N-doped Hierarchical Porous Carbon Research Articles

Utilizing in situ construction of N-doped hierarchical porous carbon to achieve electronic control of highly dispersed Pd nanoparticles for efficient catalytic hydrogenation of CO2 to formic acid

Hydrogenation of CO2 to produce formic acid/formate is a significant pathway for future energy storage and utilization. The development of heterogeneous catalysts with high activity and stability for this process is still a challenge. In this work, the in-situ N-doped hierarchical porous carbon derived from distiller's grains was used as a support for Pd-based catalysts (Pd/NC) to convert CO2 into valuable chemicals while making high-value use of waste biomass. The optimum catalyst, Pd/NC-800, shown exceptional catalytic performance, achieving a turnover frequency (TOF) of 2060h-1 at 100℃, 4MPa in the catalytic CO2 hydrogenation to formate reaction. Comprehensive experimental results and density functional theory calculations indicate that the electronic effect between the pyridine N in the support and the Pd nanoparticles (NPs) can make the Pd surface reach the state of electron enrichment and enhance the metal-support interaction. Moreover, the synthesized material has hierarchical pore structure, which provides abundant Pd anchor location sites and improves mass transfer efficiency. The results not only provide a feasible strategy for the preparation of efficient CO2 hydrogenation catalysts, but also break a new and effective avenue for the resource utilization of distiller's grains.

Hierarchical Porous N-Doped Carbon Particles Derived from ZIF-8 as Highly Efficient H2S Selective Oxidation Catalysts.

In the selective oxidation of H2S, the catalytic activity over N-doped carbon-based catalysts is significantly influenced by the accessibility of active sites and the mass transfer rates of reactant molecules (e.g., H2S and O2) as well as generated sulfur monomers. Therefore, it is crucial for enhancing the initial performance via the controlled synthesis of carbon-based catalysts with highly exposed active sites and unique porous structures. Herein, we reported on an efficient strategy to synthesize nanosized N-doped carbon particles with hierarchical porous structures by directly pyrolyzing an oversaturated NaCl-encapsulated ZIF-8 precursor mixture. The introduction of NaCl not only serves as a pollution-free template to promote the formation of graphitic carbon layers but also acts as an intercalating agent to guide the derivation of hierarchical porous structures, as well as enhances the amount of active nitrogen species in the catalysts. As a result, the as-prepared H-NC800 catalyst shows excellent H2S selective oxidation performance (sulfur formation rate is 794 gsulfur·kgcat-1·h-1), good stability (>80 h), and antiwater vapor properties. The characterization results and DFT calculations indicate the crucial role of pyridinic N in the adsorbing and activating reactant molecules (H2S, O2). Furthermore, nanoscale N-doped carbon particles accelerated the rapid transport of generated sulfur monomers under a hierarchical porous structure. This investigation introduces a distinctive strategy for synthesizing ZIF-8-derived N-doped carbon nanosized with a hierarchical porous structure, while its efficient and stable H2S selective oxidation performance highlights significant potential for practical implementation in the industrial desulfurization process.

Hierarchical porous N-doped carbon fibers enable ultrafast electron and ion transport for Zn-ion storage at high mass loadings

Zinc-ion capacitors (ZICs) are a promising and safe energy storage system for portable electronics but usually limited by relatively low areal capacity and energy density. Although increasing the mass loading has been suggested, thick electrode layers and clogged pores unavoidably lead to sluggish electron transport and ion diffusion as well as “dead volume” of active materials. Herein, a millimeter-scale 3D thick-network electrode, composed of closely intertwined hierarchical porous N-doped and free-standing carbon nanofibers (HPNCFs), was fabricated via carbonization of nanoscale zeolitic imidazolate framework (ZIF-8) particles embedded in electrospun polyacrylonitrile (PAN) nanofibers. With fast electron/ion transport, large ion-accessible surface area and high utilization rate of active materials, the mass loading of the HPNCFs electrode can reach 48.67 mg cm−2 with a thickness of 4.46 mm. Moreover, the HPNCFs-based ZICs can yield a superior areal/gravimetric capacity of 4.13 F cm−2 /280 F g−1, superior rate capability up to 193.7 F g−1 even at 100 A g−1, high energy density of 99.6 Wh kg−1, and long-term stability for 40,000 cycles. The straightforward approach can provide an opportunity to prepare efficient thick electrodes that could be applied in electrocatalysis, energy storage/conversion, and other electrochemical energy-related techniques.

