Mesoporous Carbon Catalyst Research Articles

Sulfenic Acid Doped Mesocellular Carbon Foam as Powerful Catalyst for Activation of V(II)/V(III) Reaction in Vanadium Redox Flow Battery

Sulfur-based functional group doped mesoporous carbon (MC) catalysts are prepared to investigate their effects on V(II)/V(III) and V(IV)/V(V) redox reactions as well as on the performance of vanadium redox flow battery (VRFB). According to the electrochemical analysis, although all of the catalysts applied have a similar influence on the V(IV)/V(V) reaction, for the V(II)/V(III) reaction, the sulfenic acid-doped MC shows better catalytic activity with a faster electron transfer rate and narrower peak potential separation. Nyquist plots also support the superiority of the sulfenic acid-doped MC catalyst with a smaller charge transfer resistance. When the catalysts are loaded onto a negative electrode for measuring the performance of VRFB, the VRFB using sulfenic acid-doped MC catalyst shows 6∼10% higher voltage efficiency and 5∼12% higher energy efficiency than other VRFBs. The excellent catalytic activity of the catalyst for the V(II)/V(III) reaction and superior performance of VRFB are due to an increase in the –SOxH bond that acts as an active site for the reaction.

Ruthenium nanoparticle catalyzed selective reductive amination of imine with aldehyde to access tertiary amines.

Reductive amination is one of the most frequently used transformations in organic synthesis. Herein, we developed a novel ruthenium nanoparticle embedded ordered mesoporous carbon catalyst (Ru-OMC) and a new hydrosilylation process for the synthesis of tertiary amines. We present a direct reductive amination of imines (C[double bond, length as m-dash]N bond) with aldehydes (C[double bond, length as m-dash]O bond) using hydrosilane as the reducing reagent under mild conditions. Moreover, the Ru-OMC catalysts can be reused for up to 14 runs without noticeably losing activity.

Efficient hierarchically synthesized Fe2P nanoparticles embedded in an N,P-doped mesoporous carbon catalyst for the oxygen reduction reaction

Novel Fe2P nanoparticles encapsulated in an N,P-doped three-dimensional porous carbon catalyst were synthesized and displayed excellent ORR performance.

Heterogeneous Fenton oxidation of phenol in fixed-bed reactor using Fe nanoparticles embedded within ordered mesoporous carbons

Iron nanoparticles embedded within ordered mesoporous carbon catalyst (Fe-OMC) was prepared using a facile “one-pot” synthesis method. The as-synthesized catalyst was characterized by using FTIR, XRD, SEM-EDS mapping, HRTEM and XPS. The results revealed that Fe oxide nanoparticles were highly dispersed in the OMC. The prepared Fe-OMC materials as heterogeneous Fenton catalysts were specifically applied in the fixed-bed reactor which operated under continuous-flow condition, showing a promising performance in the oxidative degradation of phenol with high catalytic activity (e.g. phenol conversion nearly 100%) and stability. The effects of feed flow rate and catalyst bed height on the conversions of phenol and H2O2, the iron leaching concentration as well as pH values of reaction solutions were also systematically investigated to determine the optimal operation conditions. The experimental results showed that the Fe-OMC catalyst achieved the highest activity (>99% phenol and H2O2 conversion) with remarkable low iron leaching concentration (10–20mg/L) under continuous-flow operations. The stability and reusability evaluations of Fe-OMC catalysts indicated the phenol conversion remains above 90% during a 39h long-term evaluation. It can be finally concluded that the prepared Fe-OMC catalyst in this work shows promising potential to be an efficient heterogeneous Fenton catalyst for the degradation of hazardous phenolic aqueous solutions.

