Low-temperature VOCs oxidation performance of Pt/zeolites catalysts with hierarchical pore structure

Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic compounds(VOCs)were evaluated.The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal.The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts,while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containingNandOheteroatoms.In addition,it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst.This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.

Tofukasu-derived biochar with interconnected and hierarchical pores for high efficient removal of Cr (Ⅵ)

Herein,we report the synthesis of interconnected hierarchical pore biochar(HTB)via an ice-templating strategy using bio-waste(tofukasu).The abundance of N-and O-containing functional groups in tofukasu makes it easy to form hydrogen bonds with water molecules and water clusters,resulting in nano-micro structures like ice clusters and snow crystals during freezing process.More importantly,tofukasu will be squeezed by micron-scale snow crystals to form coiled sheet-like structures,and its surface and interior will be affected by needle-like ice nanocrystals from several nanometers to tens of nanometers to form transverse groove needles and mesopores.The ice crystals are then removed by sublimation with tofukasu,leaving the interconnected pore structure intact.Therefore,the ice template synthesis strategy endowed the interconnected hierarchical pore structure of HTB with a large specific surface area(SBET,733 m^(2)⋅g^(−1))and hierarchical porosity(30.30%for mesopores/total pore volume ratio),which is significantly higher than the normal dry treated tofukasu biochar(TB),which had a SBET of 436 m^(2)⋅g^(−1) and contained 1.53%mesopores.In addition,the sheet-like structure with interconnected pores of HTB favors high exposure of active sites(N-and O-containing functional groups),and a fast electron transport rate.As a result,HTB had an excellent adsorption capacity of 159.65 mg⋅g^(−1),which is 4.7 times that of typical block biochar of TB(33.89 mg⋅g^(−1))according to Langmuir model.Electrochemical characterization,FTIR and XPS analysis showed that the mechanism of Cr(Ⅵ)removal by HTB included electrostatic attraction,pore filling,reduction and surface complexation.

Efficacy of hierarchical pore structure in enhancing the tribological and recyclable smart lubrication performance of porous polyimide

Herein,a porous oil-containing material with hierarchical pore structure was successfully prepared through microtexturing large pores on the surface of porous polyimide(PPI)with single-level small pores.Compared to the conventional oil-containing material,the hierarchically porous oil-containing material exhibited high oil-content,and retained excellent mechanical properties and high oil-retention because of the synergistic effects of large pores and small pores.Furthermore,the lubricant stored in the hierarchically porous polyimide could release to the interface under thermal-and-mechano-stimuli,and the released lubricant could be reabsorbed into the hierarchically porous polyimide via the capillary-force offered by the porous channel.Based on the high oil-content and recyclable oil release/reabsorption,the hierarchically porous oil-containing polyimide exhibited excellent lubrication performance(coefficient of friction was 0.057).Furthermore,the composite could perform 1,069 cycles of smart lubrication(1 h per cycle),which significantly extended the service life of the hierarchically porous oil-containing smart lubrication material.

Preparation of hydrophobic hierarchical pore carbon–silica composite and its adsorption performance toward volatile organic compounds

Carbon–silica materials with hierarchical pores consisting of micropores and mesopores were prepared by introducing nanocarbon microspheres derived from biomass sugar into silica gel channels in a hydrothermal environment.The physicochemical properties of the materials were characterized by nitrogen physical adsorption(BET),scanning electron microscopy(SEM),and thermogravimetric(TG),and the adsorption properties of various organic waste gases were investigated.The results showed that microporous carbon materials were introduced successfully into the silica gel channels,thus showing the high adsorption capacity of activated carbon in high humidity organic waste gas,and the high stability and mechanical strength of the silica gel.The dynamic adsorption behavior confirmed that the carbon–silica material had excellent adsorption capacity for different volatile organic compounds(VOCs).Furthermore,the carbon–silica material exhibited excellent desorption characteristics:adsorbed toluene was completely desorbed at 150℃,thereby showing superior regeneration characteristics.Both features were attributed to the formation of hierarchical pores.

Zn-based metal organic framework derivative with uniform metal sites and hierarchical pores for efficient adsorption of formaldehyde

A Zn-containing graphite carbon(Zn-GC)with uniform Zn metal sites and hierarchical pore structure was obtained by pyrolysis of Zn-based metal organic framework(MOF).Zn-GC exhibited excellent adsorption capacity and reproducibility for formaldehyde.The adsorption capacity of Zn-GC was 736 times that of commercial activated carbon and 5.6 times that of ZSM-5 adsorbents.The characterization and experimental results showed that the surface chemical characteristics of the adsorption material play an important role in the adsorption performance.The superior performance was attributed to Zn metal sites and oxygen-containing functional groups on the MOF derivative as well as hierarchical pore structure.The material showed a great potential in the field of organic pollutant removal.