3D hierarchical porous N-doped carbon nanoarchitecture coated bimetallic phosphides as a highly efficient bifunctional electrocatalyst for overall water splitting

As the energy and ecological crises are increasingly grim, it is challengeable but extremely attractive to fabricate highly efficient and low-cost bifunctional electrocatalysts for overall water splitting (OWS). Herein, a bimetallic phosphide embedded in N-doped hierarchical porous carbon (CoP/Ni2P@NHPC) framework was successfully constructed by calcination and phosphorization of cobalt–nickel coordination polymer nanoflowers (Co/Ni CPNFs), which were obtained by a facile hydrothermal process. Benefitting from their fascinating architecture and composition, the as-prepared CoP/Ni2P@NHPC exhibits outstanding electrochemical properties for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with small Tafel slopes (103.9 mV dec-1, 62.58 mV dec-1) and ultralow overpotentials (275 mV, 159 mV at 10 mA cm−2) in alkaline medium. Additionally, the CoP/Ni2P@NHPC can be used as a bifunctional catalyst in a two-electrode water splitting device, and it only requires a low cell voltage of 1.55 V to attain the current density of 10 mA cm−2. Meanwhile, the CoP/Ni2P@NHPC also present admirable durability (at least 20 h) under long-term electrolysis. This work gives inspiration for the preparation of highly active bifunctional electrocatalysts for OWS.

Dual-ultrasmall Sb and Sb6O13 nanodots co-anchored MXene with manipulable structural chemistry modulating bidirectional kinetics toward advanced lithium-sulfur batteries

Exfoliation and modulation of intercalated layered transition metal carbides and/or nitrides (MAX) into their derivatives (MXenes) featured with manipulable structural chemistry by remain enormous challenges toward practical applications. Herein, an extraordinary low-dimensional MXenes modulated by dual-ultrasmall Sb and Sb6O13 nanodots via in situ structural editing protocol using Lewis-basic fluorides in organic molten salts. Their original internal non-van der Waals bonds and physicochemical natures are simultaneously mediated by manipulating fluorine anions and antimony cations as chemical scissors generating into zero- and one-dimensional MXenes (MFNCTS-Z, MFNCTS-O) encapsulated by hierarchical porous N-doped carbon. Experimental and theoretical results manifest MFNCTSs as alternative dual-functional hosts toward both sulfur (S) cathode and lithium (Li) anode modulating bidirectional kinetics originated from their synergistic effect of physical confinement and chemical anchor effect accelerating polysulfides redox chemistry, and homogeneous lithium deposition. As a result, the assembled lithium-sulfur full batteries offer impressive electrochemical performances. This work paves a new avenue for developing low-dimensional MXenes by controllable structural editing strategy toward practical energy conversion and storage fields.

Synergistic Effect of Electrocatalyst for Enhanced Oxygen Reduction Reaction: Low Pt-Loaded CuPt Alloy Nanoparticles Supported on N-Doped Hierarchical Porous Carbon.

It is challenging to synthesize oxygen reduction reaction (ORR) electrocatalysts that are highly efficient, affordable, and stable for use in proton exchange membrane fuel cells. To address this challenge, we developed a low platinum-loading (only 6.68% wt) ORR catalyst (PtCu1-NC), comprising CuPt nanoparticles (average size: 1.51 nm) supported on the N-doped carbon substrates. PtCu1-NC possesses a high specific surface area of 662 m2 g-1 and a hierarchical porous structure, facilitating efficient mass transfer. The synergistic effect from introduced copper and the electron effect from nitrogen modify the electronic structure of platinum, effectively accelerating the ORR reaction and enhancing stability. Density functional theory calculations demonstrate the catalytic mechanism and further verify the synergistic effect. Electrochemical assessments indicate that PtCu1-NC exhibits specific activity and mass activity 5.3 and 5.6 times higher, respectively, than commercial Pt/C. The half-wave potential is 27 mV more positive than that of commercial Pt/C. The electrochemical active surface area value is 104.3 m2 g-1, surpassing that of Pt/C. Approximately 78% of current is retained after 10,000 s chronoamperometry measurement. These results highlight the effectiveness of alloying in improving the catalyst performance.

