Defective Titanium Dioxide Nanobamboo Arrays Architecture for Photocatalytic Nitrogen Fixation up to 780 nm

Abstract

Solar-driven nitrogen fixation is a potential solution to satisfying industrial and agricultural demand, but is severely hampered by the difficulties in capturing, activating and cleaving the dinitrogen (N₂). Here, the defect TiO₂ nanobamboo arrays (DTiO₂ NBAs) is designed with an electro-reduction strategy, which, for the first time, successfully converted N₂ to ammonia (NH₃) in the visible and near infrared light range under ambient conditions, without any sacrificial agent or noble-metal co-catalysts. A highly selective NH₃ yield of 48.3 mg m⁻² h⁻¹ (178 μmol g⁻¹ h⁻¹, no N₂H₄ formation) is obtained on the DTiO₂ NBAs haired titanium foil. The apparent quantum efficiency (AQE) was measured to be 0.39% at 365 nm, 0.12% at 405 nm, 0.11% at 450 nm, 0.15% at 532 nm, 0.24% at 650 nm, and 0.07% at 780 nm. It is found that the electro-reduction process creates amorphous surface layer with modest oxygen vacancy (O_(vac)) density so as to greatly enhance light harvesting, charge carrier, photo-thermal effect, as well as nitrogen adsorption and hydrogenation activity. The alternating photo-fixation pathway is also confirmed by density functional theory (DFT) calculations. This novel nanobamboo TiO_x architecture shows a potential as a new artificial nitrogen fixation for environmentally friendly NH₃ production.