N-Doped Mesoporous Research Articles

(Invited) Electrocatalytic Activity and Structural Insights of Cu, Fe and N-Doped Mesoporous Carbon for the Oxygen Reduction Reaction

For widespread applications of polymer electrolyte fuel cells, non-PGM electrocatalysts with high oxygen reduction reaction (ORR) activity and product selectivity to H2O need to be developed. Metal, nitrogen-doped carbon (M–N–C, M = Fe, Co, Cu, etc.) electrocatalysts have been intensively studied as non-PGM based electrocatalysts in acidic media for the ORR because they show relatively high ORR activity in the non-PGM-based electrocatalysts. Recently, heterometallic doping into nitrogen-doped carbon, which is known as dual-metal atom catalysts, can show the cooperative effect on the ORR activity and product selectivity. We have also developed such heterometallic non-PGM electrocatalysts of Cu, Fe, N-doped carbon nanotubes for the ORR in acidic media, inspired by the active site of a natural ORR catalyst of cytochrome c oxidase [1]. The co-doping of Cu and Fe in carbon nanotubes improves the ORR activity and product selectivity toward H2O via four-electron transfer. However, its ORR activity is relatively low (a turnover frequency of 0.40 e– site–1 s–1 at +0.80 V vs. RHE) and the structure of the active site remains unclear.We report the synthesis, activity and structural insight of a Cu, Fe, N-doped mesoporous carbon, (Cu,Fe)–N–mesoC, electrocatalyst for the ORR in acidic media. (Cu,Fe)–N–mesoC was prepared in pyrolysis from the composite of an iron complex of a 1,12-diazatriphenylene ligand [2], a multinuclear copper complex of 1,2,4-triazole [3] and mesoporous carbon. (Cu,Fe)–N–mesoC shows a turnover frequency of 1.35 e– site–1 s–1 at +0.80 V vs. RHE and a low hydrogen peroxide yield (< 5%). X-ray absorption and emission spectroscopy of (Cu,Fe)–N–mesoC was performed to understand the structure of the active site.References.[1] M. Kato, N. Fujibayashi, D. Abe, N. Matsubara, S. Yasuda, I. Yagi, ACS Catal., 11, 2356-2365 (2021).[2] K. Matsumoto et al., Chem. Eur. J., 28, e20210345 (2022).[3] M. Kato et al., ACS Appl. Energy Mater., 1, 2358-2364 (2018).

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

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

Improved Energy Storage Performance of N-Doped Hollow Mesoporous Carbon Spheres as Substrate for MoS2

Improved Energy Storage Performance of N-Doped Hollow Mesoporous Carbon Spheres as Substrate for MoS2

FeCo Alloy Nanoparticles Supported on N-doped Mesoporous Carbon Spheres for Hydrogen Evolution and Reduction of Organic Dyes

FeCo Alloy Nanoparticles Supported on N-doped Mesoporous Carbon Spheres for Hydrogen Evolution and Reduction of Organic Dyes

N-Doped Mesoporous Carbon from Melamine-Modified Resorcinol-Formaldehyde Polymer Resin as Catalytic Support for Electrochemical Investigation of Formic acid Oxidation Reaction

N-Doped Mesoporous Carbon from Melamine-Modified Resorcinol-Formaldehyde Polymer Resin as Catalytic Support for Electrochemical Investigation of Formic acid Oxidation Reaction

Space-Confined Guest Synthesis to Fabricate Sn-Monodispersed N-Doped Mesoporous Host toward Anode-Free Na Batteries.

Severe issues including volume change and dendrite growth on sodium metal anodes hinder the pursuit of applicable high-energy-density sodium metal batteries. Herein, an in situ reaction approach is developed that takes metal-organic frameworks as nano-reactor and pore-former to produce a mesoporous host comprised of nitrogen-doped carbon fibers embedded with monodispersed Sn clusters (SnNCNFs). The hybrid host shows outstanding sodiophilicity that enables rapid Na infusion and ultralow Na nucleation overpotential of 2mV. Its porous structure holds a high Na content and guides uniform Na deposition. Such host provides favorable Na plating/stripping with an average Coulombic efficiency of 99.96% over 2000 cycles (at 3mA cm-2 and 3mA h cm-2 ). The Na-infused SnNCNF anode delivers extreme Na utilization of 86% in symmetric cells (at 10mA cm-2 and 10mA h cm-2 ), outstanding rate capability and cycle life in Na-SnNCNF||Na3 V2 (PO4 )3 full cells (at 1 A g-1 for over 1000 cycles with capacity retention of 92.1%). Furthermore, high-energy/power-density anode-less and anode-free Na cells are achieved. This work presents an effective heteroatom-doping approach for fabricating multifunctional porous carbon materials and developing high-performance metal batteries.

