Hard Template Research Articles

Construction of silicon-rich hollow nanotubes embedded in hierarchical SSZ-13 and enhanced SCR high-temperature activity

The meso-channel structure of the SSZ-13 molecular sieve can both slightly speed up the diffusion of reactants or products and lower the chance of pore blockage. Micro-mesoporous SSZ-13 was constructed using hydroxylated carbon nanotubes (CNTs) as the hard template. CNTs not only introduced silica-rich and aluminum-poor hollow nanotubes to SSZ-13, but also shortened the crystallization period of SSZ-13 by no less than 24 h. SSZ-13–0.04 underwent a “crystallization-dissolution-re-crystallization” process during the 24th and 96th hours of crystallization. Compared with the conventional SSZ-13, the SSZ-13 constructed with adamantane-carbon nanotubes as the double template showed better adsorption capacity for NO, stronger acidity, and higher SCR high-temperature activity.

Constructing the Interconnected and Hierarchical Nanoarchitectonics in Coal-Derived Carbon for High-Performance Supercapacitor.

Because of the deep and zigzag microporous structure, porous carbon materials exhibit inferior capacitive performance and sluggish electrochemical kinetics for supercapacitor electrode materials. Herein, a single-step carbonation and activation approach was utilized to synthesize coal-based porous carbon with an adjustable pore structure, using CaO as a hard template, KOH as an activator, and oxidized coal as precursors to carbon. The obtained sample possesses an interconnected and hierarchical porous structure, higher SSA (1060 m2 g-1), suitable mesopore volume (0.25 cm3 g-1), and abundant surface heteroatomic functional groups. Consequently, the synthesized carbon exhibits an exceptionally high specific capacitance of 323 F g-1 at 1 A g-1, along with 80.3% capacitance retention at 50 A g-1. The assembled two-electrode configuration demonstrates a remarkable capacitance retention of up to 95% and achieves Coulombic efficiency of nearly 100% with 10,000 cycles in a 6 M KOH electrolyte. Furthermore, the Zn-ion hybrid capacitor also exhibits a specific capacity of up to 139.1 mA h g-1 under conditions of 0.2 A g-1. This work offers a simple method in preparation of coal-based porous carbon with controllable pore structure.

Synthesis and characterization of mesoporous caged silica for efficient adsorption of methylene blue from aqueous solution

Addressing the challenge of removing dyes from textile industry wastewater is crucial for wastewater treatment. Adsorption, utilizing suitable materials, emerges as a promising solution. This work introduces caged silica as an effective adsorption material for wastewater treatment in the textile industry. The proposed caged silica was synthesized via the hard template synthesis method, commonly used in various applications such as catalysts and wastewater treatment. Caged silica exhibited an amorphous structure with notable BET surface area (448m2/g), pore volume (0.325cm3/g), and average pore size (2.4nm), confirmed through detailed characterization. Evaluation of its adsorption capacity for methylene blue (MB) revealed an impressive removal efficiency of approximately 95% within the initial 20 min. The adsorption process followed the pseudo-second-order model and adhered more closely to the Freundlich isotherm model than the Langmuir model. Additionally, the study investigates the effects of pH, percent removal efficiency, cyclic stability, and initial MB concentration on the adsorption procedure. Consequently, the synthesized caged silica stands out as a promising mesoporous material for efficiently removing MB from aqueous solutions, offering practical application potential in wastewater treatment.

Direct photo-curing 3D printed bionic multistage Mo-doped tungsten oxide catalysts for static and dynamic oxidative desulfurization of fuels

3D printed monolithic catalysts have attracted increasing attention in the petrochemical industry due to their advantages of the freedom of configuration, the rapidity of fabrication and the control of the fluid properties of the reaction medium. However, this remains challenging in constructing of micromorphology, reliable manufacturing, and adaptive functionality. Herein, inspired by the function of acicular plant fractal structure, we have developed bionic multistage monolithic catalysts based on direct photo-curing 3D printing technology. We also design two configuration strategies for static and dynamic oxidative desulfurization of fuels. Below the catalyst surface, the porous structure prepared by the hard template method can increase the specific surface area of the catalyst to disperse the active center and adsorb organic sulfur to strengthen the oxidation effect. The 3D-MoWO/PC-CE monolithic catalyst shows excellent activity in the static reaction with 100% sulfur removal. Above the catalyst surface, microcrystalline cellulose is introduced in-situ in 3D printed ink to build needle-like structures to enhance mass transfer efficiency and reduce surface pressure in dynamic fixed bed reaction. This work provides valuable ideas for the fabrication of efficient monolithic catalysts in various reactions.

