Zeolite-templated Carbon Research Articles

Simple synthesis of nitrogen-doped zeolite-templated carbon and its use in electric double-layer capacitors

Simple synthesis of nitrogen-doped zeolite-templated carbon and its use in electric double-layer capacitors

Simple synthesis of nitrogen-doped zeolite-templated carbon and its use in electric double-layer capacitors

Nitrogen-doped zeolite-templated carbon (N-doped ZTC) is synthesized using NaY zeolite as a template and with acrylonitrile (AN) and propylene as the respective nitrogen and carbon sources. AN is directly mixed with the dried zeolite for adsorption and the mixture is heated to synthesize polyacrylonitrile (PAN) inside the zeolite micropores. Each AN adsorption and polymerization step require only 1 h and both steps were performed in a single container. The resulting zeolite/PAN composite was then subjected to chemical vapor deposition using propylene to fill the zeolite pores with carbon. Subsequently, heat treatment was used for carbonization and the zeolite was removed with hydrofluoric acid. The N-doped ZTC has three-dimensionally ordered and interconnected micropores with a uniform pore size of 1.2 nm, inheriting the structural regularity of the zeolite. The optimum volume of AN is determined to be the same as the total pore volume of the zeolite, which accounts for the high surface area of 3680 m2 g−1 and high structural regularity with a N/C molar ratio of 0.015. The performance of the N-doped ZTC as an electric double-layer capacitor electrode was evaluated using an organic electrolyte and showed a superior performance to undoped ZTC and maintained a high capacitance retention up to 2 A g−1.

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

The thermal stability of carbon materials in the air: Quantitative structural investigation of thermal stability of carbon materials in air

The variability of the nanostructure of carbon materials results in a uniquely wide range of physical and chemical properties. This work analyses how the nanostructure affects the thermal stability of 2D and 3D graphene-based materials (graphene, fullerenes, nanotubes, zeolite-templated carbon), disordered and 3D ordered mesoporous carbon materials (activated carbons, CMK-3, 3DOMM), and layered carbon materials (few-layer graphene, graphene nanoplatelets, graphite) in the air. Combination of structural, thermogravimetric and calorimetric analyses under identical conditions for all the carbon nanomaterials showed that the most decisive factor increasing the stability is the stacking of graphene layers with long-range order parallel to each other, increasing the onset oxidation temperature (Ton) with the number of graphene layers from 530 °C for graphene up to 800 °C for graphite. The unsaturated carbon atoms at the defects and edges and the bending stress in the 3D graphene layers cause that graphene, the 3D non-defective monolayer in fullerenes and the defective monolayer in zeolite-templated carbon exhibit similar stability to disordered amorphous materials, as well as 3D organised mesoporous materials. All these materials are oxidized in a narrow Ton interval from 485 to 530 °C. The most significant factor for reducing the stability is the presence of specific oxygen-containing functional groups, which decrease Ton for materials with oxidized edges and with predominant hydroxyl groups by up to 150 °C. The relationships between the carbon structure and its stability in the air facilitate targeting the nanostructure of carbon materials in relation to their stability.

Structural heterogeneity of single-atom catalysts and true active site generation via ligand exchange during electrochemical H2O2 production

Although often overlooked, single-atom catalysts inevitably contain heterogeneous active sites and their structures can further change under reaction conditions. Here, we conduct rigorous in situ X-ray absorption spectroscopy with 1–10 wt% Pt on S-doped zeolite-templated carbon (SZTC) to elucidate their remarkable electrocatalytic H2O2 synthesis properties. SZTC with a curved polyaromatic framework and abundant sulfur functional groups can stabilize isolated Pt sites with up to 10 wt% Pt loading. Although all catalysts contain apparently identical Pt–S4 sites in their as-synthesized form, the Pt-specific activity increases rapidly with increasing Pt loading. It appears that Pt first forms inert Pt–S4 in SZTC and then forms labile Pt–S4 with increasing Pt loading. Upon contact with aqueous electrolytes, only the labile sites are converted to true active sites, Pt–S2(H2O)2, via ligand exchange with H2O. The results provide invaluable insights for understanding the heterogeneity and dynamic structural changes of single-atom catalysts.