A facile template approach for the synthesis of mesoporous Fe3C/Fe-N-doped carbon catalysts for efficient and durable oxygen reduction reaction

Facile synthetic approaches toward the development of efficient and durable nonprecious metal catalysts for the oxygen reduction reaction (ORR) are very important for commercializing advanced electrochemical devices such as fuel cells and metal-air batteries. Here we report a novel template approach to synthesize mesoporous Fe-N-doped carbon catalysts encapsulated with Fe3C nanoparticles. In this approach, the layer-structured FeOCl was first used as a template for the synthesis of a three-dimensional polypyrrole (PPy) structure. During the removal of the FeOCl template, the Fe3+ can be absorbed by PPy and then converted into Fe3C nanoparticles and Fe-N-C sites during the pyrolyzing process. As a result, the as-prepared catalysts could exhibit superior electrocatalytic ORR performance to the commercial Pt/C catalyst in alkaline solutions. Furthermore, the Zn-air battery assembled using the mesoporous carbon catalyst as the air electrode could surpass the commercial Pt/C catalyst in terms of the power density and energy density.

Hydrogen production over molybdenum loaded mesoporous carbon catalysts in microwave heated reactor system

Ammonia decomposition reaction to produce COx free hydrogen over molybdenum incorporated mesoporous carbon based catalysts was studied in a microwave heated reactor system. Mesoporous carbon is acting as the catalyst support as well as the microwave receptor in the reaction medium. While the highest conversion value was 49% in conventionally heated reaction system at 600°C, total conversion value was achieved over the same catalyst at 400°C in microwave heated system with a GHSV of 36,000ml/hgcat. Transfer of microwave energy directly to the active particles, volumetric heating and hot spot formation are the main reasons of this great enhancement. While molybdenum nitride was observed under conventional heating, molybdenum carbide was formed in case of microwave application which could be another improving effect on catalytic activity of molybdenum incorporated mesoporous catalysts.

Biomass-derived heteroatoms-doped mesoporous carbon for efficient oxygen reduction in microbial fuel cells

Currently, the development of less expensive, more active and more stable catalysts like heteroatom-doped carbon based non-precious metal materials are highly desired for the cathodic oxygen reduction reaction (ORR) in microbial fuel cells (MFCs). Comparing with heteroatom sources from chemical reagents, biomass is notably inexpensive and abundant, containing more elements which contribute to ORR activity. Herein, we demonstrate an easy operating one-step and low-cost way to synthesize egg-derived heteroatoms-doped mesoporous carbon (EGC) catalysts utilizing egg as the biomass carbon and other elements source (sulphur, phosphorus, boron and iron), and porous g-C3N4 as both template and nitrogen source. After carbonized, such hybrid materials possess an outstanding electrocatalytic activity towards ORR comparable to the commercial Pt/C catalyst in neutral media. Electrochemical detections as cyclic voltammogram and rotating ring-disk electrode tests show that the potential of oxygen reduction peak of EGC1-10-2 is at + 0.10V, onset potential is at + 0.257V (vs. Ag/AgCl) and electron transfer number of that is 3.84–3.92, which indicate that EGC1-10-2 via a four-electron pathway. Reactor operation shows that the maximum power density of MFC-EGC1-10-2 (737.1mWm−2), which is slightly higher than MFC-Pt/C (20%) (704mWm−2). The low cost (0.049 $g−1), high yield (20.26%) and high performance of EGC1-10-2 provide a promising alternative to noble metal catalysts by using abundant natural biological resources, which contribute a lot to expansion and commercialization of MFCs.

Solid-state synthesis of ordered mesoporous carbon catalysts via a mechanochemical assembly through coordination cross-linking

Ordered mesoporous carbons (OMCs) have demonstrated great potential in catalysis, and as supercapacitors and adsorbents. Since the introduction of the organic–organic self-assembly approach in 2004/2005 until now, the direct synthesis of OMCs is still limited to the wet processing of phenol-formaldehyde polycondensation, which involves soluble toxic precursors, and acid or alkali catalysts, and requires multiple synthesis steps, thus restricting the widespread application of OMCs. Herein, we report a simple, general, scalable and sustainable solid-state synthesis of OMCs and nickel OMCs with uniform and tunable mesopores (∼4–10 nm), large pore volumes (up to 0.96 cm3 g−1) and high-surface areas exceeding 1,000 m2 g−1, based on a mechanochemical assembly between polyphenol-metal complexes and triblock co-polymers. Nickel nanoparticles (∼5.40 nm) confined in the cylindrical nanochannels show great thermal stability at 600 °C. Moreover, the nickel OMCs offer exceptional activity in the hydrogenation of bulky molecules (∼2 nm).