Biochar-mediated synthesis of ZSM-5 zeolite for the methanol-to-olefins reaction

The present study reports the successful synthesis of ZSM-5 zeolites with high external specific surface area by using biochar as a hard template. The physicochemical properties of the biochars (originated from grass, tea and lignin) were studied using XRD, SEM EDX, FTIR and other characterization techniques. The results showed that biochars obtained from different plants, due to the differences in morphology, particle size, composition and surface functional groups, led to significant effects on the morphology and acidity of the zeolite crystals. These ZSM-5 zeolites exhibited a significantly improved performance in the Methano-To-Olefins (MTO) reaction. Indeed, the catalyst lifetime of parent ZSM-5 started to decline after 6 h, whilst ZSM-5 modified by Grass-C only suffered a loss in conversion after 10 h on stream (at 400 °C, WHSV=8 h−1).

Enhanced CO2/N2 Separation of Mixed-Matrix Membranes Containing Hierarchical UiO-66 Synthesized from Hard Templates

Enhanced CO₂/N₂ Separation of Mixed-Matrix Membranes Containing Hierarchical UiO-66 Synthesized from Hard Templates

One-Step Decoration of Subnanometer MoOx Clusters on Bi11VO19 Nanotubes for Visible-Light-Driven Water Oxidation.

For the sluggish reaction kinetics due to a four-electron transfer process, water oxidation is always a major obstacle to solar splitting of water to hydrogen. It remains a tough challenge to develop efficient nonnoble-metal photocatalysts for water oxidation. Herein, we decorate the host photocatalyst of Bi11VO19 nanotubes with the coatalyst of subnanometer MoOx clusters (denoted as Bi11VO19/MoOx hetero-nanotubes) via a one-step cation-exchange solvothermal reaction using Na2V6O16 nanowires as the hard template. It is observed that the morphology and microstructure of Bi11VO19/MoOx hetero-nanotubes vary with the dosage of Mo source and polyvinylpyrrolidone, as well as with the solvent composition. The optimized Bi11VO19/MoOx hetero-nanotubes significantly enhance the photooxidation of water to oxygen with visible light, delivering an oxygen production rate of 790 μmol g-1 h-1, which is 12 times that of bare Bi11VO19 nanotubes. In situ X-ray photoelectron spectroscopy and (photo)electrochemical characterization suggest that the enhanced photoactivity may be caused by the decorated cocatalyst of MoOx clusters, which extracts electrons from Bi11VO19 nanotubes, leaving an abundance of holes for water photooxidation. This work demonstrates a potential strategy to develop photocatalysts for energy conversion by constructing Bi11VO19-based nanostructures.

Recent Developments on CO2 Hydrogenation Performance over Structured Zeolites: A Review on Properties, Synthesis, and Characterization

This review focuses on an extensive synopsis of the recent improvements in CO2 hydrogenation over structured zeolites, including their properties, synthesis methods, and characterization. Key features such as bimodal mesoporous structures, surface oxygen vacancies, and the Si/Al ratio are explored for their roles in enhancing catalytic activity. Additionally, the impact of porosity, thermal stability, and structural integrity on the performance of zeolites, as well as their interactions with electrical and plasma environments, are discussed in detail. The synthesis of structured zeolites is analyzed by comparing the advantages and limitations of bottom-up methods, including hard templating, soft templating, and non-templating approaches, to top-down methods, such as dealumination, desilication, and recrystallization. The review addresses the challenges associated with these synthesis techniques, such as pore-induced diffusion limitations, morphological constraints, and maintaining crystal integrity, highlighting the need for innovative solutions and optimization strategies. Advanced characterization techniques are emphasized as essential for understanding the catalytic mechanisms and dynamic behaviors of zeolites, thereby facilitating further research into their efficient and effective use. The study concludes by underscoring the importance of continued research to refine synthesis and characterization methods, which is crucial for optimizing catalytic activity in CO2 hydrogenation. This effort is important for achieving selective catalysis and is paramount to the global initiative to reduce carbon emissions and address climate change.

Doped Porous Carbon Spheres with Controllable Vesicle Structure: Preparation and the Effects of Pore Size on Electromagnetic Wave Absorption Properties.

