Porous monoliths of 3D graphene for electric double-layer supercapacitors

For delivering the nanoscaled extraordinary characteristics in macroscopical bulk,it is essential to integrate two-dimensional nanosheets into threedimensional(3D)porous monoliths,alternatively called as 3D architectures,3D networks,or aerogels.The intersupported structure of porous monolithic 3D graphene(3DG)can prevent aggregation or restacking of graphene individuals,and the interconnected sp^(2) network of 3DG not only can provide the highway for the transport of electron/phonon but also can present continual cavities/channels for mass transfer.This review summarizes the synthesis methodology of 3DG porous monoliths and highlights the application for electric double-layer capacitors.Present challenges and future prospects about the manufacture and application of 3DG are also discussed.

Preparation and Characterization of Freestanding Hierarchical Porous TiO_2 Monolith Modified with Graphene Oxide

Catalyst recovery is one of the most important aspects that restrict the application of Ti O_2 photocatalyst. In order to reduce restrictions and improve the photocatalytic efficiency, a hierarchical porous Ti O_2 monolith(PTM) with well-defined macroporous and homogeneous mesoporous structure was prepared by using a sol-gel phase separation method. P123 was used as the mesoporous template and graphene oxide was applied to increase the activity and integrity of the monolithic Ti O_2. According to scanning electron microscopy and the Barrett-Joyner-Halenda measurements, PTM_3 is mainly composed of 10 nm anatase crystallines with3.6 nm mesopores and 2-8 μm macropores. Further characterization suggests carbon and nitrogen have been maintained in the PTM during calcinations so as to induce the visible light activity. The PTM with 0.07 wt%graphene oxide dosage shows high efficiency for methyl orange(MO) decolorization under both full spectrum and visible light irradiation(λ >400 nm). Besides, the monolith remains intact and has good photocatalytic stability after four cyclic experiments.

Novel Magnetically Interconnected Micro/Macroporous Structure of Monolithic Porous Carbon Adsorbent Derived from Sodium Alginate and Wasted Black Liquor and Its Adsorption Performance

The novel and facile preparation of magnetically interconnected micro/macroporous structure of monolithic porous carbon adsorbent(MPCA)were designed and presented herein.The synthesis was achieved via conventional freezedrying and pyrolysis processes.In this study,sodium alginate and wasted black liquor were employed as starting precursors.Sodium alginate acts as a template of materials,whereas black liquor,the wasted product from the paper industry with plentiful of lignin content and alkaline solution,played an essential role in the reinforcement and activation of porosity for the resulting materials.Moreover,both the precursors were well dissolved in Fe^(3+) solution,providing a simple addition of a magnetic source in a one-pot synthesis.The interconnected micro/macroporous structures were generated through freeze-drying and,subsequently the pyrolysis process.The obtained cylindricalshaped monolithic porous carbon adsorbent(MPCA-700)showed high mechanical stability,a high BET specific surface area(902 m^(2)/g).Such aforementioned features were considered suitable to make the synthesized monolith as an adsorbent for the removal of heavy metal ions.The maximum adsorption capacity of MPCA-700 towards Pb^(2+) ions was 76.34 mg/g at pH 5.The adsorption studies illustrated that adsorption kinetics and isotherm perfectly fitted with the pseudo-second-order kinetics model and Langmuir isotherm,respectively.This work presents a promising protocol to reduce the overall costs in the preparation of renewable adsorbents with good adsorption efficiency and regeneration.

