High SBET Research Articles

Preparation of highly microporous activated carbon by utilizing inherent iron in coal through CO2 and steam co-activation for improving CO2 capture and methylene blue removal

Pore-tailoring by utilizing the inherent iron mineral in coal for highly microporous activated carbon (AC) preparation for boosting adsorption ability is a promising strategy. In this work, AC-XFeS2 (X indicates the contents of pyrite in coal, 0–3 wt.%) was prepared via blending demineralized Taixi coal and pyrite and followed by CO2 and steam co-activation. The iron minerals transformation, AC physicochemical textural development and performance were investigated by various analyses. The results indicate that: (1) Pyrite (FeS2) can transform into magnetite (Fe3O4) and hematite (Fe2O3) during CO2 and steam co-activation. Pyrite declines the graphitization degree and enhances the increment of AC’s C=O, COO, and π–π* content. Pyrite favors the increase of AC’s micropore porosity. High SBET and Smic of 1587 m2/g and 949 m2/g of AC-1FeS2 were achieved, which is higher by 13.5% and 83.6% than AC of 1398 m2/g and 517 m2/g, respectively. (2) The CO2 adsorption capacity of AC-1FeS2 is up to 2.06 mmol/g at 25 °C and 1.0 bar, which is higher by 11.3% than 1.85 mmol/g of AC. The enhancement of micropore by pyrite is the main aspect of improving CO2 capture. (3) AC-1FeS2 presents maximum MB adsorption capacity, reaching 63.3 mg/g, which is higher by 19.3% than 53.3 mg/g of AC. A serious of kinetics models was studied and the MB adsorption process could be better reflected by Pseudo second-order kinetics (R2=0.9538). The enhanced pore-filling, π–π* stacking and C=O complexation are one aspect of improving MB removal. In addition, the effect of Fe-O bonds or magnetic particles including Fe3O4 also enhances MB removal. The results of this investigation could provide new avenues and theoretical support for cost-effective AC with highly microporous production by utilizing high-iron-sulfur coal, to some extent, guide the actual industrial application.

Metal chlorides and ammonium persulfate hydrothermal carbonization for enhanced pyrolysis behavior and biochar properties

To elucidate the impact of a modified reaction medium on the hydrothermal carbonization (HTC) coupled pyrolysis process, a two-stage conversion of rice straw (RS) was investigated in the present work. RS was initially treated hydrothermally in a conventional medium (water) and a modified reaction medium (metal chlorides and ammonium persulfate AP), followed by an upgrade of the obtained hydrochar via pyrolysis. The characteristics of the modified hydrochar and the pyrolysis biochar were examined. It was shown that a modified reaction medium promoted a higher mass yield of hydrochar. Compared to conventional hydrochar, modified hydrochar exhibited higher ash and fixed carbon content, and lower carbon and oxygen content. Furthermore, the pyrolysis behavior of modified hydrochar was more complex. Not only the DTG curve entirely different was, but the values of activation energy and pre-exponential factor also significantly increased. Ultimately, the modified medium enhanced the adsorption capacity of the HTC coupled pyrolysis biochar. Among them, B-HTC-AP had the highest SBET (544.83 m²/g) and the largest pore volume (0.4644 cm³/g). The TC adsorption capacity of B-HTC-AP reached 187.31 mg/g. The pseudo-second-order kinetic model and the Freundlich isotherm model provided a better description of the TC adsorption process on B-HTC-AP. Possible adsorption mechanisms of B-HTC-AP could encompass pore filling, electron transfer, hydrogen bonding, and π-π interactions. Therefore, the use of a modified reaction medium in the two-stage process could be an effective strategy for upgrading biomass.

