Mesoporous Carbon Framework Research Articles

Study of the Secondary Heteroatoms Doping on Nitrogen‐Doped Carbon and Their Oxygen Reduction Reaction Performance Evaluation

AbstractThe dual heteroatom doped mesoporous carbon (MC) is an excellent substitute for platinum‐based catalyst in cathodic oxygen reduction reaction (ORR) of fuel cells. In this work, nitrogen (N) as the primary heteroatom doping, phosphorus (P), boron (B), and sulfur (S) as the secondary heteroatom doping are introduced in the MC framework. Santa barbara amorphous (SBA‐15) employed as the supporting material to investigate the secondary heteroatom doping effect on MC towards ORR performance. Compared with B and S doping, the P doping modifies the charge delocalization in the MC structure. In addition, it enhances the surface area (971 m2/g), defect sites (1.18), high pyridinic (28.72 %) and high graphitic content (44.42 %) thereby facilitated the remarkable ORR activity. Moreover, electrochemical studies proved that N and P dual doped mesoporous carbon (NPMC) has a better carrier concentration (5.58×1015 cm−3) and higher flat band potential (0.548 V vs RHE) which is confirmed by the Mott‐Schottky analysis. Further, ORR studies demonstrated that NPMC material exhibited more positive onset potential (0.86 V), two‐electron pathway, lower Tafel slope (63 mV/dec) as well as Rct (11 Ω/cm2). In addition, the resultant material is found to be highly active towards ORR with excellent methanol tolerance and stability.

Mesoporous carbon framework supported Cu-Fe oxides as efficient peroxymonosulfate catalyst for sustained water remediation

Large-scale green synthesis of high-performance catalysts is desirable for practical application of peroxymonosulfate (PMS) based advanced oxidation process. In this study, mesoporous carbon framework supported Cu-Fe oxides (CuO/CuFe2O4) was synthesized via calcination of cost-effective metal-plant phenolic networks for PMS activation to degrade organic pollutants. The mesoporous carbon framework enables highly spatial dispersion of nanosized Cu-Fe oxides, enhanced adsorption of organic pollutant (Bisphenol A, BPA) and improved electron transfer efficiency. Benefiting from the advantageous structure, the mesoporous carbon framework supported Cu-Fe oxides manifested excellent catalytic efficiency in PMS activation, enabling fast and sustained removal of BPA in simulated and actual contaminated water at neutral pH. Chemical scavenging experiments and electron paramagnetic resonance (EPR) tests revealed that reactive oxygen species (ROS) including SO4•−, OH• and 1O2 all participated in the degradation of BPA. The kinetic study and in situ characterization with ATR-FTIR indicated that PMS was activated by surface Cu(II) through an outer-sphere interaction, and a redox cycle of Cu(II)-Cu(I)-Cu(II) was responsible for the generation of ROS. This work demonstrates a reliable method for rational design of hybrid catalyst of metal oxide and carbon material for efficient wastewater remediation.

Bimetallic Fe and Co supported on the N‐doped mesoporous carbon frameworks with enhanced oxygen reduction reaction performance via high‐gravity technology

AbstractThe exploitation of high‐efficiency, inexpensive, as well as durable electrocatalysts for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of fuel cells. In this study, we prepared an efficient non‐precious ORR electrocatalyst via high‐gravity technology. The results of physical characterization revealed that the Fe atoms could be uniformly dispersed on the Fe/Co/N‐MCF catalyst via the high‐gravity technology. The X‐ray photoelectron spectroscopy demonstrated that the Fe can be combined with N from the ZIF‐67 to form the Fe‐Nx structures, which has already been confirmed to be acted as validly ORR active sites. The electrochemical testing results showed that the Fe/Co/N‐MCF catalyst obtained via high gravity technology expressed a 24 mV positive than commercial Pt/C in terms of half‐wave potential. Moreover, Fe/Co/N‐MCF catalyst exhibited an excellent anti‐ethanol activity and durability, its current density only decays 2.6%, far lower than 23.3% of commercial Pt/C after 10,000 s chronoamperometry aging test.

Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive black 5

High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl−, SO42−) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics (k = 2.11 × 10−2 min−1) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including 1O2, SO4·−, HO., and ·O2−, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination.

Preparation and Electrochemical Performance of N/S-Modified Mesoporous Carbon

Modifying mesoporous carbon using a single additive, i.e., thiourea, as a source of both sulfur and nitrogen, is a flexible strategy for improving electrochemical activity. In this study, sulfur and nitrogen were successfully introduced into the mesoporous carbon framework through a simple self-assembly process induced by solvent volatilization. The prepared nitrogen/sulfur co-doped mesoporous carbon (N/S-MC) material had a high specific surface area (406.64 m2·g−1) and heteroatom content (8.75 at.% nitrogen and 0.34 at.% sulfur). As a potential supercapacitor electrode material, it possessed a high specific capacitance of 230 F·g−1, which was measured using a three-electrode system at a current density of 0.5 A·−1. The electrochemical double-layer capacitor (EDLC) performance of N/S-MC enhanced significantly, compared with that of pure mesoporous carbon, owing to its increased reactivity and improved electrical properties, thereby making it more suitable for electronic power applications.

Rational design of hetero-dimensional C-ZnO/MoS2 nanocomposite anchored on 3D mesoporous carbon framework towards synergistically enhanced stability and efficient visible-light-driven photocatalytic activity

For efficient solar energy harvesting, various engineering strategies to strengthen visible-light responsivity of ZnO photocatalyst is under intensive investigation. In this work, a new ternary C-ZnO/MoS2/mesoporous carbon nanocomposite was successfully prepared by a two-step solution-processed synthesis protocol. The ternary composite exhibits a well-interconnected 3D mesoporous microstructure assembled by carbon nanosheets, which is loaded with quasi 0D ZnO nanoparticles and 2D MoS2 nanosheets. The carbonaceous nanocomposites show enhanced visible-light-driven photocatalytic performance and high photo-corrosion resistance. The incorporation of carbon in the hybrid design has manifold benefits that drastically promotes the photoactivity and photostability. The significant enhancement in photodegradation activity of the hybrid catalysts can be ascribed to a few positive synergistic effects, such as increased surface area and active reaction sites, boosted surface charge utilization efficiency, and band-gap lowering. The high porosity of the distinct microstructure raises the dye adsorption within the material. Tailored interface/surface properties enable more effective mass transport and higher separation efficiency of photo-generated carriers. The modulated electronic structure leads to the narrowing of the ZnO optical bandgap. Meanwhile, coupling with carbon prevents ZnO from photo-corrosion. Our approach highlights the roles of carbon as structure directing and stabilizing agents as well as heteroatom in defect engineering for wide band-gap oxide materials. The rational material design of multivariate mixed-dimensional architecture also provides guiding insight for the advancement of heterogeneous photocatalyst materials with superior performance and durability. The presented engineering strategy would be a promising method for the preparation of nanomaterials supported on 3D carbon network with high porosity and visible-light-driven photocatalytic performance.

Microporous Carbon Nanoparticles for Lithium-Sulfur Batteries.

Rechargeable lithium–sulfur batteries (LSBs) are emerging as some of the most promising next-generation battery alternatives to state-of-the-art lithium-ion batteries (LIBs) due to their high gravimetric energy density, being inexpensive, and having an abundance of elemental sulfur (S8). However, one main, well-known drawback of LSBs is the so-called polysulfide shuttling, where the polysulfide dissolves into organic electrolytes from sulfur host materials. Numerous studies have shown the ability of porous carbon as a sulfur host material. Porous carbon can significantly impede polysulfide shuttling and mitigate the insulating passivation layers, such as Li2S, owing to its intrinsic high electrical conductivity. This work suggests a scalable and straightforward one-step synthesis method to prepare a unique interconnected microporous and mesoporous carbon framework via salt templating with a eutectic mixture of LiI and KI at 800 °C in an inert atmosphere. The synthesis step used environmentally friendly water as a washing solvent to remove salt from the carbon–salt mixture. When employed as a sulfur host material, the electrode exhibited an excellent capacity of 780 mAh g−1 at 500 mA g−1 and a sulfur loading mass of 2 mg cm−2 with a minor capacity loss of 0.36% per cycle for 100 cycles. This synthesis method of a unique porous carbon structure could provide a new avenue for the development of an electrode with a high retention capacity and high accommodated sulfur for electrochemical energy storage applications.

