High Pore Volume Research Articles

Optimisation and effect of ionomer loading on porous Fe–N–C-based proton exchange membrane fuel cells probed by emerging electrochemical methods

The next generation of proton exchange membrane fuel cells (PEMFCs) require a substantial reduction or elimination of Pt-based electrocatalyst from the cathode, where O2 reduction takes place. The most promising alternative to Pt is atomic Fe embedded in N-doped C (Fe–N–C). Successful incorporation of Fe–N–C in PEMFCs relies on a thorough understanding of the catalyst layer properties, both ex situ and in situ, with tailored electrode interface engineering. To help resolve this conundrum, we provide a quantitative protocol on the optimisation of I/C for Fe–N–Cs. It is demonstrated that a high pore volume (3.33 cm3 g−1FeNC) Fe–N–C catalyst requires a sufficiently high ionomer to catalyst mass ratio (I/C, 2.8≤I/C ≤ 4.2) for optimum PEMFC activity under H2/O2. Emerging electrochemical techniques (distribution of relaxation times and Fourier transformed alternating current voltammetry) were used to deconvolute for the first time the trade-off between proton and electron resistance and accessible FeNx active site density with increasing ionomer loading. These findings highlight the significant impact of tuning the I/C ratio based on the catalyst layer properties and feature the power of evolving electrochemical tools for optimising performance in PEMFCs and other electrochemical devices.

Preparation of mesoporous biogas residue biochar via a self-template strategy for efficient removal of ciprofloxacin: Effect of pyrolysis temperature

Biochar preparation and application is an anticipated pathway for the resource utilization of biogas residue. In this study, biochars were prepared by the pyrolysis of biogas residue from food waste anaerobic digestion (named as BRBCs) under various pyrolysis temperatures (300, 500, 700, and 900 °C), and the effect of pyrolysis temperatures on the physicochemical characteristics of BRBCs was examined. The adsorption performance toward ciprofloxacin (CIP), a typical antibiotic in waterbodies, was also investigated. The results showed that pyrolysis temperature significantly changed the physicochemical properties of BRBCs. In addition, the minerals in the biogas residue, especially SiO2, were rearranged to form a mesoporous structure in biochar through a self-template strategy (without activator). BRBC prepared at 900 °C exhibited a high specific surface area and pore volume, well-developed mesopore structure, and more carbon structure defects, and exhibited the largest CIP adsorption capacity with 70.29 mg g−1, which was ascribed to the combined interaction of pore diffusion, π–π interactions, hydrogen bonding, complexation, and electrostatic forces. Furthermore, the adsorption of CIP by BRBC900 was well described by two-compartment kinetic and Langmuir isotherm models. BRBC900 showed good adsorption performance toward CIP at pH 7–9. The adsorption of CIP by BRBC is a spontaneous, exothermic, entropy-increasing process. Moreover, BRBC also presented a good recycling potential. Therefore, the preparation of mesoporous biochar based on a self-template strategy not only provides an option for the resource utilization of biogas residue but also offers a new option for the treatment of antibiotic wastewater.

Design and preparation of reticular superabsorbent hydrogel material with nutrient slow-release and high shear strength for ecological remediation of abandoned mines with steep slopes

In order to solve ecological remediation issues for abandoned mines with steep slopes, a kind of hydrogels with high cohesion and water-retaining were designed by inorganic mineral skeleton combining with polymeric organic network cavities. This eco-friendly hydrogel (MFA/HA-g-p(AA-co-AM)) was prepared with acrylic acid (AA)-acrylamide (AM) as network, which was grafted with humic acids (HA) as network binding point reinforcement skeleton and polar functional group donors, KOH-modified fly ash (MFA) as internal supporter. The maximum water absorption capacities were 1960 g/g for distilled water, which followed the pseudo-second-order model. This super water absorption was attributed to the first stage of 62 % fast absorption due to the high specific surface area, pore volume and low osmotic pressure, moreover, the multiple hydrophilic functional groups and network structure swell contributed to 36 % of the second stage slow adsorption. In addition, the pore filling of water in mesoporous channels contributed the additional 2 % water retention on the third stage. The high saline-alkali resistance correlated with the electrostatic attraction with MFA and multiple interactions with oxygen-containing functional groups in organic components. MFA and HA also enhanced the shear strength and fertility retention properties. After 5 cycles of natural dehydration and reabsorption process, these excellent characteristics of reusability and water absorption capacity kept above 97 %. The application of 0.6 wt% MFA/HA-g-p(AA-co-AM) at 15° slope could improve the growth of ryegrass by approximately 45 %. This study provides an efficient and economic superabsorbent material for ecological restoration of abandoned mines with steep slopes.