A convenient, economical and excellent-yield method for the preparations of zeolite imidazolate frameworks (ZIFs) and the applications in environmental purification

Zeolite imidazolate frameworks (ZIFs) are a class of highly concerned metal organic frameworks (MOFs) with zeolite like structures. In this study, a convenient, economical and excellent-yield method for ZIFs preparation was built under the chemical principle exploration of ZIFs formation. By loading stoichiometric metal salts and ligands, four ZIF samples were obtained and characterized by XRD, FTIR, BET, SEM and TG. The porous ZIF-8 and ZIF-67 got high SBET of >1700 m2 g−1 and high yields of 98.3% and 91.7%, respectively. Comparatively, the dense ZIF-zni (Zn) and ZIF-zni (Co) got high yields of 98.6% and 92.0% but very low SBET. ZIF-8 and ZIF-67 were utilized in environmental purification to exhibit good performances in dealing with heavy metals, radionuclides and organic pollutants through adsorption or photocatalysis. The scale-up reaction for ZIF-8 showed that the yield and key performance parameters were almost unchanged, which should be beneficial for mass production.

Bimetallic CPM-37(Ni,Fe) metal-organic framework: enhanced porosity, stability and tunable composition.

A newly synthesized series of bimetallic CPM-37(Ni,Fe) metal-organic frameworks with different iron content (Ni/Fe ≈ 2, 1, 0.5, named CPM-37(Ni2Fe), CPM-37(NiFe) and CPM-37(NiFe2)) demonstrated high N2-based specific SBET surface areas of 2039, 1955, and 2378 m2 g-1 for CPM-37(Ni2Fe), CPM-37(NiFe), and CPM-37(NiFe2), having much higher values compared to the monometallic CPM-37(Ni) and CPM-37(Fe) with 87 and 368 m2 g-1 only. It is rationalized that the mixed-metal nature of the materials increases the structural robustness due to the better charge balance at the coordination bonded cluster, which opens interesting application-oriented possibilities for mixed-metal CPM-37 and other less-stable MOFs. In this work, the CPM-37-derived α,β-Ni(OH)2, γ-NiO(OH), and, plausibly, γ-FeO(OH) phases obtained via decomposition in the alkaline medium demonstrated a potent electrocatalytic activity in the oxygen evolution reaction (OER). The ratio Ni : Fe ≈ 2 from CPM-37(Ni2Fe) showed the best OER activity with a small overpotential of 290 mV at 50 mA cm-2, low Tafel slope of 39 mV dec-1, and more stable OER performance compared to RuO2 after 20 h chronopotentiometry at 50 mA cm-2.

Porous carbon materials augmented with heteroatoms derived from hyperbranched biobased benzoxazine resins for enhanced CO2 adsorption and exceptional supercapacitor performance

Porous carbon materials doped with heteroatoms are an excellent alternative for applications in CO2 adsorption and supercapacitors. Herein, we present a new approach to obtain heteroatoms (N, O, and S) doped porous carbon materials using bio-based hyperbranched benzoxazine (RES-HP-BZ) as a precursor. Two types of porous carbon materials, poly(RES-HP-BZ)-700 and poly(RES-HP-BZ)-800, were synthesized through a simple calcination method by carbonization and KOH activation of benzoxazine at temperatures of 700 °C and 800 °C, respectively. The chemical structure, texture properties, and surface chemistry characteristics were validated through FTIR, NMR, SEM, XRD, and XPS, respectively. The resulting poly(RES-HP-BZ)-800 exhibited micro and meso porous characteristics with a high SBET of 841 m2 g−1, pore size of 1.14 nm, and pore volume of 0.70 cm3 g−1. The poly(RES-HP-BZ)-800 also showed a high graphitization degree and electrochemically energetic N-6, N-5, N-Q, O-2, and O-3 heteroatoms, which led to a high capacitance of 523 F g−1 (at 0.5 A g−1) as well as CO2 capture of 4.63 mmol g−1 at 298 K. These newly developed bio-based porous carbons derived from hyperbranched bio-benzoxazine with excellent electrochemical performance make them a promising candidate for eco-friendly supercapacitors.

