Defective titanium dioxide nanobamboo arrays architecture for photocatalytic nitrogen fixation up to 780 nm

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 (Ovac) 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 TiOx architecture shows a potential as a new artificial nitrogen fixation for environmentally friendly NH3 production.