Sub-3 nm Ultrafine Cu2 O 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.