Preparation of phenolic hydroxyl-modified hyper-crosslinked polymers and their adsorption performance towards small molecular aromatic amines

Herein, three phenolic hydroxyl-modified hyper-crosslinked polymers were synthesized according to two-step Friedel-Crafts alkylation, and they were applied to adsorb small aromatic amines in aqueous and organic solvents. The first low-temperature Friedel-Crafts at 313 K introduced massive phenolic –OH to the intermediates, then the second high-temperature Friedel-Crafts at 353 K, also known as post-crosslinking reaction, brought a hyper-crosslinked skeleton composed of plentiful rigid methylene bridges to the target products, greatly enhancing the Brunauer-Emmett-Teller (BET) surface area (SBET) and total pore volume (Vtotal) of the polymers. In aqueous solution, the HCPS-BNAP-FDA had great potential for efficient adsorption of aniline and p-nitroaniline (p-NANL), and the Langmuir model predicted that their maximum capacities (qmax) were 209.25 mg/g and 277.30 mg/g, respectively. In cyclohexane solution, the qmax of aniline on HCPS-BNAP-FDA was predicted to be 202.38 mg/g. The removal aniline in aqueous solution could exceed 95 % when the original concentration was less than 200 mg/L, and the final concentration was 0.12 mg/L, much lower than the emission limit of China (GB 4287–2012, China). The polymer with 1,4-bis(chloromethyl)benzene (DCX) as crosslinking agent had the highest SBET (1282 m2/g) and the best adsorption performance for aniline (qmax, 258.73 mg/g). The adsorption mechanism demonstrated that the grafting of phenolic –OH groups improved the adsorption performance, as the possible hydrogen bonds and acid-base interactions. The micropores added via post-crosslinking also achieved a significant increase in adsorption capacity, that is, the pore filling adsorption mechanism.

Structure and Catalytic Performance of Carbon-Based Solid Acids from Biomass Activated by ZnCl2

In the current investigation, carbon-based solid acid catalysts were synthesized from peanut shells (PSs) and rice straw (RS) using ZnCl2 activation and concentrated sulfuric acid sulfonation. These catalysts were then employed for the hydration of pinene to produce terpineol. The research findings suggest that the natural porous structure of RS is more amenable to ZnCl2 activation compared to PSs. Furthermore, the catalysts prepared from fully activated RS by ZnCl2 (RSA-C-S) had a higher SBET and higher density of oxygen-containing groups (–COOH) in comparison with unactivated RS-based solid acids (RSC-S). The characterization outcomes revealed that RSA-C-S possesses a specific surface area of 527.0 m2/g, significantly outperforming RSC-S, which has a surface area of 420.9 m2/g. Additionally, RSA-C-S registered a higher –COOH density of 1.37 mmol/g, as opposed to RSC-S’s, with 1.07 mmol/g, attributable to the partial oxidation of internal –OH groups during activation. Experimental data from hydration tests confirmed that the catalyst’s superior performance is largely attributed to its elevated specific surface area and a high density of –COOH functional groups. Under optimal reaction parameters, RSA-C-S demonstrated unparalleled catalytic efficiency in the synthesis of α-terpineol via hydration of α-pinene, achieving conversion and selectivity rates of 87.15% and 54.19%, respectively.

Elucidating microcystin-LR adsorption on pyrolyzed hydrochars via experiments and molecular simulations

This study focuses on synthesizing pyrolyzed hydrochar from corn stover to adsorb MCLR from aqueous solutions. The underlying hypothesis of this study is that both porosity and surface functional groups play a role in MCLR adsorption. To test the hypothesis, wet waste corn stover was first hydrothermally carbonized (HTC) at 260 ℃ for 30 min to enhance the surface functionality and hydrophobicity. Hydrochars, which are solid products of HTC, were then pyrolyzed at 400, 600, and 800 ℃ for 60 min which enhanced the BET surface area (SBET) from 1.97 ± 0.92 m2/g up to 277.53 ± 7.6 m2/g. Oxygen containing functional groups increase from 833.54 µmol/g up to 1604.24 µmol/g at pyrolysis temperature 400 °C then decrease as low as 211.74 µmol/g with increase in pyrolysis temperatures. Higher SBET (CS-P800) facilitated high uptake of MCLR compared to the other pyrolyzed hydrochars suggesting pore-filling interactions as a possible adsorption mechanism. Adsorption isotherms studies indicated that MCLR follows Freundlich-type adsorption. Fully atomistic simulations showed that MCLR molecules have a propensity to aggregate, which supports the Freundlich adsorption isotherm. Furthermore, atomistic simulations provided insight on MCLR behavior with graphene sheet proving high affinity for adsorption as the molecule conforms to stable configuration in the adsorbed state.