Role of extracted nanosilica from rice husk on the structure, property and biodegradability of low density polyethylene/starch biodegradable film

AbstractStarch blended low‐density polyethylene (LDPE) has been extensively used to produce packaging film, but it has very low mechanical properties. This work emphasises the extraction of nanosilica from rice husk as a property‐enhancing filler for producing high‐quality packaging material. Nanosilica (200 nm) was obtained by chemical treatment followed by further size reduction through cryomill. The obtained nanomaterial was found to have a high surface area (189.64 m2/g) and pore volume (.462 cc/g) with high compatibility with the other materials in the matrix. The SEM and TEM analysis indicates the uniformity in particle size of the nanomaterial with an agglomerating tendency. The X‐ray diffractometer (XRD) and fourier transform infrared spectroscopy (FTIR) analysis reveals that the obtained material is amorphous in nature. The nanomaterial is dispersed in various proportions in LDPE/starch matrix, and it is observed that the highest tensile strength (9.62 MPa) can be obtained at 1.5% nanosilica content in the matrix. A continuous increase in Young's modulus and stiffness from 372.3 to 440.12 MPa and 20 243.2 to 28 559.42 N/m, respectively, when 1.5% of nanosilica is dispersed in the biodegradable matrix. Garden soil was a better degrading medium for the sample containing 20% of starch with weight loss of 10.32% and reduction of tensile strength and tear strength values to 5.987 MPa and 99.165 N/mm respectively, in 1 year.

Order–disorder–order mesophase transitions in self-assembled mesoporous alumina for enhanced CO2 adsorption

The addition of a hydrophobic micelle pore expander to self-assembling mesostructured hybrid materials enables access to new combinations with differently ordered mesophases and enhanced structural properties. Here we detail our investigations into the influence of 1,3,5-trimethylbenzene (TMB) on the self-assembly behaviors of an F127 Pluronic triblock copolymer with an aluminum oxide sol additive. By varying the chemical mixing sequence, the TMB-to-F127 mass ratio and the acid-to-metal molar ratio, we observe that TMB exhibits dual roles, functioning both as a hydrophobic swelling agent and as a low dielectric co-solvent. This induces a mesophase transition from an ordered p6mm lattice to a disordered state and subsequently back to the ordered p6mm phase. We propose a structure formation mechanism based on the DLVO theory to describe the thermodynamics and kinetic mobility of the hybrid micelles during the order-disorder and ensuing disorder-order mesophase transitions. The resulting ordered mesoporous alumina structures, with considerable pore sizes (up to 12 nm), high surface areas (up to 314 m2/g) and pore volumes (up to 0.74 cm3/g), organized pore geometry and variable inorganic wall thicknesses, have shown excellent CO2 adsorption capacities and are appealing for various applications, including stable high temperature catalyst supports, separation and sensing.

