Jin Xuan

High photocatalytic activity of immobilized TiO2 nanorods on carbonized cotton fibers

In this study, TiO2 nanorods were successfully immobilized on carbon fibers by a facile pyrolysis of natural cotton in nitrogen atmosphere followed by a one-pot hydrothermal method. Carbonized cotton fibers (CCFs) and TiO2-CCFs composites were characterized using field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffractometer (XRD), diffuse reflectance UV-vis spectroscopy (DRS) and photoluminescence (PL) spectroscopy. Results implied that the band gap narrowing of TiO2 was achieved after integration of CCFs. Dye adsorption isotherm indicated that the maximum dye adsorption capacity (qm) of CCFs-1000 (13.4 mg/g) was 2 times higher than that of cotton fibers and qm of TiO2-CCFs-1000 (9.0mg/g) was 6-7 times higher than that of TiO2 nanorods. Photocatalytic activity of TiO2 nanorods prepared with 3 mL Ti(OBu)4 showed the highest photocatalytic activity. TiO2-CCFs-1000 exhibited higher activity than TiO2 immobilized on CCFs-400, CCFs-600 and CCFs-800. Good photostability of TiO2-CCFs-1000 was found for dye degradation under visible light irradiation. The enhancement of photocatalytic dye degradation was due to the high adsorptivity of dye molecules, enhanced light adsorption and effective separation of electron-hole pairs. This work provides a low-cost and sustainable approach to immobilize nanostructured TiO2 on carbon fibers for environmental remediation.

Facile synthesis of TiO2 hollow spheres composed of high percentage of reactive facets for enhanced photocatalytic activity

In this study, facile synthesis of hollow TiO2 spheres composed of a high percentage of reactive facets (~85%) is successfully prepared with TiOSO4 and HBF4 by the hydrothermal method. Results reveal that hollow TiO2 spheres of 605 nm to 1.21 μm in size are in the anatase phase with sulfur doping. The variation in shell morphologies (e.g. polyhedron and nanosheet) can be realized by adjusting the reactant concentrations, while the molar ratio of TiOSO4 to HBF4 is maintained at 5 : 3. Based on the time-dependent morphology evolution study, the growth mechanism of hollow structure formation via self-templating and dissolution–recrystallization processes is discussed. The effects of reactant concentrations on TiO2 morphology are investigated to understand the dual roles of HBF4. Results also indicate that hollow TiO2 spheres with nanosheet morphology having 85% (001) facets exhibit 1.4–5 times higher performance than their counterparts in photocatalytic hydrogen production. The enhanced photocatalytic activity is ascribed to the combined effects of their unique hollow structure, high BET specific surface area (139.1 m2 g−1) and high percentage of exposed reactive facets (85%). This study demonstrates a promising strategy for large-scale production of hollow TiO2 spheres using a template- and surfactant-free process for photocatalysis applications.

Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields.

Microfluidic synthesis of high-performance monodispersed chitosan microparticles for methyl orange adsorption

High-performance monodispersed chitosan microparticles for methyl orange (MO) adsorption were synthesized on a microfluidic platform coupled with a cross-linking approach. Batch adsorption experiments were carried out to evaluate the capacity and kinetics of the as-prepared microparticles on the adsorption of MO. Due to the advantage of microfluidics that all the manipulations and operations are related to independent droplets, the prepared microparticles are controlled to within a narrow size distribution (CV = 1.86%) while exhibiting uniform high performance (adsorption capacity = 182 mg g−1). Adsorption experiments were carried out under various design and operation conditions. It is found that the adsorption isotherm was well described by the Langmuir model and the adsorption kinetics followed a pseudo-second-order kinetic model. The high performance together with biodegradable feature and low-cost raw material give the microfluidic-synthesized chitosan microparticles a promising potential for future dye effluent treatment.

Additive Manufacturing: Unlocking the Evolution of Energy Materials

Abstract The global energy infrastructure is undergoing a drastic transformation towards renewable energy, posing huge challenges on the energy materials research, development and manufacturing. Additive manufacturing has shown its promise to change the way how future energy system can be designed and delivered. It offers capability in manufacturing complex 3D structures, with near‐complete design freedom and high sustainability due to minimal use of materials and toxic chemicals. Recent literatures have reported that additive manufacturing could unlock the evolution of energy materials and chemistries with unprecedented performance in the way that could never be achieved by conventional manufacturing techniques. This comprehensive review will fill the gap in communicating on recent breakthroughs in additive manufacturing for energy material and device applications. It will underpin the discoveries on what 3D functional energy structures can be created without design constraints, which bespoke energy materials could be additively manufactured with customised solutions, and how the additively manufactured devices could be integrated into energy systems. This review will also highlight emerging and important applications in energy additive manufacturing, including fuel cells, batteries, hydrogen, solar cell as well as carbon capture and storage.

