Formation Of Mesoporous Structure Research Articles

Synthesis of aluminosilicate mesoporous material MSU-S from natural resources: Investigating the effects on the structure formation

Zeolite seed-based mesoporous aluminosilicate material MSU-S is normally synthesized from pure chemicals. In the study, MSU-S material was synthesized using natural resources such as rice husk, and kaolin in Vietnam. Here, a systematic investigation is conducted to find the relationship between the synthesis conditions (aging time, hydrothermal time, hydrothermal temperature, pH environment) and the formation of mesoporous structure, as well as the material properties. The sample was characterized by XRD, TEM, N2 adsorption-desorption isotherms, and TGA-DSC. The MSU-S material has been synthesized successfully from rice husk and kaolin. The best conditions are aging time of 24 hours, and hydrothermal conditions at 95 oC during 96 hours with pH=9. The MSU-S has an ordered hexagonal mesoporous structure containing zeolite BEA seed. The pore diameter is concentrated at 2.9 nm. The BET surface area is calculated to be 770 m²/g. Thermal stability is determined to be up to 900 oC.

Adsorption mechanisms, kinetics and photoactivities of green synthesized hydroxyapatite supported ZnO and La–ZnO catalysts

In this study, hydroxyapatite (HAP) is synthesized by a co-precipitation method from the waste eggshell, utilized as a support for ZnO (ZnO-HAP) and La–ZnO (La–ZnO-HAP) and employed to degrade methyl orange (MO) and methylene blue (MB) dyes under UV irradiation. Water vapor adsorption as relative humidity (84 % RH) on the HAP structure and the as-prepared catalysts are also examined. The characteristic ZnO and HAP reflections are detected in X-ray diffraction (XRD) analysis of ZnO-HAP, La–ZnO-HAP and humidified samples. ZnO and La–ZnO existence is also verified by scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis, UV–Vis diffuse reflectance (UV–Vis DRS) spectra and X-ray photoelectron spectra (XPS). ZnO and La–ZnO loading on the HAP induce the formation of mesoporous structures with high surface areas. Dark adsorption capacities and photoactivities of the as-prepared samples are explored regarding electrostatic interactions, Lewis acid-base interactions and hydrogen bonding for both MO and MB. In particular, La–ZnO-HAP 500 °C and La–ZnO-HAP 500 °C (RH) exhibit improved adsorption abilities and photoactivities. The pseudo-second order model describes the kinetic behavior of all samples under dark conditions. Unhumidified samples follow Langmuir isotherm while Freundlich isotherm better fits humidified ones. Under irradiation, the Langmuir-Hinshelwood kinetic model describes the photoactivities of all samples. The four recycling tests confirm the stabilities of HAP 100 °C, HAP 500 °C, ZnO-HAP 500 °C and La–ZnO-HAP 500 °C. This study suggests that the ZnO or La–ZnO loaded HAP catalysts prepared in the presence and absence of humid conditions are considered promising materials for environmental remediation.

Mitigating self-discharge in supercapacitors through strategic mesoporous structural modification of NiCo layered double hydroxides

Nickel - Cobalt layered double hydroxide (NiCo LDH) based supercapacitors suffer from severe self-discharge due to their uneven charge distribution, which affects the application of supercapacitors (SCs) in real life. In this paper, three-dimensional self-supported mesoporous NiCo layered double hydroxide mesoporous on nickel foam (NF) (NiCo LDHMs/NF) was prepared by H2O2 etching. The self-discharge phenomenon of supercapacitors assembled using the reaction-derived NiCo LDHMs/NF as the positive electrode and activated carbon as the negative electrode is significantly suppressed. Comparing with the original NiCo LDH devices, the successful construction of mesoporous structures in NiCo LDH resulted in slower open-circuit voltage (OCV) decay (0.93 V vs. 0.59 V in the range of open-circuit voltage of 1.8 V for the same time of 7200 S), and lower leakage current (0.09 mA vs. 0.18 mA at 1.8 V). Due to the formation of mesoporous structure, the charged ions adsorbed on the electrode have more storage sites. Which reduces the movement or loss of charged ions to inhibit the charge redistribution, so it has a high specific capacitance and the self-discharge phenomenon has been greatly reduced.

