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

Abstract

Photocatalytic N2fixation to NH3viadefect creation on TiO2to activate ultra-stable N=N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N2preferentially adsorbs on phase-selective defect sites on TiO2in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (Ad) preferentially exhibit higher N2adsorption ability with a reduced energy barrier for a potential-determining-step (*N2to NNH*) than the disordered rutile (Rd) phase of TiO2. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO2photocatalyst (Na-Ad/Ro) by sodium-amine treatment of P25-TiO2under ambient conditions, which exhibits an efficient NH3formation rate of 432 μmol g−1h−1, which is superior to that of any other defect-rich disordered TiO2under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N2chemisorption on the defect sites of Na-Adwith enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with Roenable substantially enhanced N2fixation.