Facile assembly of mesoporous silica nanoparticles with hierarchical pore structure for CO2 capture

In the work,we propose an efficient one-pot approach for synthesis of a new type of mesoporous silica nanoparticles(MSNs).That can be successfully realized by using tetraethylorthosilicate(TEOS) and N-[3-(trimethoxysilyl)propyl]ethylenediamine(TSD) as the silica precursors and cetyltrimethylammonium bromide(CTAB) as the structure-directing agent through a facile assembly process.The as-synthesized MSNs possess a spherical morphology with about 230 nm,a relatively high surface area of133 m^2/g,and a hierarchical pore size distribution.When applied as the sorbents,the amine-functioned MSNs demonstrate the enhanced adsorption capacity for CO2 capture(at 1 bar,15 vol% CO2,up to80.5 mg/g at 75℃),high selectivity,and good cycling durability,benefiting from the suitable modification of polyethyleneimine.

Constructing a hollow core-shell structure of RuO_(2) wrapped by hierarchical porous carbon shell with Ru NPs loading for supercapacitor

Hollow core-shell structure nanomaterials have been broadly used in energy storage, catalysis, reactor,and other fields due to their unique characteristics, including the synergy between different materials,a large specific surface area, small density, large charge carrying capacity and so on. However, their synthesis processes were mostly complicated, and few researches reported one-step encapsulation of different valence states of precious metals in carbon-based materials. Hence, a novel hollow core-shell nanostructure electrode material, RuO_(2)@Ru/HCs, with a lower mass of ruthenium to reduce costs was constructed by one-step hydrothermal method with hard template and co-assembled strategy, consisting of RuO_(2) core and ruthenium nanoparticles(Ru NPs) in carbon shell. The Ru NPs were uniformly assembled in the carbon layer, which not only improved the electronic conductivity but also provided more active centers to enhance the pseudocapacitance. The RuO_(2) core further enhanced the material’s energy storage capacity. Excellent capacitance storage(318.5 F·g^(-1)at 0.5 A·g^(-1)), rate performance(64.4%) from 0.5 A·g^(-1)to 20 A·g^(-1), and cycling stability(92.3% retention after 5000 cycles) were obtained by adjusting Ru loading to 0.92%(mass). It could be attributed to the wider pore size distribution in the micropores which increased the transfer of electrons and protons. The symmetrical supercapacitor device based on RuO_(2)@Ru/HCs could successfully light up the LED lamp. Therefore, our work verified that interfacial modification of RuO_(2) and carbon could bring attractive insights into energy density for nextgeneration supercapacitors.

Enhanced MTO performance over acid treated hierarchical SAPO-34

Hierarchical SAPO‐34 crystals were synthesized by a facile acid etching post‐treatment. Butterfly‐shaped porous patterns on four side faces and hierarchical pores composed of micropores,mesopores and macropores were formed after a nitric acid or oxalic acid treatment. The catalyticperformance of the hierarchical SAPO‐34 for the methanol to olefins (MTO) process showed that thesynergistic effect of the hierarchical pores and acid sites resulted in a longer catalyst lifetime (from210 to 390 min for the acid treated SAPO‐34) and higher selectivity to light olefins of 92%–94%.The ethylene selectivity can be adjusted between 37.4% and 51.5% by the pore size. No hierarchical SAPO‐34 was obtained after a treatment with butanedioic acid, and with this sample, fast deactivation was detected after 100 min.

Creation of Triple Hierarchical Micro-Meso-Macroporous N-doped Carbon Shells with Hollow Cores Toward the Electrocatalytic Oxygen Reduction Reaction

