Ti-zeolite Y based nanocomposites modified with Au and CeO2 with photocatalytic activity in visible light

Abstract

Two series of photocatalysts (TYAu, TYCeAu) were obtained. Ti was incorporated by direct synthesis with zeolite Y, while Ce and Au were immobilized by double incipient wetness impregnation method. The experimental weight percents (XRF analysis) were for titanium (0.7 %, 1.9 %, 3.5 %), Ce (1 %), and Au (0.3 %, 0.1 %). The typical crystalline structure of zeolite Y was preserved in all samples except those with 3.5 % Ti, where XRD revealed reduced pattern intensity. SEM and TEM analyses showed morphological changes at higher Ti contents. CO₂-TPD confirmed a decrease in basicity with increasing Ti, consistent with the diminished zeolite contribution. XPS analysis indicated the presence of varying Au⁰/Au⁺ and Ce³⁺/Ce⁴⁺ ratios on the surface, depending on the Ti content. The intra- and extraframework TiO₂ as amorphous or anatase phases were Raman confirmed in cerium-containing samples. For materials with high Ti content, the dominant effect was from the Ce and Ti species, accentuated by gold. The surface plasmon resonance effect of Au nanoparticles and decreasing in band gap energy after Ce immobilization was evidenced by UV-Vis spectroscopy. The photocatalytic properties of the synthesized materials were evaluated in CO₂ reduction with water and H₂ production via water splitting under visible light (525 nm). Higher Ti content enhanced CO₂ conversion and reduced CH₄ selectivity, favoring the production of CH₃OH and CH₂O. A greater amount of hydrogen was produced by the samples with the lowest Ti concentration while the reaction was favored by the presence of cerium in the rich titanium samples.