Synthesis and Characterization of Black TiO2 Based Nanocomposites for Photocatalytic Hydrogen Generation Application

Abstract

The H2 evolution using renewable solar energy sources is an ideal way to meet potential newlinedemand for energy. Since the earth is an ample source of water, the sun is an immodest energy newlinesource with a sufficient life expectancy. Globally, substituting carbon-free hydrogen for fossil newlinefuels would drastically reduce greenhouse gas emissions. TiO2 has been recognized as a light newlineharvester due to its compatible characteristics such as non-toxicity and suitable bandgap, high newlinerefractive index, chemical, and thermal stability. However, due to the wide bandgap TiO2 newlineabsorption capability limits within the UV region. Hence, the bandgap engineering to reduce newlinethe bandgap of TiO2 to expand the absorption to the visible/NIR region of the solar spectrum newlineis an effective area of research. newlineTi3+/Oxygen vacancy defects are considered as one of the unique characteristic defects newlineof black TiO2 (TiO2-x) nanomaterials. Oxygen vacancies play a vital role in the activity and newlinekinetics of the reactions taking place on the metal oxide surface. In this work, the synthesis of newlineoxygen-deficient TiO2-x nanoparticles, with a high-rate photocatalytic performance via the newlinehydrothermal method is carried out. The structural and morphological study reveals that the newlineas-synthesized TiO2 and TiO2-x samples exhibit a tetragonal structure with a pure anatase newlinephase. The well-controlled mixed structured morphology with an average particle size of 7 nm newlinewas observed in HRTEM. Diffuse Reflectance spectra of TiO2-x indicate the bandgap was newlinetailored successfully from 3.2 eV to 2.0 eV with an increase in the L-ascorbic acid molar newlineconcentration during the synthesis of samples. The altered bandgap energies enhanced the newlineoptical properties of TiO2-x samples. Further, the photocatalytic hydrogen generation studies newlineshowed that the TiO2-x sample without loading co-catalyst resulted in the evolution of H2 gas newlineof 8.1 mmol h-1 g-1 under visible light irradiation in 4h, which was much higher than that of newlineother TiO2 and TiO2-x samples reported in the literature for