Tuo Ji

Hierarchical macrotube/mesopore carbon decorated with mono-dispersed Ag nanoparticles as a highly active catalyst

Natural wood, featuring abundant oxygen-containing functional groups, has been utilized as a reductant to synthesize monodispersed Ag nanoparticles on its surface. By further carbonization of the Ag/wood composite, wood was converted to carbon with embedded mesopore structures. Through the two-step reduction and carbonization, a macro-tube/meso-pore carbon frame with decorated mono-dispersed silver nanoparticles (Ag/C) can be conveniently synthesized. Various characterization techniques including SEM, TEM, HRTEM, BET, Raman, XRD, XPS and FT-IR have been utilized to study the material microstructure, crystalline structure, pore size and surface area and surface properties. The mechanism of Ag/wood formation has also been studied in this work. Ag/C shows outstanding activity in 4-nitrophenol and 2-nitrophenol reduction reactions with much higher reaction rate than literature reports, and no obvious activity degradation was observed after 10 cycles of durability tests. This newly developed synthetic methodology could serve as a general tool to design and synthesize other metal/carbon nanocomposite catalysts for a wider range of catalytic applications. More importantly, the utilization of a widely accessible renewable resource provides a sustainable feature of this work to reduce manufacturing cost and environmental impact.

Hierarchical Porous and High Surface Area Tubular Carbon as Dye Adsorbent and Capacitor Electrode.

Hierarchically porous tubular carbon (HPTC) with large surface area of 1094 m(2)/g has been successfully synthesized by selectively removing lignin from natural wood. No templates or chemicals are involved during the process. By further KOH activation, surface area of activated HPTC reaches up to 2925 m(2)/g. These materials show unprecedented high adsorption capacity toward organic dyes (methylene blue, 838 mg/g; methyl orange, 264 mg/g) and large electrochemical capacitance of >200 F/g. The sustainable feature of the wood precursor and demonstrated superior adsorption and energy storage properties allow promising applications of the processed materials in energy and environmental related fields.

Facile synthesis of mesoporous carbon nanocomposites from natural biomass for efficient dye adsorption and selective heavy metal removal

Mesoporous carbon with embedded iron carbide nanoparticles was successfully synthesized via a facile impregnation–carbonization method. A green biomass resource, cotton fabric, was used as a carbon precursor and an iron precursor was implanted to create mesopores through a catalytic graphitization reaction. The pore structure of the nanocomposites can be tuned by adjusting the iron precursor loadings and the embedded iron carbide nanoparticles serve as an active component for magnetic separation after adsorption. The microstructure of the nanocomposites was carefully investigated by various characterization techniques including electron microscopy, X-ray diffraction, surface analyzer, magnetic property analyzer and etc. The newly created mesopores are demonstrated as a critical component to enhance the adsorption capacity of organic dyes and embedded iron carbide nanoparticles are responsible for the selective removal of heavy metal ions (Zn2+, Cu2+, Ni2+, Cr6+ and Pb2+). Isotherm adsorption, kinetic study at three different temperatures (25, 45 and 65 °C) and cycling retention tests were performed to understand the adsorptive behavior of the nanocomposites with organic dyes (methylene blue and methyl orange). Together with the preferable removal of more toxic heavy metal species (Cr6+ and Pb2+), these mesoporous nanocomposites show promising applications in pollutant removal from water. The facile material preparation allows convenient scale-up manufacturing with low cost and minimum environmental impact.

Non-corrosive green lubricants: strengthened lignin–[choline][amino acid] ionic liquids interaction via reciprocal hydrogen bonding

A series of novel green lubricants with dissolved lignin in [choline][amino acid] ([CH][AA]) ionic liquids (ILs) have been synthesized in this work. The effect of lignin on the thermal and tribological properties of the lignin/[CH][AA] lubricants was systematically investigated by means of thermogravimetric analysis, differential scanning calorimetry, and a friction and wear tester. The lignin in [CH][AA] has been demonstrated to be an effective additive to improve thermal stability, reduce the wear rates and stabilize the friction coefficients of lignin/[CH][AA] lubricants. Density function theory calculations on the electronic structure of [CH][AA] ILs reveal the atomic natural charge of ILs and their hydrogen bonding capability with lignin. Moreover, these green lubricants show excellent anti-corrosive properties against commercial aluminum and iron boards. The strong physical adsorption of [CH][AA] ILs onto the steel surface and the reciprocal hydrogen bonding between [CH][AA] ILs and lignin synergistically contribute to the enhanced lubrication film strength and thus the tribological properties of these new lubricants. This work provides a new perspective on utilizing complete bio-products in advanced tribological lubrication systems. In addition, this will open a new application venue for lignin to improve product value in lignocellulosic biomass utilization.

Carbon-protected Au nanoparticles supported on mesoporous TiO2 for catalytic reduction of p-nitrophenol

With the introduction of carbon on Au/TiO2, the reaction rate of C/Au/TiO2 increased by 29% and the stability was enhanced by about 3 times more than Au/TiO2 in the p-nitrophenol reduction reaction. Carbon species enhanced the stability of Au nanoparticles and also increase the organic reactants adsorptive ability.