A series of triple hierarchical micro-mesomacroporous N-doped carbon shells with hollow cores have been successfully prepared via etching N-doped hollow carbon spheres with CO_2 at high temperatures.The surface areas, total pore volumes and microporepercentages of the CO_2-activated samples evidently increase with increasing activation temperature from 800 to950 °C, while the N contents show a contrary trend from7.6 to 3.8 at%. The pyridinic and graphitic nitrogen groups are dominant among various N-containing groups in the samples. The 950 °C-activated sample(CANHCS-950) has the largest surface area(2072 m^2 g^(-1)), pore volume(1.96 cm^3 g^(-1)), hierarchical micro-mesopore distributions(1.2, 2.6 and 6.2 nm), hollow macropore cores(*91 nm)and highest relative content of pyridinic and graphitic N groups. This triple micro-meso-macropore system could synergistically enhance the activity because macropores could store up the reactant, mesopores could reduce the transport resistance of the reactants to the active sites, and micropores could be in favor of the accumulation of ions.Therefore, the CANHCS-950 with optimized structure shows the optimal and comparable oxygen reduction reaction(ORR) activity but superior methanol tolerance and long-term durability to commercial Pt/C with a 4 e--dominant transfer pathway in alkaline media. These excellent properties in combination with good stability and recyclability make CANHCSs among the most promising metal-free ORR electrocatalysts reported so far in practical applications.

Fabrication of hierarchical porous ZnO and its performance in Ni/ZnO reactive-adsorption desulfurization

To investigate the effect of texture structure on the desulfurization performance in the Ni/ZnO reactive adsorption desulfurization（RADS） system,two kinds of ZnO porous materials with rod-shaped morphology were synthesized and their structure was characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and N2 adsorption/desorption.The formation mechanisms of hierarchical porous ZnO（ZnO with meso and macro pores） were also studied.Their application performance was evaluated in the RADS process over Ni/ZnO absorbent.Due to the difference in structure between the two kinds of ZnO,the two ZnO based adsorbents showed different desulfurization activity.

Optimizing the micropore-to-mesopore ratio of carbon-fiber-cloth creates record-high specific capacitance

The application of commercial carbon fiber cloth(CFC) in energy storage equipment is limited by its low specific capacitance and energy density. By a simple one-step activation treatment, the specific surface area of CFCs with porous structure can be increased considerably from 3.9 up to 875 m^2/g and the electrochemical properties of CFCs can be improved by three orders of magnitude(1324 mF/cm^2). Moreover,the hydrophobicity of CFCs can be transformed into superhydrophilicity. However, the electrochemical performance of CFCs does not show a positive correlation with specific surface area but have a strong relationship with the hierarchical pore distribution forged by the annealing treatment. Only moderate micropore and mesoporous ratio enables optimizing the electrochemical performance of CFCs.

Pyrolyzing soft template-containing poly(ionic liquid)into hierarchical N-doped porous carbon for electroreduction of carbon dioxide

Heteroatom-doped carbon materials have demonstrated great potential in the electrochemical reduction reaction of CO_(2)(CO_(2)RR)due to their versatile structure and function.However,rational structure control remains one challenge.In this work,we reported a unique carbon precursor of soft template-containing porous poly(ionic liquid)(PIL)that was directly synthesized via free-radical self-polymerization of ionic liquid monomer in a soft template route.Variation of the carbonization temperature in a direct pyrolysis process without any additive yielded a series of carbon materials with facile adjustable textural properties and N species.Significantly,the integration of soft-template in the PIL precursor led to the formation of hierarchical porous carbon material with a higher surface area and larger pore size than that from the template-free precursor.In CO_(2)RR to CO,the champion catalyst gave a Faraday efficiency of 83.0%and a current density of 1.79 mA·cm^(-2)at-0.9 V vs.reversible hydrogen electrode(vs.RHE).The abundant graphite N species and hierarchical pore structure,especially the unique hierarchical small-/ultramicropores were revealed to enable better CO_(2)RR performance.

Synthesis, characteristics of hierarchical EU-1 zeolite for xylene isomerization probe reaction

Introduced a method of synthesizing hierarchical EU-1 zeolite with organosilanes as additive, and studied the influences of following different kinds of organosilanes on the synthesis of hierarchical EU-1 zeolite: γ-glycidoxy propyl trimethoxy silane(GPTMS), N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxyl silane(APAEDMS),and N-(β-aminoethyl)-γ-aminopropyl dimethoxyl(ethyoxyl) silane(TMPED). The hierarchical EU-1 samples were characterized by XRD, SEM, N_2 adsorption, FT-IR and NH_3-TPD to analyze the crystallinity, morphology, surface area, pore size distribution and acidity. The results showed that hierarchical EU-1 zeolites were successfully synthesized; organosilanes have great influence on crystal morphology of EU-1 zeolites; the exterior surface area of hierarchical EU-1 zeolite, which synthesized with organosilanes(APAEDMS) adding into synthesis system, increased by 62.1% and mesopore volume increased by 129.1% compared with conventional EU-1 zeolites, thus can reduce the diffusional restriction markedly in catalytic reaction. The catalytic performance of hierarchical EU-1zeolites were evaluated in m-xylene isomerization on fixed bed reactor. The catalytic data showed that the isomerization activity PX/X of the hierarchical EU-1 zeolites reached around 24.09% in theoretical thermodynamic equilibrium from 23.83%, and the selectivity of C_8 aromatic hydrocarbon increased from 75.16% to 84.87%. The conversion of p-xylene increased from 16.30% to 18.41%.