Ru-Ni Alloy Nanoparticles Loaded on N-Doped Amphiphilic Mesoporous Hollow Carbon@silica Spheres as Catalyst for the Hydrogenation of α-Pinene to cis-Pinane.

N-doped mesoporous carbon spheres (NHMC@mSiO2 ) encapsulated in silica shells were prepared by emulsion polymerization and domain-limited carbonization using ethylenediamine as the nitrogen source, and Ru-Ni alloy catalysts were prepared for the hydrogenation of α-pinene in the aqueous phase. The internal cavities of this nanomaterial are lipophilic, enhancing mass transfer and enrichment of the reactants, and the hydrophilic silica shell enhances the dispersion of the catalyst in water. N-doping allows more catalytically active metal particles to be anchored to the amphiphilic carrier, enhancing its catalytic activity and stability. In addition, a synergistic effect between Ru and Ni significantly enhances the catalytic activity. The factors influencing the hydrogenation of α-pinene were investigated, and the optimum reaction conditions were determined to be as follows: 100 °C, 1.0 MPa H2 , 3 h. The high stability and recyclability of the Ru-Ni alloy catalyst were demonstrated through cycling experiments.

High-Performance Heat Storage Phase Change Composite by Highly Aligned N-Doped Mesoporous Carbon for Efficient Battery Thermal Management

Limited by leakage from inherent liquid to solid phase transition and inferior heat transfer, pristine organic phase change materials (PCMs) possess extremely low thermal storage performance. Thus, establishing shape-stable PCM composites with enhanced thermal conductivity and latent heat is a key task for practical application. Herein, we constructed N-doped mesoporous carbon monoliths with a highly aligned structure by directional freeze-drying to encapsulate polyethylene glycol. Benefiting from the mesoporous carbon matrix and pyridinic N from N-doping, the PCM composite possessed large latent heat (140 J·g–1) and leakage proof at 80 °C. Meanwhile, the highly aligned structure created a fast heat transfer pathway that improved thermal conductivity of the PCM composite by 1500%. Being different from most research studies, highly aligned carbon was utilized as the support directly without skeletons, which could increase PCM loading capacity and thermal conductivity as well. The PCM composite can be employed as promising candidates for thermal management working efficiently to decrease battery pack temperature by 13 °C and improve discharge capacity by 28%.

Impact of Sulfur Infiltration Time and Its Content in an N-doped Mesoporous Carbon for Application in Li-S Batteries

Li-S batteries are ideal candidates to replace current lithium-ion batteries as next-generation energy storage systems thanks to their high specific capacity and theoretical energy density. Composite electrodes based on carbon microstructures are often used as a host for sulfur. However, sulfur lixiviation, insoluble species formation, and how to maximize the sulfur-carbon contact in looking for improved electrochemical performance are still major challenges. In this study, a nitrogen doped mesoporous carbon is used as a host for sulfur. The S/C composite electrodes are prepared by sulfur melting-diffusion process at 155 °C. The effect of the sulfur melting-diffusion time [sulfur infiltration time] (1–24 h) and sulfur content (10–70%) is investigated by using XRD, SEM, TEM and TGA analyses and correlated with the electrochemical performance in Li-S cells. S/C composite electrode with homogeneous sulfur distribution can be reached with 6 h of sulfur melting-diffusion and 10 wt.% of sulfur content. Li-S cell with this composite shows a high use of sulfur and sufficient electronic conductivity achieving an initial discharge capacity of 983 mA h g−1 and Coulombic efficiency of 99% after 100 cycles.

Modulating the Electronic Structure of FeCo Nanoparticles in N-Doped Mesoporous Carbon for Efficient Oxygen Reduction Reaction.

