Chaorong Li

Controlled synthesis and self-assembly of dendrite patterns of Fe3O4 nanoparticles.

A method for the growth and self-assembly of Fe(3)O(4) nanoparticles that is template assisted, as well as gas diffusion and surface tension controlled, has been developed at room temperature. Well-defined dendrite patterns of Fe(3)O(4) nanoparticles were obtained upon ion (Fe(3+)/Fe(2+)) entrapment in a polyethylene glycol solution followed by NH(3) gas exposure on the surface of an aqueous solution on the glass substrate. During the formation of Fe(3)O(4) nanoparticles, the diffusion of volatile NH(3) limits the hydrolysis rate of the molecular precursor and catalyzes slow formation. The template and surface tension also provided significant driving forces to promote the formation of dendrite patterns and influence the nature of the pattern. The Fe(3+)/Fe(2+) concentration was varied in order to see the affects on the template molecular weight. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and SQUID measurements were used to characterize the final product. The derived patterned structure can be tailored by a simple combination of the physical and chemical procedure, which provides a new opportunity for obtaining a controllable pattern of nanoparticles.

Silver nanoparticles modified reduced graphene oxide wrapped Ag3PO4/TiO2 visible-light-active photocatalysts with superior performance

Silver nanoparticles (Ag NPs) modified reduced graphene oxide wrapped Ag3PO4/TiO2 (Ag3PO4/TiO2/Ag-rGO, Ag-ATG) photocatalysts have been developed through a rational design that combines the optimization of charge generation, separation and transfer in the composites, which helps to increase the photocatalytic performance. The Ag-ATG composites possess novel microstructure, in which TiO2 mesoporous spheres of hundreds of nanometers in size are decorated with dense nano-sized Ag3PO4 to form pinecone-liked Ag3PO4/TiO2 particles, which were further wrapped by rGO sheets that are selectively decorated with Ag NPs. The Ag-ATG composites exhibit improved photocatalytic performance toward degradation of methylene blue (MB) and methyl orange (MO) under visible light compared to bare Ag3PO4 and Ag3PO4/TiO2/rGO (ATG). The underlying mechanism has been studied based on the results of reactive oxygen species capture experiment, photoluminescence (PL) spectra, and photocurrent measurements under visible light and monochromatic lights. The improved photocatalytic performance is mainly ascribed to the efficient spatial separation of photo-induced electrons and holes in Ag-ATG, i.e., the electrons in Ag3PO4 transfer to Ag-rGO, meanwhile the holes in Ag3PO4 transfer to TiO2. Ag NPs play an important role in the hybrid structure owing to the synergistic effect of Ag NPs and rGO, which not only enhance the light harvest but also increase the capacity of electron accepting from Ag3PO4. Meanwhile, active photo-induced electrons at the plasmonic Ag NPs can facilitate the formation of O2˙− radicals for photocatalysis. As a result, both the stability and photocatalytic active of Ag-ATG are significantly improved.

Ni3S2 Nanosheet Flowers Decorated with CdS Quantum Dots as a Highly Active Electrocatalysis Electrode for Synergistic Water Splitting

A facile and effective strategy for fabricating a three-dimensionally (3D) structured nanocomposite catalyst based on nonprecious metals for water splitting in alkaline electrolyzers is reported in this paper. This nanocomposite catalyst consists of the CdS quantum dots (QDs) decorated Ni3S2 nanosheet flowers deposited on the plasma-treated nickel foam (PNF). The NiO formed during the plasma treatment is shown to play an important role for pushing the hydrogen and oxygen evolution reactions (HER and OER) in alkaline media. The enhanced exposure of active sites on the nanopetalages results in superior catalytic performance for promoting HER and OER in alkaline electrolyzers. Specifically, a current density of 10 mA cm-2 can be achieved for the HER with a 121 mV overpotential when the working electrode based on the 1 mM CdS/Ni3S2/PNF catalyst is employed in 1 M KOH. The corresponding Tafel slope is 110 mV/decade. For the OER, the onset potential can be as low as 1.25 V vs reversible hydrogen electrode (RHE) reference electrode, which is substantially lower than the commercial IrO2 catalyst (∼1.47 V). This nanostructured catalyst has excellent long-term stability, and the linear scan voltammetry (LSV) curves of the HER and OER in 1 M KOH solution show negligible decay after undergoing 104 cycles of cyclic voltammogram. The nanocomposite material developed in this study is an ideal candidate as a catalyst for splitting water in alkaline media with relatively low overpotentials at reasonably high current densities (≥100 mA cm-2).