Soft-templating Approach Research Articles

Mesoporous Nitrogen-Doped Carbon Support from ZIF-8 for Pt Catalysts in Oxygen Reduction Reaction

Zeolitic imidazolate framework-8 (ZIF-8) has been extensively studied as a precursor for nitrogen-doped carbon (NC) materials due to its high surface area, tunable porosity, and adjustable nitrogen content. However, the intrinsic microporous structure of the ZIF-8 limits mass transport and accessibility of reactants to active sites, reducing its effectiveness in electrochemical applications. In this study, a soft templating approach using a triblock copolymer was used to prepare mesoporous ZIF-8-derived NC (Meso-ZIF-NC) samples. The hierarchical porous structure was investigated by varying the ratios of Pluronic F-127, NaClO4, and toluene. The resulting Meso-ZIF-NC exhibited widespread pore size distribution with an enhanced mesopore (2–50 nm) volume according to the composition of the reaction mixtures. Pt nanoparticles were uniformly dispersed on the Meso-ZIF-NC to form Pt/Meso-ZIF-NC catalysts, which presented a high electrochemical surface area and improved oxygen reduction reaction activity. The study highlights the important role of mesopore structure and nitrogen doping in enhancing catalytic performance, providing a pathway for advanced fuel cell catalyst design.

Development of Co-, Fe- and N-Doped Mesoporous Carbon Catalysts for Anion-Exchange Membrane Fuel Cell Cathode

Hydrogen has a lot of promise to be utilized in sustainable transportation and energy production using low-temperature polymer electrolyte membrane fuel cells. While proton-exchange membrane fuel cells are already commercialized, they still have issues with needed substantial amount of platinum as electrocatalyst. By switching to alkaline electrolyte, cheaper and more sustainable electrocatalysts can be used for cathodic oxygen reduction reaction (ORR). For instance, transition metal and nitrogen doped nanocarbons (M-N-C, M = Fe, Co, Mn, etc.) have shown very good ORR activity in alkaline media. Anion-exchange membrane fuel cell (AEMFC) technology, however, is still in research phase, and any further developments in electrocatalysts is necessary.1-3 Herein the focus is on developing mesoporous M-N-C electrocatalysts for the ORR and studying the effect of carbon support porous structure on the AEMFC performance. Mesoporous carbons (MCs) are prepared by combining phloroglucinol with glyoxal/glyoxylic acid. In the first part, soft-templating approach by Pluronic F127 is taken,4 in the second part of the work, effect of additional hard template (MgO) is investigated through dual-templating. We have limited the amount of harsh and environmentally unfriendly chemicals, offering more sustainable approaches beyond the silica-templating for synthesizing mesoporous carbons. The prepared MCs have high specific surface area (up to 900 m2 g-1) and have high content of mesopores in 5-8 nm range. To further study the effect of porous structure of carbon support on the AEMFC performance, nanocarbon composites with MC (prepared in first part) and either highly microporous carbide-derived carbon (CDC) or carbon nanotubes (CNTs) are also prepared (Figure 1a).Our previous works have shown that bimetallic materials, containing iron and cobalt, perform the best in AEMFC.5-6 Thus herein, all prepared nanocarbon supports are doped with nitrogen (1,10-phenanthroline as source), cobalt and iron (Co- and Fe-acetate) via high-temperature pyrolysis, which yields electrocatalyst with atomically dispersed metal centers (Figure 1b). Rotating disc electrode (RDE) method is employed for preliminary ORR-activity testing with the prepared CoFe-N-C materials showing high electrocatalytic activity in 0.1 M KOH (E 1/2 up to 0.84 V vs RHE) and good stability after 10,000 potential cycles. In the first part, using nanocarbon composites with varying porous structure yielded electrocatalysts with almost identical performance in the RDE test. However, the effect of porous structure came evident during AEMFC testing, wherein presence of more mesoporous structure was beneficial.4 In the second part using dual-templating approach, the most optimal ratio of two templates (F127 and MgO) was found, together with promising AEMFC performance.In conclusion, we have employed three different mesoporous carbon synthesis routes (soft- or dual-templating), optimized the conditions, and after doping obtained highly active ORR electrocatalysts with great promise for the AEMFC application.