A novel MOF-based hollow carbon nanofiber mat with hierarchical apertures for efficient adsorption of low concentration benzene under high humidity

An ultraporous metal-organic framework (MOF)-based carbon nanofiber mat (CNFM4) with two types of hollow structure was prepared by electrospinning the mixed solution with polyacrylonitrile, polymethyl methacrylate and ZIF-8, followed by carbonization. The self-supporting CNFM4 has a higher Brunauer-Emmett-Teller (BET) specific surface area (SBET) (935.5 m2/g) and total pore volume (Vtotal) (0.69 cm3 g−1) than the PAN, PAN/PMMA, PAN/ZIF-8-derived carbon nanofiber mats (CNFMs). Static adsorption experiment showed CNFM4 had a high benzene adsorption capacity of about 12 mmol g−1 at saturated vapor pressure at 298 K, due to its high Vtotal. And even at low pressure of 0.1 kPa, its adsorption capacity still reached 2.75 mmol g−1, owing to its high SBET and rich micropore. The dynamic adsorption study showed CNFM4 has a breakthrough and saturation adsorption amount of 0.4902 and 0.5714 mmol g−1 at dry gas, respectively, and even at 60 RH%, they still can keep 0.2620 and 0.3642 mmol g−1, respectively, suggesting its application potential under the actual environment. The dynamic adsorption study also proves the important role of hollow structure at improving adsorption rate. This work provides a new idea for preparing the ultraporous MOF-based hollow CNFMs, and broadens the application of MOF-based CNFMs for VOCs removal.

Influence of furnace atmospheres and potassium hydroxide activation on the properties of bamboo activated carbon and its adsorption towards 4-nitrophenol

Bamboo activated carbon (BAC) was synthesized as adsorbent for 4-NP adsorption due to its incredible adsorptive capability that has led it to its popularity. The effect of furnace atmospheres (argon, limited-air, vacuum), carbonizing temperatures (400–600 ℃), and activating temperatures (500–700 ℃) were investigated to achieve the largest surface area (SBET) of BAC. Its properties were analysed by using BET, FTIR, LVSEM, XRD, TGA, and Elemental analysis. The 4-NP adsorption was conducted by varying the pH (3−11), BAC dosages (0.05–0.4 g L-1), and 4-NP initial concentrations (10–100 mg L-1). Consequently, the argon-treated BAC (A67) had the highest SBET (1795.38 m2 g-1), stating that 600 ℃ of carbonizing temperature with 700 ℃ of argon flow activating temperature is the best condition to synthesize the BAC. The best adsorption efficiency (95.12%) was achieved by using A67 (pH 5, 0.2 g L-1, 50 mg L-1) with its maximum adsorption capacity (411.95 mg g-1). The Redlich-Peterson was the best-fitted isotherm model whereas the Pseudo-Second-Order (PSO) and Elovich were the best-fitted kinetic models for the 4-NP adsorption on BAC. The adsorption mechanism was analysed by applying the IPD model to the experimental data and was depicted in an insightful illustration. Overall, this research provides valuable insights into the adsorbent synthesis processes and highlights the importance of furnace atmospheres and KOH activation in tailoring the properties and adsorption activity of bamboo activated carbon adsorbents. The findings contribute to the development of sustainable and efficient adsorbent materials derived from renewable resources, with significant implications for environmental remediation and waste treatment applications.