Facile synthesis of oxygen vacancies mediated Co3O4 by Mn doping for high-performance ethanol sensing

The detection of volatile organic compounds (VOCs) at extremely low concentrations holds significant importance in industry and daily life. In this study, Mn-doped Co3O4 materials with a mesoporous structure and oxygen vacancies were synthesized through manual grinding and calcination treatment. The structural characterization measurements showed that Mn doping restrained the crystal growth of the cobaltous oxides which was beneficial for the mesoporous structure, and appropriate oxygen vacancies. The 0.2Mn–Co3O4 sensor operated at the optimum operating temperature of 260 °C, showed a higher response (32.0) to 30 ppm ethanol, which was about 5.81 times as much as that of the pure Co3O4 (5.5). Additionally, to ethanol the 0.2Mn–Co3O4 sensor manifested ultra-low detection limit (11.6 ppb), fast response/recovery time (25/15 s) and superior stability. These exceptional performances may be attributed to the synergistic effect of mesoporous structure formation and appropriate oxygen vacancy concentration. Consequently, the Mn-doped Co3O4 sensor has great potential for detecting low-concentration ethanol in practical applications.

In English

Silicas of MCM-41‑type with reactive functional groups are widely used as starting substrates in large variety of post‑synthetic chemical modification pathways. Therefore, variation of their structural characteristics in the process of templated sol‑gel synthesis or post-synthetic treatment is of great importance. The aim of this work was to elucidate the influence of template agent selection on structural features of MCM-41‑type materials with surface silanol and 3‑chloropropyl groups. For this purpose, template-assisted sol-gel condensation of structure forming silanes (tetraethyl orthosilicate and 3‑chloropropyltriethoxysilane) was carried out in the presence of decyltrimethylammonium bromide as structure-directing agent. The capability of cyclic oligosaccharide (β-cyclodextrin) to interact with surfactant micelles in the process of hydrothermal sol-gel synthesis and to influence the formation of mesoporous structure of silica materials was studied. The IR spectroscopy was applied to carry out control under the complete removal of template moieties from pores by extraction procedure and to confirm introduction of 3‑chloropropyl groups into the surface layer of synthesized silicas. Arrangement of mesoscale pores and structural parameters were estimated from the results of X‑ray diffraction and low-temperature adsorption-desorption of nitrogen. It has been found that β‑cyclodextrin as component of hybrid template has positive effect on porous structure of 3-chloropropyl-functionalized MCM-41-type silica causing increase of surface area accompanied with preservation of pore ordering. Moreover, both ionic surfactant and oligosaccharide components of hybrid template act as porogens during sol-gel condensation of structure forming silanes enable to prepare silica materials with micro-mesoporosity. Proposed approach can be useful in synthesis of MCM‑41‑type silicas with surface linker groups and controlled structural characteristics (pore size, geometry and ordering), which have great potential as substrates in design of sophisticated materials.

Development of a new method for the preparation of mesoporous magnetic nanoparticles of cobalt ferrite (CoFe2O4) with applied parameters for magnetic hyperthermia

This study introduces a novel method for preparing mesoporous magnetic cobalt ferrite nanoparticles (CoFe2O4) for magnetic hyperthermia and other applications. The synthesis of nanoparticles was carried out using the solvo thermal method assisted by Cetyltrimethylammonium Bromide. TEM results revealed a spherical and mesoporous shape, and according to the histogram, the average particle size distribution is uniform, with a diameter of 132 ± 21 nm. This study provides a new platform for the application of magnetic mesoporous nanoparticles in magnetic hyperthermia therapy. The methodology is relevant because it allows the formation of mesoporous structures.