In situ mosaic strategy generated Co-based N-doped mesoporous carbon for highly selective hydrogenation of nitroaromatics

The development of heterogeneous non-noble metal catalytic architectures that can realize the high selective and stable hydrogenation of nitroaromatics under mild conditions is a profound challenge in the catalysis community. Here we report a facile synthesis of highly nitrogen doped and uniformly embedded Co-based mesoporous carbon catalyst through a thermolysis and etching combined strategy, in which the commercial cobalt phthalocyanine and colloidal silica serve as precursor and hard template, respectively. The protocol allows for simultaneous optimization of porous features and cobalt nanoparticles of N-doped mesoporous carbon catalyst by fine-tuning thermolysis temperature. Among the as-prepared catalysts, Co@NMC-800 with lower dosage of cobalt exhibits outstanding catalytic activity and chemoselectivity for various nitroaromatics under mild condition (2.0mol% Co, 1.0MPa H2, 80°C, <150min), which is significantly superior to all the existing non-noble metal-based catalytic systems. Dynamic analysis further demonstrates the apparent activation energy of nitrobenzene hydrogenation is as low as 28.0kJ/mol, accounting for the higher hydrogenation reaction rate. In addition, the synergistic effect between the CoNx and Co NPs surface wrapped thin carbon layers plays a crucial role in providing the excellent selectivity for hydrogenation of vulnerable nitroaromatics via preferential adsorption of polar nitro group.

Synthesis of 2D Nitrogen-Doped Mesoporous Carbon Catalyst for Oxygen Reduction Reaction

2D nitrogen-doped mesoporous carbon (NMC) is synthesized by using a mesoporous silica film as hard template, which is then investigated as a non-precious metal catalyst for the oxygen reduction reaction (ORR). The effect of the synthesis conditions on the silica template and carbon is extensively investigated. In this work, we employ dual templates—viz. graphene oxide and triblock copolymer F127—to control the textural features of a 2D silica film. The silica is then used as a template to direct the synthesis of a 2D nitrogen-doped mesoporous carbon. The resultant nitrogen-doped mesoporous carbon is characterized by transmission electron microscopy (TEM), nitrogen ad/desorption isotherms, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and rotating disk electrode measurements (RDE). The electrochemical test reveals that the obtained 2D-film carbon catalyst yields a highly electrochemically active surface area and superior electrocatalytic activity for the ORR compared to the 3D-particle. The superior activity can be firstly attributed to the difference in the specific surface area of the two catalysts. More importantly, the 2D-film morphology makes more active sites accessible to the reactive species, resulting in a much higher utilization efficiency and consequently better activity. Finally, it is noted that all the carbon catalysts exhibit a higher ORR activity than a commercial Pt catalyst, and are promising for use in fuel cells.

A General Silica-Templating Synthesis of Alkaline Mesoporous Carbon Catalysts for Highly Efficient H2S Oxidation at Room Temperature.

A general synthesis of alkaline mesoporous carbons (AMCs) is developed based on a simplified silica-templating method for room-temperature catalytic oxidation of H2S. The key to the success relies on dissolving the silica templates to create the interconnected mesoporous structure as well as leaving parts of the alkaline products in the pores; both of them are prerequisites for H2S oxidation. By adjusting the alkaline etching degree and organic/inorganic ratio, the porosity and basicity of the AMC could be simultaneously tuned, allowing the AMCs direct use for H2S catalytic oxidation with an unprecedented removal capacities of 4.49 ± 0.12 g/g. Such excellent catalytic performance should be attributed to the developed pore structure that stores the product sulfur and the strong basicity that promotes the dissociation of H2S into HS- ions. Moreover, this simplified silica-templating method could be easily extended to the preparation of various silica templated mesoporous carbon catalysts. All these AMCs demonstrate a successful combination of low cost with high performance, which may well be the answer for the technical development of industrial H2S removal.

Efficient chemoselective hydrogenation of halogenated nitrobenzenes over an easily prepared γ-Fe2O3-modified mesoporous carbon catalyst

An easily prepared cost-effective γ-Fe2O3/MC catalyst was used for the hydrogenation of halogenated nitrobenzenes with 100% selectivity for the corresponding halogenated anilines.