Green self-templated synthesis of P-doped mesoporous carbon from dual sodium salts with improved average pore size for capacitive deionization

Mesoporous carbon materials hold significant potential in capacitive deionization (CDI) technology owing to expansive accessible surface area, more adaptable pore structure, excellent conductivity properties and effective surface modification and functionalization. While templating is a common method for synthesizing mesoporous carbons, the commonly used hard and soft templating approaches among them suffer from the challenges of expensive precursors and templating agents, complex procedures, secondary contaminants and difficulties in template removal. In contrast, the self-templating method not only circumvents the traditional template removal or combustion steps but also eliminates the use of organic solvents and hazardous chemicals, thus minimizing environmental impact. In this paper, we have successfully synthesized phosphorus-doped mesoporous carbon with a large average pore size (paver) using a green and convenient self-templating method employing dual sodium salts of sodium alginate (SA) and sodium phytate (SP). Compared to single SA (6.76 nm) or SP (3.74 nm) self-templated carbonization, the average pore size of carbon materials obtained from dual self-templated carbonization with a proportional mixture (12.97 nm) is significantly improved. The larger average pore size provides a greater surface area for electrode-electrolyte interactions, allowing for easier access and faster diffusion of ions into the pores, thereby enhancing the electrochemical and capacitive deionization properties of the material. The resulting material demonstrates promising electrochemical and desalination performance as evidenced by possessing a specific capacitance of 175.8 A/g and an adsorption capacity of 19.65 mg/g, underlining its potential for application in capacitive deionization utilizing mesoporous carbon materials with large average pore size.

Hard and soft templating approaches in evaporative sol-gel synthesis of TiNb2O7 nanostructures as active materials for Li-ion batteries

Hard and soft templating approaches in evaporative sol-gel synthesis of TiNb2O7 nanostructures as active materials for Li-ion batteries

Structurally and mechanically tuned macroporous hydrogels for scalable mesenchymal stem cell–extracellular matrix spheroid production

Mesenchymal stem cells (MSCs) are essential in regenerative medicine. However, conventional expansion and harvesting methods often fail to maintain the essential extracellular matrix (ECM) components, which are crucial for their functionality and efficacy in therapeutic applications. Here, we introduce a bone marrow-inspired macroporous hydrogel designed for the large-scale production of MSC-ECM spheroids. Through a soft-templating approach leveraging liquid-liquid phase separation, we engineer macroporous hydrogels with customizable features, including pore size, stiffness, bioactive ligand distribution, and enzyme-responsive degradability. These tailored environments are conducive to optimal MSC proliferation and ease of harvesting. We find that soft hydrogels enhance mechanotransduction in MSCs, establishing a standard for hydrogel-based 3D cell culture. Within these hydrogels, MSCs exist as both cohesive spheroids, preserving their innate vitality, and as migrating entities that actively secrete functional ECM proteins. Additionally, we also introduce a gentle, enzymatic harvesting method that breaks down the hydrogels, allowing MSCs and secreted ECM to naturally form MSC-ECM spheroids. These spheroids display heightened stemness and differentiation capacity, mirroring the benefits of a native ECM milieu. Our research underscores the significance of sophisticated materials design in nurturing distinct MSC subpopulations, facilitating the generation of MSC-ECM spheroids with enhanced therapeutic potential.

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.

Ionic Liquid-Glycol Mixtures for Direct Air Capture of CO2: Decreased Viscosity and Mitigation of Evaporation Via Encapsulation.