The development of highly efficient and stable oxygen reduction electrocatalysts and revealing their underlying catalytic mechanism are crucial in expanding the applications of metal‐air batteries. Herein, an excellent FeCo alloy nanoparticles (NPs)‐decorated N‐doped mesoporous carbon electrocatalyst (FeCo/NC) for oxygen reduction reaction, prepared through the pyrolysis of a dual metal containing metal‐organic framework composite scaffold is reported. Benefiting from the highly exposed bimetal active sites and the carefully designed structure, the Fe0.25Co0.75/NC‐800 catalyst exhibits a promising electrocatalytic activity and a superior durability, better than those of the state‐of‐the‐art catalysts. Suggested by both the X‐ray absorption fine structures and the density functional theoretical calculation, the outstanding catalytic performance is originated from the synergistic effects of the bimetallic loading in NC catalysts, where the electronic modulation of the Co active sites from the nearby Fe species leads to an optimized binding strength for reaction intermediates. This work demonstrates a class of highly active nonprecious metals electrocatalysts and provides valuable insights into investigating the structure–performance relationship of transition metal‐based alloy catalysts.

Coupling of N-Doped Mesoporous Carbon and N-Ti3 C2 in 2D Sandwiched Heterostructure for Enhanced Oxygen Electroreduction.

2D heterostructures provide a competitive platform to tailor electrical property through control of layer structure and constituents. However, despite the diverse integration of 2D materials and their application flexibility, tailoring synergistic interlayer interactions between 2D materials that form electronically coupled heterostructures remains a grand challenge. Here, the rational design and optimized synthesis of electronically coupled N-doped mesoporous defective carbon and nitrogen modified titanium carbide (Ti3 C2 ) in a 2D sandwiched heterostructure, is reported. First, a F127-polydopamine single-micelle-directed interfacial assembly strategy guarantees the construction of two surrounding mesoporous N-doped carbon monolayers assembled on both sides of Ti3 C2 nanosheets. Second, the followed ammonia post-treatment successfully introduces N elements into Ti3 C2 structure and more defective sites in N-doped mesoporous carbon. Finally, the oxygen reduction reaction (ORR) and theoretical calculation prove the synergistic coupled electronic effect between N-Ti3 C2 and defective N-doped carbon active sites in the 2D sandwiched heterostructure. Compared with the control 2D samples (0.87-0.88V, 4.90-5.15 mA cm-2 ), the coupled 2D heterostructure possesses the best onset potential of 0.90V and limited density current of 5.50 mA cm-2 . Meanwhile, this catalyst exhibits superior methanol tolerance and cyclic durability. This design philosophy opens up a new thought for tailoring synergistic interlayer interactions between 2D materials.

N-Doped Mesoporous Carbon Prepared from a Polybenzoxazine Precursor for High Performance Supercapacitors.

Supercapacitors store energy either by ion adsorption or fast surface redox reactions. The capacitance produced by the former is known as electrochemical double layer capacitance and the latter is known as pseudo-capacitance. Carbon materials are found to be attractive materials for energy storage, due to their various micro-structures and wide source of availability. Polybenzoxazine (Pbz) is used as a source to produce carbon materials, due to the fact that the obtained carbon will be rich in N and O species for enhanced performance. Moreover, the carbon materials were produced via template-free method. In general, activation temperature plays a main role in altering the porosity of the carbon materials. The main purpose of this study is to find the suitable activation temperature necessary to produce porous carbons with enhanced performance. Considering these points, Pbz is used as a precursor to produce nitrogen-doped porous carbons (NRPCs) without using any template. Three different activation temperatures, namely 700, 800 and 900 °C, are chosen to prepare activated porous carbons; NRPC-700, NRPC-800 and NRPC-900. Hierarchical micro-/ meso-/macropores were developed in the porous carbons with respect to different activation temperatures. PBz source is used to produce carbons containing heteroatoms and an activation process is used to produce carbons with desirable pore structures. The surface morphology, pore structure and binding of heteroatoms to the carbon surface were analyzed in detail. NRPCs produced in this way can be used as supercapacitors. Further, electrodes were developed using these NRPCs and their electrochemical performance including capacitance, specific capacitance, galvanic charge/discharge, impedance, rate capability are analyzed. The obtained results showed that the activation temperature of 900 °C, is suitable to produce NRPC with a specific capacitance of 245 F g−1 at a current density of 0.5 A g−1, that are attributed to high surface area, suitable pore structure and presence of heteroatoms.

Confined Selenium in N-Doped Mesoporous Carbon Nanospheres for Sodium-Ion Batteries.