Solar thermal swing adsorption on porous carbon monoliths for high-performance CO_(2)capture

Utilizing solar energy for sorbent regeneration during the CO_(2)swing adsorption process could potentially reduce CO_(2)capture costs.This study describes a new technique—solar thermal swing adsorption(STSA)for CO_(2)capture based on application of intermittent illumination onto porous carbon monolith(PCM)sorbents during the CO_(2)capture process.This allows CO_(2)to be selectively adsorbed on the sorbents during the light-off periods and thereafter released during the light-on periods due to the solar thermal effect.The freestanding and mechanically strong PCMs have rich ultramicropores with narrow pore size distributions,displaying relatively high CO_(2)adsorption capacity and high CO_(2)/N_(2) selectivity.Given the high CO_(2)capture performance,high solar thermal conversion efficiency,and high thermal conductivity,the PCM sorbents could achieve high CO_(2)capture rate of up to 0.226 kg·kgcarbon^(-1)·h^(-1)from a gas mixture of 20 vol.%CO_(2)/80 vol.%N_(2) under STSA conditions with a light intensity of 1000 W·m^(-2).In addition,the combination of STSA with the conventional vacuum swing adsorption technique further increases the CO_(2)working capacity.

Critical impact of nanocellulose on the synthesis of porous cellulose monolith with oriented microchannels:Structure control,mechanics,mass transport

Nanocellulose harvested from biomass has attractive properties that have promoted research on its practical applications.Herein,we investigated nanocellulose-based porous monoliths with oriented microchannels that can be fabricated via a unidirectional freezing method.In this method,water-dispersed cellulose nanofibers(CNFs)were immersed into a cold source at a controlled speed,followed by subsequent freeze-drying.The structure of porous cellulose monoliths mainly depends on two factors:the freezing conditions and properties of the dispersed CNFs.The former has been investigated previously.However,the effects of the latter remain unclear.In this study,CNF suspensions prepared by 2,2,6,6-tetramethylpiperidine-1-oxylmediated oxidation cellulose nanofibers(TOCNs)with different aspect ratios and concentrations were used.The effects of these variables on the resulting structure,including the pore shape,size,wall thickness,were examined.Based on the results,the impact of TOCNs on the structure of porous cellulose monoliths was investigated.Our findings suggested that depending on their structure,the porous cellulose monoliths exhibit different mechanical strengths and mass transport properties.In particular,porous cellulose monoliths synthesized from 5.1 wt.%short TOCNs exhibited a low density(55.9 mg∙cm^(−3)),high mechanical strength(8687 kPa),fast mass transport.

Facile Fabrication of Polymeric Ionic Liquid Grafted Porous Polymer Monolith for Mixed-Mode High Performance Liquid Chromatography

A novel polymeric ionic liquid grafted porous polymer monolith has been facilely fabricated for mixed-mode chromatography.The column is prepared from poly(glycidyl methacrylate-co-ethylene dimethacrylate)monolith through hydrolyzation of the epoxy moieties into hydroxyl groups,followed by“grafting from”polymerization of ionic liquid of 1-vinyl-3-butylimidazolium chloride.Successful modification is characterized by scanning electron microscope,infrared spectroscopy,elemental analysis and mercury intrusion porosimetry.The HPLC performance of developed column is evaluated by separating acidic vitamin B analytes,neutral steroids and basic aromatic amines in mixed-mode chromatography on a single column,respectively.The ionic liquid affords the monolith with both enhanced separation ability and improved column efficiency.

Thiol-yne Click Adamantane Monolithic Stationary Phase for Capillary Electrochromatography

A porous crosslinked organic polymer based on N-acryloxysuccinimide （NAS） and ethylene dimethacrylate （EDMA） was prepared inside 75 μm i.d. fused silica capillary as functionalizable monolithic stationary phase for electrochromatographic applications. Succinimide groups on the monolith surface provide reactive sites able to re- act readily through standard electrophile-nucleophile chemistry. Propargylamine was used to prepare alkyne func- tionalized poly（NAS-co-EDMA）. Onto this thiol-reactive polymer surface was grafted adamantane units via a photochemically-driven addition reaction. Chemical characterization was performed in situ after each synthetic step by means of Raman spectroscopy and grafting kinetics was investigated to ensure quantitative grafting of 1-adamantanethiol. The as-designed monolithic stationary phase exhibited typical reversed-phase separation mechanism as evidenced by the linear increase of the logarithm of retention factor of neutral aromatic solutes with the increase of the aqueous buffer content in the mobile phase.