Vapor deposition of aluminium oxide into N-rich mesoporous carbon framework as a reversible sulfur host for lithium-sulfur battery cathode

Restraining the shuttle effects of lithium polysulfides is the key to improve the cycling reversibility and stability of lithium-sulfur (Li-S) batteries for which design of robust sulfur hosts has been regarded as the most effective strategy. In this work, we report a new type of hybrid sulfur host which is composed of Al2O3 homogenously decorated in nitrogen-rich mesoporous carbon framework (NMC-Al2O3). The NMC-Al2O3 hybrid host features a poly-dispersed spherical morphology and a mesoporous configuration with high surface area and large pore volume that can accommodate a high sulfur content up to 73.5 wt.%. As a result, the fabricated NMC-Al2O3-S cathode exhibits all-round improvements in electrochemical properties in term of capacities (1,212 mAh·g−1 at 0.2 C; 755 mAh·g−1 at 2 C), cycling charge-discharge reversibility (sustainably 100% efficiencies) and stability (1,000 cycles with only 0.023% capacity decay per cycle at 0.5 C). By contrast, the Al2O3-free NMC-S cathode shows both decreased capacities and rapidly descending Coulombic efficiencies during cycling. Density functional theory (DFT) calculations further reveal that the implanted Al2O3 can greatly enhance the chemical adsorption and catalytic conversion for various lithium polysulfides and thereby effectively prevent the polysulfide shuttling and significantly improve the utilizability, reversibility and stability of sulfur cathode.

Ultrafine SnO2 anchored in ordered mesoporous carbon framework for lithium storage with high capacity and rate capability

Improving the reversible capacity and sluggish reaction kinetics of SnO2-based anodes have attracted considerable attention. Herein, an effective strategy by anchoring ultrafine (~5 nm) and high content SnO2 nanoparticles (~90%) in ordered mesoporous carbon framework (SnO2@OMC) is proposed to advance anode materials in lithium ion batteries. The ultrafine SnO2 and ordered mesoporous, which not only shorten the diffusion distance of Li+ and decrease the polarization, but also enhance the conversion reaction of SnO2 and interfacial storage of Li+. Benefiting from the novel strategy and elaborate design, the obtained SnO2@OMC anodes deliver a high reversible capacity (930 mAh g−1 after 150 cycles at 0.2 A g−1) and excellent rate capabilities (321 mAh g−1 at 5 A g−1). After assessment of the rate capability, SnO2@OMC anodes still display stable capacity.

3D N-doped ordered mesoporous carbon supported single-atom Fe-N-C catalysts with superior performance for oxygen reduction reaction and zinc-air battery

Single-atom Fe-N-C electrocatalysts have emerged as the most promising oxygen reduction reaction (ORR) catalyst. However, the low Fe loading and inaccessibility of Fe-N-C sites limit the overall ORR activity. Here, we report an efficient single-atom electrocatalyst (Fe-N-C/N-OMC) with Fe-N-C sites embedded in three-dimensional (3D) N-doped ordered mesoporous carbon framework. Fe-N-C/N-OMC shows high half-wave potential, kinetic current density, turnover frequency and mass activity towards ORR in alkaline electrolyte. Experiments and theoretical calculations suggest that the ultra-high ORR activity stems from the boosted intrinsic activity of FeN4 sites by graphitic N dopants, high density of accessible active site generated by high Fe and N loadings and ordered mesoporous carbon structure as well as facilitated mass and electron transport in 3D interconnected pores. Fe-N-C/N-OMC also shows comparable ORR activity to Pt/C in acidic electrolyte. As the cathode for zinc-air battery, Fe-N-C/N-OMC exhibits high open-circuit voltage, high power density and remarkable durability.