The role of alkali metal exchange in zeolite-templated carbon synthesis

The role of alkali metal exchange in zeolite-templated carbon synthesis

Zeolite-templated carbon-supported Ru-based catalysts for efficient alkaline hydrogen evolution reaction.

Herein, a series of Ru/ZTCs samples were prepared using LaY zeolite-templated carbon as a support. Characterizations showed that the unique structure of the ZTCs and the chemical state of Ru facilitated superior HER performance compared to other carbon-supported samples. This work offers a new strategy for designing excellent electrocatalysts.

The role of alkali metal exchange in zeolite-templated carbon synthesis

The role of alkali metal exchange in zeolite-templated carbon synthesis

N/S co-doped microporous zeolite-templated carbon for efficient CO2 adsorption and separation

Heteroatomic doping of porous carbon materials can give rise to variations in the electronic structure and properties, and has been used to enhance the adsorption and separation of CO2. Herein, N and S doped zeolite-templated carbon (ZTC) are synthesized to study their CO2 adsorption and selective from CO2/N2. ZTC-N, ZTC-S and ZTC-NS exhibit comparatively high CO2 adsorption of 6.12, 7.73 and 9.32 mmol g−1 at 0 °C, which are more than three times than that of ZTC (1.98 mmol g−1). The CO2 adsorption capacity for ZTC-NS at 25 °C and 1 bar can reach as high as 6.03 mmol g−1, which can still occupy approximately 96% after 5 cycles. The obtained carbon materials ZTC-NS with the smallest BET surface area show the highest CO2 adsorption capacity, which indicate an obvious synergistic enhancement effect between sulfur and nitrogen doping. The detailed theoretical calculations indicate N and S co-doping into porous carbon materials assists the change of electrostatic surface potential and local electronic density, thus enhanced the CO2 adsorption.

The role of alkali metal exchange in zeolite-templated carbon synthesis

The role of alkali metal exchange in zeolite-templated carbon synthesis

Methodological Studies of the Mechanism of Anion Insertion in Nanometer-Sized Carbon Micropores.

Dual-ion hybrid capacitors (DIHCs) are a promising class of electrochemical energy storage devices intermediate between batteries and supercapacitors, exhibiting both high energy and power density, and generalizable across wide chemistries beyond lithium. In this study, a model carbon framework material with a periodic structure containing exclusively 1.2 nm width pores, zeolite-templated carbon (ZTC), was investigated as the positive electrode for the storage of a range of anions relevant to DIHC chemistries. Screening experiments were carried out across 21 electrolyte compositions within a common stable potential window of 3.0-4.0 V vs. Li/Li+ to determine trends in capacity as a function of anion and solvent properties. To achieve fast rate capability, a binary solvent balancing a high dielectric constant with a low viscosity and small molecular size was used; optimized full-cells based on LiPF6 in binary electrolyte exhibited 146 Wh kg-1 and >4000 W kg-1 energy and power densities, respectively.

Microporous three dimensional ordered zeolite-templated carbon for efficient removal of VOCs: Experimental study and molecular dynamics simulation

Zeolite-templated carbon (ZTC), a three dimensional ordered carbon material, was synthesized by chemical vapor deposition for use as an efficient adsorbent for the removal of volatile organic compounds (VOCs). A series of ZTC samples with different deposition temperatures and deposition times were evaluated, and the effect of O2, SO2, and H2O on VOCs adsorption was studied. ZTC prepared at 600 °C for 7 h had less defects and more graphite carbons, exhibited the largest specific surface area of 2011.5 m2/g, and also showed the best performance with a toluene, benzene, and m-xylene adsorption capacity of 202.5 mg/g, 147.4 mg/g, and 206.4 mg/g, respectively. O2 can promote the removal ability in the first 20 min, but then which begins to develop in the direction of inhibiting the removal ability. SO2 and H2O decreased the toluene, benzene, and m-xylene adsorption capacity due to the competition·H2O has the most obvious inhibitory effect on the removal capacity. The simulation results also demonstrated that toluene is mainly adsorbed in the micropores, and the addition of H2O, SO2, and O2 will eventually affect the diffusion and adsorption process of toluene.

