Enhanced Photocatalytic Performance toward CO₂ Hydrogenation over Nanosized TiO₂-Loaded Pd under UV Irradiation

A series of Pd/TiO 2 photocatalysts were synthesized by a simple glucose reduction method, and their photocatalysis properties were evaluated in an array of CO 2 hydrogenations. The samples were characterized by XRD, SEM, TEM, EDX, EDX mapping, UV–vis DRS, Raman spectroscopy, PL spectroscopy, XPS, and N 2 adsorption. In terms of product yields (in micromoles per gram of catalyst), a 1.0 wt % Pd/TiO 2 catalyst (CH 4, 355.62; CO, 46.35; C 2 H 6, 39.69) was found to be superior to pristine TiO 2 (CH 4, 42.65; CO, 4.73; C 2 H 6, 2.7) and other composites under UV irradiation for 3 h, possibly because of a synergistic effect between the palladium nanoparticles and the TiO 2 support. The palladium nanoparticles on the surface of TiO 2 substantially accelerated electron transfer and acted as active sites for the adsorption and activation of CO 2 molecules, to promote CO 2 hydrogenation. During the photocatalytic CO 2 hydrogenation, dissociated hydrogen reacts with CO 2 – activated on the Pd/TiO 2 photocatalyst to form a new Pd—C surface species that is stable during the reaction and further transforms to generate methane. A detailed mechanism of photocatalytic CO 2 hydrogenation is discussed to account for the performance of the Pd/TiO 2 photocatalyst in the reaction.