A green direct preparation of a magnetic ordered mesoporous carbon catalyst containing Fe–Pd alloys: application to Suzuki–Miyaura reactions in propane-1,2-diol

A mesoporous carbon containing Fe–Pd alloys showed excellent activity for Suzuki–Miyaura couplings using tiny amounts of Pd and afforded Pd-free products after reaction.

Efficient conversion of carbohydrates into 5-hydroxylmethylfurfan and 5-ethoxymethylfurfural over sufonic acid-functionalized mesoporous carbon catalyst

Catalytic conversion of carbohydrates into valuable chemical and liquid fuels has received considerable attention in recent years. In this study, sulfonic acid-functionalized ordered mesoporous carbon (OMC-SO3H) was prepared and well characterized by physical techniques such as TEM, nitrogen physisorption measurements and XRD. The as-prepared OMC-SO3H was then used for the acid-catalyzed conversion of fructose based carbohydrates into 5-hydroxylmethylfurfan (HMF) or 5-ethoxymethylfurfural (EMF). Due to the high surface area and high acidity, the OMC-SO3H catalyst showed a comparable catalytic performance as the homogeneous catalysts. The dehydration of fructose over the OMC-SO3H catalyst produced a high HMF yield of 89.4% in DMSO at 120°C within 30min. The one-pot transformation of fructose carbohydrates were also smoothly performed, affording EMF yields of 55.7%, 53.6% and 26.8% from fructose, iuline and sucrose after 24h at 140°C, respectively. Furthermore, the OMC-SO3H catalyst can be reused and no apparent loss of the activity was observed.

Microwave-assisted ammonia decomposition reaction over iron incorporated mesoporous carbon catalysts

Microwave-assisted ammonia decomposition reaction was investigated to produce COx free hydrogen, for fuel cell applications. Iron incorporated mesoporous carbon catalysts were prepared at different metal loadings, following an impregnation procedure. Mesoporous carbon acted as the catalyst support, as well as the microwave receptor. Complete conversion of ammonia was achieved at 450°C over the catalyst having 7.7wt% Fe, when the reaction was carried out in the microwave reactor system, using pure ammonia (GHSV of 36000ml/hgcat). However, in the case of using the conventionally heated reactor, complete conversion of ammonia was achieved only at 600°C. Iron oxides, namely maghemite (γ-Fe2O3), magnetite (Fe3O4) and hematite (α-Fe2O3) simultaneously appeared in the structure of the synthesized catalysts, after their calcination at 450°C, under pure N2 flow. Iron oxides present in the calcined catalytic materials then were reduced to metallic iron at 500°C. Formation of iron carbide crystals was observed in the structure of spent catalysts that were used in microwave reactor system, while metallic iron crystals were still present in the catalysts that were tested in conventionally heated system.

Direct synthesis of nitrogen-doped mesoporous carbons for acetylene hydrochlorination

Nitrogen-doped ordered mesoporous carbon (N-OMC) catalysts were directly synthesized using SBA-15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized with sucrose. A 3.6 wt% nitrogen doping of the carbon framework was achieved, with more than 70% of the nitrogen incorporated as quaternary nitrogen species. Only 0.2 wt% nitrogen doping, with only 32.7% quaternary nitrogen incorporation was obtained in an N-OMC catalyst (N-OMC-T) prepared using a two-step post-synthesis method. The acetylene hydrochlorination activities of N-OMC catalysts prepared via the one-step method were higher than that of the N-OMC-T catalyst because of the higher nitrogen loadings.

Effect of boron content on 1,4-butanediol production by hydrogenation of succinic acid over Re-Ru/BMC (boron-modified mesoporous carbon) catalysts

