Few-layer black phosphorus enables nitrogen fixation under ambient conditions

Nitrogen (N₂) fixation is a key reaction in biological and industrial chemistry, which does not occur spontaneously under ambient conditions but often depends on very specific catalysts and harsh reaction processes. Here we show that exposing exfoliated black phosphorus to the open air triggers, concomitantly, the oxidation of the two-dimensional (2D) material and the fixation of up to 100 parts per million (0.01%) of N₂ on the surface. The fixation also occurs in pristine non-exfoliated material. Besides, other allotropic forms of phosphorus, like red P, also fixes N₂ during ambient oxidation, suggesting that the N₂ fixation process is intrinsic with phosphorus oxidation and does not depend on the chemical structure or the dimensionality of the solid. Despite the low amounts of N₂ fixed, this serendipitous discovery could have fundamental implications on the chemistry and environmental stability of phosphorous and the design of related catalysts for N₂ fixation.