Herein we address the efficiency of the CO2 sorption of ionic liquids (IL) with hydrogen bond donors (e.g., glycols) added as viscosity modifiers and the impact of encapsulating them to limit sorbent evaporation under conditions for the direct air capture of CO2. Ethylene glycol, propylene glycol, 1,3-propanediol, and diethylene glycol were added to three different ILs: 1-ethyl-3-methylimidazolium 2-cyanopyrrolide ([EMIM][2-CNpyr]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). Incorporation of the glycols decreased viscosity by an average of 51% compared to bulk IL. After encapsulation of the liquid mixtures using a soft template approach, thermogravimetric analysis revealed average reductions in volatility of 36 and 40% compared to the unencapsulated liquid mixtures, based on 1 h isothermal experiments at 25 and 55 °C, respectively. The encapsulated mixtures of [EMIM][2-CNpyr]/1,3-propanediol and [EMIM][2-CNpyr]/diethylene glycol exhibited the lowest volatility (0.0019 and 0.0002 mmol/h at 25 °C, respectively) and were further evaluated as CO2 absorption/desorption materials. Based on the capacity determined from breakthrough measurements, [EMIM][2-CNpyr]/1,3-propanediol had a lower transport limited absorption rate for CO2 sorption compared to [EMIM][2-CNpyr]/diethylene glycol with 0.08 and 0.03 mol CO2/kg sorbent, respectively; however, [EMIM][2-CNpyr]/diethylene glycol capsules exhibited higher absorptions capacity at ∼500 ppm of CO2 (0.66 compared to 0.47 mol of CO2/kg sorbent for [EMIM][2-CNpyr]/1,3-propanediol). These results show that glycols can be used to not only reduce IL viscosity while increasing physisorption sites for CO2 sorption, but also that encapsulation can be utilized to mitigate evaporation of volatile viscosity modifiers.

Bioinspired Nanotubular Structures by Soft-Template Electropolymerization: 3,4-(2,3-naphtylenedioxy)Thiophene Monomers Quenched to Form Dimers

Preparing well-ordered nanotubes on materials surface is a great of interest in many applications. Bio-inspired and theoretical approaches show that porous structures such as nanotubes are key parameters for both surface hydrophobicity and water adhesion. Here, a very easy soft-template electropolymerization approach is used to form nanotubular structures, followed by a bioinspired strategy to control the wetting properties. Fully conjugated monomers based on 3,4-(2,3- naphtylenedioxy)thiophene (NaphDOT) core grafted with many rigid aromatic groups such as phenyl, naphthalene, pyrene, pyrrole, were synthesized. Then, electropolymerization is carried out with these monomers, followed by surface and morphologies characterization of corresponding polymers. We show that even if just dimers are formed by electropolymerization, the resulting polymer can be sufficiently insoluble to form structured films. 3,4-(2,3-naphtylenedioxy)thiophene (NaphDOT) is chosen as a judicious example, due to strong <i>π</i>-stacking interactions, and also their capacity to form nanotubular structures by soft template-electropolymerization in the presence of water (H<sub>2</sub>O). Here, different substituents, polymerizable or not, are grafted on the 2-position of thiophene. Films are formed with all the studied substituents. Nanotubular structures are especially observed with the following substituents: hydroxyl, pyrene and pyrrole, but in the presence of H<sub>2</sub>O. We study also their influence on the surface hydrophobicity.

Size-dependent activity of Fe-N-doped mesoporous carbon nanoparticles towards oxygen reduction reaction