ZIF derived mesoporous carbon frameworks with numerous edges and heteroatom-doped sites to anchor nano-Pt electrocatalyst

We report the use of nitrogen-doped three-dimensional carbon frameworks (N-MCF) to promote the catalytic performance of nano-sized Pt electrocatalyst for the catalysis of oxygen reduction reaction (ORR). The N-MCF, obtained by pyrolysis of zeolitic imidazolate framework, provides abundant edges, defects, and heteroatom-doped sites to anchor Pt nanoparticles, leading to strong Pt-support interaction and excellent particle dispersion within its three-dimensional mass transport channels. Electrochemical results show only 8 mV degradation in the half-wave potential after accelerated durability test for the N-MCF supported Pt catalysts. Meanwhile, the mass activity and specific activity of Pt/N-MFC could reach 246 mA mg−1Pt and 0.276 mA cm−2 at 0.90 VRHE, which is better than that of commercial Pt/C. Moreover, the high Pt utilization of Pt/N-MFC (186 mg Pt kW−1) could reach 1.9 times than that of fuel cell fabricated with commercial Pt/C cathode.

Atomically dispersed Ni/NixSy anchored on doped mesoporous networked carbon framework: Boosting the ORR performance in alkaline and acidic media

Rational and strategic fabrication of cost-effective, active and durable oxygen reduction reaction (ORR) electrocatalyst is the bottle-neck for the commercialization of fuel cells and metal-air batteries. Atomically dispersed nickel (Ni)/nickel sulfide (NixSy) anchored on heteroatom doped networked hierarchical porous carbonaceous sheets are synthesized from nickel nitrate and guanidine thiocyanate. The sample annealed at 750 °C followed by acid-treatment (Ni-GT-750-A) emerges as the best performing pH-universal ORR catalyst with an onset potential of 0.91 (0.1 M KOH) and 0.89 V (0.1 M HClO4) vs. reversible hydrogen electrode (RHE). It also exhibits better current durability (95.0 and 60%) and methanol tolerance (90.6 and 80.3%) in comparison to the commercial catalyst (65.0, 27, −33.0 and 16.5%) in alkaline and acidic media, respectively. An insight into the microstructure and ORR-active chemical sites is obtained with the aid of electron microscopic (FE-SEM and HR-TEM) and physiochemical (sorption isotherm, XRD, Raman and XPS) studies, respectively. The enhanced activity results from the synergistic influence of metallic ORR-active sites in hierarchical porous doped defective carbon support, which provides the well-interlinked conducting channel for electron transfer and additional ORR-active sites. The introduced electrocatalyst establishes Ni decorated doped carbon systems as potential revolutionary substitutes for commercial systems.

Freeze-drying assisted biotemplated route to 3D mesoporous Na3V2(PO4)3@NC composites as cathodes with high performance for sodium-ion batteries

A facile freeze-drying assisted biotemplated route is developed to synthesize Na3V2(PO4)3 embedded in a N-doped three-dimensional mesoporous carbon framework, which has a superior initial discharge capacity and stability for Na-ion batteries.

Exclusive T2 MRI contrast enhancement by mesoporous carbon framework encapsulated manganese oxide nanoparticles

Single mode (either T1 or T2) contrast agents employed during magnetic resonance imaging owe their advantage over their dual counterparts to the fact that they do not involve any quenching caused by interference between the two modes. The chemistry involving oxides of manganese is highly significant due to their applicability as MRI contrast agents. Manganese oxides are usually known to display a dominant T1 relaxation enhancement. But, in this work, an engineered structure of manganese oxide (Mn2O3) nanoparticles encapsulated within mesoporous carbon frameworks was developed which exhibited dominant T2 contrast enhancement, through regulation of contact between the magnetic ion and water. Microstructural characterization revealed that the mesoporous carbon frameworks were spherical in shape and the nanoparticles within them had an average size of 40–50 nm. Relaxivity measurement, MRI experiments and cell viability assay convincingly established the system as a new class of biocompatible T2 based magnetic resonance imaging agent.

