Visible-Light Photocatalytic Nitrogen Fixation and Electrons Transport in Bismuth Iron Molybdate

The vast majority of semiconductors photocatalysts reported for artificial nitrogen fixation have a large bandgap at around 3.0 eV, thus photocatalytic nitrogen reduction is driven mainly by ultraviolet light. In contrast, this report demonstrates that bismuth iron molybdate (Bi 3 FeMo 2 O 12 ) with a bandgap of 2.25 eV exhibits visible-light photocatalytic activity toward nitrogen conversion to ammonia. Furthermore, introduction of oxygen vacancy to this photocatalyst increases the ammonia production rate remarkably. The oxygen vacancies help adsorb and stabilize the N-H intermediate species and lower the energy barrier of intermediate reactions. Bi 3 FeMo 2 O 12 has relatively narrow band gap and active sites for nitrogen fixation. However the ammonia production rate is low. Using photoelectrochemical system, surface photovoltage spectroscopy and simulation, we revealed that photoelectrons transport is constrained, which is attributed to the strong interaction between photoelectrons and lattice phonons.