The rational design of Fe–N–C catalysts that possess easily accessible active sites and favorable mass transfer, which are usually determined by the structure of catalyst supports, is crucial for the oxygen reduction reaction (ORR). In this study, an oleic acid-assisted soft-templating approach is developed to synthesize size-controlled nitrogen-doped carbon nanoparticles (ranging from 130 nm to 60 nm and 35 nm, respectively) that feature spiral mesopores on their surface (SMCs). Next, atomically dispersed Fe–Nx sites are fabricated on the size-tunable SMCs (Fe1/SMC-x, where x represents the SMC size) and the size-dependent activity toward ORR is investigated. It is found that the catalytic performance of Fe1/SMCs is significantly influenced by the size of SMCs, where the Fe1/SMC-60 catalyst shows the highest ORR activity with a half-wave potential of 0.90 V vs. RHE in KOH electrolyte, indicating that the gas-liquid-solid three-phase interface on the Fe1/SMC-60 enhances the accessibility of Fe–Nx sites. In addition, when using Fe1/SMC-60 as the cathode catalyst in aqueous zinc-air batteries (ZABs), it delivers a higher open-circuit voltage (1.514 V), a greater power density (223 mW cm−2), and a larger specific capacity/energy than Pt/C-based counterparts. These results further highlight the potential of Fe1/SMC-60 for practical energy devices associated with ORR and the importance of size-controlled synthesis of SMCs.

Soft-templating synthesis of hierarchical mordenite as high-performance catalyst for cyclic acetals production via acetylation of glycerol and benzaldehyde

Highly active hierarchical mordenite zeolite with micro/mesoporosity (TM-n) for selective synthesis of cyclic acetals via acetylation reaction is reported. The hierarchical zeolite is synthesized using soft-templating approach with variations in octadecyltrimethoxysilane (OTMS/Al2O3 ratio, n = 0.2, 0.3 and 0.4) in precursor hydrogels. The results reveal that OTMS not only creates secondary mesoporosity in zeolite framework (larger mesopore volume, external surface area, average pore diameter), but also influences the crystallization process, altering the crystal morphology, crystallinity and Si/Al ratios. Among TM-n zeolites prepared, TM-0.3 hierarchical mordenite has the optimum OTMS amount incorporated while further increasing the OTMS amount leads to the formation of ANA/GIS intergrowth. Thanks to the accessible hierarchical porosity, reduced acidity and morphological effects, the TM-0.3 hierarchical mordenite exhibits excellent catalytic performance (84.1% conversion, TOF = 0.087 s−1, 61.5% dioxolane selectivity) in acetylation of glycerol and benzaldehyde (160 °C, 20 min) better than pristine mordenite. The catalyst is reusable for five runs with minimal loss of activity (TOF = 0.087 → 0.084 s−1), making it a promising catalyst for chemical productions involving bulky molecules. In addition, comparative catalytic tests with classical homogeneous and heterogeneous catalysts, including H2SO4, HCl, CH3COOH, H–Y, H-LTL, Na-X, Na-A, were performed.

Hollow carbon-based materials for electrocatalytic and thermocatalytic CO2 conversion.

Electrocatalytic and thermocatalytic CO2 conversions provide promising routes to realize global carbon neutrality, and the development of corresponding advanced catalysts is important but challenging. Hollow-structured carbon (HSC) materials with striking features, including unique cavity structure, good permeability, large surface area, and readily functionalizable surface, are flexible platforms for designing high-performance catalysts. In this review, the topics range from the accurate design of HSC materials to specific electrocatalytic and thermocatalytic CO2 conversion applications, aiming to address the drawbacks of conventional catalysts, such as sluggish reaction kinetics, inadequate selectivity, and poor stability. Firstly, the synthetic methods of HSC, including the hard template route, soft template approach, and self-template strategy are summarized, with an evaluation of their characteristics and applicability. Subsequently, the functionalization strategies (nonmetal doping, metal single-atom anchoring, and metal nanoparticle modification) for HSC are comprehensively discussed. Lastly, the recent achievements of intriguing HSC-based materials in electrocatalytic and thermocatalytic CO2 conversion applications are presented, with a particular focus on revealing the relationship between catalyst structure and activity. We anticipate that the review can provide some ideas for designing highly active and durable catalytic systems for CO2 valorization and beyond.