Self-nitrogen-doped hierarchical porous carbon spheres as metal-free catalyst for efficient photocatalytic CO2 reduction

It is rather important to develop an efficient, stable and economical photocatalyst for solar-driven CO2 reduction. Herein, N-doped hierarchical porous carbon spheres (NPCS-F6) with metal-like activity is synthesized using acrylamide and F127 as nitrogen source and soft template, and the effective synergy between nitrogen-containing species and hierarchical pore structure makes the samples exhibit excellent CO2 reduction properties. XPS characterization illustrates that the introduced pyridine nitrogen and pyrrole nitrogen groups contribute to the increase of CO2 reduction sites on the surface of the material. N2 adsorption analysis verifies the existence of hierarchical pore structures in which micropores facilitate the exposure of more adsorption active sites, while mesopores and macropores can be used as transfer channels to connect the internal micropores and reduce the molecular diffusion resistance to improve CO2 adsorption performance. In addition, the pore structure of the samples prepared with P123 and CTAB as templates is mainly microporous, whereas carbon spheres with hierarchical pores coexisting are obtained with F127 as template. The evaluation of photocatalytic CO2 reduction activity shows that the CO yield of NPCS-F6 could reach 17.56 μmol·g−1 for 8 h, which is 1.17 times, 1.08 times and 1.07 times of the original NCS-8 (15.05 μmol·g−1), NPCS-P6 (P123 as soft template, 16.25 μmol·g−1) and NPCS-C1 (CATB as soft template, 16.39 μmol·g−1), respectively. Comprehensive characterization results are analyzed to propose a possible mechanism for photocatalytic CO2 reduction, in which photogenerated electron-hole pairs are generated inside the material under light conditions, and the photogenerated electrons are transferred to the N-6/N-5 active sites through the electron transfer channel N-Q to react with CO2 molecules adsorbed on the surface to be reduced to CO. Finally, our results provide a favorable and feasible strategy to synthesize metal-free photocatalysts for high-efficiency CO2 adsorption and targeted reduction of CO2 to CO.

Coordination polymer and layered double hydroxide dual-precursors derived polymetallic phosphides confined in N-doped hierarchical porous carbon nanoflower as a highly efficient bifunctional electrocatalyst for overall water splitting

Controllable construction of proficient electrocatalyst with 3D hierarchical architecture to achieve low cost and high efficient overall water splitting is of great significance to the sustainable development. Hereby, trimetallic phosphides confined in N-doped carbon nanoflowers (CoNiP/CoNiFeP@NCNFs) were fabricated using CoNi coordination polymer nanoflowers/CoNiFe layered double hydroxide (CoNi CPNFs/CoNiFe LDH) as precursors followed by phosphorization. Benefiting from the unique 3D hierarchical porous architecture, preeminent conductivity, high specific surface area, efficient mass/charge transfer and synergic effect of various transition metals, the well-designed CoNiP/CoNiFeP@NCNFs exhibit extraordinary electrocatalytic performance for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. Particularly, this novel material can work as a bifunctional catalyst in an integrated water-splitting electrolyzer, which only requires a low voltage of 1.55 V to realize the current density of 10 mA cm−2 with admirable durability (at least 28 h). This work certified the foreground of composites assembled by 3D hierarchical porous carbon and polymetallic phosphides for overall water splitting. It also provided a novel proposal for the rational designing and constructing highly active electrocatalysts by using coordination polymer and LDH as dual-precursors.

