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

Abstract Cu 2 O, a low‐cost, visible light responsive semiconductor photocatalyst represents an ideal candidate for visible light driven photocatalytic reduction of N 2 to NH 3 from the viewpoint of thermodynamics, but it remains unexplored. Reported here is the successful synthesis of uniformly sized and ultrafine Cu 2 O platelets, with a lateral size of <3 nm, by the in situ topotactic reduction of a Cu II ‐containing layered double hydroxide with ascorbic acid. The supported ultrafine Cu 2 O offered excellent performance and stability for the visible light driven photocatalytic reduction of N 2 to NH 3 (the Cu 2 O‐mass‐normalized rate as high as 4.10 mmol g −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 NH 3 synthesis and other applications.