Preparation of chitosan mesoporous membrane/halloysite composite for efficiently selective adsorption of Al(III) from rare earth ions solution through constructing pore structure on substrate

The removal of impurity Al(III) from rare earth ion solution by selective adsorption method was one of the challenging tasks. Herein, calcination and acid dissolution treatment were used to construct the pore structure for the halloysite substrate (Hal-650-H) and provide conditions for the formation of the chitosan mesoporous membrane to prepare composite (Hal-H-2CS). The selective adsorption properties and mechanism of the Hal-H-2CS for Al(III) in the rare earth ion solution were studied. The results showed that the formation of mesoporous structures for chitosan provided abundant sites for the adsorption of Al(III). Hal-H-2CS showed remarkable selective adsorption properties for Al(III) in a wide pH range and the binary mixtures with high content of Al(III) or La(III). The maximum adsorption capacity of Al(III) was 106 mg/g, while the adsorption capacity of La(III) was only 1.41 mg/g at pH 4.0. In addition, the Hal-H-2CS exhibited excellent regeneration and structural stability. The remarkable selective properties of Hal-H-2CS was achieved by the synergistic effect between chitosan mesoporous membrane and Hal-650-H, the main adsorption sites were the OH, NH2, CONH2 of chitosan and the oxygen sites of the Hal-650-H. This work provides a new strategy for the design and preparation of outstanding selective adsorbent for Al(III).

Turbulence induced shear controllable synthesis of nano FePO4 irregularly-shaped particles in a counter impinging jet flow T-junction reactor assisted by ultrasound irradiation

FePO4 (FP) particles with a mesoporous structure amalgamated by nanoscale primary crystals were controllably prepared using an ultrasound-intensified turbulence T-junction microreactor (UTISR). The use of this type of reaction system can effectively enhance the micro-mixing and remarkably improve the mass transfer and chemical reaction rates. Consequently, the synergistic effects of the impinging streams and ultrasonic irradiation on the formation of mesoporous structure of FP nanoparticles have been systematically investigated through experimental validation and CFD simulation. The results revealed that the FP particles with a mesoporous structure can be well synthesised by precisely controlling the operation parameters by applying ultrasound irradiation with the input power in the range of 0–900 W and the impinging stream volumetric flow rate in the range of 17.15–257.22 mL·min−1. The findings obtained from the experimental observation and CFD modelling has clearly indicated that there exists a strong correlation between the particle size, morphology, and the local turbulence shear. The application of ultrasonic irradiation can effectively intensify the local turbulence shear in the reactor even at low Reynolds number based on the impinging stream diameter (Re < 2000), leading to an effective reduction in the particle size (from 273.48 to 56.1 nm) and an increase in the specific surface area (from 21.97 to 114.97 m2·g−1) of FP samples. The FPirregularly-shaped particles prepared by UTISR exhibited a mesoporous structure with a particle size of 56.10 nm, a specific surface area of 114.97 m2·g−1and a total pore adsorption volume of 0.570 cm3·g−1 when the volumetric flow rate and ultrasound power are 85.74 mL·min−1and 600 W, respectively.

Diels-Alder conversion of biomass-derived furans and ethylene to renewable aromatics over mesoporous titanium phosphate