A hierarchical porous N-doped carbon material as catalyst derived from the folic acid-Zn/KBr hydrogel: Reaction network and kinetics and mechanism for the oxidation of furfural to maleic acid

A novel hydrogel (named FA-Zn/KBr) was prepared, by taking advantage of the hydrogen-bonding and π-π stacking interactions between the pterin heterocycles of the folic acid (FA) molecules. The hydrogel is composed of highly dispersed KBr, coordinated zinc ions, and stacked arrays of folate tetramers. Due to the presence of KBr, a hierarchical porous nitrogen-doped carbon (PNC-800) material with a specific surface area 2807.9 m2/g can be formed through the calcination of the FA-Zn/KBr xerogel under N2. PNC-800 is used to catalyze the oxidation of furfural to maleic acid in the presence of H2O2. Representative nine reactions constitute the reaction network. The reaction rate constants and apparent activation energy were obtained for each reaction. Based on the kinetics parameters, the simulated results are in good agreement with the experimental data. The mechanism of the reaction catalyzed by PNC-800 is proposed based on ample experimental evidence. The graphitic nitrogen species in PNC-800 are the active sites. PNC-800 catalyzes the decomposition of hydrogen peroxide to generate hydroxyl radical (HȮ), which oxidizes furfural to furfural radical, and the furfural radical is subsequently converted to 5-hydroxy-furan-2(5H)-one (HFONE). The conversion of furfural to maleic acid via the formation of HFONE is the main reaction pathway. In addition, the hierarchical porous structure with a high specific surface area facilitates the interaction of reactant with the active sites. PNC-800 has been shown an excellent catalytic activity for the production of maleic acid from furfural. For the oxidation of 1000 mM furfural using 50 mg PNC-800 at 80 °C within 9 h, the conversion of furfural is 100 % with a maleic acid yield 67.5 %.

One-step green synthesis of N-doped hierarchical porous carbon from glycine for high-performance symmetric supercapacitor

N-doped hierarchical porous carbon (NHPC) was facilely fabricated by a one-step pyrolysis of glycine and water-soluble Na2CO3, which is employed as a renewable water-soluble template without additional corrosive activating reagent. Benefiting from the hierarchical porous structure, high specific surface area (2735 m2 g−1) and the suitable nitrogen content of 3.84 at%, the obtained porous carbon exhibits a high specific capacitance (Csp) of 267 F g−1 at 0.2 A g−1 in a three-electrode system and 201 F g−1 at 0.2 A g−1 in the symmetric supercapacitor. More importantly, it shows an impressive rate capability of 102 % retention at 20 A g−1, outstanding cycling stability with 99.95 % of capacitance retention at 5 A g−1 after 10,000 cycles and a high energy density of 28.8 Wh kg−1 at a power density of 20 KW kg−1 in the symmetric supercapacitor. The results indicate that the synthesized NHPC obtained from this simple synthesis method would be an effective electrode material for symmetric supercapacitors, and this eco-friendly and easily scaled-up approach would provide a valuable strategy for the synthesis of porous carbon materials.

Activation-self-activation craft for one-step synthesis of GO-inbuilt mesopore-dominated N-doped hierarchical porous carbon in capacitive deionization capture of Ni(II)

Capacitive deionization (CDI) is considered a polar-promising technology to remove heavy-metal ions from wastewater. Herein, a green activation-self-activation strategy was exploited to build graphene (GO)-inbuilt mesopore-dominated N-doped hierarchical porous carbons (ENHPCs) using sodium lignosulfonate (SLS) as carbon sources/self-activators. Different from SLS self-activation and K2C2O4-SLS activation-self-activation, ENHPCLKG gained via GO-mediated K2C2O4-SLS activation-self-activation showed suitable mesopore-dominated micro-mesoporous structures with high surface area of 1795.5 m2/g, large mesoporous volume of 0.87 m3/g, 3.65 % N-doping and excellent conductivity. Its unique hierarchical porous structure and abundant active sites facilitated the ion rapid insertion and extraction. When utilized to capture low-concentration nickel (Ni2+) ions, ENHPCLKG delivered splendid salt removal capacity of 17.86 mg/g, rapid average salt removal rate of 0.99 mg/g/min and standout cycle stability. Meanwhile, ENHPCLKG was further extended to remove NaCl, MgCl2, CaCl2 and Ni-containing wastewater, showing superior CDI property. Moreover, the recycled ENHPCLKG (10th) taken to eliminate indomethacin (IDM) depicted a splendid adsorption capacity. This work proved the significant applicant potential of the novel and green ENHPCLKG for disposing of Ni2+ ions via CDI technology.

