Micro-mesoporous Carbon Research Articles

Advanced all-solid-state lithium-selenium batteries enabled by selenium-nitrogen doped hierarchic meso-microporous carbon nanospheres composite cathode

Selenium, an element belonging to the same group in the periodic table as sulfur, has a high electronic conductivity (1 × 10−5 S/cm) and a high volumetric energy density (3253 mAh/cm3), which is a prospective cathode material for high-energy all-solid-state rechargeable batteries. However, its wide use is hindered by large volume expansion and low utilization rate. In this work, Se-infused nitrogen-doped hierarchical meso-microporous carbon composites (Se/NHPC) are prepared by a melt-diffusion process. Amorphous Se is uniformly dispersed in meso-micropores of NHPC with a high mass loading of 81%. All-solid-state Li-Se batteries fabricated by using Se/NHPC as the cathode, a Li-In alloy as the anode, and Li6PS5Cl as the solid-state electrolyte, deliver a highly reversible capacity of 621 mAh/g (92% of theoretical capacity), a good rate capability and a high capacity retention value of 80.9% after 100 cycles. It is found that the capacity decay of Se cathode is mainly related to the interfacial degradation and the separation of Se from the carbon substrate, as suggested by the continuous increase of interfacial resistance and the structural transformation from amorphous Sen chains to Se8 rings initial discharge/charge cycle and then to the trigonally crystalline Se chains structure after the long-term cycles.

Synthesis of novel and tunable Micro-Mesoporous carbon nitrides for Ultra-High CO2 and H2S capture

Carbon nitride (CN) materials with intrinsic high nitrogen content are potential candidates for acidic gas adsorption. However, these nanomaterials should be further treated to achieve tunable textural properties for ultra-high gas adsorption. Herein, we synthesized dual-pore carbon nitride materials (DP-CN) with a series of ethylenediamine to carbon tetrachloride ratios with different amounts of potassium hydroxide (KOH) as a chemical activator using nanosilica (SiO2) as a hard template to tune the physicochemical properties of the materials. The prepared DP-CN adsorbents had a large surface area (up to 2036.9 m2/g), great pore volume (up to 1.15 cm3/g), and high nitrogen content (10.6 to 15.1 wt%). The best DP-CN displayed ultra-high CO2 and H2S adsorption capacity at 1 bar (8.3 and 13.8 mmol/g, respectively), 10 bar (16.9 and 23.1 mmol/g, respectively), and 30 bar (22.9 mmol/g for CO2) at 25 °C, which was significantly higher than those of other pure mesoporous carbon nitrides (M-CN) and carbon-based adsorbents. Moreover, the best adsorbent exhibited good CO2/N2, CO2/CH4, H2S/N2, and H2S/CH4 selectivity, suitable heat of adsorption, and excellent cyclic stability. According to density functional theory calculations, H2S adsorbs more strongly than CO2 on carbon nitride surfaces, and the adsorption energies of CO2 and H2S are related to charge-transfer values from the surface to the adsorbed species. The results revealed that the exceptional textural properties and high nitrogen content of the materials could play the main role in the superior adsorption of CO2 and H2S. This generation of CN materials is expected to be practical for a various range of separation processes, catalysis, capacitors, and energy storage.

Synthesizing MOF-derived Ni[sbnd]N[sbnd]C catalyst via surfactant modified strategy for efficient electrocatalytic CO2 to CO