A series of Re-Ru bimetallic catalysts supported on mesoporous boron-modified carbon (denoted as Re-Ru/xBMC, x=B/C molar ratio) were prepared by a single-step surfactant-templating method and a subsequent incipient wetness impregnation method, and they were used for liquid-phase hydrogenation of succinic acid to 1,4-butandiol (BDO). The effect of boron addition on the catalytic activities and physicochemical properties of Re-Ru/xBMC catalysts was investigated. It was found that the addition of boron into carbon support affected surface area, metal dispersion, and reducibility of rhenium and ruthenium species in the Re-Ru/xBMC catalysts. It was also observed that boron species in carbon framework existed in several different phases such as substituted boron, partial oxidized boron, and boron oxide. In particular, the amount of substituted boron species was closely related to the hydrogen adsorption behavior of Re-Ru/xBMC catalysts. The amount of weak hydrogen-binding sites increased with increasing the amount of substituted boron species of the catalysts. Yield for BDO in the hydrogenation of succinic acid showed a volcano-shaped trend with respect to B/C molar ratio. This result was in good agreement with the amount of weak hydrogen-binding sites of the catalysts. It was revealed that TOFBDO increased with increasing the amount of weak hydrogen-binding sites of Re-Ru/xBMC catalysts. Among the catalysts, Re-Ru/0.04BMC with the largest amount of weak hydrogen-binding sites served as an efficient catalyst in the selective formation of BDO by hydrogenation of succinic acid.

Efficient metal-free N-doped mesoporous carbon catalysts for ORR by a template-free approach

A simple, cost-effective and scalable approach for the synthesis of N-doped mesoporous carbons that are effective as ORR catalysts is reported. The synthesis procedure involves two steps: a) production of mesoporous carbons using a template-free approach based on the carbonization of citrate salts of zinc and calcium, and b) N-doping by heat treatment in the presence of melamine. The resulting N-doped carbon possess a high specific surface area, a porosity made up exclusively of mesopores and a large amount of nitrogen functionalities (∼8–9 wt%). When used as an electrocatalyst for the oxygen reduction reaction (ORR), the metal-free carbon materials predominantly catalyze the 4 e− process, with an onset potential of 0.9 V (vs. RHE) and a superior kinetic current density (∼17 mA cm−2) to that of Pt/C at ∼0.6 V under basic conditions. In addition, the developed catalysts show a higher stability than commercial Pt/C and excellent electrocatalytic selectivity against methanol crossover.

Dual-doped mesoporous carbon synthesized by a novel nanocasting method with superior catalytic activity for oxygen reduction

Fe and N dual-doped mesoporous carbon catalyst demonstrated superior catalytic activity than Pt catalyst for both oxygen reduction and oxidation reactions in alkaline electrolyte. The catalyst was synthesized through a novel simple sublimation and capillary assisted nanocasting method. Using the method, multiple transition metal and nitrogen dual-doped mesoporous carbon electrocatalysts were also successfully made. It was believed that the excellent catalytic activity was resulted from the synergistic effects of highly active metal-nitrogen species, mesoporous structure, large interfacial surface and excellent conductivity. The present synthetic strategy offers a new insight into preparation of heteroatom-doped electrocatalysts with promising applications in metal-air batteries, fuel cells, and supercapacitors as well.

Electrocatalytic hydrogen peroxide formation on mesoporous non-metal nitrogen-doped carbon catalyst

Direct electrochemical formation of hydrogen peroxide (H2O2) from pure O2 and H2 on cheap metal-free earth abundant catalysts has emerged as the highest atom-efficient and environmentally friendly reaction pathway and is therefore of great interest from an academic and industrial point of view. Very recently, novel metal-free mesoporous nitrogen-doped carbon catalysts have attracted large attention due to the unique reactivity and selectivity for the electrochemical hydrogen peroxide formation [1–3]. In this work, we provide deeper insights into the electrocatalytic activity, selectivity and durability of novel metal-free mesoporous nitrogen-doped carbon catalyst for the peroxide formation with a particular emphasis on the influence of experimental reaction parameters such as pH value and electrode potential for three different electrolytes. We used two independent approaches for the investigation of electrochemical hydrogen peroxide formation, namely rotating ring-disk electrode (RRDE) technique and photometric UV–VIS technique. Our electrochemical and photometric results clearly revealed a considerable peroxide formation activity as well as high catalyst durability for the metal-free nitrogen-doped carbon catalyst material in both acidic as well as neutral medium at the same electrode potential under ambient temperature and pressure. In addition, the obtained electrochemical reactivity and selectivity indicate that the mechanisms for the electrochemical formation and decomposition of peroxide are strongly dependent on the pH value and electrode potential.