Tetracycline (TC) removal from wastewater with activated carbon (AC) obtained from waste grape marc: activated carbon characterization and adsorption mechanism

In this study, activated carbons were obtained from grape marc for tetracycline removal from wastewater. Activated carbons were obtained by subjecting them to pyrolysis at 300, 500, and 700 °C, respectively, and the effect of pyrolysis temperature on activated carbons was investigated. The physicochemical and surface properties of the activated carbons were evaluated by SEM, FTIR, XRD, elemental analysis, N2 adsorption/desorption isothermal, thermal gravimetric (TG) and derivative thermogravimetric (DTG), and BET surface area analysis. When the BET surface areas were examined, it was found that 4.25 m2/g for activated carbon was produced at 300 °C, 44.23 m2/g for activated carbon obtained at 500 °C and 44.23 m2/g at 700 °C, which showed that the BET surface areas increased with increasing pyrolysis temperatures. The pore volumes of the synthesized activated carbons were 0.0037 cm3/g, 0.023 cm3/g, and 0.305 cm3/g for pyrolysis temperatures of 300, 500, and 700 °C, respectively, while the average pore size was found to be 8.02 nm, 9.45 nm, and 10.29 nm, respectively. A better adsorption capacity was observed due to the decrease in oxygen-rich functional groups with increasing pyrolysis temperature. It was observed that the activated carbon obtained from grape skins can easily treat hazardous wastewater containing tetracycline due to its high carbon content and surface functional groups. It was also shown that the activated carbon synthesized in this study has a higher pore volume despite its low surface area compared to the studies in the literature. Thanks to the high pore volume and surface active groups, a successful tetracycline removal was achieved.Graphical

Highly Porous Carbon Materials Prepared Through KOH‐Assisted CO2‐Activation of Carbonized Waste Tires for Removal of Cr(VI) and Cd(II) from Water

AbstractIn this study, waste tires (WTs) were carbonized under an N2 atmosphere. Subsequently, KOH/WTs‐char with KOH‐assisted CO2 activation was used to prepare activated carbon (AC) as a highly porous carbon material for the removal of Cr(VI) and Cd(II) from water. Various techniques such as elemental analysis, Fourier‐transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption were employed to investigate the physical and chemical characteristics of the prepared carbons. The WTs‐char activated with KOH under CO2 exhibited a microstructure with a high BET surface area and pore volume of 1841 m2/g and 0.869 cm3/g, respectively, demonstrating excellent adsorbent performance. The maximum removal efficiencies of 99.91 % for Cd(II) and 99.81 % for Cr(VI) were achieved using AC2 carbon under the following conditions: pH 2 for Cr(VI) and pH 5 for Cd(II), contact time of 120 min, adsorbent dose of 0.4 g/100 mL, and temperature of 298 K. The adsorption kinetics followed the pseudo‐second‐order equation, and the equilibrium data fit well with the Redlich–Peterson isotherm equation. The positive values of ▵G indicated that the uptake process for both ions was nonspontaneous and nonfeasible over the temperature studied. Both ions showed negative values of ΔH and ΔS on carbon, suggesting exothermic adsorption and a decrease in disorder. Regeneration studies showed that NaOH was a better desorbing agent than HCl. Cr(VI) desorption resulted in over 90 % removal recovery by AC2 using 1.0 M NaOH even after the fifth cycle. However, the low activation energy indicated that the adsorption was favorable kinetically. Overall, this study demonstrated the effective preparation of highly porous carbon and its successful performance in removing Cr(VI) and Cd(II) ions.

Dipole-induced hydrogen bonds enhanced P/O co-doped Lyocell-based porous carbon fiber cloth for hydrogen storage under ambient pressure

Currently, the hydrogen storage application of carbon-based adsorbent materials is mostly implemented under the pressure conditions of 30–300 bar, while there is few targeted studies conducted on the unsaturated adsorption under ambient pressure conditions. Therefore, based on industrialized Lyocell biopolymer fiber precursors and the enhancement effects of dipole-induced hydrogen bonds (DIHB), this work presents a facile construction strategy for P/O co-doped Lyocell-based porous carbon fiber cloth (Ly-ACF-F40). By the technical route of thermal stabilization---sonication assisted phosphoric acid activation---hydrogen bonds introduced by interfacial fluorination, the constructed Ly-ACF-F40 acquires a high specific surface area (1870 m2/g) and total pore volume (1.277 cm3/g), and an excellent hydrogen storage capacity of 3.22 wt% under ambient pressure conditions (77 K, 1 bar). The study directly demonstrated in the experiment that dipole induced hydrogen bonding H(I)-H(II)···F can effectively enhance the atmospheric hydrogen storage density on the basis of other eliminating influencing factors of specific surface area. The simple construction strategy of porous carbon-based materials can provide reference for the research of unsaturated adsorption hydrogen storage materials under ambient pressure conditions, also assist in the application and promotion of low-cost solid hydrogen storage materials.