This work reports on the preparation of uniform vesicle-structural carbon spheres doped with heteroatoms of N, P, and S, with the pore sizes strictly controlled by the hard templates of monodisperse submicron SiO2 spheres. The uniformly doped vesicular carbon microspheres are obtained in three steps: Stöber hydrolysis for the SiO2; in situ polymerization for the immobilization; and alkaline etching after carbonization. The size of the vesicles can be easily adjusted by regulating the particle size of the submicron SiO2 spheres, which has a significant effect on its electromagnetic wave (EMW) absorption performance. Compared with microspheres with pore sizes of 180 and 480nm, when the vesicle aperture is 327nm, with only 5.5wt.% filling load and 1.9mm thickness, the material shows the best EMW absorption behavior with the effective absorption bandwidth (EAB) covers the entire Ku band (6.32GHz) and the minimum reflection loss (RLmin) of -36.10dB, suggesting the optimized pore size of the microspheres can significantly improve the overall impedance matching of the material and achieve broadband wave absorption. This work paves the way for the enhancement of EMW absorption properties of porous material by optimizing the pore size of uniform apertures while maintaining their composition.

Lab-on-Device Synthesis of Hierarchical Macro/Mesoporous WO3 Semiconducting Films for High-Performance H2S Sensing.

The performance consistency of the gas sensor is strongly dependent on the interface binding between the sensitive materials and the electrodes. Traditional powder coating methods can inevitably lead to differences in terms of substrate-film interface interaction and device performance, affecting the stability and lifetime. Thus, efficient growth of sensitive materials on device substrates is crucial and essential to enhance the sensing performance, especially for stability. Herein, hierarchically ordered macro/mesoporous WO3 films are in situ synthesized on the electrode via a facile soft/hard dual-template strategy. Orderly arrayed uniform polystyrene (PS) microspheres with tailored size (ca. 1.2µm) are used as a hard template, and surfactant Pluronic F127 as a soft template can co-assemble with tungsten precursor into ordered mesostructure in the interstitials of PS colloidal crystal induced by solvent evaporation. Benefiting from its rich porosity and high stability, the macro/mesoporous WO3-based sensor shows high sensitivity (Rair/Rgas = 307), fast response/recovery speed (5/9 s), and excellent selectivity (SH2S/Smax > 7) toward 50ppm H2S gas (a biomarker for halitosis). Significantly, the sensors exhibit an extended service life with a negligible change in sensing performance within 60 days. This lab-on-device synthesis provides a platform method for constructing stable nanodevices with good consistency and high stability, which are highly desired for developing high-performance sensors.

Fabrication of Polypyrrole Hollow Nanospheres by Hard-Template Method for Supercapacitor Electrode Material.

Conducting polymers like polypyrrole, polyaniline, and polythiophene with nanostructures offers several advantages, such as high conductivity, a conjugated structure, and a large surface area, making them highly desirable for energy storage applications. However, the direct synthesis of conducting polymers with nanostructures poses a challenge. In this study, we employed a hard template method to fabricate polystyrene@polypyrrole (PS@PPy) core-shell nanoparticles. It is important to note that PS itself is a nonconductive material that hinders electron and ion transport, compromising the desired electrochemical properties. To overcome this limitation, the PS cores were removed using organic solvents to create hollow PPy nanospheres. We investigated six different organic solvents (cyclohexane, toluene, tetrahydrofuran, chloroform, acetone, and N,N-dimethylformamide (DMF)) for etching the PS cores. The resulting hollow PPy nanospheres showed various nanostructures, including intact, hollow, buckling, and collapsed structures, depending on the thickness of the PPy shell and the organic solvent used. PPy nanospheres synthesized with DMF demonstrated superior electrochemical properties compared to those prepared with other solvents, attributed to their highly effective PS removal efficiency, increased specific surface area, and improved charge transport efficiency. The specific capacitances of PPy nanospheres treated with DMF were as high as 350 F/g at 1 A/g. And the corresponding symmetric supercapacitor demonstrated a maximum energy density of 40 Wh/kg at a power density of 490 W/kg. These findings provide new insights into the synthesis method and energy storage mechanisms of PPy nanoparticles.

How multi-level porous carbon structure affects electrocatalytic properties?

For zinc-air batteries, it is crucial to develop bifunctional electrocatalysts that exhibit exceptional activity, high stability, and low cost. Based on this, three-dimensional carbon-based catalysts with multiple pore sizes were successfully prepared by using three different combinations of soluble salts as hard templates for controlling morphology and structure. These catalysts are denoted as 3D Co/NCBMS. Because of the synergistic effect of heteroatomic doping and a multi-level porous structure, 3D Co/NCBMS exhibits better catalytic properties for OER and ORR, comparable to IrO2 and Pt/C. The half-wave potential of the 3D Co/NCBMS catalyst was 0.82 V (vs RHE) in the ORR reaction and 1.54 V in the OER reaction. 3D Co/NCBMS samples exhibit excellent stability, maintaining a charge and discharge efficiency of approximately 54 % after stable cycling for 225 h. It also demonstrates high resistance to methanol poisoning, with the current remaining at around 95 % in alkaline electrolyte solutions when assembled into zinc-air batteries.