Synthesis of hierarchically porous carbon materials from nanocapsule based on interfacial polymerization of galla chinensis extract for all-solid-state supercapacitor application

In this study, we have demonstrated a facile and economic approach to synthesize hierarchically porous carbon materials (HPCMs) derived from galla chinensis. We mixed the aqueous crude extract of galla chinensis and the triblock copolymer Pluronic F127 solution to lead to an interfacial polymerization reaction, finally resulting in the formation of nanocapsule in the solution. Compared to the soft template approach in which F127 is used as a template agent, the nanocapsule approach enables larger specific surface area (SSA) HPCM, which is attributed to the change of state of F127 in solutions measured by confocal Raman spectroscopy. We find that the optimal product called GC04 owns a high specific surface area (SSA) 236 m2∙g−1 without any post activation treatment. Benefiting from the high SSA, GC04 exhibits 33% higher areal capacitance than its counterparts obtained via conventional soft template approach in a well-sealed in-plane micro-supercapacitor (IMSC). Therefore, the present investigation provides a new approach for the high value use of galla chinensis, which is low-cost and highly sustainable for synthesis of HPCMs.

Rapid synthesis of hierarchical cerium-based metal organic frameworks for carbon dioxide adsorption and selectivity

The creation of innovative porous materials for CO2 capture and separation is proving extremely relevant for environmental sustainability and global warming mitigation. In this study, modified Ce-UiO-66 MOFs were synthesized in 10 min using simultaneous microwave and ultrasound irradiation method. The porosity of the MOF was altered using the soft-templating approach. This strategy resulted in the construction of a hierarchically micro-mesoporous structure with an average mesopore size of 11.10 nm. The as-obtained MOFs, abbreviated as CUT, were characterized with SEM, XRD, FTIR, TGA, BET, and evaluated as CO2 adsorbents. The results displayed preserved crystal structure, higher thermal stability up to 570 °C. The heightened diffusion of CO2 molecules to the micropores promoted by mesopore channels, endued CUT with an over-all CO2 adsorption uptake of 2.53 mmol/g at 273 K at 1 bar outperforming equivalent Ce-UiO-66 MOFs. Notably, the CUT adsorbent showed improved CO2/N2 IAST selectivity (34.2 vs 24.6) and CO2 isosteric heat of adsorption (Qst = 30.15 vs 25 kJ/mol) in contrast to pristine UiO-66 (Zr).

Dual role of flower-like Fe3O4/Ag microstructure in electrocatalytic detection and catalytic reduction of 4-nitrophenol

In this work, a novel Ag-incorporated 3D flower-like porous Fe3O4 magnetic microstructure (Fe3O4/Ag-FM) was effectively prepared via a quasi-reverse emulsion soft template approach and reductive deposition of Ag nanoparticles. The synthesized Fe3O4/Ag-FM material was applied for the electrochemical sensing and catalytic reduction of 4-nitrophenol (4-NP). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to determine the electrochemical sensing ability of the synthesized material. Results showed that the fabricated Fe3O4/Ag-FM-based electrode detected a low concentration of 4-NP (0.093 μM) and a linear response in the range of 1.0–15 μM. Furthermore, the Fe3O4/Ag-FM material also exhibited excellent reduction ability towards 4-NP with the assistance of NaBH4. This is because a synergistic effect formed between Ag nanoparticles and flower-like Fe3O4 magnetic microstructure enhanced the catalytic activity towards electrochemical detection and reduction of 4-NP. Overall, the current strategy could help design and synthesize future catalysts that can work as sensors and catalysts.

Photoelectrochemical Water Splitting with ITO/WO3/BiVO4/CoPi Multishell Nanotubes Enabled by a Vacuum and Plasma Soft-Template Synthesis.