Metal phosphates such as P-Beta, Zr-P and Sn-P have drawn lots of attention as emerging catalysts for biomass conversion due to its mild acidity which results in high selectivity to the targeted products while minimizing the unwanted side reactions such as coking that are prevalent in reactive biomass-derived compounds. In this study, we have investigated the production of sustainable aromatics such as p-xylene (PX) and toluene (TOL) via Diels-Alder cycloaddition (DAC) of biomass-derived 2,5-dimethylfuran (DMF) and 2-methylfuran (MF) with ethylene over titanium phosphate catalysts. Specifically, the effects of synthesis method (e.g., sol-gel vs hydrothermal), activation method and P/Ti molar ratio on the structural and acid properties of titanium phosphate catalysts were systematically studied to understand the catalytic consequences of the titanium phosphate materials for the DAC of furans. In addition, amphiphilic surfactant was applied to all catalysts for the formation of mesoporous structure. The characterization studies of the prepared catalysts using XRD, BET, FT-IR, XPS, NMR spectroscopy and TPD of ammonia indicated that the degree of Ti-O-P bond formation, catalysts surface area and surface acidity are largely affected by the catalysts synthesis conditions. Overall, the mesoporous titanium phosphate catalyst, synthesized by hydrothermal method at 180 ℃ for 12 h followed by ethanol refluxing at 60 ℃ for 24 h at a molar P/Ti ratio of 1 showed the highest surface area and the highest acid site density which arise from its distinct ordered Ti-O-P bonding structure as evidenced by XPS and NMR. The catalyst demonstrated the remarkably high PX selectivity of > 90 % at the high DMF conversion of > 90 % and the reusability after two successive reaction-regeneration cycles, showing high phosphorus leaching tolerance.

Synthesis of p-LaFeO3–n-BaTiO3 Heterojunctions and Their Room Temperature Methanol Sensing Applications

LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (LFO) and BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BT) were prepared by citrate sol gel method. X-ray diffraction pattern of developed materials were recorded to confirm their crystalline phase formation and for the strain calculations in these materials. (x)LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -(1-x)BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (x = 0.10, 0.30, 0.50 and 1.0) composites were developed by solid state method. SEM images of the developed composites confirms their mesoporous structure formation. P-n heterojunctions films of (x)LaFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -(1-x)BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> were prepared on integrated digitized electrodes using spin coating technique. These were further investigated for methanol sensing properties at room temperature (40°C) based on the I-V characteristics. The developed heterojunctions films using these materials are found to exhibit fast response and recovery times (i.e., 4.7 sec. and 3.7 sec respectively).

Preparation of Biochar with Developed Mesoporous Structure from Poplar Leaf Activated by KHCO3 and Its Efficient Adsorption of Oxytetracycline Hydrochloride

The effective removal of oxytetracycline hydrochloride (OTC) from the water environment is of great importance. Adsorption as a simple, stable, and cost-effective technology is regarded as an important method for removing OTC. Herein, a low-cost biochar with a developed mesoporous structure was synthesized via pyrolysis of poplar leaf with potassium bicarbonate (KHCO3) as the activator. KHCO3 can endow biochar with abundant mesopores, but excessive KHCO3 cannot continuously promote the formation of mesoporous structures. In comparison with all of the prepared biochars, PKC-4 (biochar with a poplar leaf to KHCO3 mass ratio of 5:4) shows the highest adsorption performance for OTC as it has the largest surface area and richest mesoporous structure. The pseudo-second-order kinetic model and the Freundlich equilibrium model are more consistent with the experimental data, which implies that the adsorption process is multi-mechanism and multi-layered. In addition, the maximum adsorption capacities of biochar are slightly affected by pH changes, different metal ions, and different water matrices. Moreover, the biochar can be regenerated by pyrolysis, and its adsorption capacity only decreases by approximately 6% after four cycles. The adsorption of biochar for OTC is mainly controlled by pore filling, though electrostatic interactions, hydrogen bonding, and π-π interaction are also involved. This study realizes biomass waste recycling and highlights the potential of poplar leaf-based biochar for the adsorption of antibiotics.

