidic, basic, and neutral media. Specific capacitance values (Cs) of 133 F g-1/167 F g-1 at 1.0 A g-1 was obtained in 3 M KNO3 in the positive/negative potential windows. Due to the observed best performance in neutral 3 M KNO3, further electrochemical analysis of the symmetric device was carried out using the same electrolyte. The device displayed a Cs value of 122 F g-1, energy and power densities of ∼14 W h kg-1 and 450 W kg-1 respectively; at 0.5 A g-1. The device also displayed an excellent stability after potentiostatic floating at a maximum voltage of 1.8 V for 120 h and ∼100% capacitance retention after 10,000 charge-discharge cycles. The excellent stability makes the cork-derived material a potential excellent, cost-effective material for supercapacitor application.

Mesoporous carbon derived from ZIF-8 for high efficient electrosorption

In this work, the capacitive deionization (CDI) behavior of mesoporous carbons (MCs) through direct carbonization of ZIF-8 at 1000°C under Ar+4%H2 atmosphere has been explored. The obtained MCs exhibit a well-defined mesoporous structure, with a high specific surface area of 723.41m2·g−1 and average pore diameter of 3.2nm. The specific electrochemical capacitance of MCs was evaluated in a three-electrode configuration with 1M NaCl electrolyte, showing that the capacitance reached as high as 215.72F·g−1 at the scan rate of 5mV·s−1 and 186F·g−1 with current density of 100mA·g−1, respectively. Moreover, it is found that the electrosorption capacity of MCs was 4.8mg·g−1 in NaCl solutions with an initial concentration of 250mg·L−1 and cell voltage of 1.2V. Remarkably, the theoretical maximum electrosorption capacity was estimated at 17mg·g−1 from Langmuir isotherm when the cell voltage was fixed at 1.2V. Finally, the well regeneration of MCs electrode was demonstrated, indicating the great potential application of MCs in desalination.