Expedited Phonon Transfer in Interfacially Constrained Polymer Chain along Self-Organized Amino Acid Crystals

In this work, poly(vinyl alcohol) (PVA)/amino acid (AA) composites were prepared by a self-organized crystallization process. Five different AAs (cysteine, aspartic acid, glutamic acid, ornithine, and lysine) were selected based on their similar functional groups but different molecular structures. The different PVA-AA interactions in the five PVA/AA composites lead to two crystal patterns, i.e., continuous network (cysteine and lysine) and discrete particles (glutamic acid, ornithine, and aspartic acid). Scanning thermal microscopy is then applied to map the distribution of thermal conduction in these composites. It is found that the interface surrounding the crystals plays a dominating role in phonon transport where the polymer chains are greatly restrained by the interfacial confinement effect. Continuous crystal network builds up a continuous interface that facilitates phonon transfer while phonon scattering occurs in discrete crystalline structures. Significantly improved thermal conductivity of ∼0.7 W/m·K is observed in PVA/cysteine composite with AA loading of 8.4 wt %, which corresponds to a 170% enhancement as compared to pure PVA. The strong PVA-AA molecular interaction and self-organized crystal structure are considered the major reasons for the unique interface property and superior thermal conductivity.

Superhydrophobic polyaniline hollow spheres with mesoporous brain-like convex-fold shell textures

Novel hollow nano/microspheres of polyaniline (PANI) with mesoporous brain-like convex-fold shell structures were prepared via a new micelle-mediated phase transfer method, using perfluorooctanoic acid (PFOA)/aniline as a soft template. These self-assembled hollow spheres possess high specific surface areas (835.7 m2 g−1), and uniform particle morphology with narrowly distributed particle size can be controlled by adjusting the PFOA/aniline molar ratio and polymerization time. The conductive emeraldine state of PANI is also confirmed by FT-IR spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In particular, these PANI spheres exhibit superhydrophobicity and high oleophobicity simultaneously, with contact angles of 165 ± 0.9°, 134 ± 0.8°, 131 ± 0.9° and 125 ± 0.7° towards water, glycerin, ethylene glycol and corn oil, respectively. Furthermore, the mechanisms of PANI structural evolution are proposed involving the formation, phase transfer and self-reassembly process of PFOA/aniline spherical micelles.

Ionic Grease Lubricants: Protic [Triethanolamine][Oleic Acid] and Aprotic [Choline][Oleic Acid].

Ionic liquid lubricants or lubricant additives have been studied intensively over past decades. However, ionic grease serving as lubricant has rarely been investigated so far. In this work, novel protic [triethanolamine][oleic acid] and aprotic [choline][oleic acid] ionic greases are successfully synthesized. These ionic greases can be directly used as lubricants without adding thickeners or other additives. Their distinct thermal and rheological properties are investigated and are well-correlated to their tribological properties. It is revealed that aprotic ionic grease shows superior temperature- and pressure-tolerant lubrication properties over those of protic ionic grease. The lubrication mechanism is studied, and it reveals that strong physical adsorption of ionic grease onto friction surface plays a dominating role for promoted lubrication instead of tribo-chemical film formation.

Grafting heteroelement-rich groups on graphene oxide: Tuning polarity and molecular interaction with bio-ionic liquid for enhanced lubrication

Two different heteroelement-rich molecules have been successfully grafted on graphene oxide (GO) sheets which were then used as lubricant additives in bio-ionic liquid. The grafting was processed with reactions between GO sheets and synthesized heteroelement-rich molecules (Imidazol-1-yl phosphonic dichloride and 1H-1,2,4-triazol-1-yl phosphonic dichloride, respectively). The modified GO (m-GO) was added into [Choline][Proline] ([CH][P]) bio-ionic liquid, and has been demonstrated effective additive in promoting lubrication. Different characterization techniques have been utilized to study the reaction between GO and the two modifiers. The effect of molecular structure of the modifiers on the rheological and tribological properties of m-GO/[CH][P] lubricants was systematically investigated. Both theoretical calculation and experimental results demonstrated that the introduced heteroelement-rich groups are beneficial to increase the robustness of lubrication film by intensified hydrogen bonding and enhance the lubricant/friction surface adhesion by increased polarity of the m-GO. As a result, the interfacial lubrication could be significantly improved by these newly developed m-GO/[CH][P] lubricants.

Confined molecular motion across liquid/liquid interfaces in a triphasic reaction towards free-standing conductive polymer tube arrays

A “water/oil/water” triphasic reaction system was employed to control diffusion and reaction at separate “water/oil” and “oil/water” interfaces. The former controls the reactant feed rate and the latter determines the reaction rate. By the synergistic integration of diffusion and reaction in one reactor, freestanding tubular-arrayed polymer thin films were successfully fabricated. Molecular dynamics simulation was performed to understand the reactant diffusion across the two interfaces.