Regulating Electronic Structure in Bi 2 O 3 Architectures by Ti Mediation: A Strategy for Dual Active Sites Synergistically Promoting Photocatalytic Nitrogen Hydrogenation.

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-Bi 2 O 3 (Ti-Bi 2 O 3 ) 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-Bi 2 O 3 created a novel adsorption geometry of O-N 2 interaction proved by density functional theory calculation and N 2 temperature-programmed desorption. The synergistic effect of dual-active sites reduced the energy barrier of hydrogenation from 2.65 (Bi 2 O 3 ) to 2.13 eV (Ti-Bi 2 O 3 ), thanks to the highly overlapping orbitals with N 2 . Results showed that 10 % Ti-doped Bi 2 O 3 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 Bi 2 O 3 . 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.