In this paper, we have adopted a simple and etching-free method to prepare mesoporous carbon spheres in one step. Selenium can be deposited in the internal cavity, which can avoid pulverization due to the combined effect of volume expansion and a solid-electrolyte interphase (SEI) film while charging and discharging. Therefore, the as-prepared selenium and nitrogen codoped mesoporous carbon nanosphere (Se@NMCS) composites can deliver an outstanding sodium-storage performance of 336.6 mAh g-1 at a present density of 200 mA g-1 and great long-cycling performance. For a further understanding of the Na+ storage mechanism of the Se@NMCS anode in sodium-ion batteries (SIBs), the phase evolution of the Se@NMCS anode has been explored during the charge/discharge process by conducting in situ Raman investigation.

High-Performance and High-Voltage Supercapacitors Based on N-Doped Mesoporous Activated Carbon Derived from Dragon Fruit Peels.

Designing the mesopore-dominated activated carbon electrodes has witnessed a significant breakthrough in enhancing the electrolyte breakdown voltage and energy density of supercapacitors. Herein, we designed N-doped mesoporous-dominated hierarchical activated carbon (N-dfAC) from the dragon fruit peel, an abundant biomass precursor, under the synergetic effect of KOH as the activating agent and melamine as the dopant. The electrode with the optimum N-doping content (3.4 at. %) exhibits the highest specific capacitance of 427 F g–1 at 5 mA cm–2 and cyclic stability of 123% capacitance retention until 50000 charge–discharge cycles at 500 mA cm–2 in aqueous 6 M KOH electrolytes. We designed a 4 V symmetric coin cell supercapacitor cell, which exhibits a remarkable specific energy and specific power of 112 W h kg–1 and 3214 W kg–1, respectively, in organic electrolytes. The cell also exhibits a significantly higher cycle life (109% capacitance retention) after 5000 GCD cycles at the working voltage of ≥3.5 V than commercial YP-50 AC (∼60% capacitance retention). The larger Debye length of the diffuse ion layer permitted by the mesopores can explain the higher voltage window, and the polar N-doped species in the dfAC enhance capacitance and ion transport. The results endow a new path to design high-capacity and high-working voltage EDLCs from eco-friendly and sustainable biomass materials by properly tuning their pore structures.

Enhancing Adsorption and Reaction Kinetics of Polysulfides Using CoP-Coated N-Doped Mesoporous Carbon for High-Energy-Density Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have shown great potential in the next-generation energy storage devices due to high theoretical energy density and low cost. To obtain high-performance Li-S batteries, it is important to inhibit the polysulfide shuttle effect and improve the reaction kinetics of polysulfides. Herein, CoP nanoparticles coated by metal-organic framework-derived N-doped mesoporous carbon (CoP@N-C) composites are synthesized and applied in both a cathode for a sulfur host and a modified layer on a separator for high-energy-density Li-S batteries since the CoP component has strong chemical anchoring capability toward soluble polysulfides and high electrochemical activity toward polysulfides transformation. Meanwhile, the porous structure of conductive N-doped mesoporous carbon can not only buffer the volume variation of sulfur during the charge/discharge process but also enhance the charge transport rate in the cathode. The constructed batteries have demonstrated a high specific capacity of 1222 mAh g-1 (8.6 mAh cm-2) with a high sulfur areal loading of ∼7.0 mg cm-2 on cathodes, and a mass loading of 0.35 mg cm-2 for modified layer on separators. Its average capacity decay is only 0.076% per cycle after 100 cycles. This work presents the highly competitive performance of Li-S batteries on the areal capacity and capacity decay.

Iron-Catalyzed Selective Denitrification over N-Doped Mesoporous Carbon.

Electrocatalytic denitrification has been considered as one of the most promising technologies to selectively reduce excessive nitrogen oxyanions to benign dinitrogen in polluted water. The development of nonprecious metal catalysts with high performance for the denitrification is imperative but still a great challenge. Herein, we report an iron-based electrocatalyst for high-efficiency and selective denitrification. This nanocatalyst is prepared by template assembly of iron-based metal organic frameworks on surface-functionalized bimodal mesoporous carbon and subsequent pyrolysis under argon atmosphere. It contains well-dispersed FeNx sites and Fe nanoparticles (most of them are wrapped by N-doped graphitic carbon), with high surface area (1080 m2 g-1) and uniform mesopore and micropore (5.0 and 1.7 nm) for the construction of electrodes. Experimental results confirm that the catalyst can achieve an excellent nitrate removal capacity of 3410 mg N/g Fe, along with a reduction efficiency up to 87% and N2 selectivity of 81% in neutral electrolyte (100 mg/L NO3--N and 0.1 M Na2SO4) within 24 h. It is proposed that the active FeNx sites cooperated with sufficient Fe nanoparticles to be conducive to adsorption of O in NO3- on the catalyst for the improved performance. The material also presents long-term durability and good adaptability in the range of pH 5-9 and simulated neutral wastewater, mainly contributed by the protection of the mesostructure and graphitic N-doped carbon. These findings open the door to rational design of nonprecious metal iron-based functional electrocatalysts for water purification and environmental remediation.