A common approach for the photoelectrochemical (PEC) splitting of water relies on the application of WO3 porous electrodes sensitized with BiVO4 acting as a visible photoanode semiconductor. In this work, we propose a new architecture of photoelectrodes consisting of supported multishell nanotubes (NTs) fabricated by a soft-template approach. These NTs are formed by a concentric layered structure of indium tin oxide (ITO), WO3, and BiVO4, together with a final thin layer of cobalt phosphate (CoPi) co-catalyst. The photoelectrode manufacturing procedure is easily implementable at a large scale and successively combines the thermal evaporation of single crystalline organic nanowires (ONWs), the magnetron sputtering deposition of ITO and WO3, and the solution dripping and electrochemical deposition of, respectively, BiVO4 and CoPi, plus the annealing in air under mild conditions. The obtained NT electrodes depict a large electrochemically active surface and outperform the efficiency of equivalent planar-layered electrodes by more than one order of magnitude. A thorough electrochemical analysis of the electrodes illuminated with blue and solar lights demonstrates that the characteristics of the WO3/BiVO4 Schottky barrier heterojunction control the NT electrode efficiency, which depended on the BiVO4 outer layer thickness and the incorporation of the CoPi electrocatalyst. These results support the high potential of the proposed soft-template methodology for the large-area fabrication of highly efficient multishell ITO/WO3/BiVO4/CoPi NT electrodes for the PEC splitting of water.

Advances in MoS2based Hollow Structural Materials for High‐Performance Metal‐Ion Batteries

AbstractThe construction of a hollow structure could promote the diffusion of electrons and ions to improve the electrochemical performance of MoS2based materials for metal‐ion batteries. Herein, we summarize the preparation technique of MoS2hollow structural materials with different dimensions. The approaches to construct 0D hollow MoS2materials for electrodes of metal‐ion batteries can be divided into the hard template approach, soft template approach, self‐template approach, and template‐free approach. Among them, the hard template approach and self‐sacrifice template approach are controllable but complicated, the soft template approach and template‐free approach are simple and scalable but not controllable. Furthermore, as the electrode material of metal‐ion batteries including lithium‐ion battery, sodium‐ion battery, potassium‐ion battery or magnesium‐ion battery, the 0D hollow structural MoS2based materials could improve the diffusion kinetics of ion and electron and restrict the stack of MoS2. Furthermore, the 1D hollow MoS2can provide oriented electron diffusion along with the axial direction, and the 3D hollow MoS2can offer perforative pores for permeation of electrolytes and more active sites, which results in excellent rate capability and cycling stability. This paper could give inspiration for constructing MoS2hollow structural materials with different dimensions and provide a constructive suggestion for synthesizing hollow materials with excellent electrochemical performance.

Sol-Gel-Derived Ordered Mesoporous High Entropy Spinel Ferrites and Assessment of Their Photoelectrochemical and Electrocatalytic Water Splitting Performance.

The novel material class of high entropy oxides with their unique and unexpected physicochemical properties is a candidate for energy applications. Herein, it is reported for the first time about the physico- and (photo-) electrochemical properties of ordered mesoporous (CoNiCuZnMg)Fe2 O4 thin films synthesized by a soft-templating and dip-coating approach. The A-site high entropy ferrites (HEF) are composed of periodically ordered mesopores building a highly accessible inorganic nanoarchitecture with large specific surface areas. The mesoporous spinel HEF thin films are found to be phase-pure and crack-free on the meso- and macroscale. The formation of the spinel structure hosting six distinct cations is verified by X-ray-based characterization techniques. Photoelectron spectroscopy gives insight into the chemical state of the implemented transition metals supporting the structural characterization data. Applied as photoanode for photoelectrochemical water splitting, the HEFs are photostable over several hours but show only low photoconductivity owing to fast surface recombination, as evidenced by intensity-modulated photocurrent spectroscopy. When applied as oxygen evolution reaction electrocatalyst, the HEF thin films possess overpotentials of 420mV at 10mA cm-2 in 1m KOH. The results imply that the increase of the compositional disorder enhances the electronic transport properties, which are beneficial for both energy applications.