Ultra-small Na3V2(PO4)3 nanoparticles decorated MOFs-derived carbon enabling fast charge transfer for high-rate sodium storage

Na3V2(PO4)3 nanoparticles are decorated on MOF (ZIF-67) derived carbon via an impregnation followed by solid-phase sintering method. The ultra-small Na3V2(PO4)3 (~5 nm) particles and underlying mesoporous carbon framework enable fast charge transportation. A high sodium ion diffusion coefficient of 2.47 × 10−13 cm2 s−1 is achieved as measured by electrochemical impedance spectroscopy (EIS). The electron transfer resistance is also greatly reduced by the incorporation of mesoporous carbon. Therefore, such composite material demonstrates outstanding high rate performance as sodium ion battery cathode. Specifically, a discharge capacity of 84.6 mA h g−1 is recorded after 5000 cycles at a current density of 20C (1C = 117 mA g−1) corresponding to 86.3% of its initial capacity. The capacities still reach 74.5 and 62 mA h g−1 after 4500 cycles at high current densities of 30C and 50C, with Coulombic efficiency remains over 98%.

Mesoporous Si/C composite anode material: experiments and first-principles calculations

Carbon-coated and doped mesoporous silicon/carbon (m-Si/C) composites were successfully prepared via carbon coating and molten magnesiothermic reduction by using mesoporous silica (SBA-15) and dopamine as raw materials. Experimental results were theoretically verified by first-principles calculation. The obtained m-Si/C composites exhibited a high initial Coulombic efficiency of 73% at 0.1 A g−1 and an excellent cycling stability with 617.5 mAh g−1 capacity after 100 cycles at 0.1 A g−1. This excellent performance was attributed to the combination of carbon and the mesoporous structure of SBA-15 to form a mesoporous carbon framework which could improve the stability and conductivity of the material. The oxygen defects that formed after molten magnesiothermic reduction could effectively alleviate the change in the volume of the Si core and shorten the diffusion path of Li+ in the Si core. Graphene layers could effectively reduce the energy of the system and the band gap, the embedding of Li+ would lead to the expansion and distortion of Si, and the carbon layer with elasticity and hardness could buffer the volume expansion of m-Si/C composites. Consistent with experimental results, theoretical results demonstrated that graphene-coated composites positively affected the Li storage of Si.

Nitrogen-doped OMCs with high electrocatalytic activity for oxygen reduction reaction

Well-defined nitrogen-doped order mesoporous carbons (NOMCs) were fabricated by a surface doping method, where melamine acts as nitrogen source to dope the pre-oxidized surface of homemade mesoporous carbon CMK-3, and the overall process avoids introduction of any metal species. Various characterizations revealed that the NOMCs possessed order mesoporous network with large specific surface area, and covalently bonded N atoms within the surface of mesoporous carbon framework with predominantly pyridinic N (Maximum value is 53.8% atomic concentration). The onset potential, half-wave potential and limited current density of Me/HNMK-5 (one of the as-prepared NOMCs), reached 0.92 V (vs. RHE), 0.82 V (vs. RHE) and −4.34 mA cm−2, respectively, as well as superior methanol tolerance and outstanding durability via four-electron pathway in alkaline media, comparable with the commercial 20 wt% Pt/C catalyst.

Highly Efficient Utilization of Nano-Fe(0) Embedded in Mesoporous Carbon for Activation of Peroxydisulfate.

