Control of Selectivity in Heterogeneous Photocatalysis by Tuning TiO₂ Morphology for Water Treatment Applications

Abstract

Heterogeneous photocatalysis using TiO 2 is a non-selective technique used for the degradation of organic molecules. Controlling the morphology of TiO 2 has recently been considered one of the important approaches for controlling the selectivity of TiO 2. In this work, TiO 2 nanotubes and nanosheets were synthesized from spherical TiO 2 nanoparticles using the hydrothermal method. The starting and prepared samples were characterized by XRD, TEM and FESEM. The selectivity of the three morphologies towards the photocatalytic degradation of three food dyes (colours yellow sunset, red allura and red carmoisine) was tested. Importantly, changes in morphology led to each dye being adsorbed preferentially by one of the three morphologies and decomposing more rapidly, where the optimum rate of degradation for sunset yellow, red allura and red carmoisine was achieved by TiO 2 nanosheets, spherical TiO 2 and TiO 2 nanotubes, respectively.

Morphological effect of titanate nanostructures on the photocatalytic degradation of crystal violet

“…In our recently published work, we found that changing the morphology of TiO 2 from spherical structure to the layered and tubular morphology made each morphology resulted in a preferential decomposition of one dye more than the others. 26 In this work, CV preferred to be adsorbing on specific morphology and decomposed more rapidly than other morphologies at certain pH values. BET: Brunauer-Emmett-Teller.…”

Selective Photodegradation Using Titanate Nanostructures

“…Zaki et al in this work reported that changing the morphology of TiO 2 from spherical to layered and tubular shape made each morphology preferentially decompose one dye of the three dyes [22]. From Figure 3a-c, it is clear that the photocatalytic degradation strongly depends on the morphology of TiO 2 .…”

“…The photocatalytic activity of TiO 2 depends on many factors such as specific surface area, size, pore structure, pore volume, exposed surface facet, and crystalline phase [20,22,23]; achieving selectivity in degradation using TiO 2 in some cases depends on crystallinity and crystal facet [24][25][26], and also depends on introducing molecular sites on TiO 2 surface which produce selective adsorption and degradation for targeted compounds are also introduced [27].…”

“…Recently, Zaki et al [22] used three different colors (color yellow sunset, color red allura, and color red carmoisine) to test the selectivity of degradation of three different morphologies of TiO 2 (spherical, layered, and tubular); the TEM images of these morphologies are shown in Figure 1. It is clear from Figure 1a that the starting TiO 2 powder consists of nanosized particles, while Figure 1b shows the TEM image of the synthesized TiO 2 nanosheets, and Figure 1c shows the TEM images of the obtained TiO 2 nanotubes.…”

Preparation and photocatalytic activity analysis of nanometer TiO2 modified by surfactant

“…[19][20][21][22][23][24] The surface area of photocatalyst is an important factor to determine the adsorption capacity of pollutants, which directly affects the strength of photocatalytic activity. 25 Because of the high surface energy of the nanometer material, the nanoparticles tend to accumulate to achieve the equilibrium state of the system, resulting in the serious agglomeration of the nanopowder and the small active surface area. Therefore, high-density block aggregates should be effectively controlled at the stage of early preparation.…”