Comparison of the effect of topology type and linker composition of zeolitic imidazolate framework fillers on the performance of mixed matrix membranes in CO2/N2 separation

Mixed matrix membranes (MMMs) combine the high separation performance of porous materials with the processibility of polymers and so possess potential for carbon capture from CO2-containing gas streams. Zeolitic imidazolate frameworks (ZIFs) are promising candidates as molecular-sieve fillers in MMMs due to their tunability and ease of synthesis. We have compared four ZIFs, all as nanoparticles of similar sizes (ca. 400 nm), as MMM fillers, to investigate the effects of ZIF structure and chemistry on MMM performance of pure gas (CO2, N2) permeation under the same conditions. The chosen ZIFs include two that exhibit strong CO2 adsorption (hybrid ZIF-7/COK-17 and ZIF-94) and two that have higher pore volumes but weaker CO2 interactions (ZIF-8 and a hybrid ZIF-11/ZIF-71). The hybrid ZIF-7/COK-17 and ZIF-94 are structurally related to ZIF-7 (rhombohedral sod topology) and ZIF-8 (cubic sod), respectively, via partial or complete substitution of benzimidazole or 2-methylimidazole by 4,5-dichloroimidazole or 4-methyl-5-imidazolecarboxaldehyde, while the hybrid ZIF-11/ZIF-71 has the rho topology but the same composition as the ZIF-7/COK-17 hybrid. In the first part of the comparative study, MMMs based on two types of commercial polymers, Matrimid®5218 and PEBAX-MH1657, were prepared containing the ZIF-7/COK-17 hybrid and also with ZIF-94. ZIF-94 shows much better compatibility with the polymers, forming homogeneous dispersions at all loadings attempted (≤35 % wt%) whereas the hybrid shows inhomogeneity above 12 wt% in each case. At 12 wt% loading, both fillers show an increase in CO2 permeability at 1.2 bar and 293 K compared to the pure membrane (in PEBAX, this increases from 49.5 to 60 and 68 Barrer) which is the result of increased solubility compensating for decreased diffusivity, and this improvement in permeability continues to increase at the higher levels of loading possible with ZIF-94. ZIF-7/COK-17 in PEBAX show higher selectivity, achieving a calculated CO2/N2 selectivity up to 70. Further investigation of CO2 and N2 permeation on MMMs with the four ZIFs at 12 wt% in PEBAX-MH1657 showed a clear distinction between the ZIF-94 and ZIF-7/COK-17 MMMs (which show higher membrane solubilities but lower diffusivities) compared to ZIF-8 and ZIF-11/ZIF-71 MMMs. At the loading chosen, the CO2 permeability increase achieved by the four ZIFs over PEBAX-MH1657 increases in the order ZIF-11/-71, ZIF-7-COK-17 (ca. 60 Barrer) < ZIF-94 (68) < ZIF-8 (81), reflecting the complex interplay between CO2 solubility (increasing with interaction strength) and diffusivity (increasing with available cage and window size). The calculated CO2/N2 selectivity is highest for the hybrid ZIF-7/COK-17 membrane (70), which is attributed to molecular sieving effects in the rhombohedral sod structure.