Recently, Ni, N-doped carbon (NiNC) electrocatalysts synthesized using metal–organic frameworks (MOFs) as templates have demonstrated attractive catalytic performances in the CO2 reduction reaction (CO2RR). However, most of the reported preparations of MOFs-based precursors are carried out in organic solvents, and the resulting NiNC materials have relatively low metal loadings and mainly exhibit microporous structures, which is unfavorable for the mass transport. Herein, Ni, N-doped meso-microporous carbon electrocatalysts with a range of Ni loadings (M−NiNCx/CNTs) were prepared by the pyrolysis of MOFs-based precursors synthesized in aqueous solution using the surfactant cetyltrimethylammonium bromide (CTAB) as a modifier to promote the adsorption of Ni2+ ions and the formation of mesopores. Owing to the unique morphology, porous structure and high contents of Ni-Nx sites and pyrrolic-N, the optimal catalyst (M−NiNC2/CNTs) shows superior electrocatalytic activity for the CO2RR with a maximum CO Faradaic efficiency (FECO) of 98 % at −0.7 V vs. reversible hydrogen electrode (RHE), and the FECO can reach over 80 % in a wide potential range of −0.5 to −1.0 V vs. RHE. This work develops a facile and environmentally friendly strategy to obtain high-performance and low-cost transition metal-nitrogen-doped porous carbon electrocatalysts for the CO2RR.

One-step green synthesis of meso-microporous carbons by self-activation of lemon wastes for high-performance supercapacitors

A green self-activating system is introduced for the synthesis of porous carbons. This system is introduced to overcome the environmental concerns regarding the harmful by-products of the conventional synthesis approaches. The introduced system is based on the circulating active gases, released during the carbonization treatments at T ≤ 500 °C. These active gases are stored in the system and participate in the activation process at T ≥ 700 °C. During the activation process, there is no exhaust gas and any need for a protective atmosphere. Lemon wastes were pyrolyzed in this system at several temperatures (400 to 900 °C). It is demonstrated that the introduced system is applicable for the synthesis of turbostratic carbons with relatively high graphitization levels. Pyrolyzation at T ≥ 800 °C can appropriately activate the lemon biomass. The prepared meso-microporous carbon has a large specific surface area of up to 2111 m2.g−1 and a pore volume of 1.28 cm3.g−1 can be obtained after pyrolyzation at 900 °C. Meso-microporous carbon are applied as an electrode for supercapacitors. The prepared supercapacitor performs an electric double layer with minor pseudo-capacitance behavior. The supercapacitor illustrates the capacitance of 254 F.g−1 at 10 A.g−1 and excellent stability of 92 % retention after 30,000 cycles.

Carboxylated graphene oxide nanosheets as efficient electrodes for high-performance supercapacitors.

In the presence of dry ice, a series of graphitic materials with carboxylated edges (ECGs) were synthesized by ball milling graphite for varied times (24, 36, and 46 h). The influence of carboxylation on the physiochemical characteristics and electrochemical performance as effective electrodes for supercapacitors were assessed and compared with pure graphite. Several characterization techniques were employed to investigate into the morphology, texture, microstructure, and modification of the materials. Due to its interconnected micro-mesoporous carbon network, which is vital for fast charge-discharge at high current densities, storing static charges, facilitating electrolyte transport and diffusion, and having excellent rate performance, the ECG-46 electrode among the investigated samples achieved the highest specific capacitance of 223 F g−1 at 0.25 A g−1 current density and an outstanding cycle stability, with capacitance retention of 90.8% for up to 10,000 cycles. Furthermore, the symmetric supercapacitor device based on the ECG-46 showed a high energy density of 19.20 W h kg−1 at 450.00 W kg−1 power density. With these unique features, ball milling of graphitic material in dry ice represents a promising approach to realize porous graphitic material with oxygen functionalities as active electrodes.

Synthesis free‐template highly micro‐mesoporous carbon nanosheet as electrode materials for boosting supercapacitor performances