Controllable Preparation of a N-Doped Hierarchical Porous Carbon Framework Derived from ZIF-8 for Highly Efficient Capacitive Deionization.

Capacitive deionization (CDI) is a promising desalination technology, and metal-organic framework (MOF)-derived carbon as an electrode material has received more and more attention due to its designable structure. However, MOF-derived carbon materials with single-pore structures have been difficult to meet the technical needs of related fields. In this work, the ordered hierarchical porous carbon framework (OMCF) was prepared by the template method using zeolitic imidazolate frameworks-8 (ZIF-8) as a precursor. The pore structures, surface properties, electrochemical properties, and CDI performances of the OMCF were investigated and compared with the microporous carbon framework (MCF), also derived from ZIF-8. The results show that the hierarchical porous carbon OMCF possessed a higher specific surface area, better hydrophilic surface (with a contact angle of 13.45°), and higher specific capacitance and ion diffusion rate than those of the MCF, which made the OMCF exhibit excellent CDI performances. The adsorption capacity and salt adsorption rate of the OMCF in a 500 mg·L-1 NaCl solution at 1.2 V and a 20 mL·min-1 flow rate were 12.17 mg·g-1 and 3.34 mg·g-1·min-1, respectively, higher than those of the MCF. The deionization processes of the OMCF and MCF closely follow the pseudo-first-order kinetics, indicating the double-layer capacitance control. This work serves as a valuable reference for the CDI application of N-doped hierarchical porous carbon derived from MOFs.

Boosting bifunctional oxygen electrocatalysis with atomically dispersed Fe and Co dual-metal sites for flexible zinc-air batteries

Rechargeable zinc-air batteries (ZABs) hold enormous promise as energy conversion and storage system of the next generation. Here, through utilizing the Co/ZIF-8@F127 precursor and a coordinated strategy that includes ‘post-absorption’ and ‘dual-pyrolysis’, a Fe/CoNx-C possesses a hierarchical porous N-doped carbon with an ultrahigh specific area and rich defects to stabilize accessible dual metallic active sites. With a narrow potential gap of 0.71 V, the Fe/CoNx-C catalyst demonstrates excellent bifunctional electrocatalytic activity toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Noteworthily, scanning electrochemical microscopy (SECM) was used to visualize the local electrocatalytic ORR activity of CoNx-C and Fe/CoNx-C. For the applications of zinc-air batteries, the Fe/CoNx-C-based cathode provides a high peak power density of 134.97 mW cm−2 for aqueous ZABs. Moreover, quasi-solid-state ZABs (including flexible ZAB and cell ZAB)-based on Fe/CoNx-C as cathode catalyst demonstrate satisfying flexibility and durability. The theoretical calculation results further elucidate the synergistic effect that the engagement of Fe atoms in the electron transfer process of the FeN4@CoN4 system reduces the energy barrier of the rate-determining-step in ORR and OER, hence facilitating the reversible oxygen electrocatalytic kinetics.

Enhanced low-frequency microwave absorption of N-doped biomass derived carbon

Hierarchical porous undoped and N-doped carbon derived from the natural spinach roots was prepared by a facile carbonization process at 600–800 ℃ respectively. The electromagnetic properties were carefully investigated in the range of 1–18 GHz in order to study the effect of the tunable permittivity on the microwave absorbing and shielding performance by modulating the intrinsic polarization of the biomass carbon. Compared with the other samples, the undoped one sintered at 650 ℃ shows the minimum reflection loss (RL) of − 42.93 dB at 16.72 GHz with a thickness of 2.0 mm, while the effective absorbing bandwidth achieves 6.46 GHz at 2.4 mm. With the N-doping, the permittivity is obviously affected by the nitrogen-containing groups and compounds induced dipolar and interfacial polarization. The RLmin of the N-doped carbon sample sintered at 700 ℃ has arrived at − 49.96 dB at 15.88 GHz with a very thin thickness of 1.5 mm. Besides, the impedance matching bandwidth can cover the L-C band in the N-doped carbon with the excellent RL of − 43.195 dB at d= 8.4 mm and f= 2.4 GHz. The competitive and tunable mechanism of the dielectric property are also studied for the tunable impedance and microwave absorption.