3D hierarchically macro-/mesoporous graphene frameworks enriched with pyridinic-nitrogen-cobalt active sites as efficient reversible oxygen electrocatalysts for rechargeable zinc-air batteries

Efficient and affordable electrocatalysts for reversible oxygen reduction and oxygen evolution reactions(ORR and OER,respectively)are highly sought-after for use in rechargeable metal-air batteries.However,the construction of high-performance electrocatalysts that possess both largely accessible active sites and superior ORR/OER intrinsic activities is challenging.Herein,we report the design and successful preparation of a 3D hierarchically porous graphene framework with interconnected interlayer macropores and in-plane mesopores,enriched with pyridinic-nitrogen-cobalt(pyri-N-Co)active sites,namely,CoFe/3D-NLG.The pyri-N-Co bonding significantly accelerates sluggish oxygen electrocatalysis kinetics,in turn substantially improving the intrinsic ORR/OER activities per active site,while copious interlayer macropores and in-plane mesopores enable ultra-efficient mass transfer throughout the graphene architecture,thus ensuring sufficient exposure of accessible pyri-N-Co active sites to the reagents.Such a robust catalyst structure endows CoFe/3D-NLG with a remarkably enhanced reversible oxygen electrocatalysis performance,with the ORR half-wave potential identical to that of the benchmark Pt/C catalyst,and OER activity far surpassing that of the noble-metal-based RuO2 catalyst.Moreover,when employed as an air electrode for a rechargeable Zn-air battery,CoFe/3D-NLG manifests an exceedingly high open-circuit voltage(1.56 V),high peak power density(213 mW cm^(–2)),ultra-low charge/discharge voltage(0.63 V),and excellent charge/discharge cycling stability,outperforming state-of-the-art noble-metal electrocatalysts.

Influence of hierarchical ZSM-5 catalysts with various acidity on the dehydration of glycerol to acrolein

The main challenge in the dehydration of glycerol to acrolein lies in overcoming catalystdeactivation and improving the selectivity to acrolein. The relationship between theacidity in the mesoporous channels and catalytic performance of glycerol dehydration israrely reported. In this work, to investigate the influence of acidity in the mesoporouschannels of hierarchical ZSM-5 catalysts on the dehydration of glycerol to acrolein, a seriesof hierarchical ZSM-5 zeolites with comparable mesoporous volume and mesoporous sizebut different acid properties in mesopores have been successfully prepared via alkalinetreatment. The sample with the abundant mesoporosity and highest acidity display thebest performance.

Preparation and Ammonia Adsorption Performance of Titanium Phosphonate Adsorbent Materials with Hierarchically Porous Structure

Titanium phosphonate adsorbent materials with hierarchically porous structure were fabricated using the hydrolysis of tetrabutyl titanate in different organophosphonic acids solutions. Based on the macroporous structure of 100-2000 nm in size, a worm-hole like mesostructure was in the macropore walls, which was supported by the scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and N2 sorption analysis. Fourier transform infrared spectroscopy（FT-IR） data indicated the organic groups inside the solid materials framework. NH3 adsorption detection was performed using titanium phosphonate adsorbent materials and some significant results were obtained. The adsorption mechanism was also discussed in this study. Large adsorption amount（75.2 mg/g） was mainly attributed to the acid site via acid-base reactions and the physical adsorption site via Van der Waals forces. Resultant materials could effectively restrain the desorption of adsorbent NH3 back into air causing secondary pollution, so it could make a promising potential use in decontamination of gas pollutants in the future.

Synthesis of ZSM-5 Monoliths with Hierarchical Porosity

A new route to synthesize ZSM-5 monoliths with hierarchical pore structure has been referred to in this study. The successful incorporation of the macropores and mesopores within the ZSM-5 struc- ture was achieved through transforming the skeleton of the macroporous silica gel into zeolite ZSM-5 using carbon materials as the transitional template. The ZSM-5 crystal covered part of the macroporous material, and provided micropores to the macroporous silica gel. The structure of carbon monolith was studied after dissolving the silica contained in the carbon/silica composite.