Porous carbon 2D nanosheets (CNSs) with micro-mesopores interconnected are indispensable for energy conversion systems and storage applications. Herein, we synthesize free-template highly micro-mesoporous carbon nanosheet as electrode material for boosting supercapacitor performances. The activated carbon nanosheets derived from bio-waste were prepared by chemical impregnation followed by high-temperature pyrolysis without hard/soft/salt template-assisted and free-binder adhesives. Garlic skin wastes were selected as a precursor. Furthermore, activated carbon was designed in pellet/coin solids without the addition of binder materials. The porous carbon pellets exhibit a thin 2D nanosheet structure of 15 nm followed by unique wooden labyrinth-like and rod-like structures. The result showed that the impregnation of different chemical concentrations increases the surface area to 273% as high as 1002.920 m2 g−1 with a total volume of 1.3270 cm3 g−1. Moreover, the mesoporosity dominated 66.4%, followed by sub-ultra-micropores. In the symmetric supercapacitor, the carbon nanosheet boosted the specific capacitance almost 3-fold to 320.95 F g−1 in the aqueous electrolyte of 1 M H2SO4. The supercapacitor cell has a high energy density of 43.12 Wh kg−1 and power density of 161.99 W kg−1 at a constant current density of 1.0 A g−1. This work proposes a more effective, green, efficient, and controlled approach to obtain bio-waste-based porous carbon 2D nanosheet with a controlled pore structure for energy conversion and storage systems. Novelty Statement The novelty of this study is a green synthesis has possessed highly micro-mesopores nanosheet bio-waste. 2D nanosheet was prepared free-template and free-binder. Sub-ultra-micropores were confirmed with dominated mesoporosity of 66.8%. Carbon nanosheet boosted specific capacitance almost 3-fold to 320.95 F g−1.

Composition, Morphology, and Interface Engineering of 3D Cauliflower‐Like Porous Carbon‐Wrapped Metal Chalcogenides as Advanced Electrocatalysts for Quantum Dot‐Sensitized Solar Cells

AbstractDesigning a low‐cost, highly efficient, and stable electrocatalyst that can synergistically speed up the reduction of polysulfide electrolytes while operative for long periods in the open air is critical for the practical application of quantum dot‐sensitized solar cells (QDSSCs), but it remains a challenging task. Herein, a simple, straightforward, and two‐step nanocomposite engineering approach that simultaneously combines metallic copper chalcogenides (MC) either Cu2−xS or Cu2−xSe with S, N dual‐doped carbon (SNC) sources for devising high‐quality counter electrode (CE) film are reported. First, the hierarchically assembled MC nanostructures are obtained using microwave‐assisted synthesis. Second, these MCs are embedded within an ordered macro–meso–microporous carbon matrix to obtain Cu2−xS@C or Cu2−xSeS@C CE. These CEs are demonstrated to have composition dependents crystal structure, surface morphologies, photovoltaic performance, and electrochemical properties. In terms of power conversion efficiency (PCE), the Cu2−xSeS@C (9.89%) and Cu2−xS@C‐CE (8.96%) constructed QDSSCs outperform both Cu2−xSe (8.96%) and Cu2−xS‐constructed (7.79%) QDSSCs, respectively. The enhanced PCE could be attributed to the synergistic interaction of S and N dopants with MC interfaces that can not only enrich electric conductivity, and a higher surface‐to‐volume ratio but also offers a 3D network for superior charge transport at the interface.

Interconnected micro-mesoporous carbon nanofiber derived from lemongrass for high symmetric supercapacitor performance

The hierarchical porous activated carbon nanofiber has been prepared and characterized from the biomass based of lemongrass leave waste (LG). The preparation process used a simple technique through impregnation of ZnCl2 with low concentrations (0.5, 0.7 and 0.9) mol/L. These three concentrations were chosen to maximize the potential of LG to produce carbon nanoporous structures with high surface area. The preparation of activated carbon is performed by a one-step technique, including carbonization and physical activation at a temperature of 800 °C in N2/CO2 atmosphere. The three sample variations resulted in a very good amorphous structure according to the XRD pattern. The sample LG-0.7 has been known to have the best physical and electrochemical properties with an SSA reaching 1694 m2 g−1 with a carbon content of 90.38%. Uniquely, the LG-0.7 sample has a combined morphological appearance of hierarchical pores such as sponges and nanofiber pores. This combined pore strongly supports the electrochemical properties of the carbon electrode with 256 F g−1, a specific energy of 35.6 Wh kg−1 and a power density of 128.3 W kg−1 obtained using the GCD method. Electrochemical testing was carried out at a low potential of 0–1 V with a scan rate of 1 mV s−1 under the influence of an aqueous electrolyte of 1 M H2SO4. These results demonstrate the tremendous potential of lemongrass leaf waste as a raw material for the produce of porous carbon electrodes for high-performance supercapacitors.

