Regulating Electronic Structure in Bi₂ O₃ Architectures by Ti Mediation: A Strategy for Dual Active Sites...

Under mild conditions, nitrogen undergoes the associative pathways to be reduced with solar energy as the driving force for fixation, avoiding the high energy consumption when undergoing dissociation. Nevertheless, this process is hindered by the high hydrogenation energy barrier. Herein, Ti was introduced as hard acid into the δ-Bi₂ O₃ (Ti-Bi₂ O₃ ) lattice to tune its local electronic structure and optimize its photo-electrochemistry performance (reduced bandgap, increased conduction band maximum, and extended carrier lifetime). Heterokaryotic Ti-Bi dual-active sites in Ti-Bi₂ O₃ created a novel adsorption geometry of O-N₂ interaction proved by density functional theory calculation and N₂ temperature-programmed desorption. The synergistic effect of dual-active sites reduced the energy barrier of hydrogenation from 2.65 (Bi₂ O₃ ) to 2.13 eV (Ti-Bi₂ O₃ ), thanks to the highly overlapping orbitals with N₂ . Results showed that 10 % Ti-doped Bi₂ O₃ exhibited an excellent ammonia production rate of 508.6 μmol g_cat ^-1  h^-1 in water and without sacrificial agent, which is 4.4 times higher than that of Bi₂ O₃ . In this work, bridging oxygen activation and synergistic hydrogenation for nitrogen with Ti-Bi dual active sites may unveil a corner of the hidden nitrogen reduction reaction mechanism and serves as a distinctive strategy for the design of nitrogen fixation photocatalysts.