A detailed study of the mesoporous structure formation in the silica monolith with interconnected macropores

A detailed study of the mesoporous structure formation in the silica monolith with interconnected macropores

Preparation of MIL100/MIL101-alginate composite beads for selective phosphate removal from aqueous solution

Numerous studies have reported various approaches for synthesizing phosphate-capturing adsorbents to mitigate eutrophication. Despite the efforts, concerns about production cost, the complexity of synthesis steps, environmental friendliness, and applicability in industrial settings continue to be a problem. Herein, phosphate-selective composite adsorbents were prepared by incorporating alginate (Alg) with MIL100 and MIL101 to produce the MIL100/Alg and MIL101/Alg beads, where Fe3+ served as the crosslinker. The unsaturated coordination bond of MIL100 and MIL101 serves as a Lewis acid that can attract phosphate. The adsorption equilibrium isotherm, uptake kinetics, and effects of operating parameters were studied. The phosphate adsorption capacity of MIL100/Alg (103.3 mg P/g) and MIL101/Alg (109.5 mg P/g) outperformed their constituting components at pH 6 and 30 °C. Detailed evaluation of the adsorbent porosity using N2 sorption reveals the formation of mesoporous structures on the Alg network upon incorporation of MIL100 and MIL101. The composite adsorbents have excellent selectivity toward anionic phosphate and can be easily regenerated. Phosphate adsorption by MIL100/Alg and MIL101/Alg was driven by electrostatic attraction and ligand exchange. Preliminary economic analysis on the synthesis of the adsorbents indicates that the composites, MIL100/Alg and MIL101/Alg, are economically viable adsorbents.

Lead stabilization in soil using P-modified biochars derived from kitchen waste

Kitchen waste is increasing rapidly worldwide. Utilization of biochar in pollution remediation is an economical approach to the sustainable management of kitchen waste. To date, information regarding the modification of kitchen waste biochar and their resulting ability to inhibit the bioavailability of toxic metals in soil is limited. Here, a novel type of kitchen waste-derived biochar was constructed through phosphate modification, and the sequestration, speciation, and migration of Pb(II) in the soil–plant system were explored through a combination of batch adsorption and pot experiment. The results indicated that the maximum adsorption capacities of P-modified biochar for Pb(II) reached 257.95 mg g −1 , which was approximately 50% higher than pristine biochar; further, P-modified biochar exhibited a greater potential to sequestrate Pb(II), compared to that commonly reported for biochar in previous investigations. In the pot experiments, as compared with the unamended soil, the application of P-modified biochar transformed 42% of acid extractable/exchangeable Pb mainly to easily reducible and residual fractions, significantly decreasing the Pb uptake of ryegrass by 37.9–62.6%. The stable speciation of Pb in soil was attributed primarily to the complexation and precipitation of P-modified biochar with Pb(II). Moreover, the binding of P-modified biochar with Pb(II) was dominated by the surface hydroxyl and phosphate groups, although phosphate modification promoted the formation of mesoporous structures and increased negative charge. The findings could lead to the development of novel methods for the reuse of waste and remediation of toxic metal-polluted soils. • A novel type of kitchen waste-derived biochar was developed using P modification. • Sequestration of Pb(II) on P-modified biochar exceeded most reported biochar. • P-modified biochar efficiently decreased Pb uptake of ryegrass by 37.9–62.6%. • Complexation and precipitation dominated the Pb(II) binding to P-modified biochar. • Pb(II) was transformed to the inert species in P-modified biochar treated soil.

Microwave assisted preparation of a hemostatic gauze with mesoporous silica through in-situ synthesis.