Synthesize C@SiO2 with independent spaces produced from carbon slices by the confinement of the silica shell for toluene adsorption

Porous carbons with controlled pore structure have attracted great interest owing to their excellent application potential. Herein, we report a simple synthetic route to synthesize the core-shell C@SiO2 spheres with various pore structures by calcining core-shell structured RF@SiO2 (RF = resorcinol-formaldehyde resin). The obtained C@SiO2 spheres had high surface areas (238.5–732.5 m2/g), large pore volume (0.111–0.647 cm3/g) and abundant micro-mesoporous structure. The mesopore size of C@SiO2 spheres can be easily turned in the range of 8–15 nm, by simply modifying the carbonization temperature, size and heating rate of RF@SiO2 spheres. Among these, S–C@SiO2-400 spheres had higher mesopore volume of 0.207 cm3/g, this was related to internal carbon slices structure. Meantime, the toluene adsorption capacity of S–C@SiO2-400 spheres could reach 448.2 mg/g, which increased by 88.73% compared to ordinary carbon spheres. Moreover, the formation mechanism of the mesopore carbon slices structure was evaluated based on controlled experiments. This work provides a new synthetic method of micro-mesoporous carbon spheres, which can further enrich the application of carbon materials.

Nitrogen and phosphorous co-doped hierarchical meso—microporous carbon nanospheres with extraordinary lithium storage for high-performance lithium-ion capacitors

Lithium-ion capacitors (LICs), consisting of a battery-like negative electrode and a capacitive porous-carbon positive electrode, deliver more than twice the energy density of electric double-layer capacitors. However, their wide application suffers from low energy density and reduced cycle life at high rates. Herein, hierarchical meso—microporous carbon nanospheres with a highly disordered structure and nitrogen/phosphorous co-doped properties were synthesized through a facile template method. Such hierarchical porous structure facilitates rapid ion transport, and the highly disordered structure and high heteroatom content provide abundant active sites for Li+ charge storage. Electrochemical experiments demonstrated that the carbon nanosphere anode delivers large reversible capability, greatly improves rate capability and exhibits excellent cycle stability. An LIC fabricated with the carbon nanosphere anode and an activated carbon cathode yields a high energy density of 103 W h kg−1, an extremely high power density of 44,630 W kg−1, and long-term cyclability of over 10,000 cycles. This work presents how structural control of carbon materials at the nano/atomic scale can significantly enhance electrochemical performance, enabling new opportunities for the design of high-performance energy-storage devices.

Preparation of nitrogen-doped porous carbon by urea–formaldehyde resin for the construction of membrane adsorption reactor to remove refractory pollutant

• UFCA was prepared by carbonization and activation of urea-formaldehyde resin. • UFCA-900 was used to adsorb quinoline, phenol and pyridine with high capacities. • Membrane adsorption reactor with UFCA-900 continuously remove quinoline. • The mechanism is electrostatic interactions, π-π interactions and hydrogen bonds. Considering the highly toxic by-products generation and environmental friendliness, the adsorption process is a suitable solution as the end of pipe treatment for refractory organics in coking wastewater. Nitrogen-doped micro-mesoporous carbon prepared by carbonization and KOH activation of urea–formaldehyde resin (UFCA) realized effective adsorption of quinoline, phenol and pyridine in coking wastewater. Among them, UFCA-900 has large specific surface area (S BET = 1469.94 m 2 g −1 ) and excellent adsorption properties: the adsorption removal rate of quinoline reached 98.40% about 16 min, and the maximum adsorption capacity of quinoline was 721.90 mg·g −1 at 318 K, the adsorption capacity of phenol and pyridine at 298 K were 341.59 mg·g −1 and 225.08 mg·g −1 , respectively. The adsorption kinetics of UFCA-900 obeyed the pseudo-second-order model, and the adsorption process was endothermic. The membrane adsorption reactor demonstrated efficient adsorption, well separation, and negligibly irreversible membrane fouling. The adsorption mechanism included electrostatic interactions, π-π interactions and hydrogen bonds. Regeneration test proved that the removal rate of the chemically regenerated UFCA-900 was similar to the fresh adsorbent after six cycles. Taken together, a simple strategy for in-situ nitrogen-doped porous carbon has been developed and the resultant composite UFCA-900 has promising application prospect in coking wastewater treatment.

