Direct sunlight photodegradation of congo red in aqueous solution by TiO2/rGO binary system: Experimental and DFT study

Photolysis was employed to produce titanium dioxide (TiO2) with exposed (001) facets, which were then modified by incorporating reduce graphene oxide (rGO) sheets at (1, 3 and 5) wt. %.The chemical composition, optical properties, morphology, and electrochemical behavior of both the pure and composite nanomaterials were analyzed. The X-ray diffraction (XRD) and Raman spectroscopy techniques confirmed the formation of the anatase phase of TiO2 in the sam-ples. The Debye Scherrer method was utilized to estimate the size of the particles. It was observed that the particle size decreased as the concentration of rGO increased; at 5 wt% rGO, the size was 11 nm. The morphology of the rGO/TiO2 nanocomposite was analyzed with transmission electron microscopy (TEM) which showed that TiO2 nanoparticles were dispersed on the surface of the rGO sheets. The analysis of the X-ray photoelectron spectrum (XPS) revealed that bonding of TiO2 with rGO occurred through the formation of Ti-C and Ti-O-C bonds. The results obtained from the dif-fuse reflectance spectroscopy (DRS) showed a decrease in band gap upon an increase in rGO con-centration. Moreover, confirmation was obtained regarding the reduction of recombination carriers through the photoluminescence (PL) spectrum. The results indicated that the prepared nanocom-posite had a high number of oxygen vacancies. The photodegradation mechanism of congo red dye under sunlight was studied by Liquid chromatography-mass spectrometry (LC-Mass) and scav-enger effect. The photodegradation of congo red dye (CR) utilizing TiO2, both pure and incorpo-rated with rGO, was observed under normal conditions in the presence of sunlight. The study revealed that the optimal condition for achieving maximum photodegradation of CR dye was pH = 7, 100 min, 50 ppm initial CR dye concentration and 10 mg of catalyst dosage. The pho-todegradation data illustrated that 5 wt% rGO doped TiO2 exhibits higher efficiency than other 3; 1 wt% rGO and pure TiO2. Finally, the improving breakdown of CR dye using direct sunlight showed high efficiency without leaving behind any secondary intermediates.(c) 2023 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Photolysis was used to produce TiO2 nanoparticles with exposed (001) facets, which were then modified by incorporating rGO sheets at different wt.% concentrations. The resulting nanocomposites were characterized using various techniques, confirming the formation of anatase phase TiO2 and revealing the morphology and surface bonding of the rGO/TiO2 nanocomposites. The optical properties and photodegradation efficiency of the nanocomposites were investigated, and it was found that the 5 wt.% rGO-doped TiO2 showed the highest efficiency for the photodegradation of CR dye. Furthermore, the nanocomposites exhibited a high number of oxygen vacancies and showed excellent performance in the breakdown of CR dye under direct sunlight.