Hydrothermal Synthesis of rGO-TiO2 Composites as High-Performance UV Photocatalysts for Ethylparaben Degradation

Abstract

A series of reduced graphene oxide-TiO2 composites (rGO-TiO2) were prepared by hydrothermal treatment using graphite and titanium isopropoxide as raw materials. The structural, surface, electronic, and optical properties of the prepared composites were extensively characterized by N2 adsorption, FTIR, XRD, XPS, Raman spectroscopy, and DRS. GO was found to be effectively reduced and TiO2 to be in pure anatase phase in all composites obtained. Finally, experiments were performed to evaluate the effectiveness of these new materials as photocatalysts in the degradation of ethylparaben (EtP) by UV radiation. According to the band-gap energies obtained (ranging between 3.09 eV for 4% rGO-TiO2 to 2.55 eV for 30% rGO-TiO2), the rGO-TiO2 composites behave as semiconductor materials. The photocatalytic activity is highest with a rGO content of 7 wt% (7% rGO-TiO2), being higher than observed for pure TiO2 (Eg = 3.20 eV) and achieving 98.6% EtP degradation after only 40 min of treatment. However, the degradation yield decreases with higher percentages of rGO. Comparison with rGO-P25 composites showed that a better photocatalytic performance in EtP degradation is obtained with synthesized TiO2 (rGO-TiO2), probably due to the presence of the rutile phase (14.1 wt %) in commercial P25.

PbS Quantum Dots Decorating TiO2 Nanocrystals: Synthesis, Topology, and Optical Properties of the Colloidal Hybrid Architecture

“…On the basis of these considerations, the fitting contributions of the TiO 2 NC PL band centered in the range of 400–450 nm can be mainly attributed to STE while the one centered at 462 nm is ascribed to indirect recombination via oxygen defects [ 77 ]. The week emission of the TiO 2 NC sample with the tail almost completely quenched at 600 nm suggests a low density of oxygen defects compared to the TiO 2 /PbS hybrid nanostructure.…”

Characteristics and Behavior of Different Catalysts Used for Water Decontamination in Photooxidation and Ozonation Processes

“…Table 12 summarizes results for the textural characterization and bandgap energy of the above composites. TiO 2 has higher S BET , V 0 , and V 0.95 values in comparison to P25, possibly due to the smaller size of TiO 2 nanoparticles, as observed in XRD analysis [81]. The addition of rGO sheets hinders the agglomeration of TiO 2 particles and augments the surface area and pore volume of % rGO-TiO 2 composites.…”

“…In this way, rGO has been combined with different metal oxides (TiO 2 , ZnO, Cu 2 O, Bi 2 WO 6 , etc.) and found to be a very effective photocatalyst for the degradation of different pollutants from water and to prevent corrosion and leaching of the metal oxide nanoparticles in water [80,81,123]. A series of rGO/TiO 2 [81] and rGO/Bi composites [80] with different rGO contents were exhaustively characterized, and their structural, chemical, and electronic properties were compared with their photocatalytic activity in the degradation of organic pollutants in aqueous solution.…”

“…Table 13. Experimental results of ethylparaben (EtP) photodegradation under UV radiation in the presence of prepared rGO-TiO 2 composites [EtP] 0 = 0.30 × 10 −3 mol/L, [catalyst] 0 = 0.7 g/L (adapted from [81]). Table 14 exhibits the results of the photocatalytic degradation of sulfamethazine (SMZ) under solar radiation in the presence of rGO/Bi composites.…”

“…Textural characteristics and bandgap energy (Eg) of rGO/metal oxide catalysts (adapted from[80,81]). …”