The sequential structural transformation of a heptanuclear zinc cluster towards hierarchical porous carbon for supercapacitor applications.

The peripheral N/O chelating of Schiff base ligands, inner bridges, counterions, and metal centers gave rise to a brucite disk cluster [Zn7L6(OCH3)6](NO3)2 (Zn7, (HL = 2-methoxy-6-((methylimino)-methyl)phenolate)) which crystallized into hexagonal prismatic plates. The combination of crystallographic studies, in situ TG-MS, and other characterization techniques showed that with a fixed metal and ligand composition in the precursors, weak correlative interactions (e.g., electrostatic interactions) and shape matching between the cluster core and counterions determine the cluster packing modes in the crystals and affect their phase and morphological changes during pyrolysis. The tracking of the pyrolysis process showed that the peripheral ligands, inner bridge, and counterion decompose first, followed by the Zn7O6 core merging with cubic ZnO, which was then reduced by carbon and eventually evaporated, leaving behind a porous carbon structure. In this process, the solid material composition change was in the sequence {Zn7}-{Zn-O core@C}-{ZnO@C}-{Zn@C}-{C}, which was accompanied by a porosity change from micropores to hierarchical pores, and then to micropores again. The core structure and packing modes of Zn7 evolved into micropores and mesopores, respectively. Micro-mesoporous carbon Zn7-1000 featured a capacitance of 1797 F g-1 at 1 A g-1, where the BET specific surface area was 3119.18 m2 g-1, which, to the best of our knowledge, is the highest value reported for a porous carbon electrode. This work represents an important benchmark for the analysis of dynamic chemical processes involving coordination clusters at high temperatures, and it could lead to important applications in high-performance devices.

Synthesis of Novel and Tunable Micro-Mesoporous Carbon Nitrides for Ultra-High Co2 and H2s Capture

Synthesis of Novel and Tunable Micro-Mesoporous Carbon Nitrides for Ultra-High Co2 and H2s Capture

Zinc chloride-activated micro-mesoporous carbon material derived from energy grass and its electrocatalytic performance toward oxygen reduction reaction

Biomass is an ideal candidate for the preparation of nano-carbon catalyst because of its inherent porous structure and abundant heteroatoms. However, the rational design of the structure remains challenging. In this work, a biomass-based carbon material with micro‑meso porous structure, high specific surface area and abundant active sites was fabricated by the activation of ZnCl2. The correct additive amount of activator is essential to affect the surface composition and structures. In order to achieve a high-performance carbon catalyst, the activation mechanism of ZnCl2 for the pyrolysis of elephant grass (EG) was also investigated. The electrochemical measurements revealed that the obtained carbon catalyst with an EG:ZnCl2 ratio of 1:1 showed superior electrocatalytic properties for ORR over a wide pH range, due to the its large surface area (1119.83 m2g−1), hierarchical structure and abundant N content (pyridine-N/graphite-N/pyrrolic-N). The abundant micro/mesoporous structure provides accessible channels for the transport of O2, H2O and intermediate products (OH*, O2*). This study provides a simple and low-cost method for the effective conversion of biomass to nano-carbon materials, which shows great application potential for fuel cells.