Three-dimensional ordered zeolite-templated carbon with covalent sulfur for efficient removal of elemental mercury: Experimental study and molecular dynamic simulation

Traditional activated carbon used to remove elemental mercury (Hg0) from coal-fired power plants exhibit an irregular porous structure, showing an adverse effect on the removal of Hg0. To obtain carbon materials with a regular porous structure, zeolite-templated carbon samples (ZTC and S-doped ZTC) with a three-dimensional ordered structure were synthesized via the chemical vapor deposition (CVD) method using C2H2 and H2S as the carbon and sulfur precursor on BEA zeolite. Several techniques including TG-MS, SEM-TEM-EDS, etc. were used to determine that ZTC replicated the regular microporous structure of zeolite and generated turbostratic carbon. Moreover, the Hg0 removal efficiency (MRE) of ZTC samples was investigated. At 30 °C, they removed Hg0 mainly by physisorption, while at 150 °C, chemisorption was the dominant approach for capturing Hg0. The influence of flue gas components (H2O, NH3, and SO2) on the MRE of ZTC-HS was further studied by experimental methods and molecular dynamic (MD). H2O and NH3 weakened the MRE of ZTC-HS due to the competing adsorption. The effect of SO2 on the MRE of ZTC-HS was related to its concentration. Because of its advantages in regeneration features, preparation cost and higher resistance to flue gas components, ZTC-HS exhibited the potential for industrial applications.

Utilization of starch and cellulose toward facile synthesis of high surface area zeolite-templated carbon

• Starch and cellulose are examined to synthesize zeolite-templated carbons (ZTCs). • Gravimetric surface area is maximized to 3760 m 2 g −1 by using starch. • Volumetric surface area is maximized to 790 m 2 g −1 by using cellulose. • EDLC performances of the ZTCs are evaluated using an organic electrolyte. • The present method does not use liquid-phase adsorption or any organic solvents. Starch and cellulose are examined to synthesize high surface area zeolite-templated carbons (ZTCs). In this method, starch or cellulose is mixed with undried NaY zeolite as a template, and the mixture is subject to chemical vapor deposition (CVD) using propylene and subsequent heat treatment, followed by zeolite removal with HF. For maximizing the structural regularity and surface area of ZTC, a necessary amount of starch is only equal to the total pore volume of the zeolite ( i.e. , 0.5 g per 1 g of the zeolite). Upon heating, starch is decomposed into oligosaccharides and the oligosaccharides are adsorbed inside the micropores of the zeolite before the CVD. The adsorbed oligosaccharides are pyrolyzed into nanographenes, and the nanographenes are extended and interconnected together to form the three-dimensional ZTC framework inside the zeolite pores during the CVD. The resulting gravimetric and volumetric surface areas are 3760 m 2 g −1 and 630 m 2 cm −3 , respectively. Meanwhile, cellulose is not readily decomposed into oligosaccharides, and a necessary amount of cellulose is 1.4 times larger than that that of starch to maximize the high structural regularity, yielding the gravimetric and volumetric surface areas of 3330 m 2 g −1 and 670 m 2 cm −3 , respectively. A decrease in the gravimetric surface area is explained by the formation of cellulose-derived amorphous carbons on the surface of ZTC particles. However, the difference in their volumetric surface areas is negligible because the amorphous carbons are so small that they do not expand the volume of the densified ZTC. Consequently, the ZTC prepared using cellulose shows high volumetric capacitance and high capacitance retention even at 10 A g −1 as an electric double-layer capacitor electrode, due to the existence of amorphous carbons that enhance the electrical conductivity of the electrode.