Scalable confined-space microwave heating strategy enables the rapid preparation of N/O co-doped activated carbons with high gas capture capacity

Heteroatom doping is essential for enhancing the performance of activated carbons (ACs) in various environmental-related applications. Herein, a scalable confined-space microwave heating (CSMH) strategy is proposed and demonstrated to achieve minute-level fast preparation of N/O co-doping ACs with well-developed porosity. The introduction of confined space prevents the escape of nitrogenous and oxygenous volatiles, enabling the sufficient reaction for heteroatom doping. Therefore, the nitrogen content of MWC-0.5 (6.0 at.%) is higher than that of MW-0.5 (3.5 at.%) and CH-0.5 (4.3 at.%). This causes a nearly 50 % reduction in the consumption of nitrogenous reagents. Moreover, through CSMH strategy, N/O co-doped ACs (6.0 at% and 8.1 at% for N and O, respectively) with high pore volume (0.53 cm3 g−1) can be acquired to achieve an excellent adsorption performance for toluene (0.31 g g−1) and CO2 (3.97 mmol g−1 at 25 °C and 1 bar) and outstanding CO2/N2 selectivity (189 at 0.02 bar). This work for the first time develops a scalable confined-space N/O co-doped strategy for enhancing the chemical activity of ACs with low-spend nitrogenous reagents.

In-situ texturing hollow carbon host anchored with Fe single atoms accelerating solid-phase redox for Li-Se batteries

Se-based cathodes have caught tremendous attention owing to their comparable volumetric capacity and better electronic conductivity to S cathodes. However, its low utilization ratio and sluggish redox kinetics due to the high reaction barrier of solid-phase transformation from Se to Li2Se limit its practical application. Herein, an in-situ texturing hollow carbon host by gas–solid interface reaction anchored with Fe single-atomic catalyst is designed and prepared for advanced Li-Se batteries. This Se host presents high pore volume of 1.49 cm3 g−1, Fe single atom content of 1.53 wt%, and its specific structure protects single-atomic catalyst from the destructive reaction environment, thus balancing catalytic activity and durability. After Se loading by reduction of H2SeO3, this homogenous Se-based cathode delivers a superior rate capacity of 431.3 mA h g−1 at 4C, and great discharge capacity of 301.8 mA h g−1 after 1000 cycles at 10C, with high Li-ion diffusion coefficient and capacitance-contributed ratio. The distribution of relaxation times analysis verifies solid-phase transformation mechanism of this cathode and density functional theory calculations confirm the adsorption and bidirectionally catalysis effect of Fe single-atomic catalyst. This work provides a new strategy to prepare high-efficient Se cathode associated with non-noble metal single atoms for high-performance Li-Se batteries.

Modulating of Bi2MoO6-based photocatalyst through manipulation of reactant ratios for enhanced visible light photocatalytic activity

In this work, a novel photocatalyst, comprising of Bi2MoO6 and Bi2O2(OH)(NO3), was successfully synthesized by the one-pot hydrothermal method, thereby illuminating an innovative avenue for structure modulation of Bi2MoO6. The characterizations proved the facile attainability of controllable modifications in the microstructure and morphology of Bi2MoO6. The comprehensive appraisal of the synergistic adsorption-photocatalytic performances of the composites in the context of ciprofloxacin (CIP) was carried out. The findings presented compelling evidence that the amalgamation of Bi2MoO6/Bi2O2(OH)(NO3) exhibited an extraordinary adsorption capacity and photocatalytic activity when compared with the pristine Bi2MoO6 and Bi2O2(OH)(NO3). By virtue of its high surface area and pore volume, the optimized BMO/BON manifested a CIP adsorption capacity that surpassed that of Bi2MoO6 and Bi2O2(OH)(NO3) by approximately 2.4 and 11.2 times, respectively. Furthermore, through the concerted effects of adsorption and photocatalytic degradation, BMO/BON demonstrated an impressive CIP removal efficiency of 99.2 % following a mere 30 min of visible light exposure. The reaction rate constant was found to be approximately 0.124 min−1 for BMO/BON, surpassing that of Bi2MoO6 and Bi2O2(OH)(NO3). The augmentation in the photocatalytic activity of BMO/BON can be ascribed to its diminutive crystalline dimensions, large specific surface area, and narrowed bandgap. Thus, this investigation introduces a practical and ingenious strategy for the tuning of the Bi2MoO6 structure by manipulation of reactant ratios, showcasing significant implications in the realm of catalysis.