Nickel-iron sulfide nanoparticles supported on biomass-derived N-doped hierarchical porous carbon as a robust electrode for supercapacitors

Biomass-based carbon electrode material with hierarchical porous structure is considered as a promising candidate for supercapacitor applications, which could enhance the electron transfer and shorten the ion diffusion pathways. However, the low energy density of carbon-based materials seriously affects their wide applications. Herein, 3D N-doped hierarchical porous carbon coupled with nickel-iron sulfide nanoparticles (Fe5Ni4S8/FeS@N-HPC) is fabricated by a simple pyrolysis process. The 3D N-doped interconnected porous structure with large specific surface area provides more channels for ion transport and electron transfer. The nickel-iron sulfide nanoparticles in the porous carbon offer numerous sites for reduction and oxidation occurring to improve the charge storage for supercapacitors. Consequently, the synthesized Fe5Ni4S8/FeS@N-HPC electrode exhibits excellent electrochemical properties. The optimized Fe5Ni4S8/FeS@N-HPC composite fabricated under 800 °C displays an excellent capacitance of 2812.4 F g−1 (734.56 C g−1) at a current density of 0.5 A g−1. Beside, the Fe5Ni4S8/FeS@N-HPC-800//active carbon asymmetric supercapacitor shows an energy density of 76.8 W h kg−1 at a power density of 395.03 W kg−1 and superior cycling stability of 93.24% over 10,000 charge-discharge cycles. Our work presents a novel approach to the construction of high-performance electrode materials for supercapacitors.

Ru-promoted NiFe oxyhydroxide anchored on the hierarchical porous N-doped carbon aerogel: Electronic structures modulation for much enhanced OER/HER dual-functional characteristics

Herein, we have demonstrated a novel Ru-promoted NiFe oxyhydroxide anchored on N-doped carbon aerogel (RuNi7FeOx(OH)y @NCA) aerogel electrocatalyst via a facile sol-gel process, combined with a supercritical drying technique. The optimal RuNi7FeOx(OH)y @NCA shows a typical "pearl-like" aerogel nanostructure with a three-dimensional network, showing a large specific surface area of 227.7 m2·g−1. The achieved RuNi7FeOx(OH)y @NCA exhibits high OER activity with a low overpotential of 278.0 mV at 10 mA·cm−2 and a high TOF of 0.107 s−1. Moreover, the RuNi7FeOx(OH)y @NCA aerogel displays excellent hydrogen evolution reaction (HER) activity under alkaline conditions, with a small overpotential of 99.0 mV at a current density of 10 mA·cm−2, and a small Tafel slope of 61.1 mV·dec−1. DFT calculations show that the enhanced OER activity is attributed to the improved binding strength of *OOH intermediate on the catalyst surface, and the introduced Ru with larger electron density and weaker spin density leads to the improved HER activity.

Designing a Hierarchical Porous Carbon with Optimized Nitrogen Doping for Efficient Oxygen Reduction Reaction.

Nitrogen-doped carbon is considered one of the most promising oxygen reduction catalysts due to its low cost and high activity, however, it still falls short of Pt/C. In this study, we report a strategy for the preparation of highly reactive N-doped hierarchical porous carbon by primary pyrolysis using zinc acetate as a stand-alone zinc source and amino-rich reactants as carbon and nitrogen sources to introduce Zn-Nx structures into mesoporous structures generated by the hard template method using the strong coordination of zinc and amino groups. Benefited from the simultaneous optimization of the hierarchical porous structure and nitrogen-doping, the half-wave potential of Zn(OAc)2-DCD/HPC is as high as 0.909 V vs. RHE, much better than that of commercial Pt/C catalysts (0.872 V vs. RHE). In addition, zinc-air batteries assembled with Zn(OAc)2-DCD/HPC (Pmax=198 mW cm-2) as the cathode exhibit higher peak power density compared to Pt/C (Pmax=168 mW cm-2). This strategy might open up new opportunities for designing and developing highly active metal-free catalysts.

