Qiuling Tay

Surfactant–Thermal Method to Synthesize a Novel Two‐Dimensional Oxochalcogenide

A new two-dimensional (2D) oxosulfide, (N2H4)2Mn3Sb4S8(μ3-OH)2 (1), has been successfully synthesized under surfactant-thermal conditions with hexadecyltributylphosphonium bromide as the surfactant. Compound 1 has a layered structure and contains a novel [Mn3(μ3-OH)2]n chain along the b-axis. The photocatalytic activity for compound 1 has been demonstrated under visible-light irradiation and continuous H2 evolution was observed. Our results indicate that surfactant-thermal synthesis could be a promising method for growing novel crystalline oxochalcogenides with interesting structures and properties.

CuInZnS-decorated graphene nanosheets for highly efficient visible-light-driven photocatalytic hydrogen production

Photocatalytic H2 production from water splitting using semiconductor photocatalysts has attracted much attention due to the increasing global energy crisis. In the past few decades, numerous photocatalysts have been proposed, however, it is still a challenge to develop highly active photocatalysts for water splitting under visible light. Here we report a new composite material consisting of Cu0.02In0.3ZnS1.47 (CIZS) nanospheres and reduced graphene oxide (rGO) nanosheets as a highly active photocatalyst for hydrogen evolution under visible light. These composites were prepared through a solvothermal method in which rGO nanosheets served as a supporting material to load CIZS nanospheres. The nanocomposites demonstrated a high H2 production rate of 3.8 mmol h−1 g−1, which is about 1.84 times that of pure CIZS nanospheres under visible-light irradiation. The high H2 production rate arose from the presence of graphene, which served as an electron collector and transporter to efficiently lengthen the lifetime of photogenerated charge carriers from CIZS nanospheres. This study presents an effective approach to synthesize graphene-based nanocomposites in the field of energy conversion.

Photocatalytic and Adsorption Performances of Faceted Cuprous Oxide (Cu2O) Particles for the Removal of Methyl Orange (MO) from Aqueous Media

Particles of sub-micron size possess significant capacity to adsorb organic molecules from aqueous media. Semiconductor photocatalysts in particle form could potentially be utilized for dye removal through either physical adsorption or photo-induced chemical process. The photocatalytic and adsorption capabilities of Cu2O particles with various exposed crystal facets have been studied through separate adsorption capacity test and photocatalytic degradation test. These crystals display unique cubic, octahedral, rhombic dodecahedral, and truncated polyhedral shapes due to specifically exposed crystal facet(s). For comparison, Cu2O particles with no clear exposed facets were also prepared. The current work confirms that the surface charge critically affects the adsorption performance of the synthesized Cu2O particles. The octahedral shaped Cu2O particles, with exposed {111} facets, possess the best adsorption capability of methyl orange (MO) dye due to the strongest positive surface charge among the different types of particles. In addition, we also found that the adsorption of MO follows the Langmuir monolayer mechanism. The octahedral particles also performed the best in photocatalytic dye degradation of MO under visible light irradiation because of the assistance from dye absorption. On top of the photocatalytic study, the stability of these Cu2O particles during the photocatalytic processes was also investigated. Cu(OH)2 and CuO are the likely corrosion products found on the particle surface after the photocorrosion in MO solution. By adding hole scavengers in the solution, the photocorrosion of Cu2O was greatly reduced. This observation confirms that the photocatalytically generated holes were responsible for the photocorrosion of Cu2O.

Cu–In–Zn–S nanoporous spheres for highly efficient visible-light-driven photocatalytic hydrogen evolution

Cu–In–Zn–S (CIZS) nanoporous spheres were prepared by using a facile room temperature method. The band gaps of the CIZS spheres could be tuned by changing the amount of Cu doped. The obtained CIZS nanoporous spheres exhibited excellent photocatalytic activity for hydrogen production from water under visible light irradiation without any co-catalysts.

Li4x/3Co2−2xTi1+2x/3O4 spinel solid solutions: order and disorder phase transition, cations distribution and adjustable microwave dielectric properties

A series of spinel solid solutions Li4x/3Co2−2xTi1+2x/3O4 (LCT, 0.2 ≤ x ≤ 0.8) were synthesized and their structures and microwave dielectric properties were characterized in detail. The distribution of cations at A and B sites in the lattice has been analyzed by using Rietveld refinement. The microstructure and dielectric properties were studied by scanning electron microscope and microwave network analyzer. The solid solutions undergo a discontinuous B-site, Li/Ti order–disorder phase transition from a disordered cubic phase to an ordered cubic phase with increasing x values from 0.4 to 0.6. With increasing the A-site lithium content, the LCT ceramics exhibit improved dielectric permittivity er (20.3–26.5), high Q × f value (≥29 400 GHz) and a tailored temperature coefficient of resonant frequency τf from −40 to 10 ppm per °C. Optimized microwave dielectric properties were achieved for the composition with x = 0.8: er = 26.5, Q × f ≈ 29 400 GHz and τf ≈ 10 ppm per °C. A correlation between the cation distribution and microwave dielectric loss is discussed in detail.