Waste to wealth: Oxygen-nitrogen-sulfur codoped lignin-derived carbon microspheres from hazardous black liquors for high-performance DSSCs

Carbon materials are effective substitutes for Pt counter electrodes(CEs) in dye-sensitized solar cells(DSSCs). However, many of these materials, such as carbon nanotubes and graphene, are expensive and require complex preparation process. Herein, waste lignin, recycled from hazardous black liquors,is used to create oxygen-nitrogen-sulfur codoped carbon microspheres for use in DSSC CEs through the facile process of low-temperature preoxidation and high-temperature self-activation. The large number of ester bonds formed by preoxidation increase the degree of cross-linking of the lignin chains, leading to the formation of highly disordered carbon with ample defect sites during pyrolysis. The presence of organic O/N/S components in the waste lignin results in high O/N/S doping of the pyrolysed carbon,which increases the electrolyte ion adsorption and accelerates the electron transfer at the CE/electrolyte interface, as confirmed by density functional theory(DFT) calculations. The presence of inorganic impurities enables the construction of a hierarchical micropore-rich carbon structure through the etching effect during self-activation, which can provide abundant catalytically active sites for the reversible adsorption/desorption of electrolyte ions. Under these synergistic effects, the DSSCs that use this novel carbon CE achieve a quite high power-conversion efficiency of 9.22%. To the best of our knowledge, the value is a new record reported so far for biomass-carbon-based DSSCs.

Towards High-Energy and Anti-Self-Discharge Zn-Ion Hybrid Supercapacitors with New Understanding of the Electrochemistry

Aqueous Zn-ion hybrid supercapacitors(ZHSs)are increasingly being studied as a novel electrochemical energy storage system with prominent electrochemical performance,high safety and low cost.Herein,high-energy and anti-self-discharge ZHSs are realized based on the fibrous carbon cathodes with hierarchically porous surface and O/N heteroatom functional groups.Hierarchically porous surface of the fabricated free-standing fibrous carbon cathodes not only provides abundant active sites for divalent ion storage,but also optimizes ion transport kinetics.Consequently,the cathodes show a high gravimetric capacity of 156 mAh g^(−1),superior rate capability(79 mAh g^(−1)with a very short charge/discharge time of 14 s)and exceptional cycling stability.Meanwhile,hierarchical pore structure and suitable surface functional groups of the cathodes endow ZHSs with a high energy density of 127 Wh kg−1,a high power density of 15.3 kW kg^(−1)and good anti-self-discharge performance.Mechanism investigation reveals that ZHS electrochemistry involves cation adsorption/desorption and Zn_(4)SO_(4)(OH)_(6)·5H_(2)O formation/dissolution at low voltage and anion adsorption/desorption at high voltage on carbon cathodes.The roles of these reactions in energy storage of ZHSs are elucidated.This work not only paves a way for high-performance cathode materials of ZHSs,but also provides a deeper understanding of ZHS electrochemistry.

Redox-etching induced porous carbon cloth with pseudocapacitive oxygenic groups for flexible symmetric supercapacitor

Constructing high-performance electrodes with both wide potential window(e.g.≥2 V in aqueous electrolyte)and excellent mechanical flexibility represents a great challenge for supercapacitors.Because of the outstanding conductivity and flexibility,carb on cloth(CC)has show n unlimited prospects for constructing flexible electrodes,but is rarely used directly as electrode material due to its electrochemical inertness and small specific surface area.To tackle these two critical limitations,we design a novel redox-etching strategy to synthesize CC-based electrode with 3D interconnecting pore structure.The sponge-like highly porous CC was further activated by strong oxidant to form abundant oxygenic groups,which occupy the interior and surface of current collector to render substantial pseudocapacitance.The as-synthesized CC electrode yielded an impressive capacitance of 4035 mF cm^(-2) at 3 mA cm^(-2) and satisfying cycling durability in a wide potential range of-1-1 V vs.SCE,which surpass the majority of reported CC-based electrodes.A symmetric supercapacitor with stable voltage of 2 V is assembled and delivers remarkable energy density of 6.57 mWh cm^(-3).Significantly,the device demonstrates an unparalleled flexibility with no capacitive decay after 100 bending cycles.This facile chemical etching and post-treatment processes are designed for large-scale manufacturing of the CC electrodes by providing high surface area and abundant electrochemically active sites,promising for industry application.The innovative synthetic strategy ope ns up new opportunities for high-performance flexible en ergy storage.