Mesoporogen-free synthesis of hierarchical zeolite A for CO2 capture: Effect of freeze drying on surface structure, porosity and particle size

Zeolite A is one of the admirable adsorbent used for CO2 adsorption. Intrinsically microporous zeolite A has the significant drawback of lower mass transfer rate and pore blockage even after functional modification. The development of hierarchical zeolite A can overcome these limitations by offering additional levels of pores. In this study, we developed hierarchical zeolite A with highly porous structure using an environmentally benign approach, i.e. hydrothermal followed by freezing-drying. This soft templating approach is economic and eliminates the use of eco-unfriendly organic templates or mesoporogen. The impact of freeze-drying (FDZA) on the development of hierarchical zeolite A was studied and compared with the traditional oven-drying (ODZA). The influence of freeze drying on the pore characteristics, crystallinity, and morphology of hierarchical zeolite A was explored. Better mass transfer rates and an 8% increase in carbon dioxide adsorption were achieved for FDZA compared to ODZA due to the increased porosity, surface area, and relatively lesser particle size. This study pointed to the freeze-drying as a novel approach for developing hierarchical pores in zeolite A.

Surfactant‐Mediated Synthesis of Novel Mesoporous Hollow CuO Nanotubes as an Anode Material for Lithium‐Ion Battery Application

AbstractIn this work, the hollow mesoporous CuO nanotubes are synthesized using a surfactant‐assisted soft template approach. It is believed that the surfactant used during the synthesis provides a skeleton for the rearrangement of nanoparticles, resulting in the formation of hollow nanotubes. Furthermore, the sample becomes mesoporous during the calcination at 500 °C due to the removal of the surfactant template. On the other hand, the porous nanostructure efficiently improves the reaction kinetics of the electrode material, which offers excellent electrochemical performance. The obtained hollow mesoporous CuO nanotube electrode manifests high Li‐ion storage such as ∼253 mAh g−1 at 1 C and 118 mAh g−1 at 3 C after 150 cycles. It is significant to highlight that the current synthesis process is straightforward, affordable, time‐efficient and environment friendly as compared to tedious physical approaches. In addition, the proposed strategy in this work also demonstrates a window for the development of new advanced nanomaterials for post‐lithium‐ion battery applications.

Metal–Nitrogen–Carbon Catalysts by Dynamic Template Removal for Highly Efficient and Selective Electroreduction of CO2

The renewable electroreduction of CO2 to CO is a key component of future clean energy scenarios. These scenarios allow for the recycling of carbon emissions into value-added chemicals which achieves the joint goal of reducing greenhouse gase(s) while producing valuable chemical product(s). A catalyst which has a high activity and selectivity for the electroreduction of CO2 to CO is highly desired for these applications. Nonprecious metal catalysts (non-PGM) and specifically metal–nitrogen–carbon (M–N–C) catalysts are prime cathode candidates as they are selective for CO and H2 formation with only trace amounts of other products such as CH4. The traditional method of production of atomically dispersed M–N–C proceeds either through a sacrificial poymer approach or through hard-templating the catalyst with silica. The other is through the direct pyrolysis of nonabundant metal macrocycles such as MOF-based precursors via a soft-templating approach. These syntheses have substantial industrial limitations as they require harsh acid or basic solvents for postpyrolytic removal of the support or they require rare chemical precursors. The method herein uses mechanochemical mixing of a fluorine-containing polymer with common pyrolytic precursors for the in situ removal of the template during the first pyrolysis. Further ball-milling and post-treatment in ammonia atmosphere yield a highly selective catalyst for CO2 reduction. The role of the metal center in these M–N–C catalysts in promoting CO2 reduction is explored (M = Fe, Ni, Co, Mn) vs the performance of metal-free N–C. A mechanistic pathway for CO2 reduction on the various M–N–C catalysts is suggested. The champion catalyst in terms of overall selectivity/activity (Ni–N–C) boasts a 98.9 ± 0.2% faradaic efficiency for CO formation (FEco) at −1.1 V vs RHE and an unmatched selectivity for CO2 reduction (FEco > 85%) even at low overpotential (E = −0.3 V vs RHE) compared to traditional Ni–N–C. The catalysts synthesized here present a promising class of electrocatalysts which may be explored for a range of electrocatalytic applications.