The medical disinfection cotton gauze is the most frequently used medical consumables for wound care. Here this ordinary commercial gauze was upgraded to a hemostatic gauze, which was loaded with mesoporous silica through in-situ synthesis and further microwave treatment. The original cotton gauze was pretreated with NaOH solutions for surface activation, soaked in double-silica source precursor solution for moderate in-situ synthesis, treated with microwave for quick template removement and dehydration. The final obtained hemostatic gauze (MS-G1) showed superior physical, biocompatible and hemostatic advantages. The newborn mesoporous silica was firmly anchored onto the cotton fiber surface with <20% leaching after 10 min of sonication. The microwave treatment not only shortened the time for template removal but also promotes the formation of mesoporous structure. The clotting blood time (CBT) of MS-G1 were only (62.00 ± 5.56s), which was 23.14% shorter than that of original medical gauze, and even 3.6% shorter than Combat Gauze (CG). MS-G1 also showed excellent biocompatibility in cytotoxicity tests of L-929 cells, with a 116% proliferation rate at the concentration of 5mg/mL. Furthermore, the hemostatic performance was explored on a rabbit wound model of hemorrhagic liver injury, and MS-G1 showed both shorter hemostasis time (113.75s) and less blood loss (1.69g) than that of CG (180.00 s, 5.13g). The hemostatic gauze anchored with mesoporous silica was expected to be an excellent prehospital hemostatic dressing for field first aid.

Synthesis and characterization of amino functionalized bimetallic metal-organic frameworks as peroxymonosulfate activator for water purification: Performance and mechanistic studies

The importance of new water purification technology for maintaining clean water resources and a high quality of life is self-evident. In this study, amino functionalized bimetallic metal-organic frameworks (NH2-MIL-101(FeCo)) were prepared to activate peroxymonosulfate (PMS) for removal of organic pollutants from water. The structure, morphology, and physicochemical properties of as-prepared NH2-MIL-101(FeCo) were comprehensively evaluated by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption isotherms, and X-ray photoelectric spectroscopy. Degradation tests were performed to study effects of PMS concentration, catalyst dosage, initial pH, and common substances on the orange G (OG) removal. The acidic and alkaline conditions promoted the formation of mesoporous structures in NH2-MIL-101(FeCo) and enhanced the mass transfer processes to remove OG. 100% of OG was removed through a rate constant of 0.0711 min-1 within 45 min in NH2-MIL-101(FeCo)− 2/PMS/OG system, where 1O2, SO4•−, and ·OH played pivotal contributions in the OG removal. The catalytic activity of NH2-MIL-101(FeCo) originated from unsaturated metal sites of Fe(II) and Co(II). This work demonstrates a feasible strategy towards the synthesis of functional MOFs for removal of organic contaminants.

Facile Synthesis of Amino-functionalized Mesoporous Fe3O4/rGO 3D Nanocomposite by Diamine compounds as Li-ion Battery Anodes

Being an essential part of lithium-ion batteries, the development of novel anode materials currently receives much attention. Among these, the high theoretical capacity of Fe3O4 (924 mAh g−1) makes it highly promising. However, massive volumetric changes and particle aggregation during repeated insertion/de-insertion of lithium ions damage the electrode structure and destroy the electrical connection with the current collectors, resulting in rapid and significant capacity losses. One strategy to overcome this problem is the employment of graphene-based compounds as a substrate in an interconnected porous conductive network using a crosslinker (e.g., ethylene diamine) to adjust the distance between the graphene layers. Such a 3D framework creates enough available space for the lithium ions to be inserted or de-inserted respectively to or from the electrode during the charge-discharge process. Moreover, this strategy prevents large electrode volume changes and the accumulation of Fe3O4 during cycling. Herein, an ex situ method was used to synthesize amino-functionalized mesoporous Fe3O4/graphene-based nanocomposites. In the first step, Fe3O4 nanoparticles were synthesized with the addition of ethylenediamine (EDA), whereby mesoporous Fe3O4 nanoparticles were obtained (Fe3O4-E). In the second step, Fe3O4-E/rGO nanocomposites were prepared with the help of electrostatic interactions. The Fe3O4-E/rGO nanocomposite showed good cycling performance vs. Li-metal and a high reversible capacity (∼465 mAh g−1) and average coulombic efficiency of ∼98% after 250 cycles at the current density of 1000 mA g−1. These promising results can be attributed to the presence of EDA in the formation of mesoporous nanoparticles and the 3D structure of the resulting composite. Itprevents the fragmentation of Fe3O4 particles induced by the formation of mesoporous structures and the restacking of rGO sheets generated by adjusting the layer spacing.

