Zaizhu Lou

Synthesis of Highly Efficient Ag@AgCl Plasmonic Photocatalysts with Various Structures

By means of a simple ion-exchange process (using different precursors) and a light-induced chemical reduction reaction, highly efficient Ag@AgCl plasmonic photocatalysts with various self-assembled structures-including microrods, irregular balls, and hollow spheres-have been fabricated. All the obtained Ag@AgCl catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and UV-visible diffuse reflectance spectroscopy. The effect of the different morphologies on the properties of the photocatalysts was studied. The average content of elemental Ag in Ag@AgCl was found to be about 3.2 mol %. All the catalysts show strong absorption in the visible-light region. The obtained Ag@AgCl samples exhibit enhanced photocatalytic activity for the degradation of organic contaminants under visible-light irradiation. The stability of the plasmonic photocatalysts was also investigated in detail.

In situ ion exchange synthesis of the novel Ag/AgBr/BiOBr hybrid with highly efficient decontamination of pollutants

A novel Ag/AgBr/BiOBr hybrid was prepared by a rational in situ ion exchange reaction between BiOBr hierarchical microspheres and AgNO(3) in ethylene glycol followed by light reduction, which displayed superior visible light driven photocatalytic activities in sterilization of pathogenic organism and degradation of organic dye compared to N-doped P25.

Highly Efficient Visible Light Plasmonic Photocatalysts Ag@Ag(Cl,Br) and Ag@AgCl‐AgI

New plasmonic photocatalysts Ag@Ag(Cl,Br) and Ag@AgCl‐AgI were synthesized by the ion‐exchange process between AgCl and a potassium halide (KBr, KI), then by reducing some Ag+ ions in the surface region of Ag(Cl,Br) and AgCl‐AgI particles to Ag0 species. The Ag nanoparticles were formed from Ag(Cl,Br) and AgCl‐AgI by a light‐induced chemical reduction. The Ag@Ag(Cl,Br) and Ag@AgCl‐AgI particles have irregular shapes and their sizes vary between 100 nm and 1.3 μm. The as‐grown plasmonic photocatalysts show strong absorption in the visible‐light region, owing to the plasmon resonance of Ag nanoparticles. The ability of this compound to oxidize methylic orange and reduce CrVI under visible light was compared with those of other reference photocatalysts. These plasmonic photocatalysts have been shown to be highly efficient under visible‐light irradiation.

Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H2 production under visible light

Controlling amount of intrinsic S vacancies was achieved in ZnS spheres which were synthesized by a hydrothermal method using Zn and S powders in concentrated NaOH solution with NaBH4 added as reducing agent. These S vacancies efficiently extend absorption spectra of ZnS to visible region. Their photocatalytic activities for H2 production under visible light were evaluated by gas chromatograph, and the midgap states of ZnS introduced by S vacancies were examined by density functional calculations. Our study reveals that the concentration of S vacancies in the ZnS samples can be controlled by varying the amount of the reducing agent NaBH4 in the synthesis, and the prepared ZnS samples exhibit photocatalytic activity for H2 production under visible-light irradiation without loading noble metal. This photocatalytic activity of ZnS increases steadily with increasing the concentration of S vacancies until the latter reaches an optimum value. Our density functional calculations show that S vacancies generate midgap defect states in ZnS, which lead to visible-light absorption and responded.

Synthesis and Activity of Plasmonic Photocatalysts

Plasmonic photocatalysts, which have intensive light absorption and high charge‐separation efficiencies, are regarded as promising candidates to solve energy and environmental issues in the future. In this Review, we summarize recent developments in the synthesis, activity, and mechanism of plasmonic photocatalysts, with the aim of stimulating improvements in photocatalytic activities and promoting the development of photocatalysis. The materials systems, energy‐transfer mechanisms, and factors that influence the photocatalytic activities of plasmonic photocatalysts are discussed. Some perspectives for the future development of the design of highly efficient plasmonic photocatalysts are proposed.

One-step synthesis of AgBr microcrystals with different morphologies by ILs-assisted hydrothermal method

AgBr microcrystals with different morphologies were synthesized by an ionic liquids (ILs)-assisted hydrothermal method. A plausible growth mechanism, and influence of ionic liquids on the morphology of AgBr, were proposed and studied systematically. The samples were characterized by scanning electronic microscopy and X-ray diffraction. The relationship of morphology and photocatalytic activity of samples was studied.

Pt–Au Triangular Nanoprisms with Strong Dipole Plasmon Resonance for Hydrogen Generation Studied by Single-Particle Spectroscopy

Three anisotropic Pt-covered, Pt-edged, and Pt-tipped Au triangular nanoprisms (TNPs) were prepared by controlling the overgrowth of Pt as photocatalysts for H2 generation. With strong electric field and more interface for the hot electrons transfer, the H2 generation rate of Pt-edged Au TNPs was 3 and 5 times higher than those of Pt-tipped and Pt-covered Au TNPs. Single-particle photoluminescence (PL) spectra and finite-difference-time-domain (FDTD) simulations demonstrated that dipole surface plasmon resonance (DSPR) of Au TNPs enhanced the hot electrons transfer from Au to Pt leading to H2 generation. SPR bands of Au TNPs depending on the size play an important role on the photocatalytic activity of Pt-edged Au TNPs.

A 3D AgCl hierarchical superstructure synthesized by a wet chemical oxidation method.

A novel 3D AgCl hierarchical superstructure, with fast growth along the 〈111〉 directions of cubic seeds, is synthesized by using a wet chemical oxidation method. The morphological structures and the growth process are investigated by scanning electron microscopy and X-ray diffraction. The crystal structures are analyzed by their crystallographic orientations. The surface energy of AgCl facets {100}, {110}, and {111} with absorbance of Cl(-) ions is studied by density functional theory calculations. Based on the experimental and computational results, a plausible mechanism is proposed to illustrate the formation of the 3D AgCl hierarchical superstructures. With more active sites, the photocatalytic activity of the 3D AgCl hierarchical superstructures is better than those of concave and cubic ones in oxygen evolution under irradiation by visible light.

CuO/CuSCN valence state heterojunctions with visible light enhanced and ultraviolet light restrained photocatalytic activity

CuSCN is applied, for the first time, in a photocatalytic system to form CuO/CuSCN valence state heterojunctions, which exhibited enhanced visible light driven photocatalytic activity and, surprisingly, ultraviolet light restrained activity. Proper migration of photo-generated carriers is proposed to explain the photocatalytic process.

Fast-generation of Ag3PO4 concave microcrystals from electrochemical oxidation of bulk silver sheet

Silver sheet is used as an anode in Na3PO4 solution to synthesize Ag3PO4 microcrystals through an electrochemical oxidation process. Ag3PO4 microcrystals with a novel concave surface are obtained in a fast-generation manner. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used to investigate the microstructure and growth process of Ag3PO4 concave microcrystals. The growth mechanism of the Ag3PO4 concave microcrystals is illustrated by the preferential overgrowth along and directions of Ag3PO4 seeds during the growth process. With the high-index facets exposed on the concave surface, the Ag3PO4 concave microcrystals have higher photocatalytic activity than that of irregularly-shaped particles made from the traditional precipitation method.