Light olefins synthesis from CO2 hydrogenation over mixed Fe–Co–K supported on micro-mesoporous carbon catalysts

Recycling CO2 into light olefins is a promising approach to reduce CO2 emissions. To promote this technology, an efficient catalyst with high activity and selectivity towards light olefins is imperative. In this work, a series of Fe–Co–K supported on micro-mesoporous carbon (MMC) and microporous carbon (MC) with different metal loading contents (20–80 wt%) were prepared for CO2 hydrogenation to light olefins. Impregnating mixed metal oxides on both MMC and MC reduced particle sizes and enhanced their dispersion and reducibility, yielding a higher CO2 conversion compared to the unsupported Fe–Co–K catalyst. The metal oxides were highly dispersed inside the micropores of MC support, achieving the highest CO2 conversion. However, the high dispersion of metal oxides inside micropores led to the formation of isolated particles with a low interfacial contact with each other, resulting in a low light olefins selectivity. The MMC support provided a lower degree of metal dispersion, creating more interfacial contact area, promoting the selectivity towards olefins. Overall, the 60 wt% Fe–Co–K supported on MMC catalyst exhibited the highest light olefins yield of 10.8% at 400 °C and 20 bar and excellent stability.

Zinc-salt assisted synthesis of three-dimensional oxygen and nitrogen co-doped hierarchical micro-meso porous carbon foam for supercapacitors

Nitrogen and oxygen co-doped hierarchical micro-mesoporous carbon foams has been synthesized by pyrolyzation treatment of a preliminary foam containing melamine and formaldehyde as nitrogen, carbon and oxygen precursors and Zn(NO3)2. 6H2O and pluronic F127 as micro-meso pores generators. Several characterizations including thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Raman spectroscopy, FTIR and X-ray photoelectron spectroscopy, N2 adsorption–desorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were performed on the prepared foams. X-ray diffraction patterns, Raman spectra and N2 adsorption–desorption results confirmed that ZnO has pronounced effect on the graphitization of the prepared carbon foam. From X-ray diffraction, thermal gravimetric and N2 adsorption–desorption analysis results it was confirmed that the carbothermal reaction and the elimination of ZnO and also the elimination of pluronic F127 are the main factors for the induction of porosities in the foam structure. The presence of Zn(NO3)2. 6H2O and pluronic F127 in the initial composition of the preliminary foam results in the specific surface area as high as 1176 m2.g−1 and pore volume of 0.68 cm3.g−1. X-ray photoelectron and FTIR spectroscopy analyses results approved the presence of nitrogen (about 1.9 at %) in the form of pyridinic, graphitic and nitrogen oxide and oxygen (about 7.5 at. %) functional groups on the surface of the synthesized carbon foam. Electrochemistry analysis results including cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) and also electrochemical impedance spectroscopy (EIS) analysis illustrated the formation of an electric double layer supercapacitor with the capacitance as high as 137 Fg−1.

The Electrochemical Behaviour of Quaternary Amine-Based Room-Temperature Ionic Liquid N4111(TFSI)

In this study, we used the in situ X-ray photoelectron spectroscopy (XPS), in situ mass spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy methods, for the first time, in a detailed exploration of the electrochemical behaviour of a quaternary amine cation-based room-temperature ionic liquid, butyl-trimethyl-ammonium bis(trifluoromethylsulfonyl)imide (N4111(TFSI)), at the negatively and positively polarised molybdenum carbide-derived micro-mesoporous carbon (mmp-C(Mo2C)) electrodes that can be used as high surface area supporting material for electrocatalysts. The shapes of the C 1s, N 1s, O 1s, F 1s and S 2p XPS spectra were stable for N4111(TFSI) within a very wide potential range. The XPS data indicated the non-specific adsorption character of the cations and anions in the potential range from −2.00 V to 0.00 V. Thus, this region can be used for the detailed analysis of catalytic reaction mechanisms. We observed strong adsorption from 0.00 V to 1.80 V, and at E > 1.80 V, very strong adsorption of the N4111(TFSI) at the mmp-C(Mo2C) took place. At more negative potentials than −2.00 V, the formation of a surface layer containing both N4111+ cations and TFSI− anions was established with the formation of various gaseous compounds. Collected data indicated the electrochemical instability of the N4111+ cation at E < −2.00 V.

