Phase-selective active sites on ordered/disordered titanium dioxide enable exceptional photocatalytic ammonia synthesis.

Photocatalytic N fixation to NH defect creation on TiO to activate ultra-stable N[triple bond, length as m-dash]N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N preferentially adsorbs on phase-selective defect sites on TiO in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (A) preferentially exhibit higher N adsorption ability with a reduced energy barrier for a potential-determining-step (N to NNH) than the disordered rutile (R) phase of TiO. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO photocatalyst (Na-A/R) by sodium-amine treatment of P25-TiO under ambient conditions, which exhibits an efficient NH formation rate of 432 μmol g h, which is superior to that of any other defect-rich disordered TiO under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N chemisorption on the defect sites of Na-A with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with R enable substantially enhanced N fixation.