Role of aluminum resource in conversion of bentonite into low silica-based zeolites via fusion technology

The low silica-based zeolites, with an extended surface area were prepared from Ca-bentonite via fusion technique, involving the application of boehmite, and sodium aluminate to compensate aluminum lack. The dependency of cation exchange capacity (CEC) on aluminum resource was interpreted by the evaluation of crystallinity, and textural properties. Although zeolite LTA produced through the employment of boehmite exhibited a lower CEC, hydroxysodalite obtained in the presence of sodium aluminate represented the superior performance attributed to the favorable formation of mesoporous structure, 8 nm, compared to that for the commercial product used as a reference material in the current investigation.

Accurately control the micropore/mesopore ratio to construct a new hierarchical porous carbon with ultrahigh capacitance and rate performance

The synthesis of porous carbon materials with high surface area is an important method to improving their specific capacitances. However, the misfitting distribution of micropore/mesopore leads to serious recession under high current densities. Herein, we report a set of combination methods to accurately control the micropore/mesopore ratio to achieve a hierarchical carbon material with ultra-large capacitance and extra-high rate performance. These methods include adjusting Al/Zn ratios, decarboxylation, zinc volatilization, removal of nano-Al2O3, and KOH–KCl activation. The first four contribute to micropore structure creation to increase the specific capacitance at low current, while the last one contributes to mesoporous structure formation to increase the specific capacitance at high current. It is found that the corrosion of the excess micropores to form new mesopores and transparent graphene greatly enhances ion diffusion kinetic process and rate performance. Based on these findings, the optimized MDAPC provides a superior specific capacitance of 433 F g−1 at 1 A g−1, 324 F g−1 at 200 A g−1, and 217 F g−1 at 750 A g−1, indicating its ultra-large specific capacitance and extra-high rate performance. These findings provide a research foundation for the future development of hierarchical porous carbon materials with outstanding capacitance, rate performance and durability.

Comparison of the effectiveness of melamine derived graphitic carbon nitrides based photocatalysts towards the degradation of Rhodamine B

Graphitic carbon nitride (GCN) is a well-known visible light photocatalyst. Bulk GCNs derived from various types of precursors often exhibit lower photocatalytic efficiencies towards degradation of organic pollutants due to their lower surface area and porosity. Exfoliation, formation of mesoporous structure, development of heterojunctions, doping with metals and non-metals, and intercalation are some of the strategies adopted to improve the efficiency of GCN. Melamine is the most commonly used precursor for the synthesis of GCN. However, the bulk GCN derived from melamine exhibits poor photocatalytic activity, warranting improvement. Mixing of melamine with ammonium based salts is considered as a useful approach to prepare GCN nanosheets with a higher surface area and porosity. The present study aims to compare the effectiveness of GCNs derived from melamine (MGCN) as well using a mixture of melamine and ammonium nitrate (ANGCN), melamine and ammonium carbonate (ACGCN) and, melamine and ammonium chloride (AGCN) in 1:4 ratios under visible light irradiation using Rhodamine B as a model pollutant. The study reveals that ANGCN, ACGCN and AGCN exhibit much better degradation efficiency than MGCN. The GCNs can be ranked as AGCN > ACGCN > ANGCN > MGCN in terms of their efficiency towards the degradation of Rhodamine B. The difference in efficacy among them is mainly due to the extent of the exfoliation of catalyst, development of nanosheets and porosity, which is relatively higher for AGCN, ANGCN and ACGCN. The study concludes that mixing melamine with NH4Cl/NH4CO3/NH4NO3 at 1:4 ratios enables the formation of GCNs with desired characteristics and among them those prepared using NH4Cl (AGCN) is promising due to its higher porosity, development of more number of nanosheets, more negative Zeta potential and lower rate of recombination of charge carriers.