Chunfeng Xue

Facile preparation of electroactive amorphous α-ZrP/PANI hybrid film for potential-triggered adsorption of Pb2+ ions

An electroactive hybrid film composed of amorphous α-zirconium phosphate and polyaniline (α-ZrP/PANI) is controllably synthesized on carbon nanotubes (CNTs) modified Au electrodes in aqueous solution by cyclic voltammetry method. Electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM) and X-ray power diffraction (XRD) analysis are applied for the evaluation of the synthesis process. It is found that the exfoliated amorphous α-ZrP nanosheets are well dispersed in PANI and the hydrolysis of α-ZrP is successfully suppressed by controlling the exfoliation temperature and adding appropriate supporting electrolyte. The insertion/release of heavy metals into/from the film is reversibly controlled by a potential-triggered mechanism. Herein, α-ZrP, a weak solid acid, can provide an acidic micro-environment for PANI to promote the electroactivity in neutral aqueous solutions. Especially, the hybrid film shows excellent potential-triggered adsorption of Pb(2+) ion due to the selective complexation of Pb(2+) ion with oxygen derived from P-O-H of α-ZrP. Also, it shows long-term cycle stability and rapid potential-responsive adsorption/desorption rate. This kind of novel hybrid film is expected to be a promising potential-triggered ESIX material for separation and recovery of heavy metal ions from wastewater.

Zeolite cage-lock strategy for in situ synthesis of highly nitrogen-doped porous carbon for selective adsorption of carbon dioxide gas

Nitrogen-doped porous carbon (NPC) was prepared by directly carbonizing zeolite ZSM-39 containing a structure-directing agent, tetramethylammonium chloride (TMACl), which also acted as a source of C and N for NPC. The cage-like pore of zeolite ZSM-39 acted as an ideal space for immobilizing the C and N species. The obtained NPCs have a high N content up to 18.14%. The quaternary N of template TMACl was transformed into pyridinic and pyrrolic/pyridonic N during the carbonization. NPCs were suitable for selective adsorption of CO2 because of their unique ultra-micropores and abundant basic sites. The adsorption selectivity of CO2 over N2 was more than 12.1 (molar ratio). The CO2 adsorption capacity of the unit surface area for a NPC-723 sample was calculated as 26.6 μmol m−2 at 0.93 bar and 273 K, which is one of the highest values among carbon adsorbents. Its excellent selectivity makes the NPC a good candidate for separating low concentrations of CO2 in the purification of gas mixtures.

Mechanisms of methane decomposition and carbon species oxidation on the Pr0.42Sr0.6Co0.2Fe0.7Nb0.1O3−σ electrode with high catalytic activity

Carbon deposition on Pr0.42Sr0.6Co0.2Fe0.7Nb0.1O3−σ (PSCFN) and Ni–yttria stabilized zirconia (Ni–YSZ) due to thermal CH4 decomposition under dry CH4 has been investigated by using temperature-programmed reaction techniques. The morphologies of carbon formed are characterized by using scanning electron microscopy (SEM). It is found that carbon nanofibers are obviously formed on PSCFN while spherical carbons are formed on Ni–YSZ. Analyses of the results on CH4 temperature-programmed decomposition and O2 temperature-programmed oxidation reveal that the high catalytic activity for the cracking of CH4 and the easier oxidation of the generated carbon species on PSCFN could be the main reason why PSCFN shows high performance and good stability in direct CH4 fuel solid oxide fuel cells (SOFCs).

Unique allosteric effect-driven rapid adsorption of carbon dioxide in a newly designed ionogel [P4444][2-Op]@MCM-41 with excellent cyclic stability and loading-dependent capacity

To achieve low cost, high rate and attractive capacity of CO2 adsorption by using ionic liquids (IL), a new mesostructured ionogel, pyridine-containing anion functionalized IL tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]) encapsulated silica MCM-41 (noted as PM-w), is fabricated by loading the IL [P4444][2-Op] with multiple active sites into porous silica MCM-41 through a simple moisture-controlled impregnation–evaporation method. Allosteric effect driven gas sorption on the electronegative oxygen and nitrogen atoms of the nanoconfined IL [P4444][2-Op] makes it take no more than 2 min for the ionogel PM-5 to achieve the 90% of saturated adsorption capacity. The corresponding adsorption rate is 30 times faster than that of the bulk IL. The ionogel PM-5 with the low IL loading of 5.0% shows the highest CO2 adsorption capacity up to 1.21 mmol (g-ionogel)−1 (14.89 mmol (g-IL)−1) at 50 °C in a gas mixture with N2, which is 9.25 times higher than that of the pure IL. Its excellent cyclic stability of more than 96% of the initial CO2 uptake repeatedly displayed after performing 10 cycles of adsorption–desorption tests. The enhanced thermal stability up to 450 °C in N2 is observed for the low loading ionogels since the strong interfacial layering of the IL prefers to dot the silica nanopores as monomolecular islands. Reversely, the high loading IL may aggregate into nanosized clusters that recover the poor thermal stability of the bulk IL. Reasonable decreases in their surface area, pore volume and pore size are observed with the IL loading up to 45%. They still exhibit highly ordered hexagonal mesostructures. The features of low loading and cost, rapid adsorption, high capacity and excellent cyclic stability make the ionogel PM-5 a competitive candidate in CO2 capture from flue gas.

Acid-free synthesis of oxygen-enriched electroactive carbon with unique square pores from salted seaweed for robust supercapacitor with attractive energy density

Oxygen-enriched porous electroactive carbon (OPEC) is prepared by simply carbonizing salted seaweed and only washing with water. The recrystallized NaCl cube is chemically stable and mainly acts as a pore filler in the pristine seaweed. It helps to maintain the innate pore system and simultaneously templates the formation of square pores. Its shielding effect not only enhances the onset decomposition temperature but also helps to achieve high yield. It can also be completely removed by washing with the green solvent water. The obtained OPEC-800 material not only shows a specific surface area of 329.3 m2 g−1 but also a microporous structure (0.8–2.0 nm) matching with the electrolyte 1.0 M H2SO4. It exhibits a specific capacitance of 324.3 F g−1 (specific surface-area capacitance is 98.5 μF cm−2) at a current density of 0.50 A g−1 in a three-electrode system. Its high oxygen content of 19.1% can lead to a wide operating voltage window of 0.0–1.40 V and an attractive energy density of 15.9 W h kg−1 at a power density of 175.0 W kg−1 in a two-electrode system. Furthermore, it also displays an excellent cyclic stability (98%, 10u2006000 cycles) and good rate performance. The whole process is a green, oxidant-free, acid-free, and low-cost method for converting green biomass into self-functionalized carbon with naturally connected pores aiming to fabricate green energy devices. All the attractive features make the environmentally friendly route a competitive candidate for preparing other porous electroactive materials.