A Simple One‐Pot Pyrolyzed Synthesis of Ternary Magnetic ZnFe2O4/α‐Fe2O3/Biochar Nanocomposites for Adsorptive Removal of Direct Red 79 in Aqueous Solution

AbstractTernary magnetic ZnFe2O4/α‐Fe2O3/biochar nanocomposites (MBCs) were successfully synthesized by one‐pot pyrolysis in oxygen‐limited environment using ZnCl2, FeCl2 as an activating agent, and precursors. The following conditions were found to be optimal for MBCs: activation temperature of 700 °C, mass ratio of ZnCl2 and FeCl2 of 1, and activation time of 2 h. The prepared MBCs were evaluated for textural characteristics such as crystalline structure, surface chemical functional groups, vabriation mode, magnetic properties, pore structure, morphology and the adsorption capacity using the methods such as X‐ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, vibrating sample magnetometer, N2 adsorption‐desorption isotherms, scanning electron microscopy and transmission electron microscopy. The prepared MBCs had porous structures, the highest SBET (782.37 m2 g−1), and pore volume (0.54 cm3 g−1) when the mass ratios of ZnCl2 and FeCl2 were 1, and the activation temperature was 700 °C, and the magnetic parameters were found at a Hc of 60 Oe, Ms of 13.03 emu g−1 and Mr of 1.07 emu g−1. Adsorption equilibrium studies indicate that the DR79 adsorption followed the Langmuir model and Sips model. The DR79 adsorption capacity of the MBC‐700‐1 has the largest value (676.8 mg g−1). The adsorption process was influenced by multiple diffusion steps, with the pore diffusion process serving as the rate‐controlling step. These findings show that MBCs adsorb DR79 efficiently and can be easily separated and recovered using an external magnetic field. The prepared MBCs have the potential to be high‐performance organic pollutant wastewater adsorbents.

Bifunctional thiophene-based covalent organic frameworks for Hg2+ removal and I2 vapor adsorption

Novel bifunctional thiophene-based COFs were constructed according to Schiff base reaction between tetrakis(4-aminophenyl)-ethane and 2,5-thiophenedicarboxaldehyde/ thieno[3;2-b]thiophene-2,5-dicarboxaldehyde. The loading of N/S heteroatoms in the skeleton not only take the COFs abundant functional groups, but also elevate the stability of the functional groups, and avoid the blocking of the pores from the post-functionlization of functional groups. The thiophene-based COFs all showed good crystalline structure, high Brunauer–Emmett–Teller (BET) surface area (SBET), pore volume (Vtotal), and N/S content, indicative of the COFs good performance in Hg2+ adsorption and I2 vapor capture. Especially, the COF-S1, which showed high SBET of 2133 m2/g and Vtotal of 1.672 cm3/g, exhibited a relative high I2 vapor capacity of 7.74 g/g. Although COF-S2 showed lower SBET (1430 m2/g) and Vtotal (1.186 cm3/g), the higher N/S content make COF-S2 higher Hg2+ adsorption capacity of 834 mg/g. The COFs also showed outstanding adsorption selectivity and good recyclability. This work provides guidance for the design and preparation of multi-functional adsorbents.

Hierarchical clinoptilolite zeolite-template carbon for highly selective separation of CO2 and CH4

