Photoelectrochemical-driven nitrogen reduction to ammonia by a V o -SnO 2 /TiO 2 composite electrode.

N 2 molecules with the NN triple bond structure are difficult to cleave under mild conditions to achieve the nitrogen fixation reaction. Photoelectrochemical (PEC) catalysis technology combining the advantages of photocatalysis and electrocatalysis provides the possibility of the nitrogen reduction reaction under ambient conditions. Herein, an SnO 2 /TiO 2 photoelectrode was first fabricated through depositing SnO 2 quantum dots on TiO 2 nanorod arrays via a simple hydrothermal method. The oxygen vacancy (V o ) content was then induced in SnO 2 through annealing SnO 2 /TiO 2 at high temperature under an inert atmosphere. The heterogeneous structure of V o -SnO 2 quantum dots and TiO 2 nanorods boosted the separation of photocarriers. The photoelectrons generated by photoexcitation were transferred from the conduction band of TiO 2 to the conduction band of V o -SnO 2 and trapped by V o . V o activates N 2 molecules adsorbed on the catalyst surface, and reacts with H + in the electrolyte to generate NH 3 . The nitrogen fixation yield of PEC catalysis and its faradaic efficiency can reach 19.41 μg cm -2 h -1 , and 59.6% at -0.2 V bias potential, respectively. The heterogeneous structure of V o -SnO 2 /TiO 2 , introduction of V o and synergistic effect between light and electricity greatly promotes the PEC nitrogen reduction to NH 3 .