Photocatalytic Activity Properties Research Articles

Origin and manifestation of semiconductor facet effects

AbstractSemiconductor crystals generally exhibit notable facet‐dependent electrical conductivity and photocatalytic activity properties. If semiconductor nanocrystals of different shapes are available, their light absorption and emission bands can also display facet dependence, although bulk plus surface absorption combines to give the recorded spectra. All these physical phenomena can be understood, assuming a thin surface layer exists with slight structural deviations as predicted by density functional theory (DFT) calculations to give dissimilar band structures and hence different degrees of band bending and barriers to charge transport across a particular crystal face. This layer thereby tunes light absorption. Recent X‐ray diffraction (XRD) and high‐resolution transmission electron microscopy (HR‐TEM) analyses begin to suggest the presence of the proposed surface layer.

Photocatalytic Performance of Ball-Milled Anatase/Rutile Mixed Phase TiO<sub>2</sub> Composite Powders

Mixed-phase anatase/rutile titanium dioxide (TiO2) composite powder is an important material due to the unique properties of photocatalytic activity that is higher than that of the only single anatase or rutile phase. In this study, the anatase/rutile mixed phase TiO2 composite powders were prepared by ball milling of TiO2 commercial grade powders. Effect of the anatase/rutile phase ratio and milling time on photocatalytic performance were investigated. The sample phase ratio is evaluated using X-ray diffraction (XRD) meanwhile the composite morphology is characterized using field emission scanning electron microscope (FE-SEM). The overall results revealed that the mixed-phase anatase/rutile provided significant enhancement in photocatalytic performance comparing to only anatase or rutile single phase. In addition, this ball-milling technique is considered as an effective process and cost-effectively on energy saving suitable for preparing anatase/rutile mixed-phase TiO2 for photocatalytic application.