Deliberate introduction of mesopores into microporous activated carbon toward efficient Se cathode of Na−Se batteries

Sodium-selenium (Na−Se) batteries are garnering increasing attention as promising energy storage systems because of the low cost of Na resources and the high volumetric capacity of Se. Nevertheless, their practical application is hindered by the low utilization rate of Se and the shuttle effect of polyselenide, which lead to unstable cycling performance. Therefore, extensive efforts are necessary to develop suitable carbon-based Se hosts. Here, we propose a simple method to introduce a controlled amount of mesopores into microporous carbon, which can remarkably improve the electrochemical performance of Na−Se batteries. The Se encapsulated in the optimized micro-mesoporous carbon exhibited a substantially improved cycling stability, with a capacity of 572 mA h g−1 at 0.5C after 150 cycles, which represents a 93% capacity retention from the second cycle. In addition, the Se could achieve a high reversible capacity of 214 mA h g−1, even at 20C. The results of this study provide guidance for distinguishing the roles of the micropores and mesopores of carbon in the Se host of Na−Se batteries: (a) Micropores are ideal reservoirs to confine Se in an amorphous form for stable electrochemical reactions with Na, and (b) mesopores provide pathways for Na+ ion diffusion and a buffer for the volume change of Se. The proposed method would be widely applicable to other types of microporous carbon with much higher specific surface areas, which can afford higher Se loading for more advanced alkali metal−Se batteries.

Role of molecular size of volatile organic compounds on their adsorption by KOH-activated micro-mesoporous carbon

KOH-activated carbon (KAC) with high surface area and abundant micropores are widely used in adsorbing volatile organic compounds (VOCs). Kinetic diameters (σ) of VOCs are an important factor controlling diffusion of VOCs into pores of adsorbent. Yet the influence of kinetic diameters of VOCs on their adsorption by KAC remains unclear. Here, we investigated the dynamic adsorption of VOCs with various kinetic diameters on a prepared KAC with high surface area of 3100 m2/g, pore volume of 2.08 cm3/g and average pore width (D) of 2.68 nm. Adsorption affinity was negatively correlated with size difference (D-σ), indicating that pore width of adsorbent should close to σ to obtain a strong interaction between VOCs and adsorbents. Amounts adsorbed were positively correlated with σ at low relative pressures (p/p0 < 0.01), and negatively correlated with σ at high relative pressures (p/p0 > 0.044). The above results suggest that larger molecules with higher affinities are preferentially adsorbed at low relative pressures, amounts adsorbed of smaller molecules are larger than that of bigger molecules at high relative pressures. This study provided new insights into adsorption mechanisms mediated by σ and the development of next generation adsorbents for efficient removal of VOCs.

The electrochemical behaviour of protic quaternary amine based room-temperature ionic liquid N2210(OTf) at negatively and positively polarized micro-mesoporous carbon electrode investigated by in situ X-ray photoelectron spectroscopy, in situ mass-spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy methods

The electrochemical behaviour of a protic quaternary amine cation based room-temperature ionic liquid (RTIL), diethylmethylammonium trifluoromethanesulfonate [N2210(OTf)], has been investigated at negatively and positively polarized molybdenum carbide derived micro-mesoporous carbon [mmp-C(Mo2C)] electrodes by in situ X-ray photoelectron spectroscopy (XPS), in situ mass-spectroscopy (MS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. Collected data indicate that N2210(OTf) adsorbs strongly at E ≤ −1.10 V (vs. Ag-QRE) at the mmp-C(Mo2C) electrode. Intensive electroreduction of N2210+ cation took place at E ≤ −1.20 V (vs. Ag-QRE) producing various organic gases, instead of hydrogen, detected in situ by a restgas analyser. At E > 1.50 V (vs. Ag-QRE), remarkable passivation of the mmp-C(Mo2C) electrode took place. C 1 s, O 1 s, F 1 s and S 2p photoelectron signals became slightly distorted at E = 1.50 V (vs. Ag-QRE) indicating the formation of a surface film at mmp-C(Mo2C) involving triflate anion decomposition products.