BackgroundSeparating CO2 from natural gas before it is released into the atmosphere is a significant challenge in the present times due to its greenhouse effect. MethodsIn this study, a series of zeolite-template carbons (ZTCs) had been synthesized from acetylene as a carbon source using clinoptilolite as a template, through hydrofluoric acid etching and potassium hydroxide (KOH) activation processes. Significant findingsThe deposition of carbon on the zeolite-template was confirmed with different characterization techniques and their CO2 adsorption capacity and selectively toward methane (CH4) was evaluated at 25 °C, over a 1‒10 bar pressure range. The CO2/CH4 selectivity of the adsorbents was optimized with various synthesis parameters including chemical vapor deposition (CVD) reaction time, acetylene flow rate as well as activation temperature and KOH to carbon (KOH:C) mixing ratio. According to the findings, medium SBET (334.06 m2 g‒1), high Vtot (0.71 cm3 g‒1), high Vmeso (0.68 cm3 g‒1) and a large Dave (8.55 nm) of the ZTC-120–12.5–800–3 adsorbent (CVD reaction time of 120 min and acetylene flow rate of 12.5 cc min−1 as well as activation temperature of 800 °C and KOH:C ratio of 3:1) results in the highest CO2 capacity of 4.81 mmol g‒1 at 25 °C and 10 bar. Moreover, regarding the optimization goal of this study, the highest CO2/CH4 separation at 25 °C and 10 bar is the result of a long CVD reaction time (180 min), a high KOH:C ratio (4:1), a low acetylene flow rate (50 cc min‒1), and a low activation temperature (700 °C). In this regard, ZTC-180–50–700–4 showed the highest CO2/CH4 (15:85) selectivity of 13.35 with a high SBET (549.31 m2 g‒1), Vtot (0.718 cm3 g‒1), Vmicro/meso (15.6014), Vmeso (0.6211 cm3 g‒1) and a medium Dave (5.22 nm). The amine-functionalization of this sample increases the quadrupole moment between CO2 and nitrogen groups, and not only was the F-ZTC-180–50–700–4 sample's CO2 adsorption capacity increased by nearly 41% (4.11 mmol g‒1) compared to the ZTC-180–50–700–4 (2.91 mmol g‒1), but it also showed 58% higher CO2/CH4 selectivity (21.12). Based on the selectivity results of the functionalized ZTCs, their potential use in the separation of CO2 over CH4 at high pressures is demonstrated.

Thermal instability-induced formation of hierarchically structured porous GaN/nitrogen-doped carbon with high performance for supercapacitor

Electrode materials with high specific surface area (SBET) and high stacking density face a dilemma, making it difficult for supercapacitor electrodes to simultaneously exhibit high areal discharge specific capacitance (Ca,dis) and high volumetric discharge specific capacitance (Cv,dis). By exploiting the high stacking density and thermal instability of metal (after group VIB) nitrides, an electrode material of GaN honeycombs/nitrogen-doped carbon is achieved that simultaneously exhibits high Ca,dis (730 mF cm−2) and Cv,dis (251 F cm−3) at 200 mF cm−2 and manifests a linear relationship between Ca,dis and electrode loading ranging from 3.4 to 7.6 mg cm−2. The GaN honeycomb-based symmetric supercapacitors can deliver high areal/volumetric specific energy of 21.8 μW h cm−2/3.12 mW h cm−3 at 5 mW cm−2/714.3 mW cm−3 after 20,500 cycles at varied current densities from 10 to 50 and then to 10 mA cm−2. The high performance of the GaN honeycomb-based electrodes is attributed to the synergistic effect of high SBET (378.3 m2 g−1), suitable pore sizes (concentrated at 1.4 nm), surface capacitive effect, and promoted kinetics of the faradaic reaction, due to the hierarchical structure combining the high SBET and fast kinetics of nanomaterials with the high stacking density of micron materials.

Nitrogen-doped microporous carbons as highly efficient adsorbents for CO2 and Hg(II) capture

Nitrogen-doped microporous carbon, which features a uniquely tunable porosity, exhibits promisingly high adsorption prospects in the greenhouse gas capture and water treatment. Herein, we propose a series of novel N-doped microporous carbons (CMPAn-C1000), and precisely tune their porosities via a direct pyrolysis of rigid conjugated microporous poly(aniline)s (CMPAn, n = 1, 2, 3) with pore size difference in a molecular level, as achieved by simply tuning their linkers with varying sizes, planarity, and symmetry. The CMPA3-C1000, with a satisfactory amount of nitrogen heteroatoms, high SBET of ∼800 m2 g−1, and large ultra-micropore volume of 0.25 cm3 g−1, has excellent CO2 capture ability (i.e., 5.1 mmol g−1 at 273 K, 1 atm) and Hg(II) adsorption performance (i.e., Qe = 571 mg g−1; k2 = 0.0031 g mg−1 min−1), respectively. CMPA3-C1000 might perform chemisorption towards Hg(II), according to calculations using density functional theory and experimental data; nitrogen atoms in porous carbon contributed to this excellent Hg(II) adsorption.