Zinc Oxide Nanostructure Deposition into Sub-5 nm Vertical Mesopores in Silica Hard Templates by Atomic Layer Deposition.

Nanostructures synthesised by hard-templating assisted methods are advantageous as they retain the size and morphology of the host templates which are vital characteristics for their intended applications. A number of techniques have been employed to deposit materials inside porous templates, such as electrodeposition, vapour deposition, lithography, melt and solution filling, but most of these efforts have been applied with pore sizes higher in the mesoporous regime or even larger. Here, we explore atomic layer deposition (ALD) as a method for nanostructure deposition into mesoporous hard templates consisting of mesoporous silica films with sub-5 nm pore diameters. The zinc oxide deposited into the films was characterised by small-angle X-ray scattering, X-ray diffraction and energy-dispersive X-ray analysis.

Carbon nanofibers supported sorbents with enhanced performance via microwave-assisted in-situ structural modifications for H2S removal

The construction of sorbent with excellent structure and highly dispersed active components is vital to improving its desulfurization activity. Herein, the Fe nanoparticles/carbon nanofibers (Fe/CNFs) desulfurization sorbents were fabricated via electrospinning, template method and microwave carbonization. The structure of sorbents was successfully regulated with the adjustments of Fe content and the types of sacrificial phases. It was found that the Fe content impacted strongly on both structural and desulfurization performance of the sorbents. The sorbents with various Fe contents showed a trend of first increasing and then decreasing with the increased Fe content in breakthrough sulfur capacity. Among the various samples, the sample with the highest sulfur content was 7.21 g S/100 g sorbent. Furthermore, the Fe/CNFs sorbents were optimized via soft and hard template methods, by taking polymethyl methacrylate (PMMA) and SiO2 nanospheres as sacrificial phases. Desulfurization tests implied that the PMMA and SiO2 modified sorbents involved sulfur capacity of 13.76 and 14.18 g S/100 g sorbent, respectively. According to the characterizations, the modified sorbents were imparted with micro- and open-type macro-porous structure, respectively, upon which, the active components were uniformly dispersed and exposed. The excellent performance of sorbent could be attributed to the synergistic effect of porous structure and widely distributed Fe nanoparticles on CNFs. This work highlights new strategy for the synthesis of desulfurization sorbent.

Largely enhanced Piezoelectric-Fenton capability in rationally designed PVDF/Fe2O3 flexible porous film

The burgeoning piezocatalysts have attracted huge attentions due to their ability to convert natural mechanical energy to degrade water pollutants. However, traditional powder-based piezocatalysts still face an inevitable bottleneck of the secondary pollution because of the diffusion of nanoparticles during the piezocatalysis process. In this work, novel porous polymer-based composite films combining Fenton fillers (α-Fe2O3) and ferroelectric polymer (polyvinylidene fluoride, PVDF) are prepared by rationally designed solution-casted method with a sacrificial “hard template” of table salt. The as-prepared porous PVDF/Fe2O3 film exhibits superior decomposition efficiency of organic pollutants under ultrasonication. Particularly, the easily recyclable porous film with optimized composition and spatial structure offers an ultrahigh rate constant of 0.0498 min−1, which means it can degrade 94.8% rhodamine B (RhB) in 60 min, exceeding that of most reported polymer-based piezocatalysts. Additionally, it has a comprehensive decomposition effect on dyes, antibiotics and natural water with a good cycle performance. The outstanding degradation performance is attributed to the massive hydroxyl radical generated from the enhanced Piezoelectric-Fenton effect, which is ascribed to the synergistic effect of improved piezoelectricity in PVDF, enhanced hydrophilicity and optimized spatial structures in the porous composite films.

Emerging trends of ferrite-based nanomaterials as photocatalysts for environmental remediation: A review and synthetic perspective

Efficient wastewater treatment processes are in high demand for removing organic and inorganic pollutants. Photocatalysis, as an environmentally friendly technology, has shown significant progress in the treatment of contaminated wastewater. This review explores the potential of spinel ferrite-based nanomaterials as efficient photocatalysts for wastewater treatment. To enhance their properties, ferrites have been combined with advanced materials, such as BiOX, MXene, and g-C3N4 to form binary and ternary nanocomposites. We highlight the state-of-the-art in these binary and ternary spinel ferrite nanocomposites in the photocatalytic degradation of organic pollutants. These ferrite nanocomposites showed superior photocatalytic performance due to enhanced properties such as increasing the capacity for light utilization, slowing electron-hole recombination, and reducing agglomeration. Furthermore, our review explores recent research on template-assisted synthesis, a novel approach for fine-tuning the morphology of spinel ferrites and enhancing their catalytic efficiency. The impact of both the soft and hard templates on the properties of the produced ferrite nanomaterials is discussed. Overall, this unique combination of advanced nanocomposite materials and structural control using template-assisted approaches paves the way for a new generation of highly efficient photocatalysts. Thus, we provide a comprehensive overview of recent advances in the development of ferrite nanocomposites, underlining their potential as photocatalysts for environmental remediation applications.

