Tingjiang Yan

Fabrication of robust M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures for improved visible-light photocatalysis

M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures were successfully fabricated by a chemical deposition route using NaBH4 as a reduction agent. The structure and optical properties of the as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and electrochemical techniques. The photocatalytic activity was evaluated by the decomposition of dyes (methyl orange, methylene blue, and rhodamine B) under visible light irradiation (λ > 420 nm). These noble metals as nanoparticles were highly dispersed on the surface of Ag3PO4 polyhedrons. The light absorption of Ag3PO4 in both the UV and visible regions was extensively increased upon noble metal deposition. The photocurrent response over M/Ag3PO4 electrodes was much higher than that of pure Ag3PO4 and followed the decreased order of Pt > Pd > Au. The metallic nanoparticles deposited on Ag3PO4 could promote the transfer of photo-generated electrons, which not only inhibited the recombination of electrons and holes effectively, but also suppressed the photocorrosion of Ag3PO4, leading to a significant increase in photocatalytic activity and stability. On the basis of radical-trapping experiments and the PL technique, h+ and ˙O2− were well-established to correspond to the quick photo-degradation of dyes and a possible mechanism was proposed.

Synergistic degradation of rhodamine B on BiOClxBr1−x sheets by combined photosensitization and photocatalysis under visible light irradiation

BiOClxBr1−x sheets were synthesized by a simple precipitation method. These samples showed good activities in the degradation of rhodamine B (RhB) under visible light irradiation (420 nm < λ < 800 nm). From a series of characterization techniques, the results showed that the degradation was driven by the photosensitization of RhB and photocatalysis of BiOClxBr1−x. The mechanism of the synergistic degradation processes was explored by comparing the degradation properties of BiOClxBr1−x (Cl : Br = 1 : 1) and BiOBr. The main active species that played important roles in the degradation process were electrons and O2˙− in the BiOClxBr1−x (Cl : Br = 1 : 1) system, while in the BiOBr system, electrons, O2˙− and holes were the main active species. Such a heterogeneous synergistic degradation reaction has much significance in revealing the degradation mechanism of organic pollutants in ordinary photocatalysis.

Relationship between surface hydroxyl groups and liquid-phase photocatalytic activity of titanium dioxide.

Both theories and experiments show that surface hydroxyl radicals (OH) are the most important intermediate species in the photocatalytic process. As a source of OH, surface hydroxyl (OH) groups play an important role in its generation. In this paper, the OH groups were divided into surface acidic hydroxyl (OH(a)) and surface basic hydroxyl (OH(b)) groups. From the detection by a method of surface acid-base, ion-exchange reactions, the total surface density of OH groups was about 9.58×10(-5) mol m(-2). The results measured by Fourier transform infrared spectroscopy, (1)H magnetic-angle spinning NMR and electron spin resonance techniques demonstrated that the role of OH(a) groups was greater than that of OH(b) groups on the generation of OH radicals. By degradation of methyl orange, rhodamine B and p-chlorophenol, the photocatalytic activities of the catalysts were directly influenced by the amount of OH groups.