Photocatalytic Conversion of Carbon Dioxide Over Silver‐Modified Lanthanide Titanate Under Photoirradiation Exceeding 300 nm

ABSTRACT The photocatalytic conversion of CO 2 into valuable chemicals is a promising approach for artificial photosynthesis. The photocatalytic conversion of CO 2 over Ag‐modified lanthanide titanates (Ln 2 Ti 2 O 7 ) was investigated in this study under photoirradiation at wavelengths longer than 300 nm using 2‐propanol as a hole scavenger. Among the various Ln 2 Ti 2 O 7 materials tested, La 2 Ti 2 O 7 exhibited superior photocatalytic performance. The photocatalytic activity was strongly dependent on the crystallinity and surface area of the La 2 Ti 2 O 7 host, with the optimal photocatalyst obtained by calcination at 1423 K for 2 h. Furthermore, the Ag cocatalyst loading method significantly affected the CO production rate, with chemical reduction facilitating the formation of highly dispersed, small metallic Ag nanoparticles (2–10 nm), which were essential for efficient CO 2 reduction. In contrast, the photodeposition and impregnation methods resulted in the formation of larger, aggregated Ag particles (20–50 nm), leading to a lower photocatalytic activity. The optimised Ag/La 2 Ti 2 O 7 photocatalyst achieved a CO formation rate of approximately 120 µmol h −1 with a high selectivity of 90%. The stoichiometric formation of acetone and isotopic labelling experiments using 13 CO 2 confirmed that the reaction proceeded via the reduction of CO 2 to CO, coupled with the oxidation of 2‐propanol.