Reactive species identification in KCl activated biochar/persulfate system under different pH condition: Theoretical calculation and column experiments

The challenges of remediating polluted water in mine areas are exacerbated by low emission dispersion and long-lasting pollution, particularly the significant fluctuations in pH value. Notably, the treatment of flotation reagent polluted water with variable pH scenarios remains a challenge. In this study, metal-free biochar-based materials (KBBC)/persulfate system was used for flotation reagent contaminated wastewater treatment with a wide pH range. Regarding the intrinsic nature of the biochar-based materials, ball milling enhanced the degree of graphitization, while introducing a hard template of KCl increased the proportion of carbonyl functional groups on their surface, thereby facilitating persulfate activation. Experimental findings revealed that the KBBC/PS system displayed efficient degradation of aniline aerofloat (AAF) as a representative flotation reagent across a wide pH range (pH = 3.6–10.4 with buffer). Investigations on the mechanism indicated that, under acidic and neutral conditions, superoxide radicals and direct electron transfer processes constituted primary pathways for pollutant degradation. Meanwhile, various active species contributed under alkaline conditions with increased involvement of free radicals (•OH and SO4•−) and singlet oxygen. Furthermore, continuous flow experiments were set up to prove the potential applicability of the KBBC/PS process. This study not only deepens the understanding of persulfate activation by metal-free carbon-based materials across a wide pH range but also expands their potential applications in mine-polluted water purification.

Study of binder effect on the lithium storage kinetics of copper phosphide nanotube anode

Copper phosphide (CP) stands out as a promising anode material for lithium-ion batteries due to its high theoretical capacity (1281 mAh g−1). However, the fast capacity decay of copper phosphide poses a significant challenge due to its huge volume change. Optimization of binder selection presents an effective way to harness the high lithium storage capacity of copper phosphide. In this study, copper phosphide nanotubes were synthesized using a hard template transformation method. The following investigation delved into the impact of different binders on the electrode structure and the lithium-ion storage performance of copper phosphide. Notably, employing polyacrylic acid (PAA) as a binder resulted in a stable capacity of 526.8 mAh g−1 over 400 cycles at 100 mA g−1 for the copper phosphide electrode. The remarkable lithium-ion storage property of the CP-PAA electrode is ascribed to the robust interaction between PAA and the P–O bond on the copper phosphide surface. This interaction not only mitigated volume expansion but also enhanced the kinetics of electrochemical reactions.

Synthesis Of Nano-Porous Strontium Titanate Materials for Photocatalysis

Strontium titanate semiconductor materials have been widely used in the field of photocatalysis due to their high dielectric constant and band gap. Uniform, micron-sized SrTiO3 particles didn’t tend to aggregate, and the low surface area of larger particles could be improved by incorporating porous structures, thus offering superior performance for a range of applications. In this study, six mainly methods to prepare nano-porous SrTiO3 particles were showed and discussed. The methods include hydrothermal method，sol gel method, chemical co-precipitation method, high temperature solid phase method, hard template method and soft template method. These processes and their advantages and disadvantages were analysised.

A REVIEW ON TEMPLATE SYNTHESIS OF NANOPARTICLE

In recent years, there has been a rise in interest in the development of novel drug delivery systems that utilize nanoparticles. In terms of high stability, high specificity, high drug-carrying capacity, controlled release, the ability to use different routes of administration, and the ability to deliver both hydrophilic and hydrophobic drug molecules, nanoparticles can offer significant advantages over conventional drug delivery. We try to provide a detailed overview of template techniques designed for nanomaterial production. The pores and channels in the nanoporous “template” structures are used to generate the desired nanomaterials in template synthesis. Because this process has advantages over other methods, like allowing precise control over their size, shape, and structure, it is commonly used to generate nanoparticles. The first half of the review provides information on various template preparation processes. Templates are classified as “hard” or “soft” templates. Soft templates are often fluid-like, whereas hard templates are typically solid-state materials with distinct morphology and structure. This study discusses the effect of templates on morphologies and methodology and compares hard and soft templates.