Low energy synthesis of crystalline mesoporous aluminosilicate consisting of Na-P1 zeolite derived from coal fly ash

Worldwide every year massive amount of coal fly ash is being generated as by product in the power plants which creates economic, environmental and most importantly health problems. Usually coal fly ash is used in cement production worldwide. At present, in Bangladesh, about 95 % of fly ash remains still unutilized. The alkali activation of fly ash has become a top research topic as it is possible to synthesize low cost and ecologically sound mesoporous zeolite type materials. In the present work, to the best of our knowledge, for the first time in Bangladesh, synthesis and characterization of crystalline mesoporous (H3 type hysteresis) aluminosilicate consisting of Na-P1 zeolite with a high BET specific surface area and a high pore volume from coal fly ash based on hydrothermal alkali activation technique have been successfully done. This product has versatile applications like catalysis, gas separation, water softening, water purification, gas sensing etc. The variable of alkali concentration was studied which has the notable influence on the development of the framework of the pores. The untreated coal fly ash (CFA) and the synthesized modified fly ashes (MFAs) were tested by WDS-XRF, XRD, N2 physisorption, FE-SEM, FT-IR, XPS, EDAX-mapping, particle size analysis and other technologies. The BET specific surface area, total pore volume and average pore diameter of the CFA were only 3 m2/g, 0.01 cc/g and 6.3 nm respectively based on nitrogen gas physisorption technique, whereas, after alkali activation at a specific temperature and time, and then curing, significant and promising increased values of the said parameters of 45 m2/g, 0.11 cc/g and 9.8 nm were obtained respectively. In methylene blue dye adsorption experiment, MFA showed higher adsorption capacity (23.87 mg/g).

Green synthesis and high-performance fluoride ion removal using lanthanum-modulated MOF-808 (Zr)

In a water solution and with a low reaction temperature of 85 °C, the green preparation of lanthanum-modulated MOF-808 (Zr) was realized, the obtained La-MOF-808 have smaller grain size, larger specific surface area, higher pore volume and larger average pore diameter. When the molar ratio of La: Zr=1:1, 1L-MOF-808 had the best fluoride ion removal performance, and its maximum adsorption capacity for F- reached 101.4 mg/g, which was higher than that of the unmodulated MOF-808 and some other reported fluorine adsorbents. Meanwhile, the regeneration experiment demonstrated that even after five cycles, 1L-MOF-808 retained 73.8 % of its initial adsorption capacity, highlighting its commendable reusability. In addition, when 1L-MOF-808 was applied to actual fluorine-containing wastewater, with the fluoride ion concentration of 25.3 mg/L and an adsorbent dosage of 0.6 g/L, 1L-MOF-808 exhibited excellent resistance to anionic interference (SO42-, Cl-), the concentration of fluoride ions in effluent was lower than 10 mg/L, meeting the stipulations of fluoride ion discharge outlined in GB39371–2020. Further adsorption mechanism investigation revealed that 1L-MOF-808's affinity for F- was attributed to electrostatic interaction and ligand exchange. Overall, the as-synthesized 1L-MOF-808 not only presents an environmentally friendly approach to producing MOF materials without organic solvents but also develops a new strategy for the design of high-performance adsorbent for effectively removing fluoride ions from wastewater.

Hierarchical porous cobalt nanoparticles encapsulated in heteroatom-doped hollow carbon as an enhancing multifunctional catalyst for hydrolysis of sodium borohydride and hydrogenation of bromate in water