Zeolite-templated sub-nanometer carbon nanotube arrays and membranes for hydrogen storage and separation

Adsorbents and membranes consisting of carbon nanotube (CNT) pores with diameters of molecular dimensions are highly desirable for hydrogen storage and selective, high-flux membrane separation. However, fabrication of such materials with precise pore sizes and monodispersity as well as evaluation of the mechanisms associated to adsorption and molecular transport are challenging. Herein, we grew aluminophsphate zeolites (CoAPO-5, AFI crystal structure) consisting of one-dimensional, monodisperse parallel pores with diameter of ∼7 Å, and utilized them as templates to grow singe-walled CNTs (SWNTs) inside the pores. The resulting materials were examined as adsorbents and membranes for hydrogen storage and separation, respectively, using single-gas and real mixture feeds. Detailed mechanistic analysis and fundamental investigation of permeance and adsorption behavior of the resulting CNT-in-zeolite systems via combined adsorption, equilibrium, and kinetic studies were carried out. A superior gravimetric hydrogen uptake of 1.2 wt% at 35 °C and 1 bar was achieved in the case of the SWNTs grown in the cobalt-richer AFI host. Permeability measurements were performed on the respective Co(x)APO@SWNT membranes with the Co-richAPO@SWNT membrane exhibiting the highest permeance for all studied gases as a consequence of larger and more densely packed AFI crystals along with higher number of SWNT-filled pores, assets attributed to the higher Co catalyst content. Notably, the produced composite membranes exhibited gas permeability values that were two orders of magnitude higher than what predicted by the Knudsen mechanism.

High-capacity hydrogen storage in zirconium decorated zeolite templated carbon: Predictions from DFT simulations

The hydrogen (H2) storage capacity of Zirconium (Zr) decorated zeolite templated carbon (ZTC) has been investigated using sophisticated density functional theory (DFT) simulations. The analysis shows that the Zr atom gets bonded with ZTC strongly with binding energy (BE) of −3.92 eV due to electron transfer from Zr 4d orbital to C 2p orbital of ZTC. Each Zr atom on ZTC can attach 7H2 molecules with average binding energy of −0.433 eV/H2 providing gravimetric wt% of 9.24, substantially above the limit of 6.5 wt% set by the DoE of the United States of America. The H2 molecules are involved via Kubas interaction with Zr atom, which involves the charge transfer between Zr 4d orbital and H 1s orbital with interaction energy higher than physisorption but lower than chemisorption. The structural integrity of the system is confirmed via molecular dynamics (MD) simulations at room temperature and at highest desorption temperature of 500 K. We have investigated the chances of metal clustering by computing diffusion energy (ED) barrier for the movement of Zr atom, and we obtained via calculation, we can infer that the presence of ED barrier of ∼2.36 eV may prevent the possibility. As the system ZTC has been synthesized, Zr doped ZTC is stable, existence of sufficient diffusion barrier prevents the clustering and adsorption energy and wt% of H2 are within the range prescribed by DoE, we feel that Zr decorated ZTC can be fabricated as promising hydrogen storage material for fuel cell applications.

Direct conversion of methane to zeolite-templated carbons, light hydrocarbons, and hydrogen

Efficient direct valorization of methane to value-added chemicals and materials remains an unsolved challenge for modern chemistry and materials science. In this work, we explored direct non-oxidative conversion of methane to hydrogen, hydrocarbons, and valuable zeolite-templated carbon materials. First, using a set of spectroscopy and microscopy characterization tools, we investigated how the reaction conditions influence the process of carbon formation inside the typical zeolite-based catalyst Mo/ZSM-5. Then, we explored the effect of the zeolite topology on the growth of carbon materials from methane decomposition over Mo/MFI, Mo/MOR, Mo/BEA, and Mo/FAU templates. Finally, we applied the obtained insights to prepare high-quality zeolite-templated carbons directly from methane using Fe/BEA and Fe/FAU templates. Altogether, our results represent a carbon-economic method of methane conversion to COx-free hydrogen gas, a mixture of light aliphatic and aromatic hydrocarbons, and valuable carbon materials.