High-yield green synthesis of N-doped hierarchical porous carbon by Nitrate-Mediated organic salt activation strategy for capacitive Deionization: Universality and commerciality

Developing a green and facile strategy for high-yield preparing N-doped hierarchical porous carbon (NHPC) for capacitive deionization (CDI) is a huge challenge for desalination. So far, there are limited reports on high-yield NHPC synthesis. Herein, a novel nitrate (NaNO3, KNO3, Zn(NO3)2 and NH4NO3)-mediated-organic salt activation strategy was exploited to construct NHPCXy (X = Na, K, Zn, NH4; Y(nitrate ratio) = 1, 3, 5). Thereinto, C6H5K3O7 served as activator and nitrate acted as assisted-activator and foaming agent. Compared with C6H5K3O7 activation, NHPCNa3 acquired by NaNO3-C6H5K3O7 co-activation achieved 35.5% high yield and depicted 3D macroarray structures with high specific surface area (SBET) of 1912.2 m2/g, large pore volume (Vpore) of 1.56 cm3/g and 1.21 % N content. Its tertiary pore structure and rich surface-exposed active sites favored the ions rapid insertion and extraction from the micropores. The final NHPCNa3 delivered an excellent salt adsorption capacity (SAC) of 19.74 mg/g. Moreover, it exhibited 14.61 mg/g high SAC at 15.5 mg/cm2 and only showed 9.4% SAC drop after 50 cycles. While using diverse biomass precursors, it obtained an optimal SAC of 23.16 mg/g. NHPCK3, NHPCZn3 and NHPC(NH4)3 also presented the feature of high-yield-high-performance. The high yield came from the foaming effect of nitrate and the property difference may be ascribed to the different cations. This work provides one span-new green universality strategy to design high-yield-high-performance NHPCs in commercial-grade CDI applications.

Fabricating self-templated and N-doped hierarchical porous carbon spheres via microfluidic strategy for enhanced CO2 capture

N-doped porous biochar is a promising material for CO2 capture due to its easy regeneration and high CO2 selectivity. In this study, a new strategy was proposed to design monodisperse porous carbon spheres by microfluidics system with chitosan in-situ grow ZIF-8, utilizing ZIF-8 as a self-sacrificing template and nitrogen dopant. The mesoporous volume and N content of carbon spheres can be adjusted through the ZIF-8 content in the microfluidic system and carbonization temperature, within 0.01 ∼ 0.48 cm3/g and 3.23 ∼ 19.25%, respectively. The optimum sample (CZ2-900) exhibited superior CO2/N2 selectivity at 40. Adsorption kinetics and diffusion resistance indicated that CO2 adsorption in CZ2-900 is controlled by the process of CO2 diffusion from the surface of the basic site to mesopores. This was the first attempt at using a microfluid chip to grow ZIF-8 in chitosan skeleton and pyrolysis approach to synthesize N-doped porous carbon sphere where both additional template agent and activator are non-used, revealing the potential of microfluidic technology for the precise synthesis of highly selective CO2 capture materials.

Zinc-Mediated Template Synthesis of Hierarchical Porous N-Doped Carbon Electrocatalysts for Efficient Oxygen Reduction.

The development of highly active and low-cost catalysts for use in oxygen reduction reaction (ORR) is crucial to many advanced and eco-friendly energy techniques. N-doped carbons are promising ORR catalysts. However, their performance is still limited. In this work, a zinc-mediated template synthesis strategy for the development of a highly active ORR catalyst with hierarchical porous structures was presented. The optimal catalyst exhibited high ORR performance in a 0.1 M KOH solution, with a half-wave potential of 0.89 V vs. RHE. Additionally, the catalyst exhibited excellent methanol tolerance and stability. After a 20,000 s continuous operation, no obvious performance decay was observed. When used as the air-electrode catalyst in a zinc-air battery (ZAB), it delivered an outstanding discharging performance, with peak power density and specific capacity as high as 196.3 mW cm-2 and 811.5 mAh gZn-1, respectively. Its high performance and stability endow it with potential in practical and commercial applications as a highly active ORR catalyst. Additionally, it is believed that the presented strategy can be applied to the rational design and fabrication of highly active and stable ORR catalysts for use in eco-friendly and future-oriented energy techniques.