ABSTRACT
It is a great challenge to simultaneously improve the visible light absorption capacity and enhance photon-generated carrier separation efficiency of photocatalysts. Herein, Zn-doped TiO2 nanoparticles with high exposure of the (001) crystal face were prepared via a one-step hydrothermal decomposition method. A detailed analysis reveals that the electronic structures were modulated by Zn doping; thus, the responsive wavelength was extended to 600 nm, which effectively improved the visible light absorption of TiO2. More importantly, the surface heterojunction of TiO2 was created because of the co-existing specific facets of (101) and (001). Therefore, the surface separation efficiency of photogenerated electron and hole pairs was greatly enhanced. So, the optimal TiO2 photocatalyst exhibited excellent photocatalytic activity, in which the Rhodamine B (RhB) degradation efficiency was 98.7% in 60 min, under the irradiation of visible light. This study is expected to provide guidance for the rational design of TiO2 photocatalysts.
ABSTRACT
The Co3O4@CdS double-layered hollow spheres were first prepared by the template-removal method with the assistance of the ZIF-67 material; the structure has been proved by transmission electron microscopy (TEM). The Co3O4@CdS hollow spheres calcinated at 400 °C exhibited the highest photodegradation activity. Nearly 90% phenol was degraded after 2 h of visible-light irradiation. More than 80% rhodamine-B (RhB) was degraded within the first 30 min and nearly eliminated after 1 h of irradiation. The mechanism of the photodegradation reaction was investigated. Based on the analysis of electron spin resonance (ESR) spectra and radical trapping test, it was found that superoxide radicals are the major oxidative species for dye degradation and holes and hydroxyl radicals are the major oxidative species for phenol degradation. These results may be used in industrial wastewater treatment. The reaction obeys first-order reaction kinetics, and the rate constant of the Co3O4@CdS hollow sphere in dye degradation is 0.05 min-1 and that in phenol degradation is 0.02 min-1, which is three times higher than that of CdS nanoparticles. These results indicated the high oxidizing ability of the samples.
ABSTRACT
Defect modulation usually has a great influence on the electronic structures and activities of photocatalysts. Here, atomically layered g-C3N4 modified via defect engineering with nitrogen vacancy and cyanogen groups is obtained through two facile steps of thermal treatment (denoted as A-V-g-C3N4). Detailed analysis reveals that the atomic-layered graphitic carbon nitride (2.3 nm) with defect engineering modifying provides more active sites and decreases the electron/hole transferring distances. More importantly, the defects that contain nitrogen vacancies and cyanogen groups extend the responsive wavelength to 650 nm, which effectively suppresses the quantum size effect of atomic-layered g-C3N4. Therefore, the as-obtained A-V-g-C3N4 exhibited a photocatalytic H2 evolution rate and apparent quantum yield of 3.7 mmol·g-1·h-1 and 14.98% (λ > 420 nm), respectively. This work is expected to provide guidance for the rational design of atomic-layered g-C3N4.