Adsorption properties of templated nanoporous carbons comprising 1–2 graphene layers

Various types of vapor adsorption (water, methanol, ethanol, dichloromethane, and n-hexane) were examined on templated nanoporous carbons comprising 1–2 graphene layers, e.g., microporous zeolite-templated carbon (ZTC), mesoporous carbon mesosponge (CMS), and graphene mesosponge (GMS). Conventional nanoporous carbon materials are used as references. Although water-vapor adsorption is unique owing to the repulsion between H2O molecules and hydrophobic carbon, organic-vapor adsorption follows a typical physisorption mechanism. Graphene-based nanoporous materials exhibit an evident degree of adsorption-induced expansion based on their extraordinary softness, except in the case of inferior water-vapor adsorption on mesoporous CMS and GMS. CMS exhibits a considerable degree of adsorption-induced expansion and can achieve high adsorption capacities up to 4.25–4.76 cm3 g−1 for organic vapors, demonstrating its feasibility as a high-capacity adsorbent. The adsorption isotherms of ZTC at 278 and 298 K for n-hexane overlap well, which is advantageous for a new heat pump working with a force-induced phase transition. Moreover, this study helps predict the ease of organic-vapor adsorption based on the product of the surface tension and molar volume.

Facile Synthesis of High Surface Area Zeolite-Templated Carbon from Sugars and Propylene

Zeolite-templated carbons (ZTCs) with high surface areas of ≥3750 m2 g–1 are facilely synthesized from sugars and propylene as carbon sources using NaY zeolite as a template. The zeolite need not be previously dried to remove adsorbed water and can be directly mixed with sugars. The mixture is subject to chemical vapor deposition (CVD) of propylene at 700 °C and subsequent heat treatment at 900 °C, followed by HF etching for zeolite removal. In this study, α-d-glucose, β-d-glucose, d-xylose, d-fructose, and d-sucrose are examined, and a necessary amount of all the sugars per 1 g of the zeolite is reduced to only 0.32 cm3, which corresponds to the total pore volume of the zeolite, for maximizing the surface area and structural regularity of ZTC. Upon heating, adsorbed water desorbs from the zeolite, and the sugars are adsorbed inside the micropores of the zeolite below 300 °C. The adsorbed sugars are carbonized into nanographenes, and the nanographenes are extended and interconnected together via a graphene growth reaction during the CVD. Consequently, the three-dimensionally ordered and interconnected pore structure with a uniform pore size of 1.2 nm is recovered by HF etching, yielding 0.3 g of ZTC per 1 g of the zeolite. The present synthetic method does not require any solvents for adsorption of sugars, and therefore, high surface area ZTCs would become widely and readily available as adsorbents and electrodes for practical applications and fundamental studies.

Novel permeable material “yttrium decorated zeolite templated carbon” for hydrogen storage: Perspectives from density functional theory

The hydrogen storage capacity of a novel permeable material viz Yttrium (Y) decorated zeolite templated carbon (ZTC) has been investigated using ab-initio DFT based simulations. The study reveals that each Y atom bonded on ZTC can attach at the most of 7H2 molecules with average binding energy of −0.35 eV/H2. The gravimetric hydrogen storage capacity of ZTC with full decoration of Y atom comes about to 8.61 wt% which is sufficiently higher than the limit of 6.5 wt% set by the energy department of the United States of America. The desorption temperature of the system is 437 K. The stability of the structure over such an elevated temperature has been ensured via molecular dynamics (MD) simulations. The stability of the structure at room temperature and presence of sufficient energy barrier for the diffusion of Y atom signifies that the chances of metal-metal clustering are negligible. It has been discerned that it is the Kubas interaction which plays the key role in the interaction between Y and H2 molecules. The outcomes show that ZTC adorned with Y is a capable material for hydrogen storage which will inspire the instrumentalists to fabricate ZTC based fuel cell device.