N-doped Hierarchical Mesoporous Carbon from Mesophase Pitch and Polypyrrole for Supercapacitors

N-doped hierarchical mesoporous carbons have been fabricated by using mesophase pitch (MP) as carbon precursor and polypyrrole as nitrogen resource through MCM-48 template. Carbonization temperatur...

Silica-Templated Covalent Organic Framework-Derived Fe–N-Doped Mesoporous Carbon as Oxygen Reduction Electrocatalyst

The rational design and synthesis of mesoporous functional materials is of great significance to tackle fundamental challenges in materials science and to yield practical solutions for efficient energy utilization. Here, a novel p-toluenesulfonic acid-assisted mechanochemical approach is used to prepare a silica-templated bipyridine-containing covalent organic framework (COF), which can be further converted into an iron–nitrogen-doped mesoporous carbon (mC-TpBpy-Fe) upon carbonization and template removal. The resulting mC-TpBpy-Fe exhibits a large pore volume and surface area, which significantly promote the mass transfer efficiency and increase the accessibility of the active sites, yielding a high ORR activity with a competitive half-wave potential of 0.845 V and limiting current density of 5.92 mA/cm2 (vs 0.852 V and 5.57 mA/cm2 for Pt/C). Application of this COF derived mesoporous carbon within a Zn–air battery revealed that it can operate in ambient conditions with a competitive discharge performanc...

Polyoxometalate Compound-Derived MoP-Based Electrocatalyst with N-Doped Mesoporous Carbon as Matrix, a Cathode Material for Zn-H+ Battery.

H2 is confirmed as a perfect substitute for traditional fossil energy, which can be obtained through hydrogen evolution reaction (HER) after electrocatalytic H2O decomposition. High-performance electrocatalysts play a significant role in HER. Here, with coordination complex-modified Standberg-type polyoxometalate and peach juice as precursors, MoP-based electrocatalysts with N-doped mesoporous carbon as a matrix (MoP@NMC) were obtained. Remarkably, during synthesis, the extremely poisonous PH3 and highly explosive H2 were avoided. MoP@NMC exhibits very excellent electrocatalytic activity in acidic electrolytes. To get 10 mA·cm-2 current, MoP@NMC only requires 92 mV overpotential with Tafel slope 56 mV·dec-1. It also possesses perfect long time stability and durability in HER. More importantly, with MoP@NMC as the cathode and the Zn plate serving as the anode, a new type of battery, Zn-H+ battery, is assembled. In this Zn-H+ battery, Zn provides electrons, which pass through an external circuit and reach the cathode. Under the catalysis of MoP@NMC, the H+ ions are reduced by these electrons and form H2. The open circuit voltage of the Zn-H+ battery is 1.19 V. Its peak power density is 89.7 mW·cm-2. The energy density of this Zn-H+ battery arrives at 809 W h·kg-1 at 10 mA·cm-2. This work establishes a new piece of research field for HER.

One-step Synthesis of N-Doped Mesoporous Carbon as Highly Efficient Support of Pd Catalyst for Hydrodechlorination of 2,4-Dichlorophenol

Although the hard template method is often employed to prepare N-doped mesoporous carbon(N-MC), the removal of the silica template commonly involves the use of highly toxic HF or repeated treatment with NaOH solution. Herein, we report a polyvinylidene fluoride-assisted one-step method for synthesis of N-MC, namely the silica-free N-MC can be prepared via temperature-programmed thermal treatment of a slurry obtained by dispersing nano-silica into a solution containing sucrose, urea, oxalic acid, polyvinylidene fluoride and dimethylacetamide. The resulting N-MC, which owns 3.47%(mass fraction) nitrogen and a surface area of 929 m2/g, is a highly suitable support of Pd catalyst used in hydrodechlorination of 2,4-dichlorophenol, with its performance being much better than those of MC and activated carbon. The excellent catalytic hydrodechlorination activity of the Pd/N-MC catalyst can be attributed to its strong metal-support interaction which results in a good Pd dispersion and high resistance to the growth of nanosized Pd under reaction conditions.