Photocatalytic Enhancement Mechanism Research Articles

3C-SiC/ZnS heterostructured nanospheres with high photocatalytic activity and enhancement mechanism

3C-SiC/n-type ZnS heterostructured nanospheres synthesized hydrothermally deliver enhanced photocatalytic performance under visible light excitation. The heterostructured catalysts consisting of 3C-SiC and ZnS nanocrystals with a mean size being less than 5 nm exhibit extended light absorption to the visible range. The proper band structure of the 3C-SiC and ZnS nanocrystals and intrinsic electric field induced by the heterojunction promote separation of photoexcited electrons and holes in the ZnS and 3C-SiC nanocrystals resulting in the increased photocatalytic efficiency. The associated mechanism is studied and proposed.

A new CdS/Bi1−xInxTaO4 heterostructured photocatalyst containing solid solutions for H2 evolution from water splitting

A new strategy has been put forward to improve the performance of photocatalytic H2 evolution of tantalate-based catalysts through designing solid solutions Bi1−xInxTaO4 combined with CdS, among which the solid solutions Bi1−xInxTaO4 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) were firstly synthesized by the citrate method using cheap and environment-friendly Ta2O5. The experimental results reveal that the Bi0.5In0.5TaO4 solid solution shows the best photocatalytic performance among the Bi1−xInxTaO4 solid solutions. And in the absence of noble metals, the 30% CdS/Bi0.5In0.5TaO4 (30CBITO) catalyst exhibits good photocatalytic hydrogen evolution from water splitting with a rate of H2 production of 511.75 μmol h−1 g−1 under simulated sunlight irradiation. And the rate of hydrogen evolution does not markedly change for 60 h. Their compositions, structures and morphologies were characterized by UV–vis diffusion reflectance spectroscopy (DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). A photocatalytic enhancement mechanism was put forward to elucidate the superior photocatalytic activity and long-term stability of the heterostructured CdS/Bi0.5In0.5TaO4 composites.

Shape-dependent localized surface plasmon enhanced photocatalytic effect of ZnO nanorods decorated with Ag

We report shape-dependent localized surface plasmon enhanced photocatalytic effect of ZnO nanorods decorated with Ag nanostructures. The plasmonic ZnO photoelectrode modified by Ag nanoprisms exhibits a significant enhancement in photoelectric conversion with a maximum photoconversion efficiency of 1.45%. The photocurrent intensity (at 0.5 V vs. Ag/AgCl) of ZnO–Ag nanoprisms is 3.1 and 10 times greater than that of ZnO–Ag nanoparticles and as-grown ZnO nanorods, respectively. Moreover, ZnO–Ag nanoprisms showed a fast photoresponse due to the fast transport of photogenerated charge carriers in ZnO nanorods with a low recombination rate. It is suggested that the mechanism of photocatalytic enhancement by Ag nanoprisms is mainly ascribed to the significantly enhanced plasmonic ‘hotspots’ in sharp tips of nanoprisms. Such shape-dependent localized surface plasmon effect is further confirmed by FDTD simulation, which revealed that Ag nanoprisms showed stronger electromagnetic field intensity than that of Ag nanoparticles.

Synergism between Fe2O3 and WO3 particles: Photocatalytic activity enhancement and reaction mechanism

In this work we have found that simple mixing of WO3 and Fe2O3 can result into significant enhancement in activity for phenol degradation in the presence of H2O2 either under UV or visible light. The enhanced activity varied with Fe2O3 content in the mixed oxide. The best catalyst was 1.0wt% Fe2O3/WO3, whose activity, in relative to bare WO3, increased to 3.8-fold under UV light, and 2.1-fold under visible light. Control experiments indicated that phenol degradation was mainly initiated by the excited WO3 in Fe2O3/WO3, and that there was a synergistic effect between two oxides. A spin trapping electron paramagnetic resourance spectroscopy revealed that the production of hydroxyl radicals over Fe2O3/WO3 was greatly enhanced. Solid characterization with X-ray diffraction, N2 adsorption and element mapping showed that Fe2O3 particles were highly dispersed in the sample, with a small size and high surface area. We propose that there occurs an electron transfer from the conduction band of WO3 to low energy trapping sites of Fe2O3, which promotes the separation of WO3 charge carriers, and consequently accelerates phenol degradation.

Thermal and photocatalytic stability enhancement mechanism of poly(propylene carbonate) due to Cu(I) impurities

The thermal and photolytic decomposition of poly(propylene carbonate) (PPC) in the presence of a photoacid generator (PAG) was studied. The mechanism of previously observed shifts in the decomposition temperature of PPC was investigated. The decomposition temperature of PPC can be altered when PPC/PAG films contact copper metal. X-ray photoelectron spectroscopy (XPS) analysis showed that a small amount Cu(I) was incorporated into the PPC/PAG film causing the increased stability and the Cu(I) concentration was similar to that of the PAG. PPC/PAG temperature stability was studied for a number of iodonium and sulfonium-based PAGs. Every iodonium-based PAG showed a PPC decomposition temperature shift and no sulfonium-based PAG showed the thermal stability effect. It appears that Cu(I) interacts with iodonium in the cation of the PAG causing a change in the acid creation mechanism of the PAG.