Nanoscale zerovalent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. However, the aggregation and oxidation of nZVI brings much difficulty in practical application of environmental remediation. In this study, we reported a composite nano-Fe(0)/mesoporous carbon by a chelation-assisted coassembly and carbothermal reduction strategy. Nano-Fe(0) particles with surface iron oxide (Fe2O3·FeO) were wrapped with graphitic layers which were uniformly dispersed in mesoporous carbon frameworks. The unique structure made the nano-Fe(0) particles stable in air for more than 20 days. It was used as a peroxydisulfate (PDS) activator for the oxidation treatment of 2,4,6-trichlorophenol (TCP). The TOF value of MCFe for TCP degradation is nearly 3 times higher than those of FeSO4 and Fe2O3·FeO and nearly 2 times than that of commercial nZVI. The reactive oxygen species (ROS) including •SO4-, HO•, and •O2-, 1O2 are efficiently generated by PDS activation with MCFe. The PDS activation process by nano-Fe(0) particles was intrinsically induced by the ferrous ions (Fe(II)) continuously generated at the solid/aqueous interface. Namely, the nano-Fe(0) particles were highly efficiently utilized in sulfate radical-based advanced oxidation processes (SR-AOP). The porous structure also assists the absorption and transfer of TCP during the degradation process.

Effect of the mercaptan alkyl chain structure on the structure and electrochemical properties of Au-doped mesoporous carbon materials

A good chelating agent such as mercaptan plays an important role in the synthesis of gold nanoparticles (AuNPs) or Au-doped carbon nano-composites. Herein, a synchronous carbonization-reduction method was employed to synthetize stable and monodispersed AuNPs embedded in the mesoporous carbon framework. A phenolic resin, mercaptan, and HAuCl4 acted as a carbon source, coordination agent, and gold source, respectively. The effect of the mercaptan chain length on the size of AuNPs and the pore structure of the mesoporous carbon materials was systematically studied. Ultraviolet spectrum analysis revealed that the coordination shifted from Cl–Au to S–Au depending on the mercaptan added to the reaction system. The as-prepared gold nanoparticles@mesoporous carbon materials (AuNPs@MPCs) were characterized by transmission electron microscopy, dynamic light scattering, X-ray diffraction, and N adsorption–desorption. The size of the AuNPs (3.71–12.86 nm) was controlled by changing the alkyl chain length of the mercaptans. The specific surface areas of the obtained AuNPs@MPCs increased from 1440 to 1603 m2/g as the mercaptan chain length increased. Square-wave stripping voltammetry (SWASV) tests on a typical MPTMS-AuNPs@MPC/GCE modified electrode revealed good detection response towards Pb2+, with a limit detection as low as 1.96 nM (S/N = 3). This detection limit was significantly lower than the value provided by the World Health Organization. This electrode also showed a relative wide linear detection range (0–2 μM). This good performance was ascribed to the excellent conductivity of AuNPs and the high specific surface area of the carbon materials. This work provides a new research strategy for the one-step synthesis of AuNPs@carbon materials with controllable NP size by using mercaptans with different alkyl chain structure. It can be believe that this approach could be expanded to nano-metal materials other than Au.

Nanocrystal supracrystal-derived atomically dispersed Mn-Fe catalysts with enhanced oxygen reduction activity

Iron-nitrogen-carbon (Fe-N-C) materials featuring Fe-N4 moieties are promising candidates to replace commercial Pt/C catalysts for the oxygen reduction reaction (ORR). Here we report a novel Mn-Fe-N/S@mC catalyst comprising atomically dispersed Fe-N4 sites and a trace amount of Mn-N2S2 sites, which are homogeneously anchored on an ordered mesoporous graphitic carbon framework. This dual-metal catalyst is realized based on the chemical conversion of self-assembled Mn0.43Fe2.57O4 nanocrystal supracrystals, with the dual metal sites and the graphitic framework derived from nanocrystal cores and the associated capping ligands, respectively. When evaluated as electrocatalysts for the ORR, Mn-Fe-N/S@mC exhibits excellent catalytic activity in alkaline media, outperforming conventional Pt/C and most non-precious-metal catalysts reported previously. Notably, the synergistic effect of having Fe and Mn together improves the catalytic activity by a factor of ~ 5. To better understand the high efficiency of Mn doping in enhancing the activity of Fe-N4 sites, density functional theory calculations were carried out, revealing that the synergistic interaction between the dual metal sites reduces the *OH reduction energy barrier during the oxygen reduction pathway.