Novel urchin-like Fe2O3@SiO2@TiO2 microparticles with magnetically separable and photocatalytic properties

Novel urchin-like microparticles with photocatalytic activity and magnetically separable properties were prepared by a layer-by-layer assembly process. Photocatalytic degradation was investigated using two types of mercury vapor lamps: an ozone generating lamp emitting at both 254 nm and 185 nm as well as a germicidal lamp emitting at 254 nm only. This novel photocatalyst demonstrated superior photocatalytic activity in the mineralization of phenol under UVC illumination compared with the commercial P25, Degussa TiO2, especially in repeated usage. Importantly, this photocatalyst can be quickly separated for reuse simply by using a magnet. The merits of 3D spiny nanostructured TiO2 microparticle photocatalysts are high specific surface area, good permeability, reduced charge recombination rate and high catalytic activity while the incorporation of magnetically separable properties enables rapid and easy retrieval of the suspended photocatalyst after use.

Selective heavy metal removal and water purification by microfluidically-generated chitosan microspheres: Characteristics, modeling and application

Many industrial wastewater streams contain heavy metals, posing serious and irreversible damage to humans and living organisms, even at low concentrations due to their high toxicity and persistence in the environment. In this study, high-performance monodispersed chitosan (CS) microspheres were prepared using a simple microfluidic method and evaluated for metal removal from contaminated water. Batch experiments were carried out to evaluate the adsorption characteristics for the removal of copper ions, one representative heavy metal, from aqueous solutions. The inherent advantages of microfluidics enabled a precise control of particle size (CV = 2.3%), while exhibiting outstanding selectivity towards target ions (adsorption capacity 75.52 mg g-1) and fair regeneration (re-adsorption efficiency 74% after 5 cycles). An integrated adsorption mechanism analytic system was developed based on different adsorption kinetics and isotherms models, providing an excellent adsorption prediction model with pseudo-second order kinetics (R2 = 0.999), while the isotherm was fitted best to the Langmuir model (R2 = 0.998). The multi-step adsorption process was revealed via quantitative measurements and schematically described. Selective adsorption performance of CS microspheres in the present of other competitive metal ions with different valence states has been demonstrated and studied by both experimental and density functional theory (DFT) analysis.

3D-printed air-blast microfluidic nozzles for preparing calcium alginate microparticles

Microfluidic technologies have emerged as a promising route for precision fabrication of uniform particles. Equipment required for a traditional microfluidic device manufacturing process is expensive and production efficiency is low. Its also difficult to separate a surfactant and continuous phase impurities from particles prepared by a liquid–liquid two-phase shear method. A novel air-blast microfluidic nozzle fabricated using low-cost and efficient 3D printing technology was proposed to prepare calcium alginate particles. Effects of control parameters and solution composition on particle diameters and homogeneity were systematically investigated. Results showed that inlet air pressure has the most significant impact. A nozzle with an outlet diameter of 300 μm can produce particles with diameters ranging from 360 μm to 2100 μm. Coefficients of variation (CV) range from 5.3% to 2.2%. For the same diameter particle prepared, a smaller nozzle outlet had a narrower particle diameter distribution and needed lower inlet air pressure. This method can be used to handle high viscosity solutions and high concentrations of solutions with insoluble solid particles. The prepared particles can be used in biological and pharmaceutical fields.

In situ photogalvanic acceleration of optofluidic kinetics: a new paradigm for advanced photocatalytic technologies

A multiscale-designed optofluidic reactor is demonstrated in this work, featuring an overall reaction rate constant of 1.32 s−1 for photocatalytic decolourization of methylene blue, which is an order of magnitude higher as compared to literature records. A novel performance-enhancement mechanism of microscale in situ photogalvanic acceleration was found to be the main reason for the superior optofluidic performance in the photocatalytic degradation of dyes as a model reaction.