Multifunctional heterogeneous catalysts have been consistently explored in recent years because of their distinctive catalytic activity in different catalysis areas at once. Here, a cobalt (Co) nanoparticles encapsulated in nitrogen-doped hollow carbon (denoted as Co@NHC) is prepared by two-step modifications of acid etching and high temperature carbonization in the inert atmosphere using a peculiar polyhedral configuration Co-ZIF as an initial template. Benefiting from an intriguing polyhedral configuration hollow structure with high specific surface area and pore volume supplying plentiful active sites, Co@NHC shows exceptional catalytic activity in catalyzing hydrolysis of NaBH4 and hydrogenation of toxic bromate in water. From experimental results, Co@NHC could efficiently enhance the generation of H2 with a H2 generation rate of 1515.4 mL min−1 gcat−1 meanwhile the activation energy (Ea) calculated from Co@NHC/NaBH4 system was only 12.6 kJ mol−1. Besides, the combination of Co@NHC and NaBH4 could further reduce toxic bromate ions into bromide via catalytic hydrogenation with a maximum bromate removal capacity of 390.6 μmol g−1. More importantly, due to its strong magnetization, Co@NHC could be simply recovered after reactions, making it well-preserve the unique structure as well as catalytic activity for multiple continuous recycles in both catalytic applications. Additionally, the plausible reaction mechanisms in catalyzing hydrolysis of NaBH4 and hydrogenation of bromate were also proposed. This work has pioneered a promising approach on preparing an engrossing magnetic heterogeneous Co-based catalyst that is practically applicable in various areas of catalysis.

Lanthanum-modified tobermorite synthesized from fly ash for efficient phosphate removal.

Phosphate removal from water by lanthanum-modified tobermorite synthesized from fly ash (LTFA) with different lanthanum concentrations was studied. LTFA samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer‒Emmett‒Teller specific surface area analysis. The results showed that the LTFA samples were mainly composed of mesoporous tobermorite-11Å, and LTFA1 with a lanthanum concentration of 0.15M had a high specific surface area (83.82 m2/g) and pore volume (0.6778 cm3/g). The phosphate adsorption capacities of LTFA samples were highest at pH 3 and gradually decreased with increasing pH. The phosphate adsorption kinetics data on LTFA samples were most accurately described by the Elovich model. The adsorption isotherms were in the strongest agreement with the Temkin model, and LTFA1 showed the highest phosphate adsorption capacity (282.51mg P/g), which was higher than that of most other lanthanum-modified adsorbents. LTFA1 presented highly selective adsorption of phosphate with other coexisting ions (HCO3-, Cl-, SO42-, and NO3-). In addition, phosphate was adsorbed onto LTFA samples by forming inner-sphere phosphate complexes and amorphous lanthanum phosphate. This study provides technical support for development of efficient fly ash-based phosphate adsorbents.

Triphenylene-derived oxygen-enriched hierarchical porous carbon nanosheets: Carbonization mechanism and application in zinc-ion hybrid capacitors

Since zinc-ion hybrid capacitor (ZIHC) was first proposed, it has become an international study hotspot in the field of secondary energy for some time. Unfortunately, the unsatisfactory specific capacity of ZIHCs has limited its application in industrial development. Thus, there is an urgent need to synthesize carbon cathode with abundant pore structure and heteroatoms to construct high performance ZIHCs. Herein, we investigate the mechanism of FeCl3-induced carbon formation of triphenylene using FeCl3 as a catalyst and template. And the oxygen-enriched hierarchical porous carbon nanosheets with large specific surface area and abundant pores are successfully synthesized with the assistance of KOH activation strategy. Due to the addition of FeCl3 and KOH, the hierarchical porous carbon nanosheets have a unique pore structure and extremely high pore volume, and oxygen atoms are introduced to provide additional pseudocapacitance. As expected, ZIHCs constructed with the best sample exhibits an impressive specific capacity of 134.1 mAh g−1, a distinguished energy density of 102.04 Wh kg−1 (80 W kg−1) and outstanding cycling stability. This work clearly elucidates the carbon formation mechanism of triphenylene under the catalytic action of FeCl3, and provides another insight for the preparation and optimization of porous carbon for ZIHCs cathode.

