Sub‐3 nm Ultrafine Cu₂O for Visible Light Driven Nitrogen Fixation

Cu₂ O, a low-cost, visible light responsive semiconductor photocatalyst represents an ideal candidate for visible light driven photocatalytic reduction of N₂ to NH₃ from the viewpoint of thermodynamics, but it remains unexplored. Reported here is the successful synthesis of uniformly sized and ultrafine Cu₂ O platelets, with a lateral size of <3 nm, by the in situ topotactic reduction of a CuII -containing layered double hydroxide with ascorbic acid. The supported ultrafine Cu₂ O offered excellent performance and stability for the visible light driven photocatalytic reduction of N₂ to NH₃ (the Cu₂ O-mass-normalized rate as high as 4.10 mmol g Cu 2 O ⁻¹ h⁻¹ at λ>400 nm), with the origin of the high activity being long-lived photoexcited electrons in trap states, an abundance of exposed active sites, and the underlying support structure. This work guides the future design of ultrafine catalysts for NH₃ synthesis and other applications.