Optimization of photocatalytic degradation of malachite green using nano-scaled V/CeO2-functionalized steel-slag-based catalyst by response surface design approach

The utilization of steel slag with high added value is an important means for sustainable development of the iron and steel industry and environment. A new nano-scaled V/CeO2-functionalized steel-slag-based catalyst (V/CeO2-SC) was prepared. The XPS results revealed that V was embedded in the CeO2 lattice with V4+ and V5+ forms. The regression equation analysis of variance told that the order of influencing factors on malachite green dye degradation rate is: catalyst dosage > V doping amount > malachite green dye concentration. The optimum values of the parameters were dye concentration 10 mg/L, catalyst dosage 0.1 g, and V doping amount 1wt%. Under the optimal condition, the predicted and actual response values of the degradation rate of malachite green dye were 100.00%. UV–Visible light absorption spectroscopy results demonstrated that after the photocatalytic degradation reaction, the absorption peak of the malachite green dye solution almost completely disappeared, indicating that the malachite green dye solution was almost completely degraded. The excellent degradation activity of the 1V/CeO2-SC specimen was attributed to the co-action of the high SBET, large mesoporous volume, and the coupled semiconductors formed by V-doped CeO2 and FeO in the catalyst carrier. A possible photocatalytic degradation mechanism of the V/CeO2-SC specimen was proposed.

Bacterial Nanocellulose from Komagataeibacter Medellinensis in Fique Juice for Activated Carbons Production and Its Application for Supercapacitor Electrodes.

This paper presents the results obtained from the chemical activation of bacterial nanocellulose (BCN) using fique juice as a culture medium. BNC activation (BNCA) was carried out with H3PO4 and KOH at activation temperatures between 500 °C to 800 °C. The materials obtained were characterized morphologically, physicochemically, superficially, and electrochemically, using scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), the physisorption of gases N2 and CO2 at 77 K and 273 K, respectively, cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy (EIS). The samples activated with H3PO4 presented specific surface areas (SBET) around 780 m2 g-1, while those activated with KOH values presented specific surface areas between 680 and 893 m2 g-1. The XPS analysis showed that the PXPS percentage on the surface after H3PO4 activation was 11 wt%. The energy storage capacitance values ranged between 97.5 F g-1 and 220 F g-1 by EIS in 1 M H2SO4. The samples with the best electrochemical performance were activated with KOH at 700 °C and 800 °C, mainly due to the high SBET available and the accessibility of the microporosity. The capacitance of BNCAs was mainly improved by electrostatic effects due to the SBET rather than that of pseudocapacitive ones due to the presence of phosphorus heteroatoms.

Salt-templated graphene nanosheet foams filled in silicon rubber toward prominent EMI shielding effectiveness and high thermal conductivity

Lightweight and multifunctional polymer-based composites with prominent electromagnetic interference (EMI) shielding effectiveness (EMI SE) and heat conductance are in urgent demand for developing highly integrated electronic devices in the 5G/6G era. Herein, ultrathin graphene nanosheet-based foams with many micropores are prepared by a general salt-template guided freeze-drying-calcination route with PEG 20000 and NaCl as a carbon source and a template, respectively. Calcination temperature (T) and PEG 20000/NaCl mass ratio (λ) were employed to modulate the texture, defects, graphitization, EM parameters, EMI SE, and thermal conductivity of graphene foams. The graphene foams formed under T = 800 °C and λ = 0.530 exhibited the optimal EMI SE and thermal conductivity. The EMI SE is beyond 20 dB over C, S, and Ku wavebands with a low filling ratio of 7 wt%, exceeding most graphene-based materials. Meanwhile, three-dimensional (3D) interconnected frameworks reduce inter-nanosheet contact thermal resistance and provide continuous frameworks for thermal and electrical conduction, engendering a larger heat conductivity (3.26–3.95 W m−1 K−1) under a lower filling ratio (3–5 wt%) compared to most reported composites. Together with their high SBET (255.6–670.5 m2 g−1) and light weight, the graphene foams synthesized in this research are expected to be utilized as a thermally conductive and EMI shielding filler for advanced electronic packaging.

