Surface modification of layered perovskite Sr₂TiO₄ for improved CO₂ photoreduction with H₂O to CH₄

Layered perovskite Sr₂TiO₄ photocatalyst was synthesized by using sol-gel method with citric acid. In order to increase the surface area of layered perovskite Sr₂TiO₄, and thus to improve its photocatalytic activity for CO₂ reduction, its surface was modified via hydrogen treatment or exfoliation. The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, elemental mapping analysis, energy-dispersive X-ray spectroscopy, N₂ adsorption-desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and electrophoretic light scattering. CO₂ photoreduction was performed in a closed reactor under 6 W/cm² UV irradiation. The gaseous products were analyzed using a gas chromatograph equipped with flame ionization and thermal conductivity detectors. The exfoliated Sr₂TiO₄ catalyst (E-Sr₂TiO₄) exhibited a narrow band gap, a large surface area, and high dispersion. Owing to these advantageous properties, E-Sr₂TiO₄ photocatalyst showed an excellent catalytic performance for CO₂ photoreduction reaction. The rate of CH₄ production from the photoreduction of CO₂ with H₂O using E-Sr₂TiO₄ was about 3431.77 μmol/g_cat after 8 h.