CuCo2S4@MnO2 hollow porous heterostructure for high-performance supercapacitors

The design and synthesis of hollow porous heterostructures from multiple components is expected to impart excellent properties to the electrochemically active materials owing to their high internal voids, high surface area, and high pore volume, which are beneficial for electrolyte infiltration. However, the development of optimized electrode materials for hollow porous heterostructure storage fell behind expectations. To address these challenges, we prepared a CuCo2S4@MnO2 composite on a foam nickel substrate to create a hollow porous heterostructure. The optimized composite possesses high areal capacitance of 14.9 F cm−2 (or a specific capacitance of 1643 F g−1) at 3 mA cm−2, and 83.4% capacitance retention after 30,000 cycles in a three-electrode configuration. The NF@CuCo2S4@MnO2//AC asymmetric supercapacitor can achieve high energy density (1.2 mWh cm−2) and power density (2.4 mW cm−2) due to the wide cell voltage in aqueous electrolyte and high particular capacitances from both CuCo2S4 and MnO2 improved by the hollow porous heterostructure. Furthermore, the NF@CuCo2S4@MnO2//AC ASC can light up an LED display screen. Overall, this work demonstrates the great potential and broad prospects for application in energy storage of hollow porous heterostructures.

Machine learning backpropagation network analysis of permeability, Forchheimer coefficient, and effective thermal conductivity of macroporous foam–fluid systems

Macroporous materials exhibit outstanding properties in heat and mass transfer due to their high pore volume, high surface area, and high Young's modulus. Consequently, understanding their thermofluidic properties is crucial in the design, synthesis, and optimal application of these materials. Therefore, this study, premieres, the use of a machine learning (ML) backpropagation network to develop and train a series of datasets for permeability, Forchheimer coefficient, and effective thermal conductivity of variable macroporous foam–fluid systems with respect to degrees of interstices, fluid and solid properties. To account for permeability values for flowing fluids in the Darcy regime, numerical simulations of slow–moving fluids were implemented over the materials' interstices. In comparison to similarly substantiated values of permeability in the Forchheimer regime, these values were a bit lower. The ML-based backpropagation algorithm was used to analyze data, which produced predictions (output signals) that are more than 90 % in correlation to CFD datasets. This provided insight into the effect of porosity and reduced mean pore openings on macroporous structures' thermofluidic behaviour. Material porosity was observed to play a dominant role in estimating Forchheimer coefficients and effective thermal conductivities for these foam-fluid systems. However, reduced mean pore openings were observed to be more critical for estimating permeability. The contributory effects of reduced mean pore openings on the effective thermal conductivity for these macroporous foam–fluid systems were determined to vary between 5.8 and 13.2 percent. Furthermore, the effective thermal conductivity of macroporous foam–fluid systems was also evaluated in relation to changes in the interstitial fluid and solid matrix thermal conductivity.

Thermochemical heat storage performance of Fe-doped MgO/Mg(OH)2: Experimental and DFT investigation

MgO/Mg(OH)2 thermochemical heat storage system can realize large-scale energy storage by repetitive hydration/dehydration reactions to enhance the stability of solar energy utilization. However, slow interconversion and incomplete reactions caused by agglomeration restrict the cyclic heat storage capability of MgO/Mg(OH)2. In this work, a low-cost efficient Fe-doped MgO was prepared by a simple wet-mixing method and its energy released performance and kinetics in MgO/Mg(OH)2 heat storage progress were examined in a twin fixed-bed reactor and a simultaneous thermal analyzer. Additionally, density functional theory calculations were used to examine the impact of Fe on the mechanisms of MgO/Mg(OH)2 heat storage process. The results shows that when the molar ratio of MgO to Fe is 95:5, the energy released density of Fe-doped MgO is about 400 % higher than that of MgO after 10 heat storage cycles. In preparation process, the existence of Fe leads to the generation of MgFe2O4, which forms layered microstructure with the high specific surface area and pore volume and mitigates agglomeration behavior of MgO. It improves the cyclic stability of MgO and reduces the dehydration temperature of Mg(OH)2, and simultaneously the activation energy of the dehydration stage is reduced by 33.2 %. Fe enhances the interaction of H2O with the MgO surface and promotes the dissociation of H2O on Mg(OH)2 surface. Combined with economic analysis, Fe-doped MgO is a suitable material for MgO/Mg(OH)2 heat storage cycles.