Integrating large specific surface area and tunable magnetic loss in Fe@C composites for lightweight and high-efficiency electromagnetic wave absorption

Porous Carbon-based composites with large specific surface area are promising as lightweight electromagnetic wave (EMW) absorbers due to their inherently rich interfaces that facilitate microwave attenuation. However, the exertion of the intrinsic advantage of large surface area was underexplored. Herein, we described a facile strategy using MOF-derived large surface area porous carbon to construct dielectric-magnetic composites for high-efficiency EMW absorbers. In particular, a series of Fe@C composites were fabricated by pyrolysis of MOF-5 to form porous carbon matrix (SBET ∼ 1800 m2/g), followed by ferrocene deposition and reduction. By altering Fe species amount, surface area and electromagnetic parameters of the composites were tuned. It is found Fe@C-0.6 composites with sufficiently high SBET ∼915.8 m2/g exhibited outstanding microwave absorption performance with the minimum reflection loss (RLmin) of −64.6 dB (1.98 mm thickness and 15 wt% loading) and the effective absorption bandwidth (EAB) up to 6.27 GHz (2.2 mm thickness). Besides, Fe@C-1 (SBET ∼820.1 m2/g) also achieved desirable loss capability, with EAB covering the whole Ku band. This work demonstrates the potential of high surface area to achieve optimal EMW attenuation, and may provide a facile alternative to develop more high-performance carbon composites for EMW absorption application.

Acrylate-functionalized hyper-cross-linked polymers: Effect of the porogens in the polymerization on their porosity and adsorption from aqueous solution

The porogens are the key components in the polymerization process, they do not participate in the polymerization reaction, but play a very important role in the pore structure of the synthetic polymers. Herein, o-xylene and paraffin were applied as the porogens and three acrylate-functionalized hyper-cross-linked polymers were fabricated according to the suspension polymerization and Friedel-Crafts reaction. The Brunauer-Emmett-Teller (BET) surface area (SBET) and pore volume (Vtotal) of the initial copolymers were nearly zero, while the Friedel-Crafts reaction resulted in a steep increase of the SBET and Vtotal. In particular, the resultant polymer, namely, HCP-PDVE-(Xy), using o-xylene as the porogen had the greatest SBET and Vtotal (1126 m2/g and 0.958 cm3/g, respectively), while the SBET and Vtotal of HCP-PDVE-(Lp) using paraffin as the porogen were the lowest (487 m2/g and 0.299 cm3/g, respectively). Meanwhile, HCP-PDVE-(Xy + Lp) using 50 % of o-xylene and 50 % of paraffin as the mixed porogens possessed the intermediate data. More importantly, HCP-PDVE-(Xy) had the hierarchical micro- and meso-porous distribution, while predominant micro-pores were distributed for HCP-PDVE-(Lp) and HCP-PDVE-(Xy + Lp). The equilibrium adsorption indicated that HCP-PDVE-(Xy + Lp) exhibited the largest equilibrium capacity (qe) to phenol while HCP-PDVE-(Xy) owned the largest qe to Rhodamine B. The phenol adsorption was subjected to the micro-pore filling mechanism while the high SBET, Vtotal and the hierarchical micro-/meso-pores were favorable for the adsorption of Rhodamine B. The kinetic adsorption revealed that HCP-PDVE-(Lp) and HCP-PDVE-(Xy + Lp) (20 min) required much less time than HCP-PDVE-(Xy) (50 min) to reach the equilibrium for the phenol adsorption, and the micro-pore diffusion model characterized the kinetic data very well. The dynamic adsorption indicated that the dynamic capacity of phenol adsorbed on HCP-PDVE-(Xy + Lp) was 160.2 mg/